Articoli di riviste: "Flooded savannas and grasslands"

1

Medina, Ernesto, e Norma Motta. "Metabolism and distribution of grasses in tropical flooded savannas in Venezuela". Journal of Tropical Ecology 6, n. 1 (febbraio 1990): 77–89. http://dx.doi.org/10.1017/s0266467400004053.

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ABSTRACTFlooded savannas in south-west Venezuela consist of seasonal, marshy and flooded grassland communities, the distribution of which depends on soil level. Seasonal grasslands are dominated by tuft-forming, rhizomatous C4-grasses (exemplified by Paspalum chaffanjonii in this study), while flooded grasslands are dominated by stoloniferous grasses which develop rooted, floating culms during the rainy season (Leersia hexandra and Hymenachne amplexi-caulis). The interface between these two communities is a marshy grassland dominated by stoloniferous grass species which tolerate flooding to a depth of 10 to 25 cm (Panicum laxum and Leersia hexandra). All perennial grass species in flooded grasslands behave as typical C3 plants, while marshy grasslands are dominated by Panicum laxum, a species with reduced photo-respiration, low RuBP/PEP-carboxylase ratios, and low absolute RuBP-carboxylase activity compared to C3 grasses. It also has lower photosynthetic rates than the other grass species. Hymenachne amplexicaulis appears to be the least drought tolerant from the species selected, in accordance with its distribution in the wettest side of the flooding gradient studied. The other species showed marked reduction in relative water content and pronounced increase in leaf proline content in drought experiments lasting 6 to 30 days. Alcohol dehydrogenase increased markedly in response to anaerobiosis in the root environment in the tuft forming grasses, while the stoloniferous species with ascending culms were least affected by this treatment, probably as a result of better aeration inside the culms and also to the production of adventitious roots in upper nodes. Nitrate reductase activity increased as a result of anaerobiosis in the roots but not in the leaves, of all species except Leersia hexandra. No difference among the species was found in malate accumulation, or the activity of malic enzyme.

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Crutzen, P. J., E. Sanhueza e C. A. M. Brenninkmeijer. "Methane production from mixed tropical savanna and forest vegetation in Venezuela". Atmospheric Chemistry and Physics Discussions 6, n. 2 (13 aprile 2006): 3093–97. http://dx.doi.org/10.5194/acpd-6-3093-2006.

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Abstract. Measurements of methane concentrations in the boundary layer in the northern part of the Guayana shield, Venezuela, during the wet season (October 1988), showed the presence of substantial methane surface emissions. The measuring site is within the savanna climate region, but is affected by emissions from savanna and forest vegetation. From day versus night concentration measurements, with higher concentrations during night, a methane source strength near the site of 3–7×1011 molecules/cm2/s can be estimated, which includes emissions from small tracts of flooded soils, termites and especially tropical vegetation. Extrapolated to the entire savanna, this may imply a methane source of ~30–60 Tg yr−1 similar to the one calculated for tropical vegetation on the basis of recently published in vitro plant emission experiments by Keppler et al. (2006), which indicate emissions of ~30 Tg yr−1 for tropical savannas and grasslands and ~78 Tg yr−1 for tropical forests.

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Cunha, Hélida Ferreira da, Tiago Fernades Carrijo, Alfredo Raul Abot e Carolina Da Silva Barbosa. "Termite diversity in the Abobral region of the Pantanal wetland complex, Brazil". Check List 11, n. 1 (15 gennaio 2015): 1545. http://dx.doi.org/10.15560/11.1.1545.

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This is the first termite survey using standard protocols in the Abobral region of the Pantanal complex of South America. Abobral, which is primarily composed of four physiognomies: 1) campo, annually flooded grassland; 2) capão, which are islands of semi-deciduous forests; 3) carandazal, annually flooded vegetation composed of a native palm; and 4) paratudal, annually flooded savanna vegetation. Ten species of termites were sampled in the capões, three in the grasslands, two in the paratudal and no species in the carandazal. The diversity of termites in the Abobral Pantanal is concentrated in the capões, which stay above water level during the flood season. In the others physiognomies of the Abobral, the termite fauna is poor. The species composition of termites of the Abobral Pantanal seems to be more related to the Cerrado and Chaco faunas than to the Amazonia and Atlantic Forest faunas.

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Good, Megan K., Jodi N. Price, Peter Clarke e Nick Reid. "Densely regenerating coolibah (Eucalyptus coolabah) woodlands are more species-rich than surrounding derived grasslands in floodplains of eastern Australia". Australian Journal of Botany 59, n. 5 (2011): 468. http://dx.doi.org/10.1071/bt11079.

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Woody plant encroachment – the conversion of grasslands to tree- or shrub-dominated ecosystems – occurs in rangelands and savannas worldwide. In eastern Australia, coolibah (Eucalyptus coolabah subsp. coolabah Blakely & Jacobs) regenerated densely following floods in the mid 1970s, converting derived grasslands to dense woodlands. We compared soil and groundstorey vegetation attributes of dense coolibah regeneration to adjacent derived grasslands at three grazed sites in the northern riverine plains of New South Wales. Groundstorey species richness and diversity were significantly higher and groundstorey biomass was significantly lower in dense regeneration plots than in derived grassland plots. Soils from dense regeneration had higher C : N and pH, and lower Na than soils from derived grasslands. Although groundstorey species composition differed significantly between derived grasslands and dense regeneration within sites, variation among sites was more pronounced, indicating that site factors influence community composition more than dense regeneration of coolibah. Our findings suggest that, in contrast to other studies of woody plant encroachment, dense regeneration of coolibah does not result in a decrease in plant biodiversity or soil condition.

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Barbosa, Reinaldo Imbrozio, Jhonson Reginaldo Silva dos Santos, Mariana Souza da Cunha, Tania Pena Pimentel e Philip Martin Fearnside. "Root biomass, root:shoot ratio and belowground carbon stocks in the open savannahs of Roraima, Brazilian Amazonia". Australian Journal of Botany 60, n. 5 (2012): 405. http://dx.doi.org/10.1071/bt11312.

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Biomass of roots, the root : shoot ratio (ratio of below- to aboveground biomass) and carbon stocks belowground (to 100-cm depth) were estimated in different open savannah environments in the extreme north of the Brazilian Amazon. Sampling was conducted in permanent plots established in two open savannah areas in the state of Roraima. We identified four phytopedounits in the 27 plots sampled in two areas: four in dry grasslands on Argisol/Ultisol soils (DG-Arg), eight in dry grasslands on Latosol/Oxisol soils (DG-Lts), five in a mosaic of grasslands with savannah-parkland on Latosol/Oxisol soils (GP-Lts) and 10 in seasonally flooded (wet) grasslands on Hydromorphic/Entisol soils (WG-Hyd). Fine roots (<2 mm diameter) dominated the 0–100-cm vertical profile in the four phytopedounits (>92.5%). Biomass of the roots in WG-Hyd (29.52 ± 7.15 Mg ha–1) was significantly higher as compared with the other phytopedounits studied, although the carbon stocks did not differ among the phytopedounits (6.20–7.21 MgC ha–1). The largest concentration of roots was found in the upper three 10-cm sections of the soil profile, ranging from 56.3 to 82.9% in the four environments. The root : shoot ratio based only on living biomass of roots with diameter ≥2 mm (standard Intergovernmental Panel on Climate Change methodology) ranged from 0 for seasonally flooded grasslands to 0.07–0.20 for unflooded grasslands on clay soils. The results indicate that the root : shoot ratio (expansion factor) for belowground biomass in open savannah ecosystems in the northern Amazon are low and differ from the default values used in Brazil’s reference report to the Climate Convention.

