PARENT SESSION
Organized Oral Session 34: Incorporating ecological processes at many scales into biogeochemical and global climate change models
Organizer(s): WM Post, JS Olson, and C Peng
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 510b, Level 5, Palais des congrès de Montréal

Improving global models by linking water, carbon, and nutrient cycles.

Jackson, Robert¹, ¹ Duke University, Durham, NC

ABSTRACT- Regional and general circulation models (GCMs) are much more realistic today than they were a decade ago in treating ecological processes. Nonetheless, we have many opportunities to improve them, balancing the needs of mechanistic processes with the dangers of over-parameterizing the models. In this presentation, I will discuss these opportunities, focusing on interactions among carbon, water and nutrients. I will also examine issues arising at larger spatial scales, such as feedbacks between vegetation and climate represented in meso-scale models and GCMs. For example, current models typically use one of three approaches to calculate soil water uptake b: (1) the minimum of a demand and a soil water supply function, (2) a derivative of an Ohm's law model that calculates soil moisture effects on canopy resistance, or (3) a direct function of soil moisture availability. In all of these approaches soil moisture availability is calculated either as a function of volumetric soil water content or of soil water potential. Transpiration of water taken up by roots is then modeled either as a function of canopy resistance, leaf biomass, or leaf area index. The assumptions of each model, and what processes are excluded, greatly influence the outcome of predictions.

Key words: global models, climate feedbacks, terrestrial processes, global change