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Добірка наукової літератури з теми "Forest canopy gaps – Environmental aspects"
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Статті в журналах з теми "Forest canopy gaps – Environmental aspects"
1
Lobo, E., and J. W. Dalling. "Effects of topography, soil type and forest age on the frequency and size distribution of canopy gap disturbances in a tropical forest." Biogeosciences 10, no. 11 (November 1, 2013): 6769–81. http://dx.doi.org/10.5194/bg-10-6769-2013.
Повний текст джерелаАнотація:
Abstract. Treefall gaps are the major source of disturbance in most tropical forests. The frequency and size of these gaps have important implications for forest ecosystem processes as they can influence the functional trait distribution of tree communities, stand-level aboveground biomass and productivity. However, we still know little about the relative importance of environmental drivers of gap disturbance regimes because existing studies vary greatly in criteria used for defining gaps, in the spatial extent of the study area, and the spatial resolution of canopy height measurements. Here we use lidar (light detecting and ranging) to explore how forest age, topography and soil type affect canopy disturbance patterns across a 1500 ha tropical forest landscape in central Panama. We characterize disturbance based on the frequency distribution of gap sizes (the "gap size distribution"), and the area of the forest affected by gaps (the "gap area fraction"). We found that slope and forest age had significant effects on the gap size distribution, with a higher frequency of large gaps associated with old-growth forests and more gentle slopes. Slope and forest age had similar effects on the gap area fraction, however gap area fraction was also affected by soil type and by aspect. We conclude that variation in disturbance patterns across the landscape can be linked to factors that act at the fine scale (such as aspect or slope), and factors that show heterogeneity at coarser scales (such as forest age or soil type). Awareness of the role of different environmental factors influencing gap formation can help scale up the impacts of canopy disturbance on forest communities measured at the plot scale to landscape and regional scales.
2
Lobo, E., and J. W. Dalling. "Effects of topography, soil type and forest age on the frequency and size distribution of canopy gap disturbances in a tropical forest." Biogeosciences Discussions 10, no. 4 (April 23, 2013): 7103–33. http://dx.doi.org/10.5194/bgd-10-7103-2013.
Повний текст джерелаАнотація:
Abstract. Treefall gaps are the major source of disturbance in most tropical forests. The frequency and size of these gaps have important implications for forest ecosystem processes as they can influence the functional trait distribution of tree communities, stand-level above-ground biomass and productivity. However, we still know little about the relative importance of environmental drivers of gap disturbance regimes because existing studies vary greatly in criteria used for defining gaps, in the spatial extent of the study area, and the spatial resolution of canopy height measurements. Here we use LiDAR (light detecting and ranging) to explore how forest age, topography and soil type affect canopy disturbance patterns across a 1500 ha tropical forest landscape in central Panama. We characterize disturbance based on the frequency distribution of gap sizes (the "gap size distribution"), and the area of the forest affected by gaps (the "gap area fraction"). We found that slope and forest age had significant effects on the gap size distribution, with a higher frequency of large gaps associated with old-growth forests and more gentle slopes. Slope and forest age had similar effects on the gap area fraction, however gap area fraction was also affected by soil type and by aspect. We conclude that variation in disturbance patterns across the landscape can be linked to factors that act at the fine scale (such as aspect or slope), and factors that show heterogeneity at coarser scales (such as forest age or soil type). Awareness of the role of different environmental factors influencing gap formation can help scale-up the impacts of canopy disturbance on forest communities measured at the plot scale to landscape and regional scales.
3
Székely, B., A. Kania, T. Standovár, and H. Heilmeier. "EVALUATION OF VERTICAL LACUNARITY PROFILES IN FORESTED AREAS USING AIRBORNE LASER SCANNING POINT CLOUDS." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences III-8 (June 7, 2016): 93–99. http://dx.doi.org/10.5194/isprsannals-iii-8-93-2016.