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Moreira, Leonardo F. B., Tainá F. Dorado-Rodrigues, Vanda L. Ferreira e Christine Strüssmann. "An inter-dependence of flood and drought: disentangling amphibian beta diversity in seasonal floodplains". Marine and Freshwater Research 68, n. 11 (2017): 2115. http://dx.doi.org/10.1071/mf16391.

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Species composition in floodplains is often affected by different structuring factors. Although floods play a key ecological role, habitat selection in the dry periods may blur patterns of biodiversity distribution. Here, we employed a partitioning framework to investigate the contribution of turnover and nestedness to β-diversity patterns in non-arboreal amphibians from southern Pantanal ecoregion. We investigated whether components of β-diversity change by spatial and environmental factors. We sampled grasslands and dense arboreal savannas distributed in 12 sampling sites across rainy and dry seasons, and analysed species dissimilarities using quantitative data. In the savannas, both turnover and nestedness contributed similarly to β diversity. However, we found that β diversity is driven essentially by turnover, in the grasslands. In the rainy season, balanced variation in abundance was more related to altitude and factors that induce spatial patterns, whereas dissimilarities were not related to any explanatory variable during dry season. In the Pantanal ecoregion, amphibian assemblages are influenced by a variety of seasonal constraints on terrestrial movements and biotic interactions. Our findings highlighted the role of guild-specific patterns and indicated that mass effects are important mechanisms creating amphibian community structure in the Pantanal.

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Barbosa da Silva, Fernando Henrique, Julia Arieira, Pia Parolin, Cátia Nunes da Cunha e Wolfgang Johannes Junk. "Shrub encroachment influences herbaceous communities in flooded grasslands of a neotropical savanna wetland". Applied Vegetation Science 19, n. 3 (7 febbraio 2016): 391–400. http://dx.doi.org/10.1111/avsc.12230.

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Daskin, Joshua H., Filipe Aires e A. Carla Staver. "Determinants of tree cover in tropical floodplains". Proceedings of the Royal Society B: Biological Sciences 286, n. 1914 (30 ottobre 2019): 20191755. http://dx.doi.org/10.1098/rspb.2019.1755.

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Tree cover differentiates forests from savannas and grasslands. In tropical floodplains, factors differentiating these systems are poorly known, even though floodplains cover 10% of the tropical landmass. Seasonal inundation potentially presents trees with both challenges (soil anoxia) and benefits (moisture and nutrient deposition), the relative importance of which may depend on ecological context, e.g. if floods alleviate water stress more in more arid ecosystems. Here, we use remotely sensed data across 13 large tropical and sub-tropical floodplain ecosystems on five continents to show that climatic water balance (i.e. precipitation—potential evapotranspiration) strongly increases floodplain tree cover in interaction with flooding, fire and topography. As predicted, flooding increases tree cover in more arid floodplains, but decreases tree cover in climatically wetter ones. As in uplands, frequent fire reduced tree cover, particularly in wet regions, but—in contrast with uplands—lower elevation and sandier soils decreased tree cover. Our results suggest that predicting the impacts of changing climate, land use and hydrology on floodplain ecosystems depends on considering climate-disturbance interactions. While outright wetland conversion proceeds globally, additional anthropogenic activities, including alteration of fire frequencies and dam construction, will also shift floodplain tree cover, especially in wet climates.

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Haase, R. "Plant communities of a savanna in northern Bolivia I. Seasonally flooded grassland and gallery forest". Phytocoenologia 18, n. 1 (7 dicembre 1989): 55–81. http://dx.doi.org/10.1127/phyto/18/1989/55.

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DE PINHO, JOÃO BATISTA, e MIGUEL ÂNGELO MARINI. "Using birds to set conservation priorities for Pantanal wetland forests, Brazil". Bird Conservation International 22, n. 2 (26 settembre 2011): 155–69. http://dx.doi.org/10.1017/s0959270911000207.

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SummaryThe Pantanal of Brazil, one of the largest wetlands in the world, is suffering severe threats, such as forest and grassland clearance on the surrounding plateau, conversion of forests and savannas for cattle ranching and effects of large development projects. We used richness, abundance and composition of bird species in four forest types to propose conservation priorities for the northern Pantanal. Birds from 11 sites (a total of 41 points) were sampled through point counts and mist-netting. In total 215 species were recorded in the forests. Two evergreen forest types (cambarazal and landi) had higher estimates of bird richness and abundance than two dry forest types (carvoeiro and cordilheira). The evergreen forests also had more species exclusive to them and were more similar to each other than the dry forests. Selection of forests to be conserved in the northern Pantanal should give priority to evergreen forests and secondarily to dry forests. Cambarazal should be the first forests to be conserved. If the Pantanal inundation cycle is altered by the construction of hydroelectric dams or the Paraguay-Paraná waterway, cambarazal and landi may no longer become flooded, decreasing local species richness. Before our recommendations are considered for conservation and management decisions, more studies on other groups of organisms should also be taken into consideration, and similar studies should be conducted in other regions of the Pantanal. Conservation of Pantanal forest birds depends on a deeper understanding of their use of several habitats, stronger protection of the forests with higher diversity, and public policies that guarantee the long term maintenance of natural flooding cycles.

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Burgess, Neil D., Colby Loucks, Sue Stolton e Nigel Dudley. "The potential of forest reserves for augmenting the protected area network in Africa". Oryx 41, n. 2 (aprile 2007): 151–59. http://dx.doi.org/10.1017/s0030605307001895.

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AbstractThe protected area network of Africa has grown from nothing to over 2 million km2 in the past 110 years. This network covers parts of all biomes and priority areas for biodiversity conservation but protected area gaps remain, as identified at the 5th World Parks Congress in 2003. Forest reserves, managed by Forest Departments, are typically excluded from global protected area lists, but in Africa they are found in 23 countries and cover at least 549,788 km2, adding 25% to the conservation estate. Forest reserves protect 5.3% (2,027 km2) of the dry forest habitats, 5% (165,285 km2) of lowland and montane moist forests, 2.6% (364,354 km2) of savannah woodlands, 1.8% (10,561 km2) of flooded grasslands, and 1.65% (1,177 km2) of mangroves. Forest reserves also protect parts of three conservation schemes: 6.5% (61,630 km2) of BirdLife's Endemic Bird Areas, 3.4% (147,718 km2) of Conservation International's Hotpots and 3.4% (346,864 km2) of WWF's Global 200 Ecoregions. Several of the global protected area gaps identified in Africa are also covered by forest reserves, in the Eastern Arc Mountains, Eastern African coastal forests, Kenyan Highlands, Cameroon-Nigerian Mountains, West African Forests and mountain areas of Malawi, Zimbabwe, Mozambique and Zambia. Some African forest reserves have a legally defined role in biodiversity conservation and are strictly protected; they thus fit criteria for protected areas. Working with forest departments in individual countries may help develop a more comprehensive protected area network without creating additional new reserves.

