To see the other types of publications on this topic, follow the link: Pollen analysis][Vegetation changes.
Journal articles on the topic 'Pollen analysis][Vegetation changes'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Pollen analysis][Vegetation changes.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Fujiki, Toshiyuki, Mitsuru Okuno, Hiroshi Moriwaki, Toshio Nakamura, Kei Kawai, Gerald McCormack, George Cowan, and Paul T. Maoate. "Vegetation Changes Viewed from Pollen Analysis in Rarotonga, Southern Cook Islands, Eastern Polynesia." Radiocarbon 56, no. 2 (2014): 699–708. http://dx.doi.org/10.2458/56.17444.
Full textAbstract:
This study presents accelerator mass spectrometry (AMS) radiocarbon dates and pollen assemblages of 400-cm core sediments collected from the Karekare Swamp in Rarotonga, Southern Cook Islands, to investigate vegetation changes on the island, in particular those induced by human impacts. Eight 14C dates of charcoal and higher plant fragment samples indicate that the sediments accumulated since ∼6.0 cal kBP, with an apparent interruption of deposition (hiatus) from 130 to 132 cm in depth, corresponding to ∼2.8 to 0.7 cal kBP. The appearance of Chenopodiaceae pollen from upland weeds, and Cucurbitaceae and Vigna pollen grains from cultivated plants suggest that human influence existed in core sediments above 130 cm in depth. The increased abundance of Pandanus pollen and monolate-type fern spores also implies the existence of human activity.
2
Seppä, Heikki, and K. D. Bennett. "Quaternary pollen analysis: recent progress in palaeoecology and palaeoclimatology." Progress in Physical Geography: Earth and Environment 27, no. 4 (December 2003): 548–79. http://dx.doi.org/10.1191/0309133303pp394oa.
Full textAbstract:
During the last decade Quaternary pollen analysis has developed towards improved pollen-taxonomical precision, automated pollen identification and more rigorous definition of pollen assemblage zones. There have been significant efforts to model the spatial representation of pollen records in lake sediments which is important for more precise interpretation of the pollen records in terms of past vegetation patterns. We review the difficulties in matching modelled post-glacial plant migration patterns with pollen-based palaeorecords and discuss the potential of DNA analysis of pollen to investigate the ancestry and past migration pathways of the plants. In population ecology there has been an acceleration of the widely advocated conceptual advance of pollen-analytical research from vaguely defined ‘environmental reconstructions’ towards investigating more precisely defined ecological problems aligned with the current ecological theories. Examples of such research have included an increasing number of investigations about the ecological impacts of past disturbances, often integrating pollen records with other palaeoecological data. Such an approach has also been applied to incorporate a time perspective to the questions of ecosystem restoration, nature conservation and forest management. New lines of research are the use of pollen analysis to study long-term patterns of vegetation diversity, such as the role of glacial-age vegetation fragmentation as a cause of Amazonian rain forest diversity, and to investigate links between pollen richness and past plant diversity. Palaeoclimatological use of pollen records has become more quantitative and has included more precise and rigorous testing of pollen-climate calibration models with modern climate data. These tests show the approximate nature of the models and warn against a too straightforward climatic interpretation of the small-scale variation in reconstructions. Pollen-based climate reconstructions over the Late Glacial-early Holocene boundary have indicated that pollen-stratigraphical changes have been rapid with no evidence for response lags. This does not rule out the possibility of migrational disequilibrium, however, as the rapid changes may be mostly due to nonmigrational responses of existing vegetation. It is therefore difficult to assess whether the amplitude of reconstructed climate change reflects real climate change. Other outstanding problems remain the obscure relationship of pollen production and climate, the role of human impact and other nonclimatic factors, and nonanalogue situations.
3
Noguchi, Makoto, Toshiyuki Fujiki, Mitsuru Okuno, Lyn Gualtieri, Virginia Hatfield, Brenn Sarata, Masayuki Torii, Keiji Wada, Toshio Nakamura, and Dixie West. "Vegetation Changes around Haven Lake, Adak Island, Central Aleutians, Alaska, Determined from Pollen Analysis." Radiocarbon 60, no. 5 (October 2018): 1483–92. http://dx.doi.org/10.1017/rdc.2018.103.
Full textAbstract:
ABSTRACTWe collected peat sediments (sediment core ADK13083002) from Haven Lake on the north side of Adak Island (central Aleutian Islands, Alaska) to determine whether the vegetation has changed. We confirmed the presence of six tephra layers, including Forty Years (0.3 cal ka BP), T2, YBO (3.3 cal ka BP), Intermediate (6.4 cal ka BP), Main (9.5 cal ka BP), and T6. We identified four major pollen assemblage zones (HL-1 to HL-4, in descending order) in the cored sediment. HL-1 was dominated by Ranunculaceae and Empetrum pollen; H-2 was dominated by Poaceae, Ranunculaceae, and Empetrum pollen; HL-3 was dominated by Poaceae and Empetrum pollen; and HL-4 was dominated by Poaceae, Cyperaceae, Lycopodiaceae, and Empetrum pollen. Small charcoal particles, likely transported from a distance, were found at low frequencies until 6.4 cal ka BP. The total cross-sectional area of charcoal particles increased to 1500 μm2 or more by 6.4 cal ka BP, implying that the large charcoal particles originated from nearby Aleut settlements, which were established around the same time.
4
Cao, Xianyong, Fang Tian, Furong Li, Marie-José Gaillard, Natalia Rudaya, Qinghai Xu, and Ulrike Herzschuh. "Pollen-based quantitative land-cover reconstruction for northern Asia covering the last 40 ka cal BP." Climate of the Past 15, no. 4 (August 8, 2019): 1503–36. http://dx.doi.org/10.5194/cp-15-1503-2019.
Full textAbstract:
Abstract. We collected the available relative pollen productivity estimates (PPEs) for 27 major pollen taxa from Eurasia and applied them to estimate plant abundances during the last 40 ka cal BP (calibrated thousand years before present) using pollen counts from 203 fossil pollen records in northern Asia (north of 40∘ N). These pollen records were organized into 42 site groups and regional mean plant abundances calculated using the REVEALS (Regional Estimates of Vegetation Abundance from Large Sites) model. Time-series clustering, constrained hierarchical clustering, and detrended canonical correspondence analysis were performed to investigate the regional pattern, time, and strength of vegetation changes, respectively. Reconstructed regional plant functional type (PFT) components for each site group are generally consistent with modern vegetation in that vegetation changes within the regions are characterized by minor changes in the abundance of PFTs rather than by an increase in new PFTs, particularly during the Holocene. We argue that pollen-based REVEALS estimates of plant abundances should be a more reliable reflection of the vegetation as pollen may overestimate the turnover, particularly when a high pollen producer invades areas dominated by low pollen producers. Comparisons with vegetation-independent climate records show that climate change is the primary factor driving land-cover changes at broad spatial and temporal scales. Vegetation changes in certain regions or periods, however, could not be explained by direct climate change, e.g. inland Siberia, where a sharp increase in evergreen conifer tree abundance occurred at ca. 7–8 ka cal BP despite an unchanging climate, potentially reflecting their response to complex climate–permafrost–fire–vegetation interactions and thus a possible long-term lagged climate response.
5
Toledo, Mauro B. de, and Mark B. Bush. "Vegetation and hydrology changes in Eastern Amazonia inferred from a pollen record." Anais da Academia Brasileira de Ciências 80, no. 1 (March 2008): 191–203. http://dx.doi.org/10.1590/s0001-37652008000100014.
Full textAbstract:
Pollen, charcoal, and C14 analyses were performed on a sediment core obtained from Lake Tapera (Amapá) to provide the palaeoenvironmental history of this part of Amazonia. A multivariate analysis technique, Detrended Correspondence Analysis, was applied to the pollen data to improve visualization of sample distribution and similarity. A sedimentary hiatus lasting 5,500 years was identified in the Lake Tapera. Because the timing of the hiatus overlapped with the highest Holocene sea-level, which would have increased the local water table preventing the lake from drying out, it is clear that sea-level was not important in maintaining the lake level. Lake Tapera probably depended on riverine flood waters, and the sedimentary gap was caused by reduced Amazon River discharge, due to an extremely dry period in the Andes (8,000-5,000 years BP), when precipitation levels markedly decreased. The lack of Andean pollen (river transported) in the record after this event supports this interpretation. The pollen analysis shows that when sedimentation resumed in 1,620 cal. years BP, the vegetation around the lake was changed from forest into savanna. This record demonstrates the need to improve our understanding of climate changes and their associated impacts on vegetation dynamics.
6
Urrego, D. H., H. Hooghiemstra, O. Rama-Corredor, B. Martrat, J. O. Grimalt, and L. Thompson. "Rapid millennial-scale vegetation changes in the tropical Andes." Climate of the Past Discussions 11, no. 3 (May 11, 2015): 1701–39. http://dx.doi.org/10.5194/cpd-11-1701-2015.
Full textAbstract:
Abstract. We compare eight pollen records reflecting climatic and environmental change from the tropical Andes. Our analysis focuses on the last 50 ka, with particular emphasis on the Pleistocene to Holocene transition. We explore ecological grouping and downcore ordination results as two approaches for extracting environmental variability from pollen records. We also use the records of aquatic and shoreline vegetation as markers for lake level fluctuations, and precipitation change. Our analysis focuses on the signature of millennial-scale variability in the tropical Andes, in particular, Heinrich stadials and Greenland interstadials. We identify rapid responses of the tropical vegetation to this climate variability, and relate differences between sites to moisture sources and site sensitivity.
7
Miyake, Nao, Kunito Nehira, Nobukazu Nakagoshi, and Takahisa Hirayama. "An Investigation of Vegetation Changes by Pollen Analysis of Forest Soils." Quaternary Research (Daiyonki-Kenkyu) 39, no. 2 (2000): 139–50. http://dx.doi.org/10.4116/jaqua.39.139.
Full text
8
Eisner, Wendy R., Torbjörn E. Törnqvist, Eduard A. Koster, Ole Bennike, and Jacqueline F. N. van Leeuwen. "Paleoecological Studies of a Holocene Lacustrine Record from the Kangerlussuaq (Søndre Strømfjord) Region of West Greenland." Quaternary Research 43, no. 1 (January 1995): 55–66. http://dx.doi.org/10.1006/qres.1995.1006.