Повний текст джерелаАнотація:
The horizontal variation and vertical layering of the vegetation are important properties of the canopy structure determining the habitat; three-dimensional (3D) distribution of objects (shrub layers, understory vegetation, etc.) is related to the environmental factors (e.g., illumination, visibility). It has been shown that gaps in forests, mosaic-like structures are essential to biodiversity; various methods have been introduced to quantify this property. As the distribution of gaps in the vegetation is a multi-scale phenomenon, in order to capture it in its entirety, scale-independent methods are preferred; one of these is the calculation of lacunarity. <br><br> We used Airborne Laser Scanning point clouds measured over a forest plantation situated in a former floodplain. The flat topographic relief ensured that the tree growth is independent of the topographic effects. The tree pattern in the plantation crops provided various quasi-regular and irregular patterns, as well as various ages of the stands. The point clouds were voxelized and layers of voxels were considered as images for two-dimensional input. These images calculated for a certain vicinity of reference points were taken as images for the computation of lacunarity curves, providing a stack of lacunarity curves for each reference points. These sets of curves have been compared to reveal spatial changes of this property. As the dynamic range of the lacunarity values is very large, the natural logarithms of the values were considered. Logarithms of lacunarity functions show canopy-related variations, we analysed these variations along transects. The spatial variation can be related to forest properties and ecology-specific aspects.
4
Székely, B., A. Kania, T. Standovár, and H. Heilmeier. "EVALUATION OF VERTICAL LACUNARITY PROFILES IN FORESTED AREAS USING AIRBORNE LASER SCANNING POINT CLOUDS." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences III-8 (June 7, 2016): 93–99. http://dx.doi.org/10.5194/isprs-annals-iii-8-93-2016.
Повний текст джерелаАнотація:
The horizontal variation and vertical layering of the vegetation are important properties of the canopy structure determining the habitat; three-dimensional (3D) distribution of objects (shrub layers, understory vegetation, etc.) is related to the environmental factors (e.g., illumination, visibility). It has been shown that gaps in forests, mosaic-like structures are essential to biodiversity; various methods have been introduced to quantify this property. As the distribution of gaps in the vegetation is a multi-scale phenomenon, in order to capture it in its entirety, scale-independent methods are preferred; one of these is the calculation of lacunarity. <br><br> We used Airborne Laser Scanning point clouds measured over a forest plantation situated in a former floodplain. The flat topographic relief ensured that the tree growth is independent of the topographic effects. The tree pattern in the plantation crops provided various quasi-regular and irregular patterns, as well as various ages of the stands. The point clouds were voxelized and layers of voxels were considered as images for two-dimensional input. These images calculated for a certain vicinity of reference points were taken as images for the computation of lacunarity curves, providing a stack of lacunarity curves for each reference points. These sets of curves have been compared to reveal spatial changes of this property. As the dynamic range of the lacunarity values is very large, the natural logarithms of the values were considered. Logarithms of lacunarity functions show canopy-related variations, we analysed these variations along transects. The spatial variation can be related to forest properties and ecology-specific aspects.
5
Kermavnar, Janez, Aleksander Marinšek, Klemen Eler, and Lado Kutnar. "Evaluating Short-Term Impacts of Forest Management and Microsite Conditions on Understory Vegetation in Temperate Fir-Beech Forests: Floristic, Ecological, and Trait-Based Perspective." Forests 10, no. 10 (October 16, 2019): 909. http://dx.doi.org/10.3390/f10100909.
Повний текст джерелаАнотація:
Forest understory vegetation is largely influenced by disturbances and given local abiotic conditions. Our research focuses on the early response of understory vegetation to various forest management intensities in Dinaric fir-beech forests in Slovenia: (i) control, (ii) 50% cut of stand growing stock, and (iii) 100% cut of stand growing stock. Apart from identifying overstory removal effects, we were interested in fine-scale variation of understory vegetation and environmental determinants of its species composition. Vegetation was sampled within 27 karst sinkholes, which represent a dominant landform in studied forests. Within each sinkhole, five sampling plots, varying in slope aspect (centre, north, east, south, west), were established (135 in total), where pre-treatment (in 2012) and post-treatment (in 2014) floristic surveys were conducted. The sampled understory species were characterized in terms of Ellenberg’s indicator values (EIVs) and plant functional traits (plant height, seed mass, specific leaf area, leaf dry matter content). Diversity metrics (species richness, total cover, Shannon index) increased in plots where the silvicultural measures were applied. Tree species richness also increased in 100% cutting. A redundancy analysis revealed that species composition was related to environmental variables, which are directly influenced by management interventions (overstory canopy cover, microclimate—maximum daily temperature, soil properties—thickness of organic soil layer) as well as by topographic factors (slope inclination and surface rockiness). EIVs for light were significantly affected by treatment intensity, whereas soil-related EIVs (moisture, reaction, nutrients) depended more on the within-sinkhole position. Canopy gaps, compared with uncut control plots, hosted a higher number of colonizing species with a higher plant height and smaller seeds, while leaf traits did not show a clear response. We found a negative correlation between pre-treatment species (functional) richness and post-treatment shifts in floristic (functional) composition. Plots with higher richness exhibited smaller changes compared with species-poor communities. Incorporating different perspectives, the results of this study offer valuable insights into patterns of understory vegetation response to forest management in fir-beech forests.
