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1
Vanderbilt, V. C. "Measuring plant canopy structure". Remote Sensing of Environment 18, n. 3 (dicembre 1985): 281–94. http://dx.doi.org/10.1016/0034-4257(85)90063-x.
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Daughtry, Craig S. T. "Direct measurements of canopy structure". Remote Sensing Reviews 5, n. 1 (gennaio 1990): 45–60. http://dx.doi.org/10.1080/02757259009532121.
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Chen, Zhe, Xu Dong Li, Shao Guang Shi, Hong Zhi Jiang e Hui Jie Zhao. "Structured-Light Based Rapid 3D Measurement of Plant Canopy Structure". Applied Mechanics and Materials 701-702 (dicembre 2014): 549–53. http://dx.doi.org/10.4028/www.scientific.net/amm.701-702.549.
Testo completoAbstract (sommario):
Density three dimensional plant canopy structure data has numerous applications in agriculture, but many existing 3D data collection approaches are time-consuming. In this paper, we present a measurement system based on structured-light for plant canopy structure data collection. The structured-light projector projects laser beam reflected by dual-oscillating mirror, arrives to the plant canopy, which is captured by a camera. We propose a new scanning mode, that is, during one exposure time of CCD camera, one mirror keeps moving in high frequency and small angle, while the other one maintains the same position, so that we can get a laser stripe rather than a spot in each image, from which about 100 sub-pixel centers of laser stripe can be extracted. Experiments show that the measurement system can rapid collect three dimensional information of the plant.
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Song, Bo, Jiquan Chen, Paul V. Desander, David D. Reed, Gay A. Bradshaw e Jerry F. Franklin. "Modeling canopy structure and heterogeneity across scales: From crowns to canopy". Forest Ecology and Management 96, n. 3 (settembre 1997): 217–29. http://dx.doi.org/10.1016/s0378-1127(97)00021-2.
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Barradas, Victor L., Hamlyn G. Jones e Jerry A. Clark. "Sunfleck dynamics and canopy structure in a Phaseolus vulgaris L. canopy". International Journal of Biometeorology 42, n. 1 (9 settembre 1998): 34–43. http://dx.doi.org/10.1007/s004840050081.
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Kane, Van R., Rolf F. Gersonde, James A. Lutz, Robert J. McGaughey, Jonathan D. Bakker e Jerry F. Franklin. "Patch dynamics and the development of structural and spatial heterogeneity in Pacific Northwest forests". Canadian Journal of Forest Research 41, n. 12 (dicembre 2011): 2276–91. http://dx.doi.org/10.1139/x11-128.
Testo completoAbstract (sommario):
Over time, chronic small-scale disturbances within forests should create distinct stand structures and spatial patterns. We tested this hypothesis by measuring the structure and spatial arrangement of gaps and canopy patches. We used airborne LiDAR data from 100 sites (cumulative 11.2 km2) in the Pacific Northwest, USA, across a 643 year chronosequence to measure canopy structure, patch and gap diversity, and scales of variance. We used airborne LiDAR’s ability to identify strata in canopy surface height to distinguish patch spatial structures as homogeneous canopy structure, matrix–patch structures, or patch mosaics. We identified six distinct stand structure classes that were associated with the canopy closure, competitive exclusion, maturation, and three patch mosaics stages of late seral forest development. Structural variance peaked in all classes at the tree-to-tree and tree-to-gap scales (10–15 m), but many sites maintained high variance at scales >30 m and up to 200 m, emphasizing the high patch-to-patch heterogeneity. The time required to develop complex patch and gap structures was highly variable and was likely linked to individual site circumstances. The high variance at larger scales appears to be an emergent property that is not a simple propagation of processes observed at smaller spatial scales.
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Lim, Kevin, Paul Treitz, Michael Wulder, Benoît St-Onge e Martin Flood. "LiDAR remote sensing of forest structure". Progress in Physical Geography: Earth and Environment 27, n. 1 (marzo 2003): 88–106. http://dx.doi.org/10.1191/0309133303pp360ra.
Testo completoAbstract (sommario):
Light detection and ranging (LiDAR) technology provides horizontal and vertical information at high spatial resolutions and vertical accuracies. Forest attributes such as canopy height can be directly retrieved from LiDAR data. Direct retrieval of canopy height provides opportunities to model above-ground biomass and canopy volume. Access to the vertical nature of forest ecosystems also offers new opportunities for enhanced forest monitoring, management and planning.
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Valverde, Teresa, e Jonathan Silvertown. "CANOPY CLOSURE RATE AND FOREST STRUCTURE". Ecology 78, n. 5 (luglio 1997): 1555–62. http://dx.doi.org/10.1890/0012-9658(1997)078[1555:ccrafs]2.0.co;2.
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Lang, A. Richard G. "An instrument for measuring canopy structure". Remote Sensing Reviews 5, n. 1 (gennaio 1990): 61–71. http://dx.doi.org/10.1080/02757259009532122.
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FINNIGAN, JOHN J., ROGER H. SHAW e EDWARD G. PATTON. "Turbulence structure above a vegetation canopy". Journal of Fluid Mechanics 637 (7 ottobre 2009): 387–424. http://dx.doi.org/10.1017/s0022112009990589.
Testo completoAbstract (sommario):
We compare the turbulence statistics of the canopy/roughness sublayer (RSL) and the inertial sublayer (ISL) above. In the RSL the turbulence is more coherent and more efficient at transporting momentum and scalars and in most ways resembles a turbulent mixing layer rather than a boundary layer. To understand these differences we analyse a large-eddy simulation of the flow above and within a vegetation canopy. The three-dimensional velocity and scalar structure of a characteristic eddy is educed by compositing, using local maxima of static pressure at the canopy top as a trigger. The characteristic eddy consists of an upstream head-down sweep-generating hairpin vortex superimposed on a downstream head-up ejection-generating hairpin. The conjunction of the sweep and ejection produces the pressure maximum between the hairpins, and this is also the location of a coherent scalar microfront. This eddy structure matches that observed in simulations of homogeneous-shear flows and channel flows by several workers and also fits with earlier field and wind-tunnel measurements in canopy flows. It is significantly different from the eddy structure educed over smooth walls by conditional sampling based only on ejections as a trigger. The characteristic eddy was also reconstructed by empirical orthogonal function (EOF) analysis, when only the dominant, sweep-generating head-down hairpin was recovered, prompting a re-evaluation of earlier results based on EOF analysis of wind-tunnel data. A phenomenological model is proposed to explain both the structure of the characteristic eddy and the key differences between turbulence in the canopy/RSL and the ISL above. This model suggests a new scaling length that can be used to collapse turbulence moments over vegetation canopies.
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Rice, Steven K., Claudia Gutman e Nicholas Krouglicof. "Laser scanning reveals bryophyte canopy structure". New Phytologist 166, n. 2 (25 gennaio 2005): 695–704. http://dx.doi.org/10.1111/j.1469-8137.2005.01327.x.
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Gratani, L., G. de Marco e M. F. Crescente. "Forest Canopy Structure and Light Interaction". Giornale botanico italiano 130, n. 1 (gennaio 1996): 510. http://dx.doi.org/10.1080/11263509609439727.
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Gutiérrez, Álvaro G., Roberto O. Chávez e Ignacio Díaz-Hormazábal. "Canopy Gap Structure as an Indicator of Intact, Old-Growth Temperate Rainforests in the Valdivian Ecoregion". Forests 12, n. 9 (31 agosto 2021): 1183. http://dx.doi.org/10.3390/f12091183.
