DOE Office of Science Biological and Environmental Research/Program for Ecosystem Research. ST Gower.
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Proposal Proposal Review
Proposal and proposal review are in Adobe PDF format.
The boreal forest biome is the second largest forest biome in the world that occurs in high-latitude regions circumpolar in the northern hemisphere. Boreal forest contain the largest soil carbon content and are anticipated to experience the greatest warming of any forest biome. A process-based understanding of the effects of warming on the structure and function of this economically and ecologically important forest biome is lacking, or in some cases results from recent studies contradict traditional ecological axioms. Autotrophic and hetertrophic respiration - two processes that have a profound influence on the carbon balance of plants and ecosystems, respectively - have traditionally been thought to increase exponentially with temperature, but the relationship between temperature and respiration has recently been questioned (Giardina and Ryan 2000, Linder et al. 2001, Gower et al. 2001). Warming may also influence soil nutrient dynamics and water and nitrogen use, which influences net primary production and carbon allocation (Jarvis and Linder 2000, Gower et al. 2001). Changes in resource availability affects plant functional groups differently, causing changes in species composition (Bisbee et al. 2001). We propose to use replicated warmed open top chambers nested on soil warming plots and fertilized plots (no warming) in young boreal forests in northern Manitoba to examine the effects of ecosystem warming versus increased nutrient availability on the structure and function of a boreal black spruce forest. The soil warming treatment will mimic that used by Linder and Gower in nothern Sweden (Linder et al. 2001) and the warmed open-top chambers will be designed to minimize changes in microenvironment inside and outside the chamber. Specific objectives and methods to address objectives are listed below.
Compare effects of warming on autotrophic respiration, above- and belowground net primary production (NPP) budgets. Autotrophic respiration budgets will be constructed using chamber measurements (Ryan et al. 1997) for each tissue, aboveground NPP will be determined using standard allometry techniques (Gower et all. 1999), and fine root production and turnover will be quantified using minirhizotrons (Steel et al. 1997, Gower et al. 2001a.
Compare microbial dynamics and net soil surface CO2 flux of control and warmed soils to identify causes for the hypothesized small to no effects of soil warming on soil surface CO2 flux. Microbial dynamics will be determined using laboratory mineralization incubations and fumigation techniques (Campbell and Gower 1999), and soil surface CO2 flux will be measured using automated soil surface CO2 flux systems (Gower et al. 2001b).
Quantify the effects of warming on nitrogen use by overstory, understory, bryophytes, and heterotrophic microbes. Nitrogen use will be determined using standard stochiometry and isotope measurements (Vogel and Gower 1999).
Examine the effect of warming on phenology and overstory, understory and bryphyte strate. Sap flux systems and dendrometer bands, operaged by data loggers, will be used to measure phenology and water use (Ewers et al. 2001). The proposed study builds on the existing research programs Gower and Linder have in northern Wisconsin and Sweden, respectively, and their on-going collaborations. In-kind services from several Canadian agenices and existing grants will greatly contribute to the cost of the proposed study, and complement the boreal ecology programs of the PI's.
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