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Bertioli, David J., Guillermo Seijo, Fabio O. Freitas, José F. M. Valls, Soraya C. M. Leal-Bertioli e Marcio C. Moretzsohn. "An overview of peanut and its wild relatives". Plant Genetic Resources 9, n. 01 (14 gennaio 2011): 134–49. http://dx.doi.org/10.1017/s1479262110000444.

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The legumeArachis hypogaea, commonly known as peanut or groundnut, is a very important food crop throughout the tropics and sub-tropics. The genus is endemic to South America being mostly associated with the savannah-like Cerrado. All species in the genus are unusual among legumes in that they produce their fruit below the ground. This profoundly influences their biology and natural distributions. The species occur in diverse habitats including grasslands, open patches of forest and even in temporarily flooded areas. Based on a number of criteria, including morphology and sexual compatibilities, the 80 described species are arranged in nine infrageneric taxonomic sections. While most wild species are diploid, cultivated peanut is a tetraploid. It is of recent origin and has an AABB-type genome. The most probable ancestral species areArachis duranensisandArachis ipaënsis, which contributed the A and B genome components, respectively. Although cultivated peanut is tetraploid, genetically it behaves as a diploid, the A and B chromosomes only rarely pairing during meiosis. Although morphologically variable, cultivated peanut has a very narrow genetic base. For some traits, such as disease and pest resistance, this has been a fundamental limitation to crop improvement using only cultivated germplasm. Transfer of some wild resistance genes to cultivated peanut has been achieved, for instance, the gene for resistance to root-knot nematode. However, a wider use of wild species in breeding has been hampered by ploidy and sexual incompatibility barriers, by linkage drag, and historically, by a lack of the tools needed to conveniently confirm hybrid identities and track introgressed chromosomal segments. In recent years, improved knowledge of species relationships has been gained by more detailed cytogenetic studies and molecular phylogenies. This knowledge, together with new tools for genetic and genomic analysis, will help in the more efficient use of peanut's genetic resources in crop improvement.

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Ramos, Desirée M., Ana B. S. Liaffa, Pedro Diniz, Cássia B. R. Munhoz, Mark K. J. Ooi, Fabian Borghetti e José F. M. Valls. "Seed tolerance to heating is better predicted by seed dormancy than by habitat type in Neotropical savanna grasses". International Journal of Wildland Fire 25, n. 12 (2016): 1273. http://dx.doi.org/10.1071/wf16085.

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Open savannas and wet grasslands are present under the same seasonal macro-climate in central Brazil. However, in open savannas, temperatures during fires are higher than in wet grasslands. Grasses dominate both ecosystems and exhibit large variation in seed dormancy. We hypothesise that seeds of grass species from open savannas are more tolerant to heating than those of wet grasslands. Also, assuming that dormant seeds remain longer in the soil than non-dormant seeds – thus being more likely to burn – we expect that dormant seeds are more tolerant to heating than non-dormant seeds. We tested the effects of heating at 80 and 110°C for 2.5 and 5.0 min on the survival of seeds of 14 species, seven from each community, containing dormant and non-dormant species. Seeds of most species survived at 80°C, but seeds from open savannas maintained greater survival for 5 min than seeds from wet grasslands. Seeds of most species died at 110°C, but dormant seeds survived more than non-dormant seeds. We conclude that species with seed dormancy experience selection for covarying characteristics that allow tolerance to heating in hotter fires. Our findings suggest that both seed dormancy and habitat-specific fire temperatures may contribute to the evolution of seed fire tolerance in Neotropical savannas.

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O’Rourke, Michael. "Cunningham on the flooded grasslands, 1825". History Australia 15, n. 1 (2 gennaio 2018): 196–98. http://dx.doi.org/10.1080/14490854.2018.1416545.

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Bond, William J. "What Limits Trees in C4 Grasslands and Savannas?" Annual Review of Ecology, Evolution, and Systematics 39, n. 1 (dicembre 2008): 641–59. http://dx.doi.org/10.1146/annurev.ecolsys.39.110707.173411.

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Montaña, Carmen G., Craig A. Layman e Donald C. Taphorn. "Comparison of fish assemblages in two littoral habitats in a Neotropical morichal stream in Venezuela". Neotropical Ichthyology 6, n. 4 (dicembre 2008): 577–82. http://dx.doi.org/10.1590/s1679-62252008000400005.

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Morichales are lowland streams in South American savannas with riparian forest dominated by the moriche palm (Mauritia flexuosa). We sampled littoral habitats from ten flooded vegetated patches (dominated by Mauritiella aculeate) and six sand banks in two months of the dry season (Feb-Mar 2005) in a stream in the savannas of Apure State, Venezuela. We collected samples that compromised 12,407 individual fishes of 107 species. Small-bodied fishes (< 100 mm), representing diverse trophic and life history strategies, were abundant. The most abundant species were in the families Characidae and Cichlidae. Fish assemblages from flooded vegetated patches differed significantly from those on adjacent sand banks. High structural complexity along vegetated shoreline habitats of morichal streams likely contributes to species richness and affects assemblage composition.

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Navarro, Gonzalo, José Antonio Molina, Emanuela Agostinelli, Ana Lumbreras e Wanderlei Ferreira. "Towards an ecological classification of flooded savannas in Beni (Bolivia)". Acta Botanica Gallica 157, n. 2 (gennaio 2010): 265–73. http://dx.doi.org/10.1080/12538078.2010.10516204.

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CARPENTIER, A., J. M. PAILLISSON, E. FEUNTEUN e L. MARION. "FISH COMMUNITY STRUCTURE IN TEMPORARY LOWLAND FLOODED GRASSLANDS". Bulletin Français de la Pêche et de la Pisciculture, n. 375 (2004): 1–14. http://dx.doi.org/10.1051/kmae:2005037.

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Ivask, Mari, Jaak Truu, Annely Kuu, Marika Truu e Aivar Leito. "Earthworm communities of flooded grasslands in Matsalu, Estonia". European Journal of Soil Biology 43, n. 2 (marzo 2007): 71–76. http://dx.doi.org/10.1016/j.ejsobi.2006.09.009.

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Plaza, Tarik Godoy D., e Carla Galbiati. "Influence of Flood Pulse on Termite Diversity (INSECTA: ISOPTERA) in the Pantanal". Sociobiology 64, n. 3 (17 ottobre 2017): 310. http://dx.doi.org/10.13102/sociobiology.v64i3.1371.