Full textAbstract:
AbstractA lacustrine sediment record from the Kangerlussuaq region, West Greenland, has resulted in a pollen, macrofossil, and sediment stratigraphy that encompasses the last 5000 14C yr. Deglaciation of the area and subsequent development of a nearby floodplain occurred before 5000 yr B.P. Since that time eolian sand and silt deposition appear to have been continuous, with a significant increase ca. 1000 14C yr B.P. Pollen analysis shows little change in the character of the vegetation throughout the record. Fluctuations in herb pollen taxa indicate changes in the extent and development of eolian sand sheets. The oldest pollen zone records relatively little pollen accumulation and low taxa diversity. This is followed by a zone of high pollen accumulation, presumably a phase of highest vegetation density, from 4400 to 3400 14C yr B.P. Thereafter, declining pollen accumulation rates reveal a gradual environmental deterioration. Macrofossil analyses record significant limnological changes, with an early eutrophic phase followed by a masotrophic phase and a reversal to more eutrophic conditions in the final phase. The preserved record illustrates the interactions of deglaciation, eolian activity, regional vegetation, and limnological change.
9
Fujiki, Toshiyuki, Mitsuru Okuno, Hiroshi Moriwaki, Toshio Nakamura, Kei Kawai, Gerald McCormack, George Cowan, and Paul T. Maoate. "Vegetation Changes Viewed from Pollen Analysis in Rarotonga, Southern Cook Islands, Eastern Polynesia." Radiocarbon 56, no. 02 (2014): 699–708. http://dx.doi.org/10.1017/s0033822200049730.
Full textAbstract:
This study presents accelerator mass spectrometry (AMS) radiocarbon dates and pollen assemblages of 400-cm core sediments collected from the Karekare Swamp in Rarotonga, Southern Cook Islands, to investigate vegetation changes on the island, in particular those induced by human impacts. Eight14C dates of charcoal and higher plant fragment samples indicate that the sediments accumulated since ∼6.0 cal kBP, with an apparent interruption of deposition (hiatus) from 130 to 132 cm in depth, corresponding to ∼2.8 to 0.7 cal kBP. The appearance of Chenopodiaceae pollen from upland weeds, and Cucurbitaceae andVignapollen grains from cultivated plants suggest that human influence existed in core sediments above 130 cm in depth. The increased abundance ofPandanuspollen and monolate-type fern spores also implies the existence of human activity.
10
Pessenda, Luiz C. R., Susy E. M. Gouveia, Marie-Pierre Ledru, Ramon Aravena, Fresia S. Ricardi-Branco, José A. Bendassolli, Adauto de S. Ribeiro, et al. "Interdisciplinary paleovegetation study in the Fernando de Noronha Island (Pernambuco State), northeastern Brazil." Anais da Academia Brasileira de Ciências 80, no. 4 (December 2008): 677–91. http://dx.doi.org/10.1590/s0001-37652008000400009.
Full textAbstract:
The aim of this research was to reconstruct vegetation changes (with climate inferences) that occurred during the Holocene in the Fernando de Noronha Island, Pernambuco State, northeastern Brazil. The research approach included the use of geochemical (mineralogy, elemental), carbon isotopes (δ13C, 14C) and pollen analyses in soil organic matter (SOM) and sediments collected in Lagoa da Viração and Manguezal do Sueste. The carbon isotopes data of SOM indicated that there was no significant vegetation changes during the last 7400 BP, suggesting that the climate was not the determinant factor for the vegetation dynamics. The pollen analysis of the sediment of a core collected in the Lagoa da Viração showed the absence of Quaternary material in the period between 720 BP and 90 BP. The mineralogical analysis of deeper layer showed the presence of diopside indicating this material was developed "in situ". Only in the shallow part of the core were found pollen of similar plant species of the modern vegetation. The geochemistry and isotope results, in association with the sediment type and pollen analyses of sediment samples of Manguezal do Sueste, indicated variations in the vegetation and in its location since the middle Holocene. Such variations can be associated with climatic events and sea level oscillations and also with anthropogenic events considering the last five hundred years.
11
Burney, David A. "Late Holocene Vegetational Change in Central Madagascar." Quaternary Research 28, no. 1 (July 1987): 130–43. http://dx.doi.org/10.1016/0033-5894(87)90038-x.
Full textAbstract:
AbstractA sediment core from Lake Kavitaha, central Madagascar, provides a stratigraphic record of changes in pollen spectra and charcoal influx in the late Holocene. The earliest pollen spectra distantly resemble the modern pollen rain of a vegetational mosaic in northern Madagascar, although results of principal component analysis suggest no close modern analog. At about 1300 yr B.P., a marked rise in charcoal is followed by a decline in pollen of woody taxa, culminating in a change to grass-dominated pollen spectra within about 4 centuries. Pollen of woody taxa decline below 15% of total terrestrial pollen and spores beginning about 600 yr B. P. The influx of charcoal from graminoid sources remains high until recent centuries. The late Holocene changes in vegetation and fire ecology at the site were approximately contemporaneous with the latest 14?C dates for the extinct megafauna and the earliest dates for human occupation.
12
Reese, C. A., K. B. Liu, and L. G. Thompson. "An ice-core pollen record showing vegetation response to Late-glacial and Holocene climate changes at Nevado Sajama, Bolivia." Annals of Glaciology 54, no. 63 (2013): 183–90. http://dx.doi.org/10.3189/2013aog63a375.
Full textAbstract:
AbstractWe present the results of pollen analysis performed on an ice core recovered from Nevado Sajama, Bolivia, dated to 25 ka BP. Low pollen concentrations from 25 to 15 ka BP are consistent with the scenario of an expanded ice cap surrounded by sparse vegetation and cold conditions on the Altiplano during the Last Glacial Maximum. After 15 ka BP, more pollen is present and percentages show vegetation response to climate fluctuations during the late Pleistocene. Initially, high concentrations of Poaceae pollen are replaced by Asteraceae pollen, suggesting the occurrence of dry conditions towards the end of the Bølling–Allerød/Guantiva interstadial. A deglacial climatic reversal is registered in the pollen record by an abrupt decline in Asteraceae and maximum percentages of Poaceae, indicating wet conditions during 14–12 ka BP. The climate changed abruptly to warm and dry after 12 ka BP, but vegetation remained in disequilibrium with climate until 10 ka BP. Pollen results indicate dry conditions at the beginning of the Holocene, with humidity increasing steadily until 8.5 ka BP. Decreased pollen concentration values (used as a moisture availability proxy) place the mid-Holocene dry period between 8 and 5 ka BP. This was followed by wetter conditions to the present day.
13
Iglesias, Virginia, Flavia Quintana, William Nanavati, and Cathy Whitlock. "Interpreting modern and fossil pollen data along a steep environmental gradient in northern Patagonia." Holocene 27, no. 7 (November 25, 2016): 1008–18. http://dx.doi.org/10.1177/0959683616678467.
Full textAbstract:
Vegetation reconstructions rest on modern vegetation–pollen rain relationships and deductive reasoning. Establishing this relationship is a nontrivial task because differences among pollen assemblages are not necessarily proportional to differences in vegetation. This task is particularly challenging in Patagonia, where some tree taxa have indistinguishable pollen, and pollen grains can be transported long distances. In this study, we describe the modern pollen of 48 lake and wetland samples from northern Patagonia (40.5–44°S) to better discriminate the major vegetation zones of the region through pollen analysis. Specifically, we focus on the performance of three methodological approaches, namely, pollen indicators, classification trees, and optimal thresholds of dissimilarity. As a proof of concept, we use the modern pollen–vegetation relationships to reconstruct the vegetation history at Laguna el Trébol (41.07°S; 71.5°W). Our results revealed that (1) pollen sums exceeding 260 grains ensured replicable vegetation reconstructions, (2) modern vegetation zones could not be separated solely by visual inspection of their pollen spectra, (3) the classification tree and optimal thresholds of dissimilarity permitted discrimination of most vegetation zones, (4) detection of nonanalog communities required use of pollen indicators or optimal thresholds of dissimilarity, and (5) vegetation at L. el Trébol was likely dominated by late glacial shrubland with no modern analogs in the study area (15,000–12,180 cal. yr BP), modern shrubland (12,180–6500 cal. yr BP) and mixed forest (6500 cal. yr BP–present). This study allows a more realistic understanding of the pollen–vegetation relationship and provides new tools for interpreting past vegetation in northern Patagonia.
14
Urrego, Dunia H., Henry Hooghiemstra, Oscar Rama-Corredor, Belen Martrat, Joan O. Grimalt, Lonnie Thompson, Mark B. Bush, et al. "Millennial-scale vegetation changes in the tropical Andes using ecological grouping and ordination methods." Climate of the Past 12, no. 3 (March 21, 2016): 697–711. http://dx.doi.org/10.5194/cp-12-697-2016.
Full textAbstract:
Abstract. We compare eight pollen records reflecting climatic and environmental change from northern and southern sites in the tropical Andes. Our analysis focuses on the last 30 000 years, with particular emphasis on the Pleistocene to Holocene transition. We explore ecological grouping and downcore ordination results as two approaches for extracting environmental variability from pollen records. We also use the records of aquatic and shoreline vegetation as markers for lake level fluctuations and moisture availability. Our analysis focuses on the signature of millennial-scale climate variability in the tropical Andes, in particular Heinrich stadials (HS) and Greenland interstadials (GI). The pollen records show an overall warming trend during the Pleistocene–Holocene transition, but the onset of post-glacial warming differs in timing among records. We identify rapid responses of the tropical vegetation to millennial-scale climate variability. The signatures of HS and the Younger Dryas are generally recorded as downslope upper forest line (UFL) migrations in our transect, and are likely linked to air temperature cooling. The GI1 signal is overall comparable between northern and southern records and indicates upslope UFL migrations and warming in the tropical Andes. Our marker for lake level changes indicated a north-to-south difference that could be related to moisture availability. The air temperature signature recorded by the Andean vegetation was consistent with millennial-scale cryosphere and sea surface temperature changes but suggests a potential difference between the magnitude of temperature change in the ocean and the atmosphere. We also show that arboreal pollen percentage (AP %) and detrended correspondence analysis (DCA) scores are two complementary approaches to extract environmental variability from pollen records.
