chapter  1
36 Pages

Biogeography and Dynamics of Global Tropical and Subtropical Savannas: A Spatiotemporal View

ByMichael J. Hill, Miguel O. Román, Crystal B. Schaaf

The global savanna biome is a complex entity. Savannas occupy the continuum between forest and grassland steppe with a variable mixture of trees and grassland. A range of definitions is provided by Mistry (2000), some of which are climatic and some of which are based on vegetation. In our opinion, the best definition is provided by Dansereau (1957): “a mixed physiognomy of grasses and woody plants in any geographical area.” However, this mixture may encompass a very wide set of ecosystems: McPherson (1997) considers that savannas of various types covered much of North America, including many systems in which the woody plants are shrubs and grass cover is extremely sparse. Most of temperate and tropical Australia was originally covered in savanna (Moore, 1975a; Harrington et al., 1984a). At the

CONTENTS

Introduction .............................................................................................................3 Concept and Assumptions .....................................................................................5 Spatial Definition of Global Savannas: Ecoregions and Land Cover ..............8 Vegetation and Biodiversity ................................................................................ 14 Climate and Soils of Global Savannas ................................................................ 19 Fire ........................................................................................................................... 24 Rural Population, Livestock, and Human Appropriation of

Net Primary Productivity ...........................................................................25 Temporal Dynamics ..............................................................................................30 Conclusions ............................................................................................................ 32 Acknowledgments ................................................................................................33 References ...............................................................................................................33