Rapid Simulations of Vegetation Stand Dynamics with Mixed Life-Forms

Abstract

The goal formulated by the global vegetation modeling project at The International Institute for Applied Systems Analysis, IIASA, (Prentice et al. 1989) was to develop a mechanistic vegetation model suitable for exploring processes of global vegetation change in a changing environment over time-scales of decades to centuries, taking into account the processes of plant growth, regeneration, mortality, disturbance regimes, and dispersal that mediate the response to environmental change. Gap models, a class of vegetation dynamics simulation models, have desirable features for use in such a project. They operate at the relevant time-scale and have proven useful in clarifying processes of forest succession and response to disturbance (Shugart 1984) and climatic change (Solomon 1986) on local and regional scales in a variety of environments. So far, however, gap models have mainly been applied to forests and have not included the mixture of life-forms characteristic of most plant communities. (However, see Burton and Urban 1989; and Coffin and Lauenroth 1990.) Another limitation of gap models for global simulation purposes is that they appear to include an excessive amount of detail; for example, vegetation patches are described in terms of explicit characteristics of all individual plants rather than in terms of canopy and population structure, which are the effective variables governing competition (Fulton 1991).