Causes and Consequences of Plant Functional Diversity in Arctic Ecosystems

Abstract

Broad-scale predictions about the response of terrestrial ecosystems to global changes in climate and land use and feedbacks to the atmosphere require the simplest possible framework to be useful. This framework must contain sufficient detail to incorporate the major controlling mechanisms and be broadly applicable but omit details that are site-specific or unnecessarily complicate predictive models (O’Neill et al. 1989). What is the simplest possible framework for understanding the role of arctic ecosystems in global change? More specifically, how much do we need to know about the species composition and diversity of arctic ecosystems to predict how these ecosystems will respond to global change? At one extreme, we might consider vegetation to be a single component, as it is currently treated in most models of biogeochemistry (Agren et al. 1991), hydrometeorology (Jarvis and McNaughton 1986; Field 1991), and land-surface interfaces to general circulation models (Running and Coughlan 1988). At the opposite extreme, we might include each species in a multi-species biogeochemical model (Miller et al. 1984). In this chapter, we argue that, by grouping plant speices into functional groups, we achieve an intermediate level of detail that is useful in predicting response to and effects on ecosystem processes. More specifically, we present a framework for classifying species into functional groups in arctic ecosystems and evaluate its utility in addressing two questions: 1. What kinds of species will respond most strongly to global changes in chmate and land use? 2. What are the consequences of changes in species composition for ecosystem function?