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Institute of the Environment and Sustainability, University of California, Los Angeles, CA 90095, USA


Earth and Environment, Boston University, Boston, MA 02215, USA


Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA


Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523, USA


Agence National des Parks Nationaux, Battery 4, Libreville B.P. 20379, Gabon


Author to whom correspondence should be addressed.

Academic Editors: Sangram Ganguly, Compton Tucker, Nicolas Baghdadi and Prasad S. Thenkabail

Abstract Spatial variation of tropical forest tree height is a key indicator of ecological processes associated with forest growth and carbon dynamics. Here we examine the macroscale variations of tree height of humid tropical forests across three continents and quantify the climate and edaphic controls on these variations. Forest tree heights are systematically sampled across global humid tropical forests with more than 2.5 million measurements from Geoscience Laser Altimeter System GLAS satellite observations 2004–2008. We used top canopy height TCH of GLAS footprints to grid the statistical mean and variance and the 90 percentile height of samples at 0.5 degrees to capture the regional variability of average and large trees globally. We used the spatial regression method spatial eigenvector mapping-SEVM to evaluate the contributions of climate, soil and topography in explaining and predicting the regional variations of forest height. Statistical models suggest that climate, soil, topography, and spatial contextual information together can explain more than 60% of the observed forest height variation, while climate and soil jointly explain 30% of the height variations. Soil basics, including physical compositions such as clay and sand contents, chemical properties such as PH values and cation-exchange capacity, as well as biological variables such as the depth of organic matter, all present independent but statistically significant relationships to forest height across three continents. We found significant relations between the precipitation and tree height with shorter trees on the average in areas of higher annual water stress, and large trees occurring in areas with low stress and higher annual precipitation but with significant differences across the continents. Our results confirm other landscape and regional studies by showing that soil fertility, topography and climate may jointly control a significant variation of forest height and influencing patterns of aboveground biomass stocks and dynamics. Other factors such as biotic and disturbance regimes, not included in this study, may have less influence on regional variations but strongly mediate landscape and small-scale forest structure and dynamics. View Full-Text

Keywords: tropical forest; height; lidar; climate; soil; biomass tropical forest; height; lidar; climate; soil; biomass

Autor: Yan Yang 1,2, Sassan S. Saatchi 1,3,* , Liang Xu 1, Yifan Yu 3, Michael A. Lefsky 4, Lee White 5, Yuri Knyazikhin 2 and Ranga B. Myneni 2

Fuente: http://mdpi.com/


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