Testo completoAbstract (sommario):
Forest degradation continues to increase globally, threatening biodiversity and the survival of species. In this context, identifying intact, old-growth forest stands is both urgent and vital to ensure their existence and multiple contributions to society. Despite the global ecological importance of the Valdivian temperate rainforests, they are threatened by forest degradation resulting from constant and intense human use in the region. Identification of remnant intact forests in this region is urgent to global forest protection efforts. In this paper, we analyzed whether forests-canopy alterations due to logging produce a distinctive canopy gap structure (e.g., a gap area and a fraction of canopy gaps in the forest) that can be used to remotely distinguish intact from altered forests. We tested this question by comparing the canopy gap structure of 12 old-growth temperate rainforests in south-central Chile (39–40° S), with different levels of canopy alterations due to logging. At each stand, we obtained aerial or satellite very high spatial-resolution images that were automatically segmented using the Mean-Shift segmentation algorithm. We validated the results obtained remotely with ground data on the canopy gap structure. We found that, in the variables, canopy gap fraction, gap area frequency distribution, and mean gap area could be measured remotely with a high level of accuracy. Intact forests have a distinct canopy gap structure in comparison to forests with canopy alterations due to logging. Our results provided a fast, low-cost, and reliable method to obtain canopy gap structure indicators for mapping and monitoring intact forests in the Valdivian ecoregion. The method provided valuable information for managers interested in maintaining and restoring old-growth forest structures in these southern-temperate rainforests.
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Naka, Luciano Nicolás. "Structure and Organization of Canopy Bird Assemblages in Central Amazonia". Auk 121, n. 1 (1 gennaio 2004): 88–102. http://dx.doi.org/10.1093/auk/121.1.88.
Testo completoAbstract (sommario):
AbstractI analyzed the species composition, structure, and trophic organization of bird assemblages in the forest canopy around Manaus, Brazil. Using three canopy towers located in primary terra firme forests, I conducted 117 censuses over a 13 month period, recording 160 bird species. The three study sites had similar species richness (between 126 and 128 species), sharing 95 species in common, which accounted for >90% of all individual records. Most species recorded in the canopy (110) belonged to the core canopy avifauna. The other 50 species included migrants (13), species that feed overhead (8), species from lower strata (15), night birds (3), and vagrants or visitors from open areas and second-growth forests (11). Most of those species, however, appeared in very low numbers in the forest canopy, except understory frugivores, which regularly fed on canopy fruits. Among the migratory species were some Nearctic (6), Austral (3), and species probably holding both migratory and resident populations in the area (4). Additionally, I found evidence that two species of parrots perform seasonal movements, leaving the forest canopy around Manaus during the dry season. Frugivores dominated the canopy avifauna in abundance, but contradicting results reported from other Neotropical forest canopies, insectivores and frugivores had equal species richness. The canopy avifauna was highly homogeneous among sites in terms of species richness, distribution among abundance classes, and number of species in each feeding guild, habitat, and microhabitat. As in Costa Rica, the canopy avifauna of Manaus was mostly composed by typical canopy bird species, and not by edge-living species as reported from Panama. I suggest that habitat fragmentation may affect the bird community composition in the forest canopy, allowing a higher influx of opportunistic species.
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Chagot, Loïc, Frédéric Moulin, Olivier Eiff e Pierre Elyakime. "Turbulent structure inside and above shallow to deep canopies". E3S Web of Conferences 40 (2018): 05059. http://dx.doi.org/10.1051/e3sconf/20184005059.
Testo completoAbstract (sommario):
Multi-plane PIV measurements were performed in an open-channel flume filled with elongated prisms of height k and width l to investigate the effect of the deepening of the canopy on the flow structure. Velocity measurements were performed both inside the canopy and above it. Analysis of the spatial convergence for the double-averaged quantities shows that for canopy flow investigations (z < k), at least 5 measurement planes are required to obtain a relative spatial convergence error below 3% for the dispersive shear stress, the quantity the most sensible to spatial sampling. With only three measurement planes, the spatial convergence is below 1% only in the flow region above the canopy (z > k). Three canopy aspect ratios, k/l = [1, 3, 6] were investigated for a fixed modified-submergence ratio β = (h - k)=l = 3 where h is the water depth. As the canopy deepens, the hydraulic roughness decreases and the velocity near the bottom of the canopy becomes gradually constant, as expected for deep canopies. We show how the highly converged (both in space and time) profiles of double-averaged longitudinal velocity and total shear stress can be used to calculate the vertical distribution of drag in the canopy. With this methodology, values of the drag coefficient CD(z) can be calculated, and are found to be always close to unity, even in the upper part of the canopy.
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Fahey, Robert T., Jeff W. Atkins, John L. Campbell, Lindsey E. Rustad, Meghan Duffy, Charles T. Driscoll, Timothy J. Fahey e Paul G. Schaberg. "Effects of an experimental ice storm on forest canopy structure". Canadian Journal of Forest Research 50, n. 2 (febbraio 2020): 136–45. http://dx.doi.org/10.1139/cjfr-2019-0276.
Testo completoAbstract (sommario):
Intermediate disturbances are an important component of many forest disturbance regimes, with effects on canopy structure and related functions that are highly dependent on the nature and intensity of the perturbation. Ice storms are an important disturbance mechanism in temperate forests that often result in moderate-severity, diffuse canopy damage. However, it has not previously been possible to distinguish the specific effect of ice storm intensity (as ice accretion) from predisturbance stand characteristics and physiographic factors. In this study, we utilized a novel experimental ice storm treatment to evaluate the effects of variable ice accretion levels on forest canopy structure. Our results verified significant impacts of ice storm disturbance on near-term canopy structural reorganization. Canopy openness, light transmission, and complexity increased significantly relative to predisturbance baselines and undisturbed controls. We documented variable impacts with disturbance intensity, as significant canopy changes largely occurred with ice accretion levels of ≥12.7 mm. Repeated ice storm disturbance (two consecutive years) had marginal, rather than compounding, effects on forest canopy structure. Our findings are relevant to understanding how ice storms can affect near-term forest canopy structural reorganization and ecosystem processes and add to a growing base of knowledge on the effects of intermediate disturbances on canopy structure.
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Ouyang, Jingyun, Roberta De Bei, Sigfredo Fuentes e Cassandra Collins. "UAV and ground-based imagery analysis detects canopy structure changes after canopy management applications". OENO One 54, n. 4 (23 novembre 2020): 1093–103. http://dx.doi.org/10.20870/oeno-one.2020.54.4.3647.
