Reflections in Bumpy Terrain: Implications of Canopy Surface Variations for the Radiation Balance of Vegetation

Ogunjemiyo, Segun; Parker, Geoffrey G.; Roberts, David C.

doi:10.1109/lgrs.2004.841418

Cited by 26 publications

(19 citation statements)

References 23 publications

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“…Changes in canopy structure which rearrange leaf area within the canopy have implications for canopy light interception and thus carbon storage rates [8,9,[40][41][42][43]. Such patterns were observed in a hemlock-dominated forest in southern Appalachia, where growth of successor species increased due to increased light availability in the first two years following mortality of Eastern hemlock [37] and similar results in numerous stand thinning experiments document increased stand production rates [12,13,18,32,33,36,37,39,[44][45][46][47]. These studies document ecosystem functional resilience to partial stand disturbance despite mortality rates of canopy dominants approaching 40%, and attribute such resilience to redistribution of light in the canopy and rearrangement of foliage such that light interception and canopy carbon uptake rates do not decline in proportion to disturbance.…”

Section: Functional Consequencesmentioning

confidence: 85%

Canopy Structural Changes Following Widespread Mortality of Canopy Dominant Trees

Hardiman

Bohrer

Gough

et al. 2013

Forests

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Abstract:Canopy structure affects forest function by determining light availability and distribution. Many forests throughout the upper Great Lakes region are dominated by mature, even-aged, early successional aspen and birch, which comprise 35%-40% of canopy leaf area, and which are senescing at accelerating rates. In 2008 at the University of Michigan Biological Station, we initiated the Forest Accelerated Succession ExperimenT (FASET) by stem girdling all aspen and birch in replicated stands to induce mortality. Our objective was to understand type and rate of canopy structural changes imposed by rapid but diffuse disturbance consisting of mortality of a single age-species cohort. We characterized changes in canopy structural features in 2008-2011 using ground-based Portable Canopy Lidar (PCL) in paired treated and control stands. As aspen and birch in treated plots died, gap fraction of the upper canopy increased, average leaf height decreased, total canopy height declined, and openness of the whole-canopy increased. All of these trends became more pronounced with time. Our findings suggest that as forests throughout the region pass through the impending successional transition prompted by widespread mortality of canopy-dominant early successional aspen and birch species, the canopy will undergo significant structural reorganization with consequences for forest carbon assimilation. OPEN ACCESSForests 2013, 4 538

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Section: Functional Consequencesmentioning

confidence: 85%

Canopy Structural Changes Following Widespread Mortality of Canopy Dominant Trees

Hardiman

Bohrer

Gough

et al. 2013

Forests

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“…When compared with earlier stages of succession, lower albedos have been observed for mature forests throughout the world, including boreal (Amiro et al 2006), temperate (Roberts et al 2004;Ogunjemiyo et al 2005) and tropical forests (Culf et al 1995;Giambelluca et al 1997). High rates of evaporative fluxes (i.e.…”

Section: Discussionmentioning

confidence: 99%

Trends in entropy production during ecosystem development in the Amazon Basin

Holdaway

Sparrow

Coomes

2010

Phil. Trans. R. Soc. B

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Understanding successional trends in energy and matter exchange across the ecosystematmosphere boundary layer is an essential focus in ecological research; however, a general theory describing the observed pattern remains elusive. This paper examines whether the principle of maximum entropy production could provide the solution. A general framework is developed for calculating entropy production using data from terrestrial eddy covariance and micrometeorological studies. We apply this framework to data from eight tropical forest and pasture flux sites in the Amazon Basin and show that forest sites had consistently higher entropy production rates than pasture sites (0.461 versus 0.422 W m 22 K 21 , respectively). It is suggested that during development, changes in canopy structure minimize surface albedo, and development of deeper root systems optimizes access to soil water and thus potential transpiration, resulting in lower surface temperatures and increased entropy production. We discuss our results in the context of a theoretical model of entropy production versus ecosystem developmental stage. We conclude that, although further work is required, entropy production could potentially provide a much-needed theoretical basis for understanding the effects of deforestation and land-use change on the land-surface energy balance.

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“…Average radiometric variation ranged from 2.0%-5.9% and was correlated with the mean rugosity [61] or meters standard deviation of surface height within landcovers (R 2 = 0.74, Figure S3). …”

Section: Radiometric Quality Of Ecosynth Point Cloudsmentioning

confidence: 99%

Optimal Altitude, Overlap, and Weather Conditions for Computer Vision UAV Estimates of Forest Structure

2015

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Ecological remote sensing is being transformed by three-dimensional (3D), multispectral measurements of forest canopies by unmanned aerial vehicles (UAV) and computer vision structure from motion (SFM) algorithms. Yet applications of this technology have out-paced understanding of the relationship between collection method and data quality. Here, UAV-SFM remote sensing was used to produce 3D multispectral point clouds of Temperate Deciduous forests at different levels of UAV altitude, image overlap, weather, and image processing. Error in canopy height estimates was explained by the alignment of the canopy height model to the digital terrain model (R 2 = 0.81) due to differences in lighting and image overlap. Accounting for this, no significant differences were observed in height error at different levels of lighting, altitude, and side overlap. Overall, accurate estimates of canopy height compared to field measurements (R 2 = 0.86, RMSE = 3.6 m) and LIDAR (R 2 = 0.99, RMSE = 3.0 m) were obtained under optimal conditions of clear lighting and high image overlap (>80%). Variation in point cloud quality appeared related to the behavior of SFM 'image features'. Future research should consider the role of image features as the fundamental unit of SFM remote sensing, akin to the pixel of optical imaging and the laser pulse of LIDAR.

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Reflections in Bumpy Terrain: Implications of Canopy Surface Variations for the Radiation Balance of Vegetation

Cited by 26 publications

References 23 publications

Canopy Structural Changes Following Widespread Mortality of Canopy Dominant Trees

Canopy Structural Changes Following Widespread Mortality of Canopy Dominant Trees

Trends in entropy production during ecosystem development in the Amazon Basin

Optimal Altitude, Overlap, and Weather Conditions for Computer Vision UAV Estimates of Forest Structure

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