15
Abdallah, Amel Hassan, and Dafaala Ali Ibrahim. "Paleoecological studies of an archeological site in Sudan (Musawarat ElSufra)." World Journal of Science, Technology and Sustainable Development 12, no. 4 (October 5, 2015): 246–56. http://dx.doi.org/10.1108/wjstsd-10-2015-0048.
Full textAbstract:
Purpose – The purpose of this paper is to measure the environmental changes, which took place in the study area Musawarat ElSufra and the authors try to find the causes of these changes and establish a comparison of the present and past vegetation of the area. Design/methodology/approach – Present vegetation was investigated using fresh plant materials for pollen analysis. Fossils were taken from the hafir (basin) to study the fossil pollen grains at different soil depths. Soil surface samples were taken to analyze the chemical and physical properties of the soil. Findings – The pollen analysis of the samples taken from the hafir (basin) of Musawarat reveals that there are 21 species belonging to 16 families. The dominant families were Cyperaceae, Commelinaceae, Mimosaceae and Amaranthaceae. Originality/value – Comparison of past and present vegetation reveal the causes of environmental change and insure sustainable development in arid region.
16
Masi, Alessia, Alexander Francke, Caterina Pepe, Matthias Thienemann, Bernd Wagner, and Laura Sadori. "Vegetation history and paleoclimate at Lake Dojran (FYROM/Greece) during the Late Glacial and Holocene." Climate of the Past 14, no. 3 (March 13, 2018): 351–67. http://dx.doi.org/10.5194/cp-14-351-2018.
Full textAbstract:
Abstract. A new high-resolution pollen and NPP (non-pollen palynomorph) analysis has been performed on the sediments of Lake Dojran, a transboundary lake located at the border between Greece and the former Yugoslav Republic of Macedonia (FYROM). The sequence covers the last 12 500 years and provides information on the vegetational dynamics of the Late Glacial and Holocene for the southern Balkans. Robust age model, sedimentological diatom, and biomarker analyses published previously have been the base for a multi-perspective interpretation of the new palynological data. Pollen analysis revealed that the Late Glacial is characterized by steppic taxa with prevailing Amaranthaceae, Artemisia and Poaceae. The arboreal vegetation starts to rise after 11 500 yr BP, taking a couple of millennia to be definitively attested. Holocene vegetation is characterized by the dominance of mesophilous plants. The Quercus robur type and Pinus are the most abundant taxa, followed by the Quercus cerris type, the Quercus ilex type and Ostrya–Carpinus orientalis. The first attestation of human presence can be presumed at 5000 yr BP from the contemporary presence of cereals, Juglans and Rumex. A drop in both pollen concentration and influx together with a δ18Ocarb shift indicates increasing aridity and precedes clear and continuous human signs since 4000 yr BP. Also, a correlation between Pediastrum boryanum and fecal stanol suggests that the increase in nutrients in the water is related to human presence and pasture. An undoubted expansion of human-related plants occurs since 2600 yr BP when cereals, arboreal cultivated and other synanthropic non-cultivated taxa are found. A strong reduction in arboreal vegetation occurred at 2000 yr BP, when the Roman Empire impacted a landscape undergoing climate dryness in the whole Mediterranean area. In recent centuries the human impact still remains high but spots of natural vegetation are preserved. The Lake Dojran multi-proxy analysis including pollen data provides clear evidence of the importance of this approach in paleoenvironmental reconstruction. Cross-interpretation of several proxies allows us to comprehend past vegetation dynamics and human impact in the southern Balkans.
17
Wolter, Juliane, Hugues Lantuit, Ulrike Herzschuh, Samuel Stettner, and Michael Fritz. "Tundra vegetation stability versus lake-basin variability on the Yukon Coastal Plain (NW Canada) during the past three centuries." Holocene 27, no. 12 (June 1, 2017): 1846–58. http://dx.doi.org/10.1177/0959683617708441.
Full textAbstract:
Palaeoclimatic reconstructions of the northern Yukon show cooler conditions before AD 1850 followed by gradual warming, and 20th-century temperature measurements indicate decadal-scale temperature fluctuations. The impact of climate on regional vegetation and lake systems has seldom been observed on this scale, however. With this study, we provide a sub-decadal reconstruction of regional vegetation and lake-basin development for the past 300 years, covering the ‘Little Ice Age’ and the period of recent warming, in low Arctic tundra. We analysed a short lake sediment core from the Yukon Coastal Plain. The age–depth relationship of the core is based on 210Pb/137Cs validated by AMS radiocarbon dating. We analysed terrestrial pollen abundances as proxies for regional vegetation development, and we used grain size and biogeochemical analyses (TOC, TN, TOC/TN, δ13C) and the analysis of semiaquatic pollen to describe the lake development. Stable abundances of regional pollen taxa between AD 1730 and AD 2012 accompanied by climatic warming indicated that the regional vegetation was not sensitive to climate change. Based on changes in TOC/TN, δ13C and pollen of shallow-water taxa, we reconstructed an increase in lake water depth after AD 1910 that likely followed climatic warming. We attributed this development to climate-driven thaw subsidence in the lake basin. The impact of widespread permafrost thaw on regional vegetation needs to be better constrained in order to predict the limits of vegetation stability and drivers of lake changes in the region.
18
Donders, Timme H., Friederike Wagner, and Henk Visscher. "Quantification Strategies for Human-Induced and Natural Hydrological Changes in Wetland Vegetation, Southern Florida, USA." Quaternary Research 64, no. 3 (November 2005): 333–42. http://dx.doi.org/10.1016/j.yqres.2005.08.016.
Full textAbstract:
AbstractAn accurately dated peat profile from a mixed cypress swamp in the Fakahatchee Strand Preserve State Park (FSPSP, Florida, USA) has been examined for pollen and spores. The near-annual resolved pollen record shows a gradual shift from a wet to a relatively dry assemblage during the past 100 years. Timing of drainage activities in the region is accurately reflected by the onset and duration of vegetation change in the swamp. The reconstructed vegetation record has been statistically related to pollen assemblages from surface sediment samples. The response range of the FSPSP wetland to environmental perturbations could thus be determined and this allows better understanding of naturally occurring vegetation changes. In addition, the human impact on Florida wetlands becomes increasingly apparent. Superimposed high-frequency variation in the record suggests a positive correlation between winter-precipitation and pollen productivity of the dominant tree taxa. However, further high-resolution analysis is needed to confirm this relation. The response range of the FSPSP wetland to environmental perturbations on both annual- and decadal-scales documented in this study allows recognition and quantification of natural hydrological changes in older deposits from southwest Florida. The strong link between local hydrology and the El Niño Southern Oscillation makes the palynological record from FSPSP highly relevant for studying past El Niño–variability.
19
Dallmeyer, Anne, Martin Claussen, Jian Ni, Xianyong Cao, Yongbo Wang, Nils Fischer, Madlene Pfeiffer, et al. "Biome changes in Asia since the mid-Holocene – an analysis of different transient Earth system model simulations." Climate of the Past 13, no. 2 (February 9, 2017): 107–34. http://dx.doi.org/10.5194/cp-13-107-2017.
Full textAbstract:
Abstract. The large variety of atmospheric circulation systems affecting the eastern Asian climate is reflected by the complex Asian vegetation distribution. Particularly in the transition zones of these circulation systems, vegetation is supposed to be very sensitive to climate change. Since proxy records are scarce, hitherto a mechanistic understanding of the past spatio-temporal climate–vegetation relationship is lacking. To assess the Holocene vegetation change and to obtain an ensemble of potential mid-Holocene biome distributions for eastern Asia, we forced the diagnostic biome model BIOME4 with climate anomalies of different transient Holocene climate simulations performed in coupled atmosphere–ocean(–vegetation) models. The simulated biome changes are compared with pollen-based biome records for different key regions.In all simulations, substantial biome shifts during the last 6000 years are confined to the high northern latitudes and the monsoon–westerly wind transition zone, but the temporal evolution and amplitude of change strongly depend on the climate forcing. Large parts of the southern tundra are replaced by taiga during the mid-Holocene due to a warmer growing season and the boreal treeline in northern Asia is shifted northward by approx. 4° in the ensemble mean, ranging from 1.5 to 6° in the individual simulations, respectively. This simulated treeline shift is in agreement with pollen-based reconstructions from northern Siberia. The desert fraction in the transition zone is reduced by 21 % during the mid-Holocene compared to pre-industrial due to enhanced precipitation. The desert–steppe margin is shifted westward by 5° (1–9° in the individual simulations). The forest biomes are expanded north-westward by 2°, ranging from 0 to 4° in the single simulations. These results corroborate pollen-based reconstructions indicating an extended forest area in north-central China during the mid-Holocene. According to the model, the forest-to-non-forest and steppe-to-desert changes in the climate transition zones are spatially not uniform and not linear since the mid-Holocene.
20
Yonebayashi, Chuh. "Changes in vegetation, climate and snowfall regime since the late Pleistocene in a snowy mountainous region of central Japan." Holocene 29, no. 1 (October 10, 2018): 77–84. http://dx.doi.org/10.1177/0959683618804644.
Full textAbstract:
Although the most crucial factor shaping vegetation history is temperature, snowfall regime is also important in regions of heavy snow. Pollen analysis in a mire in a snowy mountainous region of central Japan revealed histories of vegetation and precipitation regimes since the latest Pleistocene. The abundance of pinaceous pollen during the latest Pleistocene indicates a subalpine regional coniferous forest and cooler conditions; moreover, sandy sediment and significant occurrence of pollen from Artemisia along with several alpine elements suggest local plant communities of poor vegetation cover in an erosive environment. The increase in Betula and Quercus subgen. Lepidobalanus pollen and the decline in pinaceous pollen in 13,550 cal. yr BP indicates climatic amelioration favourable to temperate trees, and the invasion of sedges and Reynoutria to the small basin and the onset of peat deposition suggest an increase in summer rain. The increase in Fagus crenata pollen after 11,130 cal. yr BP and onwards indicates that the present heavy snowfall regime induced by inflow of the Tsushima Current has been established since that age. The climatic amelioration delayed establishment of the heavy snowfall regime for more than 2400 years. In addition, the retreat of sedges and subsequent invasion of several species of drier habitat after 11,130 cal. yr BP indicate a drier mire condition caused by increased summer temperatures. The recovery of sedges after 3740 cal. yr BP indicates the wettest mire conditions induced by climatic deterioration. A general increasing tendency of conifers in this period supports this interpretation.