Testo completoAbstract (sommario):
Aim: To analyse unmanned aerial vehicle (UAV)-based imagery to assess canopy structural changes after the application of different canopy management practices in the vineyard.Methods and results: Four different canopy management practices: i–ii) leaf removal within the bunch zone (eastern side/both eastern and western sides), iii) bunch thinning and iv) shoot trimming were applied to grapevines at veraison, in a commercial Cabernet-Sauvignon vineyard in McLaren Vale, South Australia. UAV-based imagery captures were taken: i) before the canopy treatments, ii) after the treatments and iii) at harvest to assess the treatment outcomes. Canopy volume, projected canopy area and normalized difference vegetation index (NDVI) were derived from the analysis of RGB and multispectral imagery collected using the UAV. Plant area index (PAI) was calculated using the smartphone app VitiCanopy as a ground-based measurement for comparison with UAV-derived measurements. Results showed that all three types of UAV-based measurements detected changes in the canopy structure after the application of canopy management practices, except for the bunch thinning treatment. As expected, ground-based PAI was the only technique to effectively detect internal canopy structure changes caused by bunch thinning. Canopy volume and PAI were found to better detect variations in canopy structure compared to NDVI and projected canopy area. The latter were negatively affected by the interference of the trimmed shoots left on the ground.Conclusions: UAV-based tools can provide accurate assessments to some canopy management outcomes at the vineyard scale. Among different UAV-based measurements, canopy volume was more sensitive to changes in canopy structure, compared to NDVI and projected canopy area, and demonstrated a greater potential to assess the outcomes of a range of canopy management practices. Significance and impact of the study: Canopy management practices are widely applied to regulate canopy growth, improve grape quality and reduce disease pressure in the bunch zone. Being able to detect major changes in canopy structure, with some limitations when the practice affects the internal structure (i.e., bunch thinning), UAV-based imagery analysis can be used to measure the outcome of common canopy management practices and it can improve the efficiency of vineyard management.
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Wang, Jizhang, Yun Zhang e Rongrong Gu. "Research Status and Prospects on Plant Canopy Structure Measurement Using Visual Sensors Based on Three-Dimensional Reconstruction". Agriculture 10, n. 10 (8 ottobre 2020): 462. http://dx.doi.org/10.3390/agriculture10100462.
Testo completoAbstract (sommario):
Three-dimensional (3D) plant canopy structure analysis is an important part of plant phenotype studies. To promote the development of plant canopy structure measurement based on 3D reconstruction, we reviewed the latest research progress achieved using visual sensors to measure the 3D plant canopy structure from four aspects, including the principles of 3D plant measurement technologies, the corresponding instruments and specifications of different visual sensors, the methods of plant canopy structure extraction based on 3D reconstruction, and the conclusion and promise of plant canopy measurement technology. In the current research phase on 3D structural plant canopy measurement techniques, the leading algorithms of every step for plant canopy structure measurement based on 3D reconstruction are introduced. Finally, future prospects for a standard phenotypical analytical method, rapid reconstruction, and precision optimization are described.
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Maurer, K. D., G. Bohrer e V. Y. Ivanov. "Large eddy simulations of surface roughness parameter sensitivity to canopy-structure characteristics". Biogeosciences Discussions 11, n. 11 (27 novembre 2014): 16349–89. http://dx.doi.org/10.5194/bgd-11-16349-2014.
Testo completoAbstract (sommario):
Abstract. Surface roughness parameters are at the core of every model representation of the coupling and interactions between land-surface and atmosphere, and are used in every model of surface fluxes. However, most models assume these parameters to be a fixed property of plant functional type and do not vary them in response to spatial or temporal changes to canopy structure. In part, this is due to the difficulty of reducing the complexity of canopy structure and its spatiotemporal dynamic and heterogeneity to less than a handful of parameters describing its effects of atmosphere–surface interactions. In this study we use large-eddy simulations to explore, in silico, the effects of canopy structure characteristics on surface roughness parameters. We performed a virtual experiment to test the sensitivity of resolved surface roughness to four axes of canopy structure: (1) leaf area index, (2) the vertical profile of leaf density, (3) canopy height, and (4) canopy gap fraction. We found roughness parameters to be highly variable, but were able to find positive relationships between displacement height and maximum canopy height, aerodynamic canopy height and maximum canopy height and leaf area index, and eddy-penetration depth and gap fraction. We also found negative relationships between aerodynamic canopy height and gap fraction, and between eddy-penetration depth and maximum canopy height and leaf area index. Using a decade of wind and canopy structure observations in a site in Michigan, we tested the effectiveness of our model-resolved parameters in predicting the frictional velocity over heterogeneous and disturbed canopies. We compared it with three other semi-empirical models and with a decade of meteorological observations. We found that parameterizations with fixed representations of roughness performed relatively well. Nonetheless, some empirical approaches that incorporate seasonal and inter-annual changes to the canopy structure performed even better than models with temporally fixed parameters.
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Maurer, K. D., G. Bohrer, W. T. Kenny e V. Y. Ivanov. "Large-eddy simulations of surface roughness parameter sensitivity to canopy-structure characteristics". Biogeosciences 12, n. 8 (30 aprile 2015): 2533–48. http://dx.doi.org/10.5194/bg-12-2533-2015.
Testo completoAbstract (sommario):
Abstract. Surface roughness parameters, namely the roughness length and displacement height, are an integral input used to model surface fluxes. However, most models assume these parameters to be a fixed property of plant functional type and disregard the governing structural heterogeneity and dynamics. In this study, we use large-eddy simulations to explore, in silico, the effects of canopy-structure characteristics on surface roughness parameters. We performed a virtual experiment to test the sensitivity of resolved surface roughness to four axes of canopy structure: (1) leaf area index, (2) the vertical profile of leaf density, (3) canopy height, and (4) canopy gap fraction. We found roughness parameters to be highly variable, but uncovered positive relationships between displacement height and maximum canopy height, aerodynamic canopy height and maximum canopy height and leaf area index, and eddy-penetration depth and gap fraction. We also found negative relationships between aerodynamic canopy height and gap fraction, as well as between eddy-penetration depth and maximum canopy height and leaf area index. We generalized our model results into a virtual "biometric" parameterization that relates roughness length and displacement height to canopy height, leaf area index, and gap fraction. Using a decade of wind and canopy-structure observations in a site in Michigan, we tested the effectiveness of our model-driven biometric parameterization approach in predicting the friction velocity over heterogeneous and disturbed canopies. We compared the accuracy of these predictions with the friction-velocity predictions obtained from the common simple approximation related to canopy height, the values calculated with large-eddy simulations of the explicit canopy structure as measured by airborne and ground-based lidar, two other parameterization approaches that utilize varying canopy-structure inputs, and the annual and decadal means of the surface roughness parameters at the site from meteorological observations. We found that the classical representation of constant roughness parameters (in space and time) as a fraction of canopy height performed relatively well. Nonetheless, of the approaches we tested, most of the empirical approaches that incorporate seasonal and interannual variation of roughness length and displacement height as a function of the dynamics of canopy structure produced more precise and less biased estimates for friction velocity than models with temporally invariable parameters.
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Wedeux, B. M. M., e D. A. Coomes. "Landscape-scale changes in forest canopy structure across a partially logged tropical peat swamp". Biogeosciences 12, n. 22 (25 novembre 2015): 6707–19. http://dx.doi.org/10.5194/bg-12-6707-2015.
Testo completoAbstract (sommario):
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.
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Wedeux, B. M. M., e D. A. Coomes. "Landscape-scale changes in forest canopy structure across a partially logged tropical peat swamp". Biogeosciences Discussions 12, n. 13 (14 luglio 2015): 10985–1018. http://dx.doi.org/10.5194/bgd-12-10985-2015.
Testo completoAbstract (sommario):
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 interplaying effects of environmental factors and disturbance legacies on forest canopy structure across landscapes are practically unexplored. We used high-fidelity 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, consistently 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 informal 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; 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 the peat deph gradient within the old-growth tropical peat swamp. This relationship breaks down after selective logging, with canopy structural recovery being modulated by environmental conditions.