6
Stevenson, Pablo, and Adriana Guzmán. "Seed dispersal, habitat selection and movement patterns in the Amazonian tortoise, Geochelone denticulata." Amphibia-Reptilia 29, no. 4 (2008): 463–72. http://dx.doi.org/10.1163/156853808786230442.
Повний текст джерелаАнотація:
AbstractThe Amazonian tortoise Geochelone denticulata may play an important role in forest dynamics due to its highly frugivorous diet, ability to disperse viable seeds, and predilection for resting in forest gaps for thermoregulation. The purpose of our study was to evaluate the species' effectiveness as a seed disperser. We measured dispersal quantity (abundance of seeds in feces, frequency of droppings, and population density of the disperser) and dispersal quality (movement patterns, habitat use, germination rates of dispersed seeds, and recruitment probabilities of seedlings) in a SW Amazonian forest, in Peru. Population density was calculated by mark-recapture and line-transect methods. Eight individuals were radio-tracked to monitor habitat use. Diet was described from fecal samples, which were washed to count seeds and for germination experiments. Seedling survival in different environmental conditions was monitored for three plant species. Population densities with mark-recapture estimates (0.15-0.31 individuals/ha) were much higher than with line transects estimates (0.0025 individuals/ha). Diet included fruit of 55 different plant species. Dispersed seeds had high germination rates (average 76%). In spite of their low activity, we documented long seed dispersal distances (average 89.6 m). Tortoises showed a marked preference for the open-canopy swampy forest, where long term recruitment was not favorable for seedlings of the species examined. However, the high solar radiation in this forest type promoted survival of pioneer seedlings in the short term. In conclusion, while G. denticulata did not perform a very efficient role in terms of the quantity of seed dispersal, the species can be considered efficient in many aspects of dispersal quality.
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Jones, Kelsey L., Victor A. Shegelski, Nathan G. Marculis, Asha N. Wijerathna, and Maya L. Evenden. "Factors influencing dispersal by flight in bark beetles (Coleoptera: Curculionidae: Scolytinae): from genes to landscapes." Canadian Journal of Forest Research 49, no. 9 (September 2019): 1024–41. http://dx.doi.org/10.1139/cjfr-2018-0304.
Повний текст джерелаАнотація:
Dispersal by flight is obligatory for bark beetles in the subfamily Scolytinae. Adult bark beetles must leave the natal host and fly to seek new hosts for brood production. Because of the eruptive nature of some bark beetle populations, dispersal capacity has implications for beetle spread and invasion across the landscape. Bark beetle dispersal can occur over short distances within a stand or over long distances above the forest canopy, where wind aids dispersal. Despite the obvious importance of dispersal for predicting population spread, knowledge gaps in understanding factors that influence bark beetle dispersal remain. In this review, we synthesize information on bark beetle flight to gain a better understanding of this important life history trait. We assess the impact of genetic, physiological, and morphological traits on flight in different bark beetle species. We also consider the impact of abiotic and biotic environmental conditions on flight. We discuss how measurements of these factors could contribute to the development of comprehensive models to better predict spread of bark beetle populations. Through the synthesis of flight research on a variety of bark beetle species, this review provides suggestions for future avenues of research on this important aspect of bark beetle ecology.
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Pryke, James S., Sven M. Vrdoljak, Paul B. C. Grant, and Michael J. Samways. "Butterfly behavioural responses to natural Bornean tropical rain-forest canopy gaps." Journal of Tropical Ecology 28, no. 1 (December 8, 2011): 45–54. http://dx.doi.org/10.1017/s0266467411000502.