21
Xiao, Xiayun, Xiangdong Yang, Ji Shen, Sumin Wang, Bin Xue, and Xiufang Tong. "Vegetation history and dynamics in the middle reach of the Yangtze River during the last 1500 years revealed by sedimentary records from Taibai Lake, China." Holocene 23, no. 1 (July 12, 2012): 57–67. http://dx.doi.org/10.1177/0959683612450195.
Full textAbstract:
Pollen and charcoal records of a 150 cm long lake sediment core from Taibai Lake in the middle reach of the Yangtze River reveal seven major changes in regional vegetation over the last 1500 years. During the period c. ad 480–710, evergreen broadleaved forest dominated by Castanopsis/Lithocarpus and evergreen oaks occurred in the Taibai Lake catchment. From c. ad 710 to 1050, the vegetation shifted to a mixed conifer and broadleaved forest, with Pinus expanding at the expense of Castanopsis/Lithocarpus. Between c. ad 1050 and 1320, evergreen broadleaved forest reoccupied the studied area. From c. ad 1320 to 1650, the area of primary forest decreased markedly with synchronous reduction in broadleaved trees and Pinus. Between c. ad 1650 and 1740, the biomass declined rapidly, while secondary Pinus forest began to expand. During c. ad 1740–1950, forest extent increased slightly compared with the previous stage, but the landscape was still secondary forest with the minimum proportion of broadleaved trees. After c. ad 1950, the biomass in the surrounding area was very low, with vegetation types similar to that at present (secondary Pinus forest and mixed conifer and broadleaved forest). A detrended correspondence analysis (DCA) with 125 samples and 34 main pollen types is used to separate human and climatic impacts on vegetation. Then, the pollen assemblage, DCA, charcoal record, and magnetic susceptibility are combined to discuss the key factors inducing these vegetation changes. The vegetation changes were mainly controlled by the climatic changes, with the weak impacts of human activities before c. ad 1320. Since then, the intensity of human influences on vegetation increased gradually, entering a transitional period of main controlling factors of vegetation changes from nature to human activities. After c. ad 1740, the vegetation changes were chiefly controlled by human activities, and the climatic signal was weak.
22
Shriver, Robert K., and Thomas A. Minckley. "Late-Holocene response of limber pine (Pinus flexilis) forests to fire disturbance in the Pine Forest Range, Nevada, USA." Quaternary Research 78, no. 3 (August 20, 2012): 465–73. http://dx.doi.org/10.1016/j.yqres.2012.07.010.
Full textAbstract:
AbstractDespite growing concerns that ecological stressors (fire, insect and pathogen outbreaks) may force vegetation change, few studies have attempted to use paleoecological data to understand small-scale interactions between disturbance and vegetation. Using charcoal and pollen data, we infer past fire episodes and subsequent vegetation responses for a limber pine (Pinus flexilis) forest in northwestern Nevada, USA, to determine local vegetation recovery from disturbance. Using superimposed epoch analysis we examined average-vegetation and individual-taxon responses to eight randomly selected fire events over the past 4.0 ka. Pollen evidence shows that on average fires produce a weak response of declining Pinus while other taxa including Artemisia and Poaceae increase directly after fire episodes. Within 30 yr of a disturbance, pollen data indicate ecosystem recovery to pre-fire composition, consistent with modern studies of fire recovery of limber pine forests. Similar to short-term changes of pollen abundance, long-term vegetation responses indicate Pinus abundance weakly declining and Artemisia increasing when fire episodes are frequent. However, despite fire-episode frequencies varying between 75 and 250 yr, the overall vegetation structure has remained relatively stable over the past 4.0 ka. Our study contributes to the limited information on the disturbance ecology of isolated, subalpine forests in the intermountain West.
23
Elzinga, William J. "Short-term Vegetation Changes on an Abandoned Mining Site as Determined by Pollen Analysis." American Midland Naturalist 120, no. 2 (October 1988): 371. http://dx.doi.org/10.2307/2426009.
Full text
24
Scaife, Rob. "Flag Fen: the vegetation environment." Antiquity 66, no. 251 (June 1992): 462–66. http://dx.doi.org/10.1017/s0003598x0008162x.
Full textAbstract:
The discovery of the timber platform in fen peat poses a number of questions relating to the local ecology and environment in which the structure was constructed and the character of local land use and economic subsistence. Pollen and plant macro-fossil studies were initiated at the outset of discovery of the Flag Fen structure. Special attention has been paid to the changing fen flora reflecting local hydrological changes as well as evidence for the vegetation and land use on areas of nearby dry land. In addition to the evidence for temporal changes in the environment obtained from ‘long peat cores’, sampling on a grid-square basis is being carried out on sands thought to have been floor covering. It is hoped that these will yield information on the use of the platform. Pollen data are now available from Flag Fen and the nearby Power Station site at Fengate. This short contribution seeks to provide a general summary of the vegetation and environment of the fen and its near terrestrial environs with data coming largely from the analysis of the ‘Mere Section’ (see Introduction, FIGURE 6 for location) although some reference will be made to the Fengate site (see Introduction, FIGURE6 for location). Results ofthe completed study will be presented in a forthcoming monograph.
25
Gajewski, K. "The Global Pollen Database in biogeographical and palaeoclimatic studies." Progress in Physical Geography: Earth and Environment 32, no. 4 (August 2008): 379–402. http://dx.doi.org/10.1177/0309133308096029.
Full textAbstract:
The Global Pollen Database is an example of a successful data synthesis effort that has uses for biogeographical and climate change studies. Results are of interest in many fields of physical geography. Continental-scale maps of past conditions have been used in data-model comparison studies. Time series, developed by averaging quantitative reconstructions from many sites, have indicated that millennial-scale climate variability has affected the vegetation of Europe and North America during the Holocene. Major transitions in the vegetation of Europe and North America occurred at the same time, suggesting the overriding climate effect on the vegetation of both continents. The database can also be used to test biogeographical hypotheses, as several examples illustrate, without the need for collecting new data. Hundreds of studies over the past 50 years show that pollen analysis is more precise than frequently acknowledged: vegetation responds rapidly to climate variations, changes in vegetation are spatially coherent and the taxonomic resolution available in the database is greater than frequently acknowledged. The availability of a public, freely available database enables different analyses to be performed on the same data, thereby ensuring that results are not dependent on methodology.
26
Gerasimenko, N., T. Yurchenko, and Ye Rohozin. "Vegetation changes in the Hotyn Upland over the last 2000 years (based on pollen data)." Journal of Geology, Geography and Geoecology 28, no. 1 (April 17, 2019): 51–58. http://dx.doi.org/10.15421/111906.
Full textAbstract:
Pollen study of two soil sections, located in two different relief positions (the gully bottom at Sadgora 1 and the upper part of a slope at Ridkivtsi I) enables us to show vegetational and climatic changes in the Bukovyna area (the Chernivtsi region) during the last 2000 years (the end of the Early Subatlantic, the Middle and Late Subatlantic). The reconstructions of past vegetation are based on the analyses of pollen surface samples, taken from the soils of different ecotops in the sites’ vicinity. The reconstructed short-period phases of environmental change correspond well with those established in other areas. These are the end of the “Roman warm period” (before the 14C date of 1.74 ka BP), with the humid climate; the relatively dry “Dark Ages cool period” (before the 14C date of 1.19 ka BP); the wet “Medieval warm period”; the cool “Little Ice Age” (with its wetter beginning and drier ending) and the modern warm phase (the last 150 years).Centennial environmental changes − the cooling within the Medieval Warming (XI cent.) and the warming within the “Little Ice Age” (XV cent.) – have been detected. Human impact on the vegetation can be demonstrated – forest clearance (with the presence of particles of microscopic charcoal and pollen of pyrophitic plants), the introduction of thermophilous walnut during warm periods, and the appearance of pasture lands in the place of former fern patches and woods during the “Little Ice Age”, and the last warm phase (with the presence of pollen of pastoral synanthropic plants). In the last 2000 years, broad-leaved woodland, dominated by hornbeam, grew extensively near Sadgora and Ridkivtsi only during the “Medieval Warm Period”.
27
Moreno-Gonzalez, Ricardo, Thomas Giesecke, and Sonia L. Fontana. "The impact of recent land-use change in the Araucaria araucana forest in northern Patagonia." Holocene 30, no. 8 (April 23, 2020): 1101–14. http://dx.doi.org/10.1177/0959683620913918.
Full textAbstract:
Land-use change in the form of extensive Pinus plantations is currently altering the natural vegetation cover at the forest–steppe ecotone in northern Patagonia. Providing recommendations for conservation efforts, with respect to this recent and earlier land-use changes, requires a longer time perspective. Using pollen analysis, we investigated to what degree the colonization of the area by Euro-American settlers changed the forest composition and the vegetation cover, and to explore the spread of the European weed Rumex acetosella. This study is based on short sediment cores from six lakes in the Araucaria araucana forest region, across the vegetation gradient from the forest to the steppe. Results document that although Araucaria araucana has been extensively logged elsewhere, near the investigated sites, populations were rather stable and other elements of the vegetation changed little with the initiation of Euro-American settlements. A reduction of Nothofagus dombeyi-type pollen occurred at some sites presumably due to logging Nothofagus dombeyi trees, while toward the steppe, Nothofagus antarctica shrubs may have been removed for pasture. The appearance of Rumex acetosella pollen is consistent with the initiation of land use by Euro-American settlers in all cores, probably indicating the onset of animal farming. The rise of the Rumex acetosella pollen curve during the 1950s marks more recent land-use change. These observations indicate that the spread and local expansion of the weed requires disturbance. Overall, the study shows that the initial colonization of the area by Euro-American settlers had little effect on the natural vegetation structure, while developments since the 1950s are strongly altering the natural vegetation cover.