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Olioso, Albert, Maurice Méthy e Bernard Lacaze. "Simulation of canopy fluorescence as a function of canopy structure and leaf fluorescence". Remote Sensing of Environment 41, n. 2-3 (agosto 1992): 239–47. http://dx.doi.org/10.1016/0034-4257(92)90081-t.
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Ogaya, Romà, e Josep Peñuelas. "Wood vs. Canopy Allocation of Aboveground Net Primary Productivity in a Mediterranean Forest during 21 Years of Experimental Rainfall Exclusion". Forests 11, n. 10 (14 ottobre 2020): 1094. http://dx.doi.org/10.3390/f11101094.
Testo completoAbstract (sommario):
A Mediterranean holm oak forest was subjected to experimental partial rainfall exclusion during 21 consecutive years to study the effects of the expected decrease in water availability for Mediterranean vegetation in the coming decades. Allocation in woody structures and total aboveground allocation were correlated with annual rainfall, whereas canopy allocation and the ratio of wood/canopy allocation were not dependent on rainfall. Fruit productivity was also correlated with annual rainfall, but only in Quercus ilex. In the studied site, there were two types of forest structure: high canopy stand clearly dominated by Quercus ilex, and low canopy stand with more abundance of a tall shrub species, Phillyrea latifolia. In the tall canopy stand, the allocation to woody structures decreased in the experimental rainfall exclusion, but not the allocation to canopy. In the low canopy stand, wood allocation in Quercus ilex was very small in both control and plots with rainfall exclusion, but wood allocation in Phillyrea latifolia was even higher than that obtained in tall canopy plots, especially in the plots receiving the experimental rainfall exclusion. These results highlight likely future changes in the structure and functioning of this ecosystem induced by the decrease in water availability. A serious drop in the capacity to mitigate climate change for this Mediterranean forest can be expected, and the ability of Phillyrea latifolia to take advantage of the limited capacity to cope with drought conditions detected in Quercus ilex makes likely a forthcoming change in species dominance, especially in the low canopy stands.
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Clark, David B., Steven F. Oberbauer, Deborah A. Clark, Michael G. Ryan e Ralph O. Dubayah. "Physical structure and biological composition of canopies in tropical secondary and old-growth forests". PLOS ONE 16, n. 8 (20 agosto 2021): e0256571. http://dx.doi.org/10.1371/journal.pone.0256571.
Testo completoAbstract (sommario):
The area of tropical secondary forests is increasing rapidly, but data on the physical and biological structure of the canopies of these forests are limited. To obtain such data and to measure the ontogeny of canopy structure during tropical rainforest succession, we studied patch-scale (5 m2) canopy structure in three areas of 18–36 year-old secondary forest in Costa Rica, and compared the results to data from old-growth forest at the same site. All stands were sampled with a stratified random design with complete harvest from ground level to the top of the canopy from a modular portable tower. All canopies were organized into distinct high- and low-leaf-density layers (strata), and multiple strata developed quickly with increasing patch height. The relation of total Leaf Area Index (LAI, leaf area per area of ground) to patch canopy height, the existence of distinct high and low leaf- density layers (strata and free air spaces), the depth and LAI of the canopy strata and free air spaces, and the relation of the number of strata to patch canopy height were remarkably constant across the entire successional gradient. Trees were the most important contributor to LAI at all stages, while contribution of palm LAI increased through succession. We hypothesize that canopy physical structure at the patch scale is driven by light competition and discuss how this hypothesis could be tested. That canopy physical structure was relatively independent of the identity of the species present suggests that canopy physical structure may be conserved even as canopy floristics shift due to changing climate.
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Welles, Jon M. "Some indirect methods of estimating canopy structure". Remote Sensing Reviews 5, n. 1 (gennaio 1990): 31–43. http://dx.doi.org/10.1080/02757259009532120.
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Elsheikh, Ahmed, e Christoph Gengnagel. "Structural Assessment of Rapid Deployment Canopy Structure". Advances in Structural Engineering 9, n. 2 (aprile 2006): 241–56. http://dx.doi.org/10.1260/136943306776987029.
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Confalonieri, Roberto, Livia Paleari, Marco Foi, Ermes Movedi, Fosco M. Vesely, William Thoelke, Cristina Agape et al. "PocketPlant3D: Analysing canopy structure using a smartphone". Biosystems Engineering 164 (dicembre 2017): 1–12. http://dx.doi.org/10.1016/j.biosystemseng.2017.09.014.
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Hakkenberg, Christopher R., Hao Tang, Patrick Burns e Scott J. Goetz. "Canopy structure from space using GEDI lidar". Frontiers in Ecology and the Environment 21, n. 1 (febbraio 2023): 55–56. http://dx.doi.org/10.1002/fee.2585.
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Adams, Jennifer, Philip Lewis e Mathias Disney. "Decoupling Canopy Structure and Leaf Biochemistry: Testing the Utility of Directional Area Scattering Factor (DASF)". Remote Sensing 10, n. 12 (29 novembre 2018): 1911. http://dx.doi.org/10.3390/rs10121911.
Testo completoAbstract (sommario):
Biochemical properties retrieved from remote sensing data are crucial sources of information for many applications. However, leaf and canopy scattering processes must be accounted for to reliably estimate information on canopy biochemistry, carbon-cycle processes and energy exchange. A coupled leaf-canopy model based on spectral invariants theory has been proposed, that uses the so-called Directional Area Scattering Factor (DASF) to correct hyperspectral remote sensing data for canopy structural effects. In this study, the reliability of DASF to decouple canopy structure and biochemistry was empirically tested using simulated reflectance spectra modelled using a Monte Carlo Ray Tracing (MCRT) radiative transfer model. This approach allows all canopy and radiative properties to be specified a priori. Simulations were performed under idealised conditions of directional-hemispherical reflectance, isotropic Lambertian leaf reflectance and transmittance and sufficiently dense (high LAI) canopies with black soil where the impact of canopy background is negligible, and also departures from these conditions. It was shown that both DASF and total canopy scattering could be accurately extracted under idealised conditions using information from both the full 400–2500 nm spectral interval and the 710–790 nm interval alone, even given no prior knowledge of leaf optical properties. Departures from these idealised conditions: varying view geometry, bi-directional reflectance, LAI and soil effects, were tested. We demonstrate that total canopy scattering could be retrieved under conditions of varying view geometry and bi-directional reflectance, but LAI and soil effects were shown to reduce the accuracy with which the scattering can be modelled using the DASF approach. We show that canopy architecture, either homogeneous or heterogeneous 3D arrangements of canopy scattering elements, has important influences over DASF and consequently the accuracy of retrieval of total canopy scattering. Finally, although DASF and total canopy scattering could be retrieved to within 2.4% of the modelled total canopy scattering signal given no prior knowledge of leaf optical properties, spectral invariant parameters were not accurately retrieved from the simulated signal. This has important consequences since these parameters are quite widely used in canopy reflectance modelling and have the potential to help derive new, more accurate canopy biophysical information. Understanding and quantifying the limitations of the DASF approach as we have done here, is an important step in allowing the wider use of these methods for decoupling canopy structure and biochemistry.
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Ozturk, Nazmiye. "A workshop on the design of canopy structures". New Trends and Issues Proceedings on Humanities and Social Sciences 2, n. 1 (19 febbraio 2016): 478–85. http://dx.doi.org/10.18844/prosoc.v2i1.333.