Повний текст джерелаАнотація:
Abstract:Natural tree canopy gaps allow sunlight to penetrate to the forest floor, a major environmental component and resource for many tropical rain-forest species. We compare here how butterflies use sunny areas created by the natural gaps in canopies in comparison with adjacent closed-canopy areas. We chose butterflies as our focal organisms as they are taxonomically tractable and mobile, yet habitat sensitive. Previous studies have shown that butterfly diversity in tropical forests responds to varying degrees of canopy openness. Here we assess butterfly behavioural responses to gaps and equivalent sized closed-canopy patches. Butterfly occupancy time and behaviour were simultaneously observed 61 times in gaps and 61 times in equivalent sized closed-canopy patches across four sites in a tropical rain forest in northern Borneo. Out of the 20 most frequently recorded species, 12 were more frequently recorded or spent more time in gaps, four occurred more frequently in closed-canopy areas, and four showed no significant differences. Overall agonistic, basking, patrolling and resting were more common in gaps compared with the closed canopy. Many butterfly species have complex behavioural requirements for both gaps and closed canopies, with some species using these different areas for different behaviours. Each butterfly species had particular habitat requirements, and needed both canopy gaps and closed canopy areas for ecological and behavioural reasons, emphasizing the need for natural light heterogeneity within these systems.
9
VAN DER MEER, PETER J., FRANK J. STERCK, and FRANS BONGERS. "Tree seedling performance in canopy gaps in a tropical rain forest at Nouragues, French Guiana." Journal of Tropical Ecology 14, no. 2 (March 1998): 119–37. http://dx.doi.org/10.1017/s026646749800011x.
Повний текст джерелаАнотація:
The effect of natural canopy gaps on the performance of naturally occurring tree seedling populations was studied in a tropical rain forest in French Guiana. This was done at two levels of scale. Firstly, on a 20 m × 250 m forest transect intersecting four canopy gaps, it was investigated how patterns of recruitment, growth and survival of seedlings of Cecropia obtusa, Dicorynia guianensis and Pourouma bicolor differed between canopy gaps and closed forest. Secondly, for one large natural canopy gap, performance of seedling cohorts established before (‘pre-gap’ cohorts) and after (‘post-gap’ cohorts) gap formation was studied in relation to environmental heterogeneity. The direct site factor (DSF) was used as an indicator of light availability in the gap zone. Cecropia specialised in large gaps, and also in specific sites within the large gap: seedling performance was increased by light, and by dead wood. Pourouma mainly germinated under closed forest conditions, where it can survive for a long period until a canopy gap is formed nearby. Pourouma seedlings adjusted well to the new gap environment but they did not specialise in specific places within the gap. Seedling location of Pourouma seedlings was mainly determined by accidental positioning before gap formation. Dicorynia was able to germinate both in gaps and under closed forest conditions. Although the number of gaps studied in this study was low, the results show that seedling establishment, early growth and survival of the three tree species were affected by canopy gaps and by the environmental heterogeneity within a large gap.
10
Wedeux, B. M. M., and D. A. Coomes. "Landscape-scale changes in forest canopy structure across a partially logged tropical peat swamp." Biogeosciences 12, no. 22 (November 25, 2015): 6707–19. http://dx.doi.org/10.5194/bg-12-6707-2015.