28
Amaral, P. G. C., A. Vincens, J. Guiot, G. Buchet, P. Deschamps, J. C. Doumnang, and F. Sylvestre. "Palynological evidence for gradual vegetation and climate changes during the "African Humid Period" termination at 13° N from a Mega-Lake Chad sedimentary sequence." Climate of the Past Discussions 8, no. 3 (June 18, 2012): 2321–67. http://dx.doi.org/10.5194/cpd-8-2321-2012.
Full textAbstract:
Abstract. Located at the transition between the Saharian and Sahelian zones, at the center of one of the largest endoreic basins, the Lake Chad is ideally located to record regional environmental changes that occurred in the past. However, until now, no continuous archive from Lake Chad covering the Holocene has been studied. In this paper, we present pollen data from the first Holocene sedimentary sequence collected in Lake Chad (13° N; 14° E; Sahel region). Dated between ca. 6700 and ca. 5000 cal yr BP, this record encompasses the termination of the African Humid Period (AHP). Vegetational reconstructions are based on standard analyses of the pollen diagrams and are strengthened by quantitative approaches. Potential biomes that occurred at that time around Mega-Lake Chad are reconstructed using the biomization method and mean annual precipitation is estimated using the modern analogues technique. Results show that between ca. 6700 and ca. 6050 cal yr BP, a vegetation close to humid woodland or humid savanna, including elements currently found much further southward, thrived in the vicinity and/or the extra-local environment of the Mega-Lake Chad in place of the modern steppe, dry woodland and desert vegetation observed today. At the same time, montane forest populations extended further southward on the Adamawa plateau. This vegetation distribution is supported by biome reconstructions as well as by mean annual precipitation estimates of ca. 800 (−400/+700) mm for the period. The high abundance of lowland humid pollen taxa is interpreted as the result of a northward migration of the corresponding plants during the AHP driven by more favorable climatic conditions. Our interpretation in favor of a regional vegetation response to climatic changes is supported by other pollen data from several Northwestern African records. However, we cannot rule out that an increase of Chari-Logone inputs into the Mega-Lake Chad due to variations in hydrological regime might have contributed to the higher abundance of lowland humid pollen taxa observed in the mid-Holocene sedimentary sequence. Changes in the structure and floristic composition of the vegetation towards more open and drier formations occurred after ca. 6050 cal yr BP. This is also evidenced by a decrease in mean annual precipitation estimates to approximately 600 (−230/+600) mm. This change corresponds to the onset of the AHP termination. The constant presence of lowland humid taxa until ca. 5000 cal yr BP, even if displaying a slight decrease, contemporaneous with an increase in steppic taxa, demonstrates that at ca. 5000 cal yr BP the modern vegetation was not yet established in the vicinity of Lake Chad. Our data indicate that vegetational change during this period must have occurred progressively, at least over 1000 yr, and are inconsistent with an abrupt aridification and a collapse of the vegetation cover in the East-Central Saharan and Sahelian regions at the AHP termination.
29
Sorrel, Philippe, Speranta-Maria Popescu, Stefan Klotz, Jean-Pierre Suc, and Hedi Oberhänsli. "Climate variability in the Aral Sea basin (Central Asia) during the late Holocene based on vegetation changes." Quaternary Research 67, no. 3 (May 2007): 357–70. http://dx.doi.org/10.1016/j.yqres.2006.11.006.
Full textAbstract:
AbstractHigh-resolution pollen analyses (∼ 50 yr) from sediment cores retrieved at Chernyshov Bay in the NW Large Aral Sea record shifts in vegetational development from subdesertic to steppe vegetation in the Aral Sea basin during the late Holocene. Using pollen data to quantify climatic parameters, we reconstruct and date for the first time significant changes in moisture conditions in Central Asia during the past 2000 yr. Cold and arid conditions prevailed between ca. AD 0 and 400, AD 900 and 1150, and AD 1500 and 1650 with the extension of xeric vegetation dominated by steppe elements. These intervals are characterized by low winter and summer mean temperatures and low mean annual precipitation (Pmm < 250 mm/yr). Conversely, the most suitable climate conditions occurred between ca. AD 400 and 900, and AD 1150 and 1450, when steppe vegetation was enriched by plants requiring moister conditions (Pmm ∼ 250–500 mm/yr) and some trees developed. Our results are fairly consistent with other late Holocene records from the eastern Mediterranean region and the Middle East, showing that regional rainfall in Central Asia is predominantly controlled by the eastern Mediterranean cyclonic system when the North Atlantic Oscillation (NAO) is in a negative phase.
30
Rochon, André, Anne de Vernal, Hans-Petter Sejrup, and Haflidi Haflidason. "Palynological Evidence of Climatic and Oceanographic Changes in the North Sea during the Last Deglaciation." Quaternary Research 49, no. 2 (March 1998): 197–207. http://dx.doi.org/10.1006/qres.1997.1956.
Full textAbstract:
Palynological analyses performed on cores from the Norwegian Channel (Troll 8903) led to reconstruction of the late-glacial variations in sea-surface conditions using dinoflagellate cyst data and permitted direct correlation with the vegetation history of northwestern Europe derived from pollen assemblages. By ∼15,000 yr B.P., ice rapidly receded from the Norwegian shelf and relatively warm summer conditions prevailed in surface waters. A first late-glacial cooling marked by extensive seasonal sea–ice cover is dated at ca. 13,600–13,000 14C yr B.P., which coincides with the Oldest Dryas interval. During the Bølling–Allerød interval, a rise in sea-surface temperature both in February (up to 3°C) and August (up to 15°C) led to the establishment of ice-free conditions in the northern North Sea, while pollen data reveal a densification of the vegetation cover. The beginning of the Younger Dryas interval is marked by an increase in nonarboreal pollen input indicative of the opening of the forest vegetation cover, concomitant with a cooling of surface waters during winter and development of sea–ice cover. However, sea-surface conditions remained relatively warm in summer until about 10,300 yr B.P., when extremely cold conditions and extensive sea–ice cover developed (up to 7 months/yr). Improving conditions are recorded in surface waters by ∼10,100 yr B.P., a few hundred years before the development of forest cover onshore, as shown by the pollen record. Such a discrepancy between marine and terrestrial indicators at the end of Younger Dryas time suggests a delayed response of the vegetation to regional climate warming.
31
Haenfling, Carolin, Rewi Newnham, Andrew Rees, Ignacio Jara, Aline Homes, and Beverley Clarkson. "Holocene history of a raised bog, northern New Zealand, based on plant cuticles." Holocene 27, no. 2 (July 28, 2016): 309–14. http://dx.doi.org/10.1177/0959683616658524.
Full textAbstract:
We present a method for analysing subfossil plant cuticles preserved in peat and apply the method to provide a preliminary, coarse resolution reconstruction of Holocene vegetation history at Moanatuatua Bog, northern North Island, New Zealand. The plant cuticle record reveals the early-Holocene development of a swamp and its transition to a raised bog, which is not apparent from other proxies. Comparison with a pollen record from the same sequence highlights the advantages of plant cuticle analysis in cases where pollen is hard to identify or poorly preserved. In particular, distinguishing between the pollen grains of the two main bog species, the restiads Empodisma robustum and Sporadanthus ferrugineus, relies on subtle gradational characteristics, whereas their cuticular patterns are very distinct. Furthermore, Cyperaceae pollen is poorly preserved at Moanatuatua Bog, being almost completely absent, whereas the Cyperaceae cuticles are present throughout the sequence. Therefore, we suggest that Cyperaceae pollen at this site is a less reliable indicator of local sedge communities than the cuticle record. The wide dispersal capabilities of these wind-dispersed pollen types also make them less suitable for determining local site vegetation and environmental change in comparison with cuticle remains. These results suggest that plant cuticle analysis may be a useful tool for the reconstruction of long-term vegetation changes from peat sequences, especially when used in concert with palynology. Sample preparation also proved to be fast with little equipment or chemicals needed.
32
Rachman, Rizki Satria, Winantris Winantris, Budi Muljana, and Nana Sulaksana. "Perubahan Iklim Danau Bandung Purba Berdasarkan Analisis Palinologi, Daerah Cihideung, Lembang, Jawa Barat." Jurnal Geologi dan Sumberdaya Mineral 21, no. 1 (February 13, 2020): 1. http://dx.doi.org/10.33332/jgsm.geologi.v21i1.404.
Full textAbstract:
IClimate is the prevailing weather condition of an area throughout the year. Climate affects the vegetation in a region. The research aimed to study the climate and humidity change during the Holocene in Bandung Paleo-Lake based on palynomorph analysis. The twenty-four samples were taken using hand drill in 172.5 - 52.5 cm depth, continued with preparation and determination. In this study, descriptive analysis and comparison between pollen, spores and their sediments to show the climate and humidity change in Bandung Paleo-Lake. The results show that the samples which were taken on peat deposits showing four times climate changes in five zones, which characterized by montane forest pollens, i.e. Podocarpaceae and Pinaceae, lowland forest pollen i.e. Commelinaceae, Moraceae, spores from the Family Polypodiaceae, Pteridaceae and Dennstaedtiaceae, and Gramineae at the study area.Keywords: Climate, palaeo, analysis, palinology, Bandung Lake.
33
Flakne, Robyn. "The Holocene vegetation history of Isle Royale National Park, Michigan, U.S.A." Canadian Journal of Forest Research 33, no. 6 (June 1, 2003): 1144–66. http://dx.doi.org/10.1139/x03-063.