Testo completoAbstract (sommario):
This paper is related to a workshop implemented in Anadolu University, Faculty of Architecture and Design. The “Canopy Structure Design Workshop†lasts 4 weeks. The mentioned workshop was done with a group of 70 2nd year undergraduate students. 14 teams of 5 were made out of these students. They were asked to develop their projects with models. At the end of the process, the students made 14 canopy structures of wood with a 1:1 scale. Some of these are called Flexible Structure, Armadillo and Tensegrity. This study comprises the photographs and evaluations of the designs obtained at the end of the “Canopy Structure Design Workshopâ€. In the assertion is explained the positive and negative properties of these designs.Keywords: structural design, canopy structure design, design education, evaluation of students projects
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Huang, Zhi-Cheng, Wen-Yang Hsu e Jay Yang. "OBSERVATIONS OF CANOPY FLOW STRUCTURE AND FRICTIONAL VELOCITY OF CORAL COLONIES IN DONGSHA ATOLL". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 15. http://dx.doi.org/10.9753/icce.v36.currents.15.
Testo completoAbstract (sommario):
Understanding the hydrodynamics is important for biological, ecological, and biogeochemical processes in coral reef systems. The near-bed flow motion affects the benthic organism distributions, morphological evolution, larvae settlement, and nutrient uptake. The near-bed flow structures have been characterized as planar boundary-layer flows when the bottom roughness scale created by benthic organisms is much smaller than the water depth. On the other hand, when the bottom roughness scale becomes much larger, the resistance drag forces caused by these canopy elements should be considered (Rosman and Hench, 2011). The form drag of the multiple coral colonies generates turbulent wakes, enhances turbulent mixing, and changes the flow structure (Huang, 2015). Many laboratory and modeling studies have reported the drag parameterization and the flow structure for unidirectional flows through submerged canopy or vegetation (e.g., Finnigan, 2000; among many others). However, the vertical flow structures of the canopy layer caused by coral colonies (bommies) are rarely reported in fields. Here we present field measurements of flow structure over coral colonies using acoustic Doppler velocimetry (ADV) and pulse-coherent Doppler velocity profiler (PCADP) techniques. The measured current profiles and turbulence are used to study the flow dynamics in the canopy-layer created by coral colonies.
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Ji, Yongjie, Jimao Huang, Yilin Ju, Shipeng Guo e Cairong Yue. "Forest structure dependency analysis of L-band SAR backscatter". PeerJ 8 (30 settembre 2020): e10055. http://dx.doi.org/10.7717/peerj.10055.
Testo completoAbstract (sommario):
Forest structure plays an important role in forest biomass inversion using synthetic aperture radar (SAR) backscatter. Synthetic aperture radar (SAR) sensors with long-wavelength have the potentiality to provide reliable and timely forest biomass inversion for their ability of deep penetration into the forest. L-band SAR backscatter shows useful for forest above-ground biomass (AGB) estimation. However, the way that forest structure mediating the biomass-backscatter affects the improvement of the related biomass estimation accuracy. In this paper, we have investigated L-band SAR backscatter sensitivity to forests with different mean canopy density, mean tree height and mean DBH (diameter at breast height) at the sub-compartment level. The forest species effects on their relationship were also considered in this study. The linear correlation coefficient R, non-linear correlation parameter, Maximal Information Coefficient (MIC), and the determination coefficient R2 from linear function, Logarithmic function and Quadratic function were used in this study to analyze forest structural properties effects on L-band SAR backscatter. The HV channel, which is more sensitive than HH to forest structure parameters, was chosen as the representative of SAR backscatter. 6037 sub-compartment were involved in the analysis. Canopy density showed a great influence on L-band backscatter than mean forest height and DBH. All of the R between canopy density and L-band backscatter were greater than 0.7 during the forest growth cycle. The sensitivity of L-band backscatter to mean forest height depends on forest canopy density. When canopy density was lower than 0.4, R values between mean forest height are smaller than 0.5. In contrast, the values of R were greater than 0.8 if canopy density was higher than 0.4. The sensitivity SAR backscatter to DBH fluctuated with canopy density, but it only showed obvious sensitivity when canopy density equals to 0.6, where both the linear and non-liner correlation values are higher than others. However, their effects on L-bang HV backscatter are affected by forest species, the effects on three forest structural parameters depend on tree species.
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Russell, Micah, Jan U. H. Eitel, Timothy E. Link e Carlos A. Silva. "Important Airborne Lidar Metrics of Canopy Structure for Estimating Snow Interception". Remote Sensing 13, n. 20 (19 ottobre 2021): 4188. http://dx.doi.org/10.3390/rs13204188.
Testo completoAbstract (sommario):
Forest canopies exert significant controls over the spatial distribution of snow cover. Canopy snow interception efficiency is controlled by intrinsic processes (e.g., canopy structure), extrinsic processes (e.g., meteorological conditions), and the interaction of intrinsic-extrinsic factors (i.e., air temperature and branch stiffness). In hydrological models, intrinsic processes governing snow interception are typically represented by two-dimensional metrics like the leaf area index (LAI). To improve snow interception estimates and their scalability, new approaches are needed for better characterizing the three-dimensional distribution of canopy elements. Airborne laser scanning (ALS) provides a potential means of achieving this, with recent research focused on using ALS-derived metrics that describe forest spacing to predict interception storage. A wide range of canopy structural metrics that describe individual trees can also be extracted from ALS, although relatively little is known about which of them, and in what combination, best describes intrinsic canopy properties known to affect snow interception. The overarching goal of this study was to identify important ALS-derived canopy structural metrics that could help to further improve our ability to characterize intrinsic factors affecting snow interception. Specifically, we sought to determine how much variance in canopy intercepted snow volume can be explained by ALS-derived crown metrics, and what suite of existing and novel crown metrics most strongly affects canopy intercepted snow volume. To achieve this, we first used terrestrial laser scanning (TLS) to quantify snow interception on 14 trees. We then used these snow interception measurements to fit a random forest model with ALS-derived crown metrics as predictors. Next, we bootstrapped 1000 calculations of variable importance (percent increase in mean squared error when a given explanatory variable is removed), keeping nine canopy metrics for the final model that exceeded a variable importance threshold of 0.2. ALS-derived canopy metrics describing intrinsic tree structure explained approximately two-thirds of the snow interception variability (R2 ≥ 0.65, RMSE ≤ 0.52 m3, relative RMSE ≤ 48%) in our study when extrinsic factors were kept as constant as possible. For comparison, a generalized linear mixed-effects model predicting snow interception volume from LAI alone had a marginal R2 = 0.01. The three most important predictor variables were canopy length, whole-tree volume, and unobstructed returns (a novel metric). These results suggest that a suite of intrinsic variables may be used to map interception potential across larger areas and provide an improvement to interception estimates based on LAI.
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Tanioka, Yosuke, Hideyuki Ida e Mitsuru Hirota. "Relationship between Canopy Structure and Community Structure of the Understory Trees in a Beech Forest in Japan". Forests 13, n. 4 (22 marzo 2022): 494. http://dx.doi.org/10.3390/f13040494.