Повний текст джерелаАнотація:
Abstract. Forest canopy structure is strongly influenced by environmental factors and disturbance, and in turn influences key ecosystem processes including productivity, evapotranspiration and habitat availability. In tropical forests increasingly modified by human activities, the interplay between environmental factors and disturbance legacies on forest canopy structure across landscapes is practically unexplored. We used airborne laser scanning (ALS) data to measure the canopy of old-growth and selectively logged peat swamp forest across a peat dome in Central Kalimantan, Indonesia, and quantified how canopy structure metrics varied with peat depth and under logging. Several million canopy gaps in different height cross-sections of the canopy were measured in 100 plots of 1 km2 spanning the peat dome, allowing us to describe canopy structure with seven metrics. Old-growth forest became shorter and had simpler vertical canopy profiles on deeper peat, consistent with previous work linking deep peat to stunted tree growth. Gap size frequency distributions (GSFDs) indicated fewer and smaller canopy gaps on the deeper peat (i.e. the scaling exponent of Pareto functions increased from 1.76 to 3.76 with peat depth). Areas subjected to concessionary logging until 2000, and illegal logging since then, had the same canopy top height as old-growth forest, indicating the persistence of some large trees, but mean canopy height was significantly reduced. With logging, the total area of canopy gaps increased and the GSFD scaling exponent was reduced. Logging effects were most evident on the deepest peat, where nutrient depletion and waterlogged conditions restrain tree growth and recovery. A tight relationship exists between canopy structure and peat depth gradient within the old-growth tropical peat swamp forest. This relationship breaks down after selective logging, with canopy structural recovery, as observed by ALS, modulated by environmental conditions. These findings improve our understanding of tropical peat swamp ecology and provide important insights for managers aiming to restore degraded forests.
Дисертації з теми "Forest canopy gaps – Environmental aspects"
1
Strojny, Carol. "Effects of Harvest Gaps and Natural Canopy Gaps on Amphibians within a Northeastern Forest." Fogler Library, University of Maine, 2004. http://www.library.umaine.edu/theses/pdf/StrojnyC2004.pdf.
Повний текст джерела
2
Malahlela, Oupa. "Intergrating environmental variables with worldview-2 data to model the probability of occurence of invasive chromolena odata in forest canopy gaps : Dukuduku forest in KwaZulu-Natal, South Africa." Thesis, 2013. http://hdl.handle.net/10413/10562.
Повний текст джерелаАнотація:
Several alien plants are invading subtropical forest ecosystems through canopy gaps,
resulting in the loss of native species biodiversity. The loss of native species in such habitats
may result in reduced ecosystem functioning. The control and eradication of these invaders
requires accurate mapping of the levels of invasion in canopy gaps. Our study tested (i) the
utility of WorldView-2 imagery to map forest canopy gaps, and (ii) an integration of
WorldView-2 data with environmental data to model the probability of occurrence of
invasive Chromolaena odorata (triffid weed) in Dukuduku forest canopy gaps of KwaZulu-
Natal, South Africa. Both pixel-based classification and object-based classification were
explored for the delineation of forest canopy gaps. The overall classification accuracies
increased by ± 12% from a spectrally resampled 4 band image similar to Landsat (74.64%) to
an 8 band WorldView-2 imagery (86.90%). This indicates that the new bands of WorldView
such as the red edge band can improve on the capability of common red, blue, green and
near-infrared bands in delineating forest canopy gaps. The maximum likelihood classifier
(MLC) in pixel-based classification yielded the overall classification accuracy of 86.90% on
an 8 band WorldView-2 image, while the modified plant senescence reflectance index
(mPSRI) in object-based classification yielded 93.69%. The McNemar’s test indicated that
there was a statistical difference between the MLC and the mPSRI. The mPSRI is a
vegetation index that incorporates the use of the red edge band, which solves a saturation
problem common in sensors such as Landsat and SPOT.
An integrated model (with both WorldView-2 data and environmental data) used to predict
the occurrence of Chromolaena odorata in forest gaps yielded a deviance of about 42% (D2 =
0.42), compared to the model derived from environmental data only (D2 = 0.12) and
WorldView-2 data only (D2 = 0.20). A D2 of 0.42 means that a model can explain about 42%
of the variability of the presence/absence of Chromolaena odorata in forest gaps. The
Distance to Stream and Aspect were the significant environmental variables (ρ < 0.05) which
were positively correlated with presence/absence of Chromolaena in forest gaps.
WorldView-2 bands such as the coastal band (λ425 nm) yellow band (λ605 nm) and the nearinfrared-
1 (λ833 nm) are positively and significantly related to the presence/absence of
invasive species (ρ < 0.05). On the other hand, a significant negative correlation (ρ < 0.05) of
near-infrared-2 band (λ950 nm) and the red edge normalized difference vegetation index
(NDVI725) suggests that the probability of occurrence of invasive Chromolaena increases forest gaps with low vegetation density. This study highlights the importance of WorldView-
2 imagery and its application in subtropical indigenous coastal forest monitoring.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.