Full textAbstract:
A vegetation history for Isle Royale National Park, Michigan, U.S.A., is reconstructed using pollen and spores extracted from two lake sediment cores. Lily Lake is on the southwestern end of the main island of Isle Royale surrounded by northern hardwoods forest. Lake Ojibway is on the northeastern end of the main island surrounded by boreal forest. Pollen and spore records were analyzed using pollen percentage diagrams, nonmetric multidimensional scaling ordination, and modern analog analysis. Squared chord distances for temporally paired subsamples from each site were calculated to determine palynological dissimilarities between the sites through time. These analyses revealed an overall vegetation history that is consistent with other regional reconstructions. High percentages of spruce pollen, indicating a cool climate, are present in the early Holocene, whereas high percentages of pine pollen, indicating a dry climate, occur in the mid-Holocene. The pollen records from the two sites diverge with increased precipitation during the late Holocene. At this time, birch-dominated forest is established near Lily Lake on till-derived soils. At Lake Ojibway, a mixed birch, pine, spruce, and fir forest is established on bedrock-derived soils. The divergence in forest composition is most pronounced within the last 500 years, and this divergence is tentatively attributed to the response of taxa on different substrates to increasing precipitation. Other possible explanations for the recent divergence include changing microclimates or disturbance regimes.
34
Toledo, Mauro B. de, and Mark B. Bush. "A Holocene pollen record of savanna establishment in coastal Amapá." Anais da Academia Brasileira de Ciências 80, no. 2 (June 2008): 341–51. http://dx.doi.org/10.1590/s0001-37652008000200013.
Full textAbstract:
The main goal of this study was to investigate how climate and human activities may have influenced ecotonal areas of disjoint savannas within Brazilian Amazonia. The fossil pollen and charcoal records of Lake Márcio (Amapá) were used to provide a Holocene palaeoecological history of this region. Detrended correspondence analysis (DCA) was used to enhance the patterns of sample distribution along the sediment core. A marked vegetation change from closed forests with swamp elements to open flooded savanna at c. 5000 yrs BP was evident from the pollen record. Charcoal analysis revealed a pattern of increased accumulation of particles coincident with the establishment of savannas, suggesting higher fire frequency and human impacts near the lake. A 550-year sedimentary hiatus suggests that the lake depended heavily on floodwaters from the Amazon River, and that it became suddenly isolated from it. When sedimentation restarted in the lake, the environment had changed. A combination of factors, such as reduced river flooding, palaeofires and human occupation may have had a tremendous impact on the environment. As there are no other major changes in vegetation, after 4700 yrs BP, it is plausible to assume that the modern mosaic vegetation formed at that time.
35
Li, Furong, Yan Zhao, Marie-José Gaillard, Huan Li, Jinghui Sun, and Qinghai Xu. "Modern pollen–climate relationships in north Xinjiang, northwestern China: Implications for pollen-based reconstruction of Holocene climate." Holocene 27, no. 7 (December 1, 2016): 951–66. http://dx.doi.org/10.1177/0959683616678464.
Full textAbstract:
Fossil pollen records are widely used to reconstruct past climate. Such reconstructions require that the relationships between pollen assemblages, vegetation, and climate are well understood. These can be studied in present circumstances given we assume that modern vegetation and climate are analogous to past ones. In this study, we analyze pollen–vegetation–climate relationships in the Jungar desert and Altay Mountains, northwestern China, a region for which careful reconstruction of past climate is needed to answer unsolved questions on past climate in an area located at the boundary between two different climate regimes (westerlies and monsoon). We use a dataset of 66 surface pollen samples from forest, meadow, steppe, and desert vegetation and six related climate variables, Tann, TJan, TJul, Pann, PJan, and PJul. Principal components analysis, redundancy analysis, Monte Carlo permutation tests, and variation partitioning are applied to quantify these relationships. We also assess pollen ratios as indices of aridity. We find that (1) Pann is the major climatic factor influencing pollen assemblages, followed by PJul, (2) the two variables are not correlated, and (3) the shared effect of (1) PJan and PJul, (2) PJan and Pann, (3) PJul and Tann, and (4) Tann, TJan, and TJul explains a larger portion of the variation in pollen data than the individual effect of each variable. Therefore, robust pollen–climate transfer functions can be developed for Pann and PJul, and several climate variables treated in combination. Artemisia/Chenopodiaceae is a strong index of aridity and Artemisia/Gramineae might be a useful index of Pann and PJul.
36
Fiłoc, Magdalena, Mirosława Kupryjanowicz, and Danuta Drzymulska. "Late Glacial and Holocene Vegetation Changes in the Wigry National Park, Ne Poland – New Pollen Data from Three Small Dystrophic Lakes." Studia Quaternaria 31, no. 1 (April 1, 2014): 5–16. http://dx.doi.org/10.2478/squa-2014-0001.
Full textAbstract:
Abstract The main phases of the Late Glacial and Holocene development of vegetation in the Wigry National Park were reconstructed based on the pollen analysis of sediments from three small dystrophic lakes (Lake Suchar Wielki, Lake Suchar II and Lake Ślepe). At the current stage of research, the age of the studied deposits was determined by AMS radiocarbon dating of few samples only. This meant that the chronology of the investigated sections had to be estimated also indirectly using their palynological correlation with the radiometrically well-dated section from Lake Wigry. The obtained pollen data confirmed the picture of the postglacial vegetation changes of the Wigry National Park, which was based on earlier studies of Lake Wigry. Furthermore, it documented the existence, mainly in the Preboreal and Atlantic chronozones, of temporary changes in vegetation, which might be a reaction to a short-lived cold fluctuations of climate.
37
Knight, Clarke A., Mark Baskaran, M. Jane Bunting, Marie Champagne, Matthew D. Potts, David Wahl, James Wanket, and John J. Battles. "Linking modern pollen accumulation rates to biomass: Quantitative vegetation reconstruction in the western Klamath Mountains, NW California, USA." Holocene 31, no. 5 (January 13, 2021): 814–29. http://dx.doi.org/10.1177/0959683620988038.
Full textAbstract:
Quantitative reconstructions of vegetation abundance from sediment-derived pollen systems provide unique insights into past ecological conditions. Recently, the use of pollen accumulation rates (PAR, grains cm−2 year−1) has shown promise as a bioproxy for plant abundance. However, successfully reconstructing region-specific vegetation dynamics using PAR requires that accurate assessments of pollen deposition processes be quantitatively linked to spatially-explicit measures of plant abundance. Our study addressed these methodological challenges. Modern PAR and vegetation data were obtained from seven lakes in the western Klamath Mountains, California. To determine how to best calibrate our PAR-biomass model, we first calculated the spatial area of vegetation where vegetation composition and patterning is recorded by changes in the pollen signal using two metrics. These metrics were an assemblage-level relevant source area of pollen (aRSAP) derived from extended R-value analysis ( sensu Sugita, 1993) and a taxon-specific relevant source area of pollen (tRSAP) derived from PAR regression ( sensu Jackson, 1990). To the best of our knowledge, aRSAP and tRSAP have not been directly compared. We found that the tRSAP estimated a smaller area for some taxa (e.g. a circular area with a 225 m radius for Pinus) than the aRSAP (a circular area with a 625 m radius). We fit linear models to relate PAR values from modern lake sediments with empirical, distance-weighted estimates of aboveground live biomass (AGLdw) for both the aRSAP and tRSAP distances. In both cases, we found that the PARs of major tree taxa – Pseudotsuga, Pinus, Notholithocarpus, and TCT (Taxodiaceae, Cupressaceae, and Taxaceae families) – were statistically significant and reasonably precise estimators of contemporary AGLdw. However, predictions weighted by the distance defined by aRSAP tended to be more precise. The relative root-mean squared error for the aRSAP biomass estimates was 9% compared to 12% for tRSAP. Our results demonstrate that calibrated PAR-biomass relationships provide a robust method to infer changes in past plant biomass.
38
Edwards, Kevin J., and Glen M. MacDonald. "Holocene palynology: II human influence and vegetation change." Progress in Physical Geography: Earth and Environment 15, no. 4 (December 1991): 364–91. http://dx.doi.org/10.1177/030913339101500402.
Full textAbstract:
Much palynological research has focused upon the role of humans in influencing the development of vegetation. This continues to be the case in Europe and anthropogenic studies in pollen analysis now extend to most parts of the world. An attempt is made to present some of the major research published between 1985 and mid-1991. The material selected represents a broad range of palynological applications and geographical areas. Methodological aspects include fine resolution, spatial and absolute pollen studies. Area studies concentrate upon Europe (with particular emphasis on the Corylus maximum, the Alnus rise and the Ulmus decline horizons in northwest European pollen diagrams), and to a lesser extent on North America, although available literature from other continents is also examined. It is concluded that a relatively small quantity of literature is devoted to methodology, but that it points the way to likely advances in elucidating human involvement in vegetation change. Fine resolution investigations may enable temporally precise changes in pollen spectra to be discerned and hence remove some of the inadequacies of coarse sampling procedures. Spatial studies reveal the complexity of palaeovegetational landscapes and the role of humans in their disturbance. Optimizing methods in the detection of cereal-type pollen grains provides challenges to both palynologists and archaeologists concerning the evidence for early agriculture. The potential of absolute data in examining human activity in forested areas is also shown. The palynological demonstration of hunter-gatherer and agricultural impacts beyond Europe is welcomed. The increasing use of microscopic charcoal data for investigating fire-vegetation relationships in cultural contexts is promising.
39
Koehler, Peter A., and R. Scott Anderson. "Thirty Thousand Years of Vegetation Changes in the Alabama Hills, Owens Valley, California." Quaternary Research 43, no. 2 (March 1995): 238–48. http://dx.doi.org/10.1006/qres.1995.1024.
Full textAbstract:
AbstractTwenty packrat (Neotoma) middens recovered from three sites (1265-1535 m) in the Alabama Hills, Inyo County, California, provide a ca. 31,450-yr record of vegetation change. Located ca. 7 km east of the Sierra Nevada, the middens document that Utah juniper (Juniperus osteosperma), Joshua tree (Yucca brevifolia), and bitterbush (Purshia tridentata) occupied the site between 31,450 and 19,070 yr B.P. Joshua tree and bitterbush departed by ca. 17,760 yr B.P., with cliffrose (Purshia mexicana) and joint-fir (Ephedra viridis) appearing. By 13,350 yr B.P., blackbush (Coleogyne ramosissima) and cholla (Opuntia echinocarpa) entered the record. Between 9540 and 7990 yr B.P., Utah juniper and other species now extralocal to the sites departed and modern components such as wolfberry (Lycium andersonii) and rubber rabbitbrush (Chrysothamnus teretifolius) appeared. The middle Holocene records little variation in plant macrofossil composition; however, pollen analysis reflects an increase in aquatic pollen types which might suggest more-open conditions. The transition to the modern vegetation associations at the sites occurred after ca. 2800 yr B.P. The record from the Alabama Hills correlates well with that of other regional vegetation data but documents conditions of increasing aridity earlier than many other packrat midden sites. A shift in understory vegetation between 19,070 and 17,760 yr B.P. may reflect a transition from glacial maximum to post-maximum conditions in the eastern Sierra Nevada.