Testo completoAbstract (sommario):
Understory trees occupy a spatially heterogeneous light environment owing to light interception by patchily distributed canopy leaves. We examined the spatial distribution of canopy leaves and the spatial structure of the understory tree community (height < 5 m) and their relationships in a beech forest in Nagano, Japan. We measured the canopy leaf area index (LAI) at 10 m intervals (n = 81) in a permanent research plot (1 ha). We established a circular subplot centered on each LAI measurement point, and determined the species composition and the aboveground net primary production of wood (ANPPW) of the understory tree community by using tree size data from an open database in the Monitoring Sites 1000 project. There was a significant negative correlation between canopy LAI and the ANPPW of understory trees and a significant positive correlation between the ANPPW of understory and understory tree density. The dominant species of understory trees differed between subplots with high and low LAI values. Our results suggest that niche differentiation allows trees in the understory community to make use of various light conditions, thereby enhancing the primary productivity of the entire community.
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Kuester, Theres, e Daniel Spengler. "Structural and Spectral Analysis of Cereal Canopy Reflectance and Reflectance Anisotropy". Remote Sensing 10, n. 11 (8 novembre 2018): 1767. http://dx.doi.org/10.3390/rs10111767.
Testo completoAbstract (sommario):
The monitoring of agricultural areas is one of the most important topics for remote sensing data analysis, especially to assist food security in the future. To improve the quality and quantify uncertainties, it is of high relevance to understand the spectral reflectivity regarding the structural and spectral properties of the canopy. The importance of understanding the influence of plant and canopy structure is well established, but, due to the difficulty of acquiring reflectance data from numerous differently structured canopies, there is still a need to study the structural and spectral dependencies affecting top-of-canopy reflectance and reflectance anisotropy. This paper presents a detailed study dealing with two fundamental issues: (1) the influence of plant and canopy architecture changes due to crop phenology on nadir acquired cereal top-of-canopy reflectance, and (2) the anisotropic reflectance of cereal top-of-canopy reflectance and its inter-annual variations as affected by varying contents of biochemical constituents and changes on canopy structure across green phenological stages between tillering and inflorescence emergence. All of the investigations are based on HySimCaR, a computer-based approach using 3D canopy models and Monte Carlo ray tracing (drat). The achieved results show that the canopy architecture significantly influences top-of-canopy reflectance and the bidirectional reflectance function (BRDF) in the VNIR (visible and near infrared), and SWIR (shortwave infrared) wavelength ranges. In summary, it can be said that the larger the fraction of the radiation reflected by the plants, the stronger is the influence of the canopy structure on the reflectance signal. A significant finding for the anisotropic reflectance is that the relative row orientation of the cereal canopies is mapped in the 3D-shape of the BRDF. Summarised, this study provides fundamental knowledge for improving the retrieval of biophysical vegetation parameters of agricultural areas for current and upcoming sensors with large FOV (field of view) with respect to the quantification of uncertainties.
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Gao, Qiong, e Mei Yu. "Elevation Regimes Modulated the Responses of Canopy Structure of Coastal Mangrove Forests to Hurricane Damage". Remote Sensing 14, n. 6 (20 marzo 2022): 1497. http://dx.doi.org/10.3390/rs14061497.
Testo completoAbstract (sommario):
Mangrove forests have unique ecosystem functions and services, yet the coastal mangroves in tropics are often disturbed by tropical cyclones. Hurricane Maria swept Puerto Rico and nearby Caribbean islands in September 2017 and caused tremendous damage to the coastal mangrove systems. Understanding the vulnerability and resistance of mangrove forests to disturbances is pivotal for future restoration and conservation. In this study, we used LiDAR point clouds to derive the canopy height of five major mangrove forests, including true mangroves and mangrove associates, along the coast of Puerto Rico before and after the hurricanes, which allowed us to detect the spatial variations of canopy height reduction. We then spatially regressed the pre-hurricane canopy height and the canopy height reduction on biophysical factors such as the elevation, the distance to rivers/canals within and nearby, the distance to coast, tree density, and canopy unevenness. The analyses resulted in the following findings. The pre-hurricane canopy height increased with elevation when elevation was low and moderate but decreased with elevation when elevation was high. The canopy height reduction increased quadratically with the pre-hurricane canopy height, but decreased with elevation for the four sites dominated by true mangroves. The site of Palma del Mar dominated by Pterocarpus, a mangrove associate, experienced the strongest wind, and the canopy height reduction increased with elevation. The canopy height reduction decreased with the distance to rivers/canals only for sites with low to moderate mean elevation of 0.36–0.39 m. In addition to the hurricane winds, the rainfall during hurricanes is an important factor causing canopy damage by inundating the aerial roots. In summary, the pre-hurricane canopy structures, physical environment, and external forces brought by hurricanes interplayed to affect the vulnerability of coastal mangroves to major hurricanes.
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Brygadyrenko, Viktor V. "Effect of canopy density on litter invertebrate community structure in pine forests". Ekológia (Bratislava) 35, n. 1 (1 marzo 2016): 90–102. http://dx.doi.org/10.1515/eko-2016-0007.
Testo completoAbstract (sommario):
Abstract We investigated the structure of the litter invertebrate community in 141 pine (Pinus sylvestris Linnaeus, 1753) forest sites with five variants of canopy density (30-44, 45-59, 60-74, 75-89 and 90-100%) in the steppe zone of Ukraine. The total number of litter macrofauna specimens collected at each site decreased from an average of 84/100 trap-days in the sparsest stands (30-40% density) to 4-39 specimens/100 trap-days in the forests with a denser canopy. The number of macrofauna species caught in the pitfall traps does not vary significantly with different degrees of canopy density. The Shannon-Weaver and Pielou diversity indexes show increases corresponding to increasing stages of canopy density. The average share of phytophages in the trophic structure of the litter macrofauna does not vary with canopy density. The relative number of saprophages decreases from 54% in the forests with the sparsest canopy to 11-13% in the forests with denser canopies. The relative number of saprophages in pine forests (22%) is lower than that in deciduous forests (40%). The share of zoophages in the trophic structure of the litter macrofauna increases significantly with the increase in the pine forest canopy density (from 21% in the sparsest plots to 59% in the densest). The relative number of polyphages is highest (47-65%) when the canopy density is 45-89%. At canopy densities below or above this range, the share of polyphages in the community decreases to 20 and 24%, respectively. Regardless of canopy density, Formicidae and Lycosidae invariably rank amongst the first three dominant families. Nine families of invertebrates dominate in the pine forest stands with the highest density (90-100%), and 5-7 families dominate in the stands with lower density. For the pine forest litter macrofauna, we have observed an extreme simplification of the community size structure compared with natural and planted deciduous forests of the steppe zone of Ukraine.
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Lertzman, Kenneth P., e Charles J. Krebs. "Gap-phase structure of a subalpine old-growth forest". Canadian Journal of Forest Research 21, n. 12 (1 dicembre 1991): 1730–41. http://dx.doi.org/10.1139/x91-239.
Testo completoAbstract (sommario):
We examined four stands in a subalpine old-growth forest in the Coast Mountains of southwestern British Columbia for gap-phase structure. Though the stands varied in the proportions of each species, all had a similar distribution of area under closed canopy and in gaps (overall means: 29% closed canopy, 52% expanded gap, 18% canopy gap). Median areas of canopy gaps and expanded gaps were 41 and 203 m2, respectively. Most gaps (90%) had more than one gap maker, and gap makers within a gap were often from mortality events separated in time. Half of all gap makers died standing, and only 13% were windthrown. Pacific silver fir (Abiesamabilis (Dougl.) Forbes) was represented among gap makers in a much higher proportion than among canopy trees in general (64 vs. 45%). The estimated forest turnover time varied from 280–1000 years, depending on assumptions about the time taken for gaps to be filled. Distinctive features of gap-phase structure and dynamics in this forest are the high proportion of area in gap, small gap size, multiple gap makers of varying stages of decay, and long tenure of gaps before they are filled.
