chapter  8
20 Pages

Quantifying Carbon in Savannas: The Role of Active Sensors in Measurements of Tree Structure and Biomass

ByRichard M. Lucas, Alex C. Lee, John Armston, Joao M. B. Carreiras, Karin M. Viergever, Peter Bunting, Daniel Clewley, Mahta Moghaddam, Paul Siqueira, Iain Woodhouse

Richard M. Lucas, Alex C. Lee, John Armston, Joao M. B. Carreiras, Karin M. Viergever, Peter Bunting, Daniel Clewley, Mahta Moghaddam, Paul Siqueira, and Iain Woodhouse

CONTENTS

Introduction ......................................................................................................... 156 The Distribution of Carbon in Savannas ................................................ 156 Remote Sensing of Savannas .................................................................... 156

Common Descriptors of Savannas ................................................................... 157 Vegetation Structure .................................................................................. 157 Vegetation Biomass (Carbon) ................................................................... 158

Active Remote Sensing ....................................................................................... 158 LiDAR .......................................................................................................... 158 SAR .............................................................................................................. 160 Ground-Based Sensors .............................................................................. 161

Retrieving Structural Attributes from Active Sensors ................................... 162 Vegetation Height ...................................................................................... 162 Stem Location, Diameter, and Number Density ................................... 165 Crown and Canopy Descriptors .............................................................. 165 Combined Retrieval of Structural Attributes ......................................... 166

Retrieval of Biomass ........................................................................................... 167 Above-Ground Biomass ..................................................................................... 167

Component Biomass .................................................................................. 169 Quantifying Changes in Carbon ....................................................................... 169 Future Outlook .................................................................................................... 170 Acknowledgments .............................................................................................. 171 References ............................................................................................................. 172

The Distribution of Carbon in Savannas

Savannas occupy approximately 20% (depending on definition) of the global land surface and occur largely in the tropics and subtropics. Most occupy seasonal environments where average monthly temperatures exceed 18°C and annual precipitation is relative low (<600 mm) and seasonal. Savannas are structurally diverse ecosystems in terms of the varying proportions, spatial distributions and architectures of tree, shrub, and grass cover. Where savannas are wooded, tree density varies primarily with mean annual rainfall; and these ecosystems merge with closed canopy forest and semidesert in moister and drier regions, respectively.