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This research aimed to associate termite diversity to flood pulse by Paraguay River, and with savannas and pasture areas. The study was conducted nearby the town of Cáceres, in Pantanal - Mato Grosso, on six livestock farms subject to Paraguay River flood pulse. Types of land use sampled were native savanna and cultivated pasture. Flooded and dry plots were selected, both the savanna and the pasture in each sampling area. Termite richness and abundance was analysed based on the environments as an explanatory variable (FP – flooded pasture, DP – dry pasture, FS – flooded savanna, DS – dry savanna) through GLM; Tukey’s test was subsequently performed to determine whether land use and/or flood pulse can significantly affect the termite community. There were 37 termite species and 19 genera. Richness and abundance of termite species cannot be explain by flooding pulse, but were explained only by land use (pasture and savanna). The similarity analysis also identified that species composition was quite affected by flood in grazing areas, but this disturbance does not affect the savanna areas. In conclusion, flood pulse is not a determining factor for savannas or pasture termite richness, but change the composition of the termite fauna in the environment.

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van Langevelde, Frank, Casper de Groot, Thomas A. Groen, Ignas M. A. Heitkönig e Ian Gaigher. "Effect of patches of woody vegetation on the role of fire in tropical grasslands and savannas". International Journal of Wildland Fire 23, n. 3 (2014): 410. http://dx.doi.org/10.1071/wf13119.

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In tropical grasslands and savannas, fire is used to reduce woody vegetation expansion. Woody vegetation in these biomes is often patchily distributed, and micro-climatic conditions can largely vary locally with unknown consequences for fire effects. We hypothesised that (1) fire has higher temperature and maintains high temperatures for a longer period at the windward side than at the leeward side of wooded patches, (2) this difference increases with patch size, (3) fire has a larger effect on woody vegetation at the windward side than at the leeward side of wooded patches and (4) this effect increases with patch size. We planted tree seedlings around wooded patches in a grassland and burnt these plots. We found that fire had a lower temperature and had an elevated temperature for a shorter time period at the leeward side of wooded patches than at the windward side. Also, we found smaller effect of fire on the seedlings at the leeward side. We conclude that patches of woody vegetation can have a large effect on the role of fire in tropical grasslands and savannas. This effect suggests a ‘safe zone’ for seedlings at the leeward side, which consequently promotes woody vegetation expansion. This paper contributes to understanding of the effect of patchiness of woody vegetation on the role of fire in tropical grasslands and savannas in reducing woody vegetation expansion.

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Bond, William, e Nicholas P. Zaloumis. "The deforestation story: testing for anthropogenic origins of Africa's flammable grassy biomes". Philosophical Transactions of the Royal Society B: Biological Sciences 371, n. 1696 (5 giugno 2016): 20150170. http://dx.doi.org/10.1098/rstb.2015.0170.

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Africa has the most extensive C4 grassy biomes of any continent. They are highly flammable accounting for greater than 70% of the world's burnt area. Much of Africa's savannas and grasslands occur in climates warm enough and wet enough to support closed forests. The combination of open grassy systems and the frequent fires they support have long been interpreted as anthropogenic artefacts caused by humans igniting frequent fires. True grasslands, it was believed, would be restricted to climates too dry or too cold to support closed woody vegetation. The idea that higher-rainfall savannas are anthropogenic and that fires are of human origin has led to initiatives to ‘reforest’ Africa's open grassy systems paid for by carbon credits under the assumption that the net effect of converting these system to forests would sequester carbon, reduce greenhouse gases and mitigate global warming. This paper reviews evidence for the antiquity of African grassy ecosystems and for the fires that they sustain. Africa's grassy biomes and the fires that maintain them are ancient and there is no support for the idea that humans caused large-scale deforestation. Indicators of old-growth grasslands are described. These can help distinguish secondary grasslands suitable for reforestation from ancient grasslands that should not be afforested. This article is part of the themed issue ‘The interaction of fire and mankind’.

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Naito, Adam T., e David M. Cairns. "Patterns and processes of global shrub expansion". Progress in Physical Geography: Earth and Environment 35, n. 4 (5 maggio 2011): 423–42. http://dx.doi.org/10.1177/0309133311403538.

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Shrub expansion is a global phenomenon that is occurring on savannas, rangelands, and grasslands. In addition, this is an increasingly documented occurrence in the Arctic. Numerous recent studies have strived to pinpoint the drivers of this phenomenon, quantify the changes, and understand their implications for regional and global land use, disturbance regimes, and nutrient cycling. Inquiry into these topics has been facilitated by recent technological developments in satellite remote sensing, aerial photograph analysis, and computer simulation modeling. We provide a new review that accounts for more recent studies in these regions, Arctic shrub expansion, and technological and analytical developments. This four-part discussion focuses on observed patterns of shrub expansion in three rangeland types (desert grasslands, mesic grasslands, savannas) and the Arctic tundra, the primary causes of this expansion, critical comparisons and contrasts between these land types, and recommendations for future avenues of research. These new avenues can inform the development of future land management policies, as well as ongoing investigations to understand and mitigate the effects of climate change.

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Veldman, Joseph W., Elise Buisson, Giselda Durigan, G. Wilson Fernandes, Soizig Le Stradic, Gregory Mahy, Daniel Negreiros et al. "Toward an old-growth concept for grasslands, savannas, and woodlands". Frontiers in Ecology and the Environment 13, n. 3 (aprile 2015): 154–62. http://dx.doi.org/10.1890/140270.

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Nippert, Jesse B., e Ricardo M. Holdo. "Challenging the maximum rooting depth paradigm in grasslands and savannas". Functional Ecology 29, n. 6 (12 gennaio 2015): 739–45. http://dx.doi.org/10.1111/1365-2435.12390.

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Ratajczak, Zakary, Jesse B. Nippert e Scott L. Collins. "Woody encroachment decreases diversity across North American grasslands and savannas". Ecology 93, n. 4 (aprile 2012): 697–703. http://dx.doi.org/10.1890/11-1199.1.

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GODOI, MAURICIO N., e EDIVALDO O. DE SOUZA. "The effects of forest-savanna-grassland gradients on bird communities of Chiquitano Dry Forests domain, in western Brazil". Anais da Academia Brasileira de Ciências 88, n. 3 suppl (22 settembre 2016): 1755–67. http://dx.doi.org/10.1590/0001-3765201620150615.

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ABSTRACT Different vegetation types are distributed in mountains according to altitude, topography and soil. The composition and structure of bird communities in these areas can change in relation to the vegetation gradient, with particular communities occupying each habitat type. In this study we present the changes in composition, species richness and bird abundance over the gradient of forests, savannas and altitudinal grasslands of Maciço do Urucum, a mountainous region located in the Chiquitano Dry Forests domain in western Brazil. We recorded 165 bird species through qualitative and quantitative methods. Forested savannas, riparian forests and submontane forests presented the highest richness and abundance of birds, while arboreal savannas and altitudinal grasslands had intermediate and low values, respectively. The bird composition was similar between riparian and submontane forests, while other vegetation types present more dissimilar bird communities. Our results show differences in composition, richness and bird abundance among the vegetation types present at Maciço do Urucum, and highlight an important function of vegetation gradients for the conservation of bird communities in mountains. Additionally, this is the first study of the bird communities in the Brazilian Chiquitano Dry Forests, an important domain in the west of Brazil which has been poorly studied.

