The Effect of Moisture and Temperature Manipulation on Plant Allocation and Soil Carbon Dynamics in Black Spruce Forests: Using Radiocarbon to Detect Multiple Climate Change Impacts on Boreal Ecosystem Carbon Cycling

Principle Investigator: Dr. Edward A.G. Schuur, University of Florida

Co-Investigators: Dr. Jason G. Vogel, University of Florida
Dr. Stith T. Gower, University of Wisconsin

Abstract: Our primary research objective is to understand how the carbon (C) cycle of black spruce (Picea mariana) forests, the largest boreal forest type in North America, will respond to climate change. A second objective is to provide an explicit link between the extensive research conducted on this forest type in Alaska to ongoing international research conducted in Canada where climate and substrates can differ. These objectives will be achieved by connecting observational and experimental field measurements to a common modeling framework.

Location: The proposed work will take place across a climate gradient that spans four distinct climatic regions in Alaska, combined with an intensive site in northern Manitoba that is the location of a temperature and moisture manipulation in a black spruce forest. This climate manipulation (DOE-PER#84953) is the only soil, air, and moisture manipulation experiment currently ongoing in a black spruce forest. Thus, it is invaluable for elucidating the dynamics of this important forest type that covers almost 50% of Interior Alaska.

Questions: The primary hypothesis of this research is that black spruce C allocation and microbial decomposition will respond to changes in temperature and moisture regimes. Microbial decomposition will be stimulated by increased temperature (in the absence of drying), increasing outputs from the soil C pool. At the same time, warming (in the absence of drying) will decrease allocation to roots, decreasing inputs to the soil C pool. Together these processes will determine the net storage of C in the soil organic matter (SOM) pool with climate change.

Methods: Our methodological approach will primarily rely on the use of radiocarbon measurements of SOM and soil respiration. Radiocarbon measurements of soil respiration and the component sources will be used to detect changing plant and microbial respiration with changing moisture and temperature. In addition, radiocarbon measurements of SOM will be used to quantify decadal rates of inputs and outputs to the soil C pool across sites with different temperature and precipitation regimes. We will link this research with a new parameterization of a boreal forest process model (BIOME-BGC) in order to explore model sensitivity to changes in both precipitation and temperature that are expected to occur over the next decades to century. Deliverables include: (1) presentations of results at scientific meetings and in peer-reviewed journals, and (2) modified model code that will include a dynamic plant allocation component. These deliverables will be made publicly available through the Bonanza Creek LTER data dissemination protocol.

last updated: 28 August 2006 PLH