Global Warming and Terrestrial Ecosystems: A Conceptual Framework for Analysis

raise global mean temperature over the next century by 1.0–3.5 °C (Houghton et al. 1995, 1996). Ecologists from around the world have begun experiments to investigate the effects of global warming on terrestrial ecosystems, the aspect of global climate change that attracts the most public attention (Woodwell and McKenzie 1995, Walker and Steffen 1999). The effort to understand response to warming builds on a history of investigations of the effects of elevated CO 2 on plants and ecosystems (Koch and Mooney 1996, Schulze et al. 1999). There are important differences, however, between increases in atmospheric CO 2 and temperature change, both in the temporal and spatial patterns of change and in how they affect ecosystems. The scientists involved in temperature change research have had to face new technical and conceptual challenges in designing and interpreting their experiments (Schulze et al. 1999). In this paper we describe these challenges and present a conceptual framework for interpreting experimental results and predicting effects of warming on ecosystems.