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Rood, B. E., J. F. Gottgens, J. J. Delfino, C. D. Earle e T. L. Crisman. "Mercury accumulation trends in Florida Everglades and Savannas Marsh flooded soils". Water, Air, & Soil Pollution 80, n. 1-4 (febbraio 1995): 981–90. http://dx.doi.org/10.1007/bf01189752.

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29

Fieker, CZ, MG Reis e MM Dias Filho. "Structure of bird assemblages in dry and seasonally flooded grasslands in Itirapina Ecological Station, São Paulo state". Brazilian Journal of Biology 73, n. 1 (febbraio 2013): 91–101. http://dx.doi.org/10.1590/s1519-69842013000100011.

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Grasslands are characteristic physiognomies of the Brazilian Cerrado domain. One of last remnants of these threatened environments in the state of São Paulo is located in Itirapina Ecological Station, considered as an Important Bird Area (IBA). We investigated bird assemblages that use seasonally flooded grasslands, and predominantly dry grasslands, from August 2010 until July 2011. We focused on aspects of assemblage structure, and possible responses of birds to environmental changes. We recorded 76 species, of which 23.7% are threatened. Some basic aspects of assemblages were similar between environments, such as diversity descriptors, and the tendency of increase richness in the same periods. Other parameters differed between environments, such as absolute richness, recorded monthly (lower in seasonally flooded grasslands). Considering time dimension in analyses, we observed differences in assemblage structure over time, within and between environments. When birds were grouped in guilds, assemblage structure did also differ. We identified significant correlations between the abundance of some guilds and environmental variables. Changes in the availability of resources and microhabitats may affect structure and organization of the studied bird assemblages.

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30

Mamede, S. B., e C. J. R. Alho. "Response of wild mammals to seasonal shrinking-and-expansion of habitats due to flooding regime of the Pantanal, Brazil". Brazilian Journal of Biology 66, n. 4 (novembre 2006): 991–98. http://dx.doi.org/10.1590/s1519-69842006000600006.

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The Pantanal is a large savanna wetland (138,183 km² in Brazil), important for its wildlife, fed by tributaries of the upper Paraguay River, center of South America (Brazil, touching Bolivia and Paraguay). Uplands are plateaus (250-1,200 m high, 215,000 km² in Brazil) and flatland is the Pantanal (80-150 m high, 147,574 km² in Brazil). Rivers are slow moving when they meet the flatland (slope 0.3-0.5 m/km east-west; 0.03-0.15 m/km north-south), periodically overflowing their banks, creating a complex seasonal habitat range. Recurrent shallow flooding occupies 80% of the Pantanal; during the dry season flooded areas dry up. Fluctuating water levels, nutrients and wildlife form a dynamic ecosystem. A flooding regime forms distinct sub-regions within the Pantanal. A mammal survey was carried out in the sub-region of the Rio Negro from April, 2003 through March, 2004 to study the diversity and abundance of terrestrial mammals during the dry and flooding seasons. A total of 36 species were observed in the field. The capybara Hydrochaeris hydrochaeris was the most frequent species, followed by the crab-eating-fox Cerdocyon thous and the marsh deer Blastocerus dichotomus. The highest abundance of species was observed during the dry season (August and September), when there is a considerable expansion of terrestrial habitats, mainly seasonally flooded grassland. Animal abundance (in terms of observed individual frequencies) varied during the dry and wet seasons and the seasonally flooded grassland was the most utilized habitat by mammals in the dry season.

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31

Serling, T. E. "Development of grasslands and savannas in East Africa during the Neogene". Global and Planetary Change 5, n. 3 (marzo 1992): 241–47. http://dx.doi.org/10.1016/0921-8181(92)90013-z.

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32

Cerling, T. E. "Development of grasslands and savannas in East Africa during the Neogene". Palaeogeography, Palaeoclimatology, Palaeoecology 97, n. 3 (marzo 1992): 241–47. http://dx.doi.org/10.1016/0031-0182(92)90211-m.

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33

BUIJ, RALPH, e BARBARA M. CROES. "Raptor habitat use in the Lake Chad Basin: insights into the effect of flood-plain transformation on Afrotropical and Palearctic raptors". Bird Conservation International 23, n. 2 (8 aprile 2013): 199–213. http://dx.doi.org/10.1017/s0959270913000014.

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SummaryWest African flood-plains have undergone major land-use transformations in the second half of the 20th century. To obtain insight in the effect of flood-plain development for irrigated rice cultivation on the abundance, richness, and diversity of Palearctic and Afrotropical raptors, we conducted monthly transect surveys covering dry and wet seasons in four major habitats on the Waza-Logone flood-plain of Cameroon: dry grasslands, cultivated grasslands, rice fields, and seasonally flooded grasslands resembling natural flood-plain vegetation. We recorded 36 raptor species among 2,533 individuals, dominated by Black Kite Milvus migrans, which comprised 42% of counts. Although richness and diversity were not related to land-use for Palearctic raptors, Afrotropical raptor diversity was higher on the flooded grasslands compared to the newly created cultivated habitats and dry grasslands. The abundance of Afrotropical raptors did not significantly differ across habitats but was lower in rice-fields when Black Kite and Hooded Vulture Necrosyrtes monachus were excluded. Conversely, Palearctic raptor abundance was highest in post-harvest rice fields, demonstrating the importance of the rice fields as foraging habitat for Palearctic raptors. Further transformation of West Africa’s flood-plains is expected, reducing their capacity for Afrotropical raptors, while Palearctic raptors may benefit from expansion of rice-fields, but more research is needed on their vulnerability to pesticide use.

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34

Bendini, H. N., L. M. G. Fonseca, M. Schwieder, P. Rufin, T. S. Korting, A. Koumrouyan e P. Hostert. "COMBINING ENVIRONMENTAL AND LANDSAT ANALYSIS READY DATA FOR VEGETATION MAPPING: A CASE STUDY IN THE BRAZILIAN SAVANNA BIOME". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B3-2020 (21 agosto 2020): 953–60. http://dx.doi.org/10.5194/isprs-archives-xliii-b3-2020-953-2020.

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Abstract. The Cerrado biome in Brazil covers approximately 24% of the country. It is one of the richest and most diverse savannas in the world, with 23 vegetation types (physiognomies) consisting mostly of tropical savannas, grasslands, forests and dry forests. It is considered as one of the global hotspots of biodiversity because of the high level of endemism and rapid loss of its original habitat. This work aims to analyze the potential of Landsat Analysis Ready Data (ARD) in combination with different environmental data to classify the vegetation in the Cerrado in two different hierarchical levels. Here we present results of a pixel-based modelling exercise, in which field data were combined with a set of input variables using a Random Forest classification approach. On the first hierarchical level, with the three classes savanna, grasslands and forest, our model results reached f1-scores of 0.86, 0.87 and 0.85 leading to an overall accuracy of 0.86. In the second hierarchical level we differentiated a total of 12 vegetation physiognomies with an overall accuracy of 0.77.