40
Tang, Hao, e Ralph Dubayah. "Light-driven growth in Amazon evergreen forests explained by seasonal variations of vertical canopy structure". Proceedings of the National Academy of Sciences 114, n. 10 (21 febbraio 2017): 2640–44. http://dx.doi.org/10.1073/pnas.1616943114.
Testo completoAbstract (sommario):
Light-regime variability is an important limiting factor constraining tree growth in tropical forests. However, there is considerable debate about whether radiation-induced green-up during the dry season is real, or an apparent artifact of the remote-sensing techniques used to infer seasonal changes in canopy leaf area. Direct and widespread observations of vertical canopy structures that drive radiation regimes have been largely absent. Here we analyze seasonal dynamic patterns between the canopy and understory layers in Amazon evergreen forests using observations of vertical canopy structure from a spaceborne lidar. We discovered that net leaf flushing of the canopy layer mainly occurs in early dry season, and is followed by net abscission in late dry season that coincides with increasing leaf area of the understory layer. Our observations of understory development from lidar either weakly respond to or are not correlated to seasonal variations in precipitation or insolation, but are strongly related to the seasonal structural dynamics of the canopy layer. We hypothesize that understory growth is driven by increased light gaps caused by seasonal variations of the canopy. This light-regime variability that exists in both spatial and temporal domains can better reveal the drought-induced green-up phenomenon, which appears less obvious when treating the Amazon forests as a whole.
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Olvera-Vargas, Miguel, Blanca L. Figueroa-Rangel e Christiam Solís Robles. "Floristic composition, structure and environmental characterization of Cyathea costaricensis population in a remnant cloud forest in Mexico". Revista de Biología Tropical 69, n. 3 (21 settembre 2021): 1079–97. http://dx.doi.org/10.15517/rbt.v69i3.47359.
Testo completoAbstract (sommario):
Introduction: Tree ferns are significant components of temperate, tropical and subtropical forests, contributing to shape complex forest stand structures. Objectives: 1) to describe the population structure of Cyathea costaricensis in a remnant cloud forest of West-central Mexico; 2) to characterize and relate the floristic composition and the structure of the most important tree species associated to the C. costaricensis population and; 3) to describe the environment where C. costaricensis occurs. Methods: We estimated the Importance Value Index (IVI) to select the most important canopy-dominant species associated to C. costaricensis; we constructed height and Diameter at Breast Height (DBH) frequency distributions for those selected species according to IVI as well as for C. costaricensis population; we computed the asymmetry of the frequency distributions through the coefficient of skewness and the probability density function via the Kernel density estimation. We tested for differences between canopy-dominant tree species and C. costaricensis population structure by the non-parametric Wilcoxon rank sum test. Results: C. costaricensis individuals presented the smallest heights and intermediate DBH sizes as compared with the canopy-dominant species, with statistically significant differences for height but not for DBH according to the Wilcoxon test. Most of the tree fern individuals were located in uneven terrains and over the base slope of the terrain; canopy openness and Total Radiation Under the Canopy values were similar to those reported for Cyathea species elsewhere. Conclusions: We confirm the hypothesis of comparable structure between the canopy-dominant species and the C. costaricensis population only for DBH; on the contrary, for trunk height, there were statistically significant differences; the small heights of C. costaricensis suggest their coexistence in the understory through sheltering from the taller canopy-dominants. Mostly all individuals of C. costaricensis were confined to local environmental conditions, particularly to physiography.
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RIKHARI, H. C., L. M. S. PALNI, S. SHARMA e S. K. NANDI. "Himalayan yew: stand structure, canopy damage, regeneration and conservation strategy". Environmental Conservation 25, n. 4 (dicembre 1998): 334–41. http://dx.doi.org/10.1017/s0376892998000411.
Testo completoAbstract (sommario):
Taxus baccata L. subsp. wallichiana (Zucc.) Pilger has come into prominence in recent times due to its uncontrolled harvesting from the Himalayan wilds for the extraction of the anti-cancer drug Taxol. It is a very slow growing tree with poor regeneration, and the extent of canopy damage is likely to have serious consequences on biomass yield, plant survival and natural regeneration by affecting 'seed' output. The present study in the Jageshwar area of the Central Himalaya aimed to determine the stand and canopy structure, microsite characteristics, extent of canopy removal, and regeneration in human-disturbed and undisturbed sites. The number of trees, saplings and seedlings varied amongst plots. Leaf area index and canopy volume increased with increasing circumference at breast height. Of the total canopy volume, 57.4% was found to have been removed from the study area (9.54 ha; representing about 8% of the total T. baccata habitat). Regeneration of the species was found to be better in moist and shady microsites at undisturbed locations than in disturbed sites. Efforts made thus far for its conservation, and future strategies are discussed.
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Maimaitijiang, Maitiniyazi, Vasit Sagan, Paheding Sidike, Ahmad M. Daloye, Hasanjan Erkbol e Felix B. Fritschi. "Crop Monitoring Using Satellite/UAV Data Fusion and Machine Learning". Remote Sensing 12, n. 9 (25 aprile 2020): 1357. http://dx.doi.org/10.3390/rs12091357.
Testo completoAbstract (sommario):
Non-destructive crop monitoring over large areas with high efficiency is of great significance in precision agriculture and plant phenotyping, as well as decision making with regards to grain policy and food security. The goal of this research was to assess the potential of combining canopy spectral information with canopy structure features for crop monitoring using satellite/unmanned aerial vehicle (UAV) data fusion and machine learning. Worldview-2/3 satellite data were tasked synchronized with high-resolution RGB image collection using an inexpensive unmanned aerial vehicle (UAV) at a heterogeneous soybean (Glycine max (L.) Merr.) field. Canopy spectral information (i.e., vegetation indices) was extracted from Worldview-2/3 data, and canopy structure information (i.e., canopy height and canopy cover) was derived from UAV RGB imagery. Canopy spectral and structure information and their combination were used to predict soybean leaf area index (LAI), aboveground biomass (AGB), and leaf nitrogen concentration (N) using partial least squares regression (PLSR), random forest regression (RFR), support vector regression (SVR), and extreme learning regression (ELR) with a newly proposed activation function. The results revealed that: (1) UAV imagery-derived high-resolution and detailed canopy structure features, canopy height, and canopy coverage were significant indicators for crop growth monitoring, (2) integration of satellite imagery-based rich canopy spectral information with UAV-derived canopy structural features using machine learning improved soybean AGB, LAI, and leaf N estimation on using satellite or UAV data alone, (3) adding canopy structure information to spectral features reduced background soil effect and asymptotic saturation issue to some extent and led to better model performance, (4) the ELR model with the newly proposed activated function slightly outperformed PLSR, RFR, and SVR in the prediction of AGB and LAI, while RFR provided the best result for N estimation. This study introduced opportunities and limitations of satellite/UAV data fusion using machine learning in the context of crop monitoring.
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Olson, B. E., R. T. Wallander e J. M. Beaver. "Comparing nondestructive measures of forage structure and phytomass". Canadian Journal of Plant Science 80, n. 3 (1 luglio 2000): 565–73. http://dx.doi.org/10.4141/p99-073.
