Disentangling Complex Landscapes: New Insights into Arid and Semiarid System Dynamics

Abstract

D esertification is a worldwide phenomenon in arid and semiarid regions. In many areas, it is manifested by the broadscale expansion of woody plants into perennial grasslands, with associated grass loss and soil degradation. Nearly 40% of the land's surface and a fifth of the world's human population occur in regions that are directly susceptible to desertification Conversion from grasslands to woody plant-dominated landscapes has important local, regional, and global consequences, including changes in carbon dynamics Although desertification is recognized as an important issue, and numerous studies have provided information on the dynamics of particular sites (Havstad et al. 2006), spatial and temporal variations in rates and patterns of woody plant invasion and grass loss (or conversely, grass recovery) have led to alternative, and often controversial, hypotheses about the key factors that determine desertification dynamics In addition, such variation results in complex landscapes that are mosaics of vegetation types, including grasslands, savannas, and woodlands. These mosaics are influenced by different processes, and are expected to have very different dynamics in response to changes in environmental driving variables, such as climate (figure