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35

Grundel, Ralph, e Noel B. Pavlovic. "Distinctiveness, Use, and Value of Midwestern Oak Savannas and Woodlands as Avian Habitats". Auk 124, n. 3 (1 luglio 2007): 969–85. http://dx.doi.org/10.1093/auk/124.3.969.

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Abstract Oak savannas and woodlands historically covered millions of hectares in the midwestern United States but are rare today. We evaluated the ecological distinctiveness and conservation value of savannas and woodlands by examining bird distributions across a fire-maintained woody-vegetation gradient in northwest Indiana encompassing five habitats—open habitats with low canopy cover, savannas, woodlands, scrublands, and forests—during migration, breeding, and overwintering. Savannas and woodlands were significantly different in overall bird species composition from open and forest habitats but were often intermediate between open and forest in guild densities. Few bird species were consistently and highly concentrated in savannas or woodlands, and the Red-headed Woodpecker (Melanerpes erythrocephalus) was the only species significantly more abundant in savannas and woodlands than in open, scrub, and forest habitats. Fire frequency over a 15-year interval was a significant predictor of bird community composition and was positively related to species diversity, spring transient migrant density, and density of the most threatened species. Each habitat type had characteristics potentially important for avian conservation. Scrub had the highest density of transient migrants, which suggests it plays an important role as migration stopover habitat. More species were significantly concentrated in open or forest habitats than in the other habitats. Lack of species concentration and intermediate community composition suggested that birds experienced savannas and woodlands more as ecotones than as habitats distinct from forests or grasslands. However, this intermediate character can benefit conservation, as evidenced by savannas and woodlands having the highest density of the most threatened species along this woody-vegetation gradient. Características Únicas, Uso y Valor de las Sabanas y Bosques Abiertos de Roble del Oeste Central como Hábitats para las Aves

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36

Buisson, Elise, Soizig Le Stradic, Fernando A. O. Silveira, Giselda Durigan, Gerhard E. Overbeck, Alessandra Fidelis, G. Wilson Fernandes et al. "Resilience and restoration of tropical and subtropical grasslands, savannas, and grassy woodlands". Biological Reviews 94, n. 2 (24 settembre 2018): 590–609. http://dx.doi.org/10.1111/brv.12470.

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37

Veldman, Joseph W., Julie C. Aleman, Swanni T. Alvarado, T. Michael Anderson, Sally Archibald, William J. Bond, Thomas W. Boutton et al. "Comment on “The global tree restoration potential”". Science 366, n. 6463 (17 ottobre 2019): eaay7976. http://dx.doi.org/10.1126/science.aay7976.

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Bastin et al.’s estimate (Reports, 5 July 2019, p. 76) that tree planting for climate change mitigation could sequester 205 gigatonnes of carbon is approximately five times too large. Their analysis inflated soil organic carbon gains, failed to safeguard against warming from trees at high latitudes and elevations, and considered afforestation of savannas, grasslands, and shrublands to be restoration.

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38

Räsänen, Matti, Mika Aurela, Ville Vakkari, Johan P. Beukes, Juha-Pekka Tuovinen, Pieter G. Van Zyl, Miroslav Josipovic et al. "Carbon balance of a grazed savanna grassland ecosystem in South Africa". Biogeosciences 14, n. 5 (7 marzo 2017): 1039–54. http://dx.doi.org/10.5194/bg-14-1039-2017.

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Abstract. Tropical savannas and grasslands are estimated to contribute significantly to the total primary production of all terrestrial vegetation. Large parts of African savannas and grasslands are used for agriculture and cattle grazing, but the carbon flux data available from these areas are limited. This study explores carbon dioxide fluxes measured with the eddy covariance method for 3 years at a grazed savanna grassland in Welgegund, South Africa. The tree cover around the measurement site, grazed by cattle and sheep, was around 15 %. The night-time respiration was not significantly dependent on either soil moisture or soil temperature on a weekly temporal scale, whereas on an annual timescale higher respiration rates were observed when soil temperatures were higher. The carbon dioxide balances of the years 2010–2011, 2011–2012 and 2012–2013 were −85 ± 16, 67 ± 20 and 139 ± 13 gC m−2 yr−1, respectively. The yearly variation was largely determined by the changes in the early wet season fluxes (September to November) and in the mid-growing season fluxes (December to January). Early rainfall enhanced the respiratory capacity of the ecosystem throughout the year, whereas during the mid-growing season high rainfall resulted in high carbon uptake.

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39

Sun, Z. G., X. H. Long, C. M. Sun, W. Zhou, W. M. Ju e J. L. Li. "Evaluation of net primary productivity and its spatial and temporal patterns in southern China’s grasslands". Rangeland Journal 35, n. 3 (2013): 331. http://dx.doi.org/10.1071/rj12061.

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The net primary productivity (NPP) of grassland ecosystems is an important indicator of the capacity for carbon (C) absorption. The Global Production Efficiency Model was adopted to simulate NPP in southern China’s grasslands and to analyse the temporal and spatial dynamics from 1981 to 2000. There was a high correlation between measured and simulated values (R2 = 0.84). Based on the data from 1981 to 2000, the mean annual NPP was 1082 g C m–2 year–1, and the highest value (1798 g C m–2 year–1) was in Hainan province, and the lowest value (500 g C m–2 year–1) was in south-western Tibet. The highest mean NPP values were in the permanent wetlands (1193 g C m–2 year–1) and savannas (1137 g C m–2 year–1); woody savannas had an intermediate value (1087 g C m–2 year–1), and the lowest NPP occurred in typical grasslands and open shrubs, the mean values were 709 and 689 g C m–2 year–1, respectively. Temporally, the total NPP in southern China’s grasslands slightly increased in the 20-year period, especially from 1981 to 1990. The mean annual total of NPP in the 20 years was 0.758 Pg C. Inter-annual variation in total NPP was driven mainly by mean annual temperature rather than mean annual precipitation. The results suggest that grassland ecosystems in southern China have a large C sink.

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40

Mleczko, M., M. Mroz e M. Fitrzyk. "WETLAND MAPPING WITH SAR/QUAD-POL DATA ACQUIRED DURING TANDEM-X SCIENCE PHASE". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (22 giugno 2016): 809–13. http://dx.doi.org/10.5194/isprsarchives-xli-b7-809-2016.