Testo completoAbstract (sommario):
Nondestructive radiative transfer and canopy volume methods were compared with the destructive hand-clipping method to determine forage structure and phytomass. On a native range site, fifteen 1-m2 circular plots were located at each of five microsites. On a crested wheatgrass site, thirty 1-m2 plots were located in grazed and in ungrazed areas. At peak standing crop, all plots were measured with a LI-COR Plant Canopy Analyzer to determine leaf area index (LAI), diffuse non-intercepted radiation (DNIR), and mean tilt angle (MTA) of leaves. Then, plants within plots were measured with a ruler to determine volume. Finally, all phytomass within plots was harvested. At the native range site, plant volume was related with LAI and DNIR on four of five microsites. Phytomass was related with LAI and DNIR on two microsites. At the crested wheatgrass site, volume and phytomass were related with LAI, DNIR, and MTA on grazed plots. Only phytomass was related with LAI and DNIR on ungrazed plots. The Plant Canopy Analyzer measures canopy structure and phytomass; it is fast, and its data are transferred directly to a computer. Measuring plant volume is inexpensive and requires minimal training. Determining phytomass by clipping is accurate and requires minimal training, but it is time-consuming and destructive. Key words: Leaf area, canopy, volume, phytomass, radiative transfer
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Davies, Andrew B., Marc Ancrenaz, Felicity Oram e Gregory P. Asner. "Canopy structure drives orangutan habitat selection in disturbed Bornean forests". Proceedings of the National Academy of Sciences 114, n. 31 (18 luglio 2017): 8307–12. http://dx.doi.org/10.1073/pnas.1706780114.
Testo completoAbstract (sommario):
The conservation of charismatic and functionally important large species is becoming increasingly difficult. Anthropogenic pressures continue to squeeze available habitat and force animals into degraded and disturbed areas. Ensuring the long-term survival of these species requires a well-developed understanding of how animals use these new landscapes to inform conservation and habitat restoration efforts. We combined 3 y of highly detailed visual observations of Bornean orangutans with high-resolution airborne remote sensing (Light Detection and Ranging) to understand orangutan movement in disturbed and fragmented forests of Malaysian Borneo. Structural attributes of the upper forest canopy were the dominant determinant of orangutan movement among all age and sex classes, with orangutans more likely to move in directions of increased canopy closure, tall trees, and uniform height, as well as avoiding canopy gaps and moving toward emergent crowns. In contrast, canopy vertical complexity (canopy layering and shape) did not affect movement. Our results suggest that although orangutans do make use of disturbed forest, they select certain canopy attributes within these forests, indicating that not all disturbed or degraded forest is of equal value for the long-term sustainability of orangutan populations. Although the value of disturbed habitats needs to be recognized in conservation plans for wide-ranging, large-bodied species, minimal ecological requirements within these habitats also need to be understood and considered if long-term population viability is to be realized.
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Roşca, Sabina, Juha Suomalainen, Harm Bartholomeus e Martin Herold. "Comparing terrestrial laser scanning and unmanned aerial vehicle structure from motion to assess top of canopy structure in tropical forests". Interface Focus 8, n. 2 (16 febbraio 2018): 20170038. http://dx.doi.org/10.1098/rsfs.2017.0038.
Testo completoAbstract (sommario):
Terrestrial laser scanning (TLS) and unmanned aerial vehicles (UAVs) equipped with digital cameras have attracted much attention from the forestry community as potential tools for forest inventories and forest monitoring. This research fills a knowledge gap about the viability and dissimilarities of using these technologies for measuring the top of canopy structure in tropical forests. In an empirical study with data acquired in a Guyanese tropical forest, we assessed the differences between top of canopy models (TCMs) derived from TLS measurements and from UAV imagery, processed using structure from motion. Firstly, canopy gaps lead to differences in TCMs derived from TLS and UAVs. UAV TCMs overestimate canopy height in gap areas and often fail to represent smaller gaps altogether. Secondly, it was demonstrated that forest change caused by logging can be detected by both TLS and UAV TCMs, although it is better depicted by the TLS. Thirdly, this research shows that both TLS and UAV TCMs are sensitive to the small variations in sensor positions during data collection. TCMs rendered from UAV data acquired over the same area at different moments are more similar (RMSE 0.11–0.63 m for tree height, and 0.14–3.05 m for gap areas) than those rendered from TLS data (RMSE 0.21–1.21 m for trees, and 1.02–2.48 m for gaps). This study provides support for a more informed decision for choosing between TLS and UAV TCMs to assess top of canopy in a tropical forest by advancing our understanding on: (i) how these technologies capture the top of the canopy, (ii) why their ability to reproduce the same model varies over repeated surveying sessions and (iii) general considerations such as the area coverage, costs, fieldwork time and processing requirements needed.
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Zhan, Dongxia, Chao Zhang, Ying Yang, Honghai Luo, Yali Zhang e Wangfeng Zhang. "Water Deficit Alters Cotton Canopy Structure and Increases Photosynthesis in the Mid-Canopy Layer". Agronomy Journal 107, n. 5 (settembre 2015): 1947–57. http://dx.doi.org/10.2134/agronj14.0426.
Testo completo
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van Leeuwen, Martin, Nicholas C. Coops, Thomas Hilker, Michael A. Wulder, Glenn J. Newnham e Darius S. Culvenor. "Automated reconstruction of tree and canopy structure for modeling the internal canopy radiation regime". Remote Sensing of Environment 136 (settembre 2013): 286–300. http://dx.doi.org/10.1016/j.rse.2013.04.019.
Testo completo
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Thornton, Peter E., e Niklaus E. Zimmermann. "An Improved Canopy Integration Scheme for a Land Surface Model with Prognostic Canopy Structure". Journal of Climate 20, n. 15 (1 agosto 2007): 3902–23. http://dx.doi.org/10.1175/jcli4222.1.
Testo completoAbstract (sommario):
Abstract A new logical framework relating the structural and functional characteristics of a vegetation canopy is presented, based on the hypothesis that the ratio of leaf area to leaf mass (specific leaf area) varies linearly with overlying leaf area index within the canopy. Measurements of vertical gradients in specific leaf area and leaf carbon:nitrogen ratio for five species (two deciduous and three evergreen) in a temperate climate support this hypothesis. This new logic is combined with a two-leaf (sunlit and shaded) canopy model to arrive at a new canopy integration scheme for use in the land surface component of a climate system model. An inconsistency in the released model radiation code is identified and corrected. Also introduced here is a prognostic canopy model with coupled carbon and nitrogen cycle dynamics. The new scheme is implemented within the Community Land Model and tested in both diagnostic and prognostic canopy modes. The new scheme increases global gross primary production by 66% (from 65 to 108 Pg carbon yr−1) for diagnostic model simulations driven with reanalysis surface weather, with similar results (117 PgC yr−1) for the new prognostic model. Comparison of model predictions to global syntheses of observations shows generally good agreement for net primary productivity (NPP) across a range of vegetation types, with likely underestimation of NPP in tundra and larch communities. Vegetation carbon stocks are higher than observed in forest systems, but the ranking of stocks by vegetation type is accurately captured.
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Wang, Zhihui, Andrew K. Skidmore, Tiejun Wang, Roshanak Darvishzadeh, Uta Heiden, Marco Heurich, Hooman Latifi e John Hearne. "Canopy foliar nitrogen retrieved from airborne hyperspectral imagery by correcting for canopy structure effects". International Journal of Applied Earth Observation and Geoinformation 54 (febbraio 2017): 84–94. http://dx.doi.org/10.1016/j.jag.2016.09.008.
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