Carbon Exchange Dynamics in a Temperate Forested Watershed: A Laboratory and Field Multidisciplinary StudyEPA Grant Number: R824979
Title: Carbon Exchange Dynamics in a Temperate Forested Watershed: A Laboratory and Field Multidisciplinary Study
Investigators: Walter, Lynn M. , Teeri, James A. , Meyers, Philip A. , Budai, Joyce M. , Abriola, Linda M. , Zak, Donald R. , Kling, George W.
Institution: University of Michigan
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1996 through September 30, 1999 (Extended to September 30, 2000)
Project Amount: $800,000
RFA: Water and Watersheds Research (1996) RFA Text | Recipients Lists
Research Category: Water and Watersheds , Water
Description:The project is an integrated hydrogeologic and biogeochemical investigation of organic carbon transformations in the Cheboygan Watershed. Based on earlier studies of aspen growth in elevated CO2 microcosms conducted at the University of Michigan Biological Station (UMBS), one important biotic response to growth in elevated CO2 conditions is the increase in below ground root structures and in microbial respiration rates. The research problem addressed in the present study is whether the increase in below ground carbon can be transferred to the regional groundwater system or whether it is recycled to the atmosphere. The fate of this carbon may play an important role in moderating Earth's response to CO2 released by fossil fuel burning.
One approach to this research problem involves further study of carbon transformations in a new generation of elevated CO2 microcosm growth experiments using aspen and sugar maple trees. Soil water chemistry at different depth horizons (10, 20, and 150 cm) will be characterized completely for dissolved components with special focus on carbon transformations (dissolved organic carbon (DOC) oxidation to CO2, CO2 solubilization via mineral weathering reactions). Prepared mineral substrates (carbonates, aluminosilicates) will also be emplaced in the rooted zones of the experimental microcosms to observe directly the coupling between mineral weathering and enhanced carbon turnover in elevated CO2 experiments.
Arrays of soil water and groundwater samplers have been emplaced in two nearby natural forests (one aspen, one sugar maple) to better relate the results from the experimental microcosms to regional scale watershed systems. In this watershed, shallow aquifers are in glacial drift with a mixed carbonate and silicate mineral assemblage. The fate of the organic carbon transferred to the regional flow system as either DOC or dissolved CO2 will be studied by integrated geochemical and hydrologic characterization. How much of this is accomplished by weathering of carbonates vs. aluminosilicates will be determined also. Obtaining regional distributions of water samples will involve emplacing arrays of groundwater wells along established flow paths in the watershed for chemical characterization, stable isotope determinations (C, O, H) and relative age-dating (C-14, tritium).
The working hypotheses is that both organic and inorganic carbon fluxes to regional flow systems are significant in modulating this effect. The carbon transformation mechanisms and rates determined for natural forests, coupled with the regional hydrologic budget and ground water flow rates, will be a powerful framework for predictive modeling of fate of enhanced below ground carbon production in the face of elevated atmospheric CO2 levels.