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The aim of this study was to exploit fully polarimetric SAR data acquired during TanDEM-X – Science Phase (2014/2015) over herbaceous wetlands of the Biebrza National Park (BbNP) in North-Eastern Poland for mapping seasonally flooded grasslands and permanent natural vegetation associations. The main goal of this work was to estimate the advantage of fully polarimetric radar images (QuadPol) versus alternative polarization (AltPol) modes. The methodology consisted in processing of several data subsets through polarimetric decompositions of complex quad-pol datasets, classification of multitemporal backscattering images, complementing backscattering images with Shannon Entropy, exploitation of interferometric coherence from tandem operations. In each case the multidimensional stack of images has been classified using ISODATA unsupervised clustering algorithm. With 6 QUAD-POL TSX/TDX acquisitions it was possible to distinguish correctly 5 thematic classes related to their water regime: permanent water bodies, temporarily flooded areas, wet grasslands, dry grasslands and common reed. This last category was possible to distinguish from deciduous forest only with Yamaguchi 4 component decomposition. The interferometric coherence calculated for tandem pairs turned out not so efficient as expected for this wetland mapping.

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41

Mleczko, M., M. Mroz e M. Fitrzyk. "WETLAND MAPPING WITH SAR/QUAD-POL DATA ACQUIRED DURING TANDEM-X SCIENCE PHASE". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (22 giugno 2016): 809–13. http://dx.doi.org/10.5194/isprs-archives-xli-b7-809-2016.

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Abstract (sommario):

The aim of this study was to exploit fully polarimetric SAR data acquired during TanDEM-X – Science Phase (2014/2015) over herbaceous wetlands of the Biebrza National Park (BbNP) in North-Eastern Poland for mapping seasonally flooded grasslands and permanent natural vegetation associations. The main goal of this work was to estimate the advantage of fully polarimetric radar images (QuadPol) versus alternative polarization (AltPol) modes. The methodology consisted in processing of several data subsets through polarimetric decompositions of complex quad-pol datasets, classification of multitemporal backscattering images, complementing backscattering images with Shannon Entropy, exploitation of interferometric coherence from tandem operations. In each case the multidimensional stack of images has been classified using ISODATA unsupervised clustering algorithm. With 6 QUAD-POL TSX/TDX acquisitions it was possible to distinguish correctly 5 thematic classes related to their water regime: permanent water bodies, temporarily flooded areas, wet grasslands, dry grasslands and common reed. This last category was possible to distinguish from deciduous forest only with Yamaguchi 4 component decomposition. The interferometric coherence calculated for tandem pairs turned out not so efficient as expected for this wetland mapping.

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42

Nerlekar, Ashish N., e Joseph W. Veldman. "High plant diversity and slow assembly of old-growth grasslands". Proceedings of the National Academy of Sciences 117, n. 31 (16 luglio 2020): 18550–56. http://dx.doi.org/10.1073/pnas.1922266117.

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Earth’s ancient grasslands and savannas—hereafter old-growth grasslands—have long been viewed by scientists and environmental policymakers as early successional plant communities of low conservation value. Challenging this view, emerging research suggests that old-growth grasslands support substantial biodiversity and are slow to recover if destroyed by human land uses (e.g., tillage agriculture, plantation forestry). But despite growing interest in grassland conservation, there has been no global test of whether old-growth grasslands support greater plant species diversity than secondary grasslands (i.e., herbaceous communities that assemble after destruction of old-growth grasslands). Our synthesis of 31 studies, including 92 timepoints on six continents, found that secondary grasslands supported 37% fewer plant species than old-growth grasslands (log response ratio = −0.46) and that secondary grasslands typically require at least a century, and more often millennia (projected mean 1,400 y), to recover their former richness. Young (<29 y) secondary grasslands were composed of weedy species, and even as their richness increased over decades to centuries, secondary grasslands were still missing characteristic old-growth grassland species (e.g., long-lived perennials). In light of these results, the view that all grasslands are weedy communities, trapped by fire and large herbivores in a state of arrested succession, is untenable. Moving forward, we suggest that ecologists should explicitly consider grassland assembly time and endogenous disturbance regimes in studies of plant community structure and function. We encourage environmental policymakers to prioritize old-growth grassland conservation and work to elevate the status of old-growth grasslands, alongside old-growth forests, in the public consciousness.

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Mureva, Admore, Pauline Chivenge e David Ward. "Soil organic carbon and nitrogen in soil physical fractions in woody encroached grassland in South African savannas". Soil Research 59, n. 6 (2021): 595. http://dx.doi.org/10.1071/sr20245.

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Woody plant encroachment has transformed land-cover patterns in savannas and grasslands throughout the world, with implications for changes in soil organic carbon (SOC) dynamics. However, our understanding of the effects of woody encroachment on SOC is very limited. In a study of pairs of neighbouring, woody encroached and grassland plots along a rainfall gradient (300–1500 mm mean annual precipitation, MAP) in South African savannas, we quantified the changes in SOC and nitrogen pools to a depth of 100 cm, in three soil physical fractions (coarse particulate organic matter, macroaggregates and silt and clay) and bulk soil. The 0–10 cm soil layer of the 1500 mm MAP site lost 26% of SOC stocks due to shrub encroachment. Contrastingly, the 300 and 350 mm MAP sites gained 24% and 27% total SOC, respectively, due to shrub encroachment. In the soil fractions, the largest changes in SOC, ranging within 2.64–464%, were in the coarse particulate organic matter (unprotected organic matter > 250 μm), and the lowest in the silt and clay fraction (6–32%) across all sites and depths. Soil nitrogen increased across all encroached sites compared with open grasslands, regardless of MAP. For every 1-unit increase in MAP and soil fraction size there was a change of –0.06 and 0.1 SOC (gC/kg soil) in encroached grasslands, respectively. We conclude that shrub-encroached grasslands potentially sequester more C in soils of arid regions than in humid regions. At three of our sites, we were unable to differentiate SOC between encroached and open-grassland soils from bulk soil but could do so from soil fraction analysis. Thus, soil fraction analysis is a more effective way to assess changes in soil C than bulk soil.

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44

Pott, A., AKM Oliveira, GA Damasceno-Junior e JSV Silva. "Plant diversity of the Pantanal wetland". Brazilian Journal of Biology 71, n. 1 suppl 1 (aprile 2011): 265–73. http://dx.doi.org/10.1590/s1519-69842011000200005.

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This is a review of current studies in diversity of the flora and main vegetation types in the Brazilian Pantanal. The flora of this wetland, nearly 2,000 species, constitutes a pool of elements of wide distribution and from more or less adjacent phytogeographic provinces, such as Cerrado, dry seasonal forests, Chaco, Amazonia and Atlantic Forest. The most numerous group includes wide-distribution species, mainly herbs, while the second contingent comes from the Cerrado. Endemic plants are rare, numbering only seven. The vegetation of the sedimentary floodplain is a mosaic of aquatics, floodable grasslands, riparian forests, savannas (cerrados), cerrado woodlands, dry forests, and a large area of mono-dominant savannas, and pioneer woodlands. The main vegetation types are briefly described with their characteristic species, and their estimated areas are given according to the latest mapping.

