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Metolius Flux Sites

Carbon and water vapour exchange in successional stages of Pacific Northwest forest ecosystems: integration of eddy flux, plant, and soil measurements.

Objective

To quantify how successional stages and management practices in forest ecosystems influence processes controlling net ecosystem exchange of CO₂ in varying climatic conditions.

Approach

We will focus on measuring and modeling differences in carbon storage and fluxes in relation to climate, age and management in chronosequences of ponderosa pine. We will make micrometeorological and meteorological measurements at our 250 and 14-year old pine flux sites at Metolius, which are current AmeriFlux sites. We will continue biological measurements and model parameter measurements necessary to develop carbon budgets for the flux sites (e.g. soil surface CO2 fluxes, foliage respiration, litterfall, annual productivity, LAI, foliar and soil chemistry), and begin identical measurements in a mature (45-year old) pine forest nearby so that we cover the range of successional stages commonly observed in the region. The carbon budgets will be used to estimate annual net ecosystem production (NEP = -NEE), evaluate where and how much carbon is stored at different successional stages (e.g. soils, above- and belowground living biomass), and to evaluate controls on CO2 exchange. We will build and install a second automated soil chamber system, so that we have continuous soil flux measurements at both of our eddy flux sites, as soils appear to account for ~70% of total ecosystem respiration. To improve our understanding of changes in ecosystem processes associated with climate and disturbance, we will continue to work at the sites with collaborators to estimate autotrophic and heterotrophic sources of respired CO2. By making associated biological and soil measurements and by ecosystem modeling (Biome-BGC and 3-PG), as well as by collaborating with other researchers, we will investigate how weather and other environmental factors affect components of carbon dioxide and water vapor exchange. We will model how annual and seasonal NEP and LE vary with successional stage across the chronosequence (14, 45, old) of ponderosa pine, and compare results with a chronosequence of slash pine in the SE U.S. Such analyses could then be used to assess regional carbon budgets. Our project will evaluate the ability of ponderosa pine forests of different ages in Central Oregon to sequester carbon dioxide, and investigate climate and disturbance effects on carbon uptake and water vapor exchange. The results will allow forest managers to assess the carbon sequestration implications of various management options.