40
Fréchette, Bianca, Anne de Vernal, and Pierre J. H. Richard. "Holocene and Last Interglacial cloudiness in eastern Baffin Island, Arctic CanadaThis article is one of a series of papers published in this Special Issue on the theme Polar Climate Stability Network.GEOTOP Publication 2008-0027." Canadian Journal of Earth Sciences 45, no. 11 (November 2008): 1221–34. http://dx.doi.org/10.1139/e08-053.
Full textAbstract:
This study presents Last Interglacial and Holocene vegetation and climate changes at Fog Lake (67°11′N, 63°15′W) on eastern Baffin Island, Arctic Canada. The vegetation cover is reported as vegetation structural types (or biomes). July air temperature and sunshine during the growing season (June–July–August–September) were reconstructed from pollen assemblages using the modern analogue technique. The vegetation of the Last Interglacial period evolved from a prostrate dwarf-shrub tundra to a low- and high-shrub tundra vegetation. The succession of four Arctic biomes was distinguished from the Last Interglacial sediments, whereas only one Arctic biome was recorded in the Holocene sediments. From ca. 8300 cal. years BP to present, hemiprostrate dwarf-shrub tundra occupied the soils around Fog Lake. During the Last Interglacial, growing season sunshine was higher than during the Holocene and July air temperature was 4 to 5 °C warmer than present. A principal component analysis helped in assessing relationship between floristic gradients and climate. The major vegetation changes through the Last Interglacial and Holocene were driven by July air temperature variations, whereas the minor, or subtle, vegetation changes seem rather correlated to September sunshine. This study demonstrates that growing season sunshine conditions can be reconstructed from Arctic pollen assemblages, thus providing information on feedbacks associated with cloud cover and summer temperatures, and therefore growing season length.
41
Bakker, J., E. Paulissen, D. Kaniewski, J. Poblome, V. De Laet, G. Verstraeten, and M. Waelkens. "Climate, people, fire and vegetation: new insights into vegetation dynamics in the Eastern Mediterranean since the 1st century AD." Climate of the Past 9, no. 1 (January 16, 2013): 57–87. http://dx.doi.org/10.5194/cp-9-57-2013.
Full textAbstract:
Abstract. Anatolia forms a bridge between Europe, Africa and Asia and is influenced by all three continents in terms of climate, vegetation and human civilisation. Unfortunately, well-dated palynological records focussing on the period from the end of the classical Roman period until subrecent times are rare for Anatolia and completely absent for southwest Turkey, resulting in a lacuna in knowledge concerning the interactions of climatic change, human impact, and environmental change in this important region. Two well-dated palaeoecological records from the Western Taurus Mountains, Turkey, provide a first relatively detailed record of vegetation dynamics from late Roman times until the present in SW Turkey. Combining pollen, non-pollen palynomorphs, charcoal, sedimentological, archaeological data, and newly developed multivariate numerical analyses allows for the disentangling of climatic and anthropogenic influences on vegetation change. Results show changes in both the regional pollen signal as well as local soil sediment characteristics match shifts in regional climatic conditions. Both climatic as well as anthropogenic change had a strong influence on vegetation dynamics and land use. A moist environmental trend during the late-3rd century caused an increase in marshes and wetlands in the moister valley floors, limiting possibilities for intensive crop cultivation at such locations. A mid-7th century shift to pastoralism coincided with a climatic deterioration as well as the start of Arab incursions into the region, the former driving the way in which the vegetation developed afterwards. Resurgence in agriculture was observed in the study during the mid-10th century AD, coinciding with the Medieval Climate Anomaly. An abrupt mid-12th century decrease in agriculture is linked to socio-political change, rather than the onset of the Little Ice Age. Similarly, gradual deforestation occurring from the 16th century onwards has been linked to changes in land use during Ottoman times. The pollen data reveal that a fast rise in Pinus pollen after the end of the Beyşehir Occupation Phase need not always occur. The notion of high Pinus pollen percentages indicating an open landscape incapable of countering the influx of pine pollen is also deemed unrealistic. While multiple fires occurred in the region through time, extended fire periods, as had occurred during the Bronze Age and Beyşehir Occupation Phase, did not occur, and no signs of local fire activity were observed. Fires were never a major influence on vegetation dynamics. While no complete overview of post-BO Phase fire events can be presented, the available data indicates that fires in the vicinity of Gravgaz may have been linked to anthropogenic activity in the wider surroundings of the marsh. Fires in the vicinity of Bereket appeared to be linked to increased abundance of pine forests. There was no link with specifically wet or dry environmental conditions at either site. While this study reveals much new information concerning the impact of climate change and human occupation on the environment, more studies from SW Turkey are required in order to properly quantify the range of the observed phenomena and the magnitude of their impacts.
42
Noguchi, Makoto, Toshiyuki Fujiki, Mitsuru Okuno, Lyn Gualtieri, Virginia Hatfield, Brenn Sarata, Masayuki Torii, Keiji Wada, Toshio Nakamura, and Dixie West. "Vegetation Changes Around Haven Lake, Adak Island, Central Aleutians, Alaska, Determined from Pollen Analysis - ERRATUM." Radiocarbon 61, no. 2 (February 1, 2019): 659. http://dx.doi.org/10.1017/rdc.2018.151.
Full text
43
Bakker, J., E. Paulissen, D. Kaniewski, J. Poblome, V. De Laet, G. Verstraeten, and M. Waelkens. "Climate, people, fire and vegetation: new insights into vegetation dynamics in the Eastern Mediterranean since the 1st century AD." Climate of the Past Discussions 8, no. 4 (August 13, 2012): 3379–444. http://dx.doi.org/10.5194/cpd-8-3379-2012.
Full textAbstract:
Abstract. Anatolia forms a bridge between Europe, Africa and Asia and is influenced by all three continents in terms of climate, vegetation and human civilisation. Unfortunately, well dated palynological records focussing on the period from the end of the classical Roman period until subrecent times are rare for Anatolia and completely absent for southwest Turkey, resulting in a lacuna in knowledge concerning the interactions of climatic change, human impact, and environmental change in this important region. Two well dated palaeoecological records from the Western Taurus Mountains, Turkey, provide a first relatively detailed record of vegetation dynamics from late Roman times until the present in SW Turkey. Combining pollen, non-pollen palynomorphs, charcoal, sedimentological, archaeological data, and newly developed multivariate numerical analyses, allows for the disentangling of climatic and anthropogenic influences on vegetation change. Results show both the regional pollen signal as well as local soil sediment characteristics respond accurately to shifts in regional climatic conditions. Both climatic as well as anthropogenic change had a strong influence on vegetation dynamics and land use. A moist environmental trend during the late 3rd century caused an increase in marshes and wetlands in the moister valley floors, limiting possibilities for intensive crop cultivation at such locations. A mid 7th century shift to pastoralism coincided with a climatic deterioration as well as the start of Arab incursions into the region, the former driving the way in which the vegetation developed afterwards. Resurgence in agriculture was observed in the study during the mid 10th century AD, coinciding with the Medieval Climate Anomaly. An abrupt mid 12th century decrease in agriculture is linked to socio-political change, rather than the onset of the Little Ice Age. Similarly, gradual deforestation occurring from the 16th century onwards has been linked to changes in lands use during Ottoman times. The pollen data reveals that the old model of a fast rise in Pinus pollen after the end of the Beyşehir Occupation Phase is not necessarily accurate. The notion of high Pinus pollen percentages indicating an open landscape incapable of countering the influx of pine pollen is also deemed unrealistic. While multiple fires occurred in the region through time, they were never a major influence on vegetation dynamics and were mostly linked to increased abundance of pine forests, rather than the presence of human impact or of specifically wet or dry environmental conditions. While this study reveals much new information concerning the impact of climate change and human occupation on the environment, more studies from SW turkey are required in order to properly quantify the range of the observed phenomena and the magnitude of their impacts.
44
Combourieu Nebout, N., O. Peyron, I. Dormoy, S. Desprat, C. Beaudouin, U. Kotthoff, and F. Marret. "Rapid climatic variability in the west Mediterranean during the last 25 000 years from high resolution pollen data." Climate of the Past 5, no. 3 (September 11, 2009): 503–21. http://dx.doi.org/10.5194/cp-5-503-2009.
Full textAbstract:
Abstract. High-temporal resolution pollen record from the Alboran Sea ODP Site 976, pollen-based quantitative climate reconstruction and biomisation show that changes of Mediterranean vegetation have been clearly modulated by short and long term variability during the last 25 000 years. The reliability of the quantitative climate reconstruction from marine pollen spectra has been tested using 22 marine core-top samples from the Mediterranean. The ODP Site 976 pollen record and climatic reconstruction confirm that Mediterranean environments have a rapid response to the climatic fluctuations during the last Termination. The western Mediterranean vegetation response appears nearly synchronous with North Atlantic variability during the last deglaciation as well as during the Holocene. High-resolution analyses of the ODP Site 976 pollen record show a cooling trend during the Bölling/Allerød period. In addition, this period is marked by two warm episodes bracketing a cooling event that represent the Bölling-Older Dryas-Allerød succession. During the Holocene, recurrent declines of the forest cover over the Alboran Sea borderlands indicate climate events that correlate well with several events of increased Mediterranean dryness observed on the continent and with Mediterranean Sea cooling episodes detected by alkenone-based sea surface temperature reconstructions. These events clearly reflect the response of the Mediterranean vegetation to the North Atlantic Holocene cold events.
45
Macedo, Renato B., Paulo A. Souza, Soraia G. Bauermann, and Sérgio A. L. Bordignon. "Palynological analysis of a late Holocene core from Santo Antônio da Patrulha, Rio Grande do Sul, Southern Brazil." Anais da Academia Brasileira de Ciências 82, no. 3 (September 2010): 731–45. http://dx.doi.org/10.1590/s0001-37652010000300020.
