PARENT SESSION
Plenary Lectures 1
Monday August 30th, 2004 8:30 AM Room 210A

Global Photosynthesis. Christopher Field^*,1, ¹ Department of Global Ecology, Stanford, CA, USA

ABSTRACT- It is useful to think of two controls on large-scale photosynthesis. One is the amount of light that is harvested. The second is the efficiency of light utilization. Most of the past research on global photosynthesis has focused on quantifying the former, especially using satellite data. Though the challenges of this research are still far from resolved, it is increasingly important to improve the techniques for quantifying large-scale efficiency of light utilization. Some of the necessary advances concern characterizing the architecture of the photosynthesizing assemblage, including canopy structure in land plants and community architecture in aquatic habitats. Others concern quantifying the biochemical machinery for photosynthesis, including both long-term structure and short-term regulation. Past approaches have come to these challenges from very different conceptual frameworks. Approaches for capitalizing on complementarities among approaches based on biochemical, ecological, and physical approaches need to be developed. The potential for increased understanding of the earth system from improved estimates of large-scale photosynthesis is vast, with immediate relevance to climate and ecosystem dynamics, in addition to agriculture. In the realm of climate research, it is increasingly clear that photosynthesis exerts short-term influences through links with stomatal conductance, medium-term influences through canopy architecture, and long-term influences through the global carbon cycle. Ecologists increasingly understand enough about mechanisms to ask deep questions about photosynthesis and not only primary production, but also biological diversity and a wide range of ecosystem goods and services. Answering these questions will, however, require a new level of sophistication and a new level of interdisciplinary integration.

KEY WORDS: primary production, global, satellite, light-use efficiency