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Bond, William J., e Guy F. Midgley. "A proposed CO2 -controlled mechanism of woody plant invasion in grasslands and savannas". Global Change Biology 6, n. 8 (dicembre 2000): 865–69. http://dx.doi.org/10.1046/j.1365-2486.2000.00365.x.

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46

Andela, Niels, Guido R. van der Werf, Johannes W. Kaiser, Thijs T. van Leeuwen, Martin J. Wooster e Caroline E. R. Lehmann. "Biomass burning fuel consumption dynamics in the tropics and subtropics assessed from satellite". Biogeosciences 13, n. 12 (28 giugno 2016): 3717–34. http://dx.doi.org/10.5194/bg-13-3717-2016.

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Abstract. Landscape fires occur on a large scale in (sub)tropical savannas and grasslands, affecting ecosystem dynamics, regional air quality and concentrations of atmospheric trace gasses. Fuel consumption per unit of area burned is an important but poorly constrained parameter in fire emission modelling. We combined satellite-derived burned area with fire radiative power (FRP) data to derive fuel consumption estimates for land cover types with low tree cover in South America, Sub-Saharan Africa, and Australia. We developed a new approach to estimate fuel consumption, based on FRP data from the polar-orbiting Moderate Resolution Imaging Spectroradiometer (MODIS) and the geostationary Spinning Enhanced Visible and Infrared Imager (SEVIRI) in combination with MODIS burned-area estimates. The fuel consumption estimates based on the geostationary and polar-orbiting instruments showed good agreement in terms of spatial patterns. We used field measurements of fuel consumption to constrain our results, but the large variation in fuel consumption in both space and time complicated this comparison and absolute fuel consumption estimates remained more uncertain. Spatial patterns in fuel consumption could be partly explained by vegetation productivity and fire return periods. In South America, most fires occurred in savannas with relatively long fire return periods, resulting in comparatively high fuel consumption as opposed to the more frequently burning savannas in Sub-Saharan Africa. Strikingly, we found the infrequently burning interior of Australia to have higher fuel consumption than the more productive but frequently burning savannas in northern Australia. Vegetation type also played an important role in explaining the distribution of fuel consumption, by affecting both fuel build-up rates and fire return periods. Hummock grasslands, which were responsible for a large share of Australian biomass burning, showed larger fuel build-up rates than equally productive grasslands in Africa, although this effect might have been partially driven by the presence of grazers in Africa or differences in landscape management. Finally, land management in the form of deforestation and agriculture also considerably affected fuel consumption regionally. We conclude that combining FRP and burned-area estimates, calibrated against field measurements, is a promising approach in deriving quantitative estimates of fuel consumption. Satellite-derived fuel consumption estimates may both challenge our current understanding of spatiotemporal fuel consumption dynamics and serve as reference datasets to improve biogeochemical modelling approaches. Future field studies especially designed to validate satellite-based products, or airborne remote sensing, may further improve confidence in the absolute fuel consumption estimates which are quickly becoming the weakest link in fire emission estimates.

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Lima, Daniela Oliveira de, Maria Lucia Lorini e Marcus Vinícius Vieira. "Conservation of grasslands and savannas: A meta-analysis on mammalian responses to anthropogenic disturbance". Journal for Nature Conservation 45 (settembre 2018): 72–78. http://dx.doi.org/10.1016/j.jnc.2018.08.008.

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48

Calcaterra, Luis A., Sonia M. Cabrera, Fabiana Cuezzo, Ignacio Jiménez Peréz e Juan A. Briano. "Habitat and Grazing Influence on Terrestrial Ants in Subtropical Grasslands and Savannas of Argentina". Annals of the Entomological Society of America 103, n. 4 (1 luglio 2010): 635–46. http://dx.doi.org/10.1603/an09173.

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49

Henchiri, Malak, Qi Liu, Bouajila Essifi, Tehseen Javed, Sha Zhang, Yun Bai e Jiahua Zhang. "Spatio-Temporal Patterns of Drought and Impact on Vegetation in North and West Africa Based on Multi-Satellite Data". Remote Sensing 12, n. 23 (25 novembre 2020): 3869. http://dx.doi.org/10.3390/rs12233869.

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Abstract (sommario):

Studying the significant impacts of drought on vegetation is crucial to understand its dynamics and interrelationships with precipitation, soil moisture, and temperature. In North and West Africa regions, the effects of drought on vegetation have not been clearly stated. Therefore, the present study aims to bring out the drought fluctuations within various types of Land Cover (LC) (Grasslands, Croplands, Savannas, and Forest) in North and West Africa regions. The drought characteristics were evaluated by analyzing the monthly Self-Calibrating Palmer Drought Severity Index (scPDSI) in different timescale from 2002 to 2018. Then, the frequency of droughts was examined over the same period. The results have revealed two groups of years (dry years and normal years), based on drought intensity. The selected years were used to compare the shifting between vegetation and desert. The Vegetation Condition Index (VCI), the Temperature Condition Index (TCI), the Precipitation Condition Index (PCI), and the Soil Moisture Condition Index (SMCI) were also used to investigate the spatiotemporal variation of drought and to determine which LC class was more vulnerable to drought risk. Our results revealed that Grasslands and Croplands in the West region, and Grasslands, Croplands, and Savannas in the North region are more sensitive to drought. A higher correlation was observed among the Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST), Tropical Rainfall Measuring Mission (TRMM), and Soil Moisture (SM). Our findings suggested that NDVI, TRMM, and SM are more suitable for monitoring drought over the study area and have a reliable accuracy (R2 > 0.70) concerning drought prediction. The outcomes of the current research could, explicitly, contribute progressively towards improving specific drought mitigation strategies and disaster risk reduction at regional and national levels.

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Lim, Burton, e Thomas Lee. "Community Ecology and Phylogeography of Bats in the Guianan Savannas of Northern South America". Diversity 10, n. 4 (13 dicembre 2018): 129. http://dx.doi.org/10.3390/d10040129.

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The Guiana Shield of South America contains savannas within one of the largest contiguous expanses of pristine tropical rainforest remaining in the world, but biodiversity in the grasslands is poorly known. In lowland Neotropical areas, bats typically comprise the most species-rich group of mammals. We compare the bat faunal community and phylogeography in the savanna habitats of the Llanos in Venezuela, Rupununi in Guyana, and Sipaliwini in Suriname. Measures of species diversity and relative abundance from standardized field survey methodology enable comparison among these three grassland regions. Genetic variation is summarized by DNA barcoding to examine biogeographic patterns across larger forest–savanna landscapes. A total of 76 species of bats is documented, of which 18 species are reported from all 3 savannas and 30 species are reported from only 1 of the savannas. Endemism is low with 5 taxa restricted primarily to dry, open habitats. However, 7 other species have divergent phylogeographic lineages associated with savanna populations. Although bat species are usually distributed over wide regions of the Neotropics, the habitat mosaics of the Guiana Shield have different faunal assemblages. Going back into the Miocene, the contractions and expansions of forest–savanna paleoenvironments over time have contributed to speciation and the current high levels of biodiversity in South America.

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