Full textAbstract:
A sedimentar core collected at Santo Antônio da Patrulha, Rio Grande do Sul State, southmost Brazil, was submitted to pollen analysis to provide the vegetational history of this region, and the paleoecological and paleoclimatic changes. A total of 98 taxa of palynomorphs was identified from 35 subsamples. Three radiocarbonic datings were obtained along a section of 115 cm depth, including the basal age of 4730 ± 50 yr BP. Pollen diagrams and cluster analysis were performed based on palynomorphs frequencies, demonstrating five distinct phases (SAP-I to SAP-V), which reflected different paleoecological conditions. The predominance of plants associated with grasslands in the phase SAP-I suggests warm and dry climate conditions. A gradual increasing of humidity conditions was observed mainly from the beginning of the phase SAP-III, when the vegetation set a mosaic of grasslands and Atlantic rainforest. Furthermore, the presence of some forest taxa ( Acacia-type, Daphnopsis racemosa, Erythrina-type and Parapiptadenia rigida-type), from the phase SAP-IV, is interpreted as an influence of the seasonal semideciduous forest in the study region. From the phase SAP-V (ca. 4000 yrs BP), the vegetation became similar to the modern one (extant Atlantic rainforest Biome), especially after 2000 yrs BP (calibrated age).
46
Lozano-García, Socorro, Blanca Figueroa-Rangel, Susana Sosa-Nájera, Margarita Caballero, Anders J. Noren, Sarah E. Metcalfe, Oswaldo Tellez-Valdés, and Beatriz Ortega-Guerrero. "Climatic and anthropogenic influences on vegetation changes during the last 5000 years in a seasonal dry tropical forest at the northern limits of the Neotropics." Holocene 31, no. 5 (January 17, 2021): 802–13. http://dx.doi.org/10.1177/0959683620988054.
Full textAbstract:
Seasonal dry tropical forest (STDF) is a widespread vegetation type in western Mexico. Generally, this type of forest develops in semihumid habitats where lacustrine basins are scarce, preventing documentation of the vegetation history and forest dynamics using a paleoecological approach. Here, we present a palynological record from the Santa Maria del Oro crater lake, located within the distribution area of the STDF and the adjacent dry oak forest which gives insight into the changes in diversity and human impact at this tropical site. Pollen data, in combination with geochemical analysis and microcharcoal data from a lacustrine sequence, are used to discuss vegetation change and diversity in the plant assemblages related to drought or anthropogenic activity over the last 5000 years. Our results show three distinct periods of drought in the basin, from 4200 to 3850, 3100 to 2300, 1570 to 1100 and 300 cal year BP, with changes in vegetation composition mainly related to a decrease in taxa diversity during these periods. Based on the presence of maize pollen, two periods of human activity (3790–2160 and 280 cal year BP to present) were detected with an increase in herbaceous pollen used as a surrogate for deforestation. These two disturbance periods, pre-Columbian and postcolonial, occurred during wet conditions in the basin. Our results highlight the correlation between El Niño events, drought and fire with changes in the composition and diversity of STDF.
47
Hruševar, Dario, Nikolina Ilijanić, Božena Mitić, Martina Weber, Katarina Husnjak Malovec, Anita Vucić, Tatjana Puljak, et al. "Dvije tisuće godina okolišnih promjena na području središnje Hrvatske – vegetacija, požari i hidrologija utjecani klimatskim prilikama i ljudskim pritiskom." Prilozi Instituta za arheologiju u Zagrebu 37 (2020): 117–64. http://dx.doi.org/10.33254/piaz.37.5.
Full textAbstract:
This paper presents the paleoenvironmental reconstruction of a mire sequence near the village Blatuša, with a focus on changes in vegetation composition, hydrological regime and fire history of the Banovina/Kordun area during the last two millennia. For this purpose, pollen, non-pollen and charcoal analysis were done. By the application of CONISS statistical analysis three different pollen assemblage (sub)zones could have been distinguished: a dominance of alder-beech/oaks from the 2nd to the middle of the 7th century, followed by a prevalence of grasses-beech/oaks till the end of the 13th century. Finally, an assemblage of grasses-hornbeam/oaks populated the area from the 14th to the beginning of the 20th century. The high abundance of peat mosses (Sphagnum) from the 11th to the end of the 14th century must indicate increased precipitation and higher frequencies of rainfall during the Medieval Climate Anomaly. Transition from an ombrotrophic to minerotrophic phase of mire evolution during the Little Ice Age is caused by changing in moisture level, with somewhat wetter period prevailing till the middle of the 17th century followed by drier conditions till the beginning of the 20th century. Although cereal pollen grains first appear from the layers dated to the late 14th century and the proportion of secondary anthropogenic indicators were low during the entire Middle Ages, a large number of charcoal particles suggests stronger anthropogenic activity than indicated by observed changes in vegetation composition. Still, a sharp rise of non-arboreal pollen during the Migration period most likely reflect a general natural succession process on mire surface than persuable proof of Avaric-Slavic impact on vegetation. Direct anthropogenic pressure indicated by weeds and cereal pollen can be tracked from the Late Middle Ages onwards.
48
Horn, Sally P. "Postglacial Vegetation and Fire History in the Chirripó Páramo of Costa Rica." Quaternary Research 40, no. 1 (July 1993): 107–16. http://dx.doi.org/10.1006/qres.1993.1061.
Full textAbstract:
AbstractPollen and charcoal analysis of a 5.6-m sediment core from Lago de las Morrenas (9°29′N, 83°29′W; 3480 m) provides evidence of postglacial vegetation and fire history in the highlands of the Cordillera de Talamanca, Costa Rica. The site is presently surrounded by treeless páramo vegetation and apparently has been so since deglaciation about 10,000 yr B.P. Pollen spectra suggest no pronounced changes in vegetation since ice retreat. Fires set by people or lightning have burned the páramo repeatedly, with fire activity probably highest during the late Holocene, but these fires have not carved páramo from forest. Pollen percentages for Gramineae and other páramo taxa decline upward, whereas percentages for certain subalpine, lower montane, and lowland forest taxa increase slightly; these changes may reflect the impact of prehistoric human activity or slight upslope migrations of forest taxa owing to climatic warming. There is no clear evidence of higher timberlines during the mid-Holocene.
49
Schüler, L., A. Hemp, and H. Behling. "Pollen-based temperature and precipitation inferences for the montane forest of Mt. Kilimanjaro during the last Glacial and the Holocene." Climate of the Past Discussions 10, no. 1 (January 15, 2014): 195–234. http://dx.doi.org/10.5194/cpd-10-195-2014.
Full textAbstract:
Abstract. The relationship between modern pollen-rain taxa and measured climate variables was explored along the elevational gradient of the southern slope of Mt. Kilimanjaro, Tanzania. Pollen assemblages in 28 pollen traps positioned on 14 montane forest vegetation plots were identified and their relationship with climate variables was examined using multivariate statistical methods. Canonical correspondence analysis revealed that the mean annual temperature, mean annual precipitation and minimum temperature each account for significant fractions of the variation in pollen taxa. A training set of 107 modern pollen taxa was used to derive temperature and precipitation transfer functions based on pollen subsets using weighted-averaging-partial-least-squares (WA-PLS) techniques. The transfer functions were then applied to a fossil pollen record from the montane forest of Mt. Kilimanjaro and the climate parameter estimates for the Late Glacial and the Holocene on Mt. Kilimanjaro were inferred. Our results present the first quantitatively reconstructed temperature and precipitation estimates for Mt Kilimanjaro and give highly interesting insights into the past 45 000 yr of climate dynamics in tropical East Africa. The climate reconstructions are consistent with the interpretation of pollen data in terms of vegetation and climate history of afro-montane forest in East Africa. Minimum temperatures above the frostline as well as increased precipitation turn out to be crucial for the development and expansion of montane forest during the Holocene. In contrast, consistently low minimum temperatures as well as about 25% drier climate conditions prevailed during the pre LGM, which kept the montane vegetation composition in a stable state. In prospective studies, the quantitative climate reconstruction will be improved by additional modern pollen rain data, especially from lower elevations with submontane dry forests and colline savanna vegetation in order to extend the reference climate gradient.
50
Combourieu-Nebout, N., O. Peyron, V. Bout-Roumazeilles, S. Goring, I. Dormoy, S. Joannin, L. Sadori, G. Siani, and M. Magny. "Holocene vegetation and climate changes in central Mediterranean inferred from a high-resolution marine pollen record (Adriatic Sea)." Climate of the Past Discussions 9, no. 2 (April 5, 2013): 1969–2014. http://dx.doi.org/10.5194/cpd-9-1969-2013.
Full textAbstract:
Abstract. To understand the effects of future climate change on the ecology of the central Mediterranean we can look to the impacts of long-term, millennial to centennial-scale climatic variability on vegetation in the basin. Pollen data from the Adriatic Marine core MD 90-917 allows us to reconstruct vegetation and regional climate changes over the south central Mediterranean during the Holocene. Clay mineral ratios from the same core reflect the relative contributions of riverine (illite and smectite) and eolian (kaolinite) contributions to the site, and thus act as an additional proxy with which to test precipitation changes in the Holocene. Vegetation reconstruction shows vegetation responses to the late-Glacial Preboreal oscillation, most likely driven by changes in seasonal precipitation. Pollen-inferred temperature declines during the early-mid Holocene, but increases during the mid-late Holocene, similar to southern-western Mediterranean climatic patterns during the Holocene. Several short climatic events appear in the record, indicating the sensitivity of vegetation in the region to millennial-scale variability. Reconstructed summer precipitation shows a regional maximum between 8000 and 7000 cal yr BP similar to the general pattern across southern Europe. Two important shifts in vegetation occur at 7700 and between 7500 and 7000 yr. These vegetation shifts are linked to changes in seasonal precipitation and are correlated to increased river inputs respectively from the north (7700 event) and from the central Adriatic borderlands (7500–7000 event). These results reinforce the strengths of multi-proxy analysis and provide a deeper understanding of the role of precipitation and particularly the seasonality of precipitation in mediating vegetation change in the central Mediterranean during the Holocene.