HR: 08:00h
AN: B51E-01 INVITED     [Abstracts]
TI: The contribution of plant-soil interactions to biogeochemical cycles in a changing world
AU: * Pregitzer, K
EM: kspregit@mtu.edu
AF: Ecosystem Science Center, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 United States
AB: In terrestrial ecosystems, plants are the transducers that provide the energy for microbial metabolism through root exudation, cell sloughing, and the turnover of leaves and roots. Changes in the Earth's atmosphere such as increasing concentrations of atmospheric carbon dioxide, tropospheric ozone, and the atmospheric deposition of nitrogen, will modify plant net primary productivity (NPP) and plant carbon (C) allocation. These changes will, in turn, initiate a series of biochemical alterations in dead leaves and fine roots, responses which move through the soil to structure food webs and control rates of biogeochemical cycling. In our conceptual framework, plant physiology, plant tissue biochemistry, and the production and mortality of plant modules (leaves and roots) are pivotal control points in the soil for the regulation of ecosystem biogeochemistry. In other words, understanding how plant form and function as well as the associated microbial dynamics respond to changes in the Earth's atmosphere is important to understanding the biogeochemical feedbacks which may ultimately constrain long-term ecosystem responses. We will review examples of how changes in the Earth's atmosphere directly modify plant growth and C allocation, which initiates a series of physiological and biochemical changes in live and dead leaves and fine roots. We will then examine how these plant responses structure rhizosphere food webs and control rates of microbial metabolism. Microbial enzyme activity regulates many of the transformation and weathering processes in the soil, thus changes in the microbial community can strongly alter ecosystem biogeochemistry. For example, we will explore how plants and microbes are linked to ecosystem-level feedbacks between soil respiration, dissolved inorganic carbon (DIC), and dissolved organic carbon (DOC) leaching. The basic premise of our conceptual model is that altered atmospheric chemistry directly impacts plant form and function. Theses human-induced changes to the Earth's atmosphere will cascade through plants into the soil, where microbial communities mediate the ecosystem functions that regulate biogeochemical cycles. There are several key research opportunities as we attempt to understand how changes in the Earth's atmosphere cascade through terrestrial ecosystems to alter biogeochemical cycles. For example, far too little attention has been given to how the interactions between changes in atmospheric chemistry (e.g. carbon dioxide and nitrogen, or carbon dioxide and ozone) will impact C transformations in the soil. If we deliberately set out to understand how variable plant and microbial physiology are to interactive changes in atmospheric chemistry, it should be possible to build a deeper understanding of the fundamental processes controlling ecosystem response to global change.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
DE: 0469 Nitrogen cycling
DE: 0486 Soils/pedology (1865)
SC: Biogeosciences [B]
MN: Fall Meeting 2005