Long-term isoprene flux measurements above a northern hardwood forest
نویسندگان
چکیده
[1] We report continuous whole canopy isoprene emission fluxes from a northern hardwood forest in Michigan for the 1999–2002 growing seasons. The eddy covariance fluxes of isoprene, CO2, latent heat, and sensible heat are presented along with an analysis of the seasonal and year-to-year variations. Measurements were made in collaboration with the AmeriFlux site located at the University of Michigan Biological Station (UMBS) and the Program for Research on Oxidants: PHotochemistry, Emissions, and Transport (PROPHET). In general, isoprene emissions increased throughout the day with increasing temperature and light levels, peaked at midafternoon, and declined to zero by night. There were significant variations from one 30-min period to the next, and from one day to the next. Average midday isoprene fluxes were 2.8, 3.2, and 2.9 mg C m 2 h 1 for 2000 through 2002, respectively. Insufficient data were available to include 1999. Last frost and full leaf out were significantly later in 2002 compared to the other years; however, total accumulated isoprene emissions for each year varied by less than 10%. Fully developed isoprene emissions occurred between 400 and 500 heating degree days, roughly half those required at other sites. Using long-term net ecosystem exchange measurements from the UMBS Flux group, isoprene emissions represent between 1.7 to 3.1% of the net carbon uptake at this site. Observations for 2000–2002 were compared with the BEIS3 emission model. Estimates agree well with observations during the midsummer period, but BEIS3 overestimates observations during the spring onset of emissions and the fall decline in emissions. This work provides a unique long-term data set useful for verifying canopy scale models and to help us better understand the dynamics of biosphere-atmosphere exchange of isoprene.
منابع مشابه
Stomatal and non-stomatal fluxes of ozone to a northern mixed hardwood forest
Measurements of ozone, sensible heat, and latent heat fluxes and plant physiological parameters were made at a northern mixed hardwood forest located at the University of Michigan Biological Station in northern Michigan from June 27 to September 28, 2002. These measurements were used to calculate total ozone flux and partitioning between stomatal and non-stomatal sinks. Total ozone flux varied ...
متن کاملLong - term water flux changes from converting old - growth pine forests to hardwood forests in northern Wisconsin
متن کامل
Snow depth, soil freezing, and fluxes of carbon dioxide, nitrous oxide and methane in a northern hardwood forest
Soil–atmosphere fluxes of trace gases (especially nitrous oxide (N2O)) can be significant during winter and at snowmelt. We investigated the effects of decreases in snow cover on soil freezing and trace gas fluxes at the Hubbard Brook Experimental Forest, a northern hardwood forest in New Hampshire, USA. We manipulated snow depth by shoveling to induce soil freezing, and measured fluxes of N2O,...
متن کاملDevelopment of the Selection System in Northern Hardwood Forests of the Lake States: An 80-Year Silviculture Research Legacy
Abstract The northern hardwood research program at the Dukes Experimental Forest in Michigan and Argonne Experimental Forest in Wisconsin has been adapting to changing management and social objectives for more than 80 years. In 1926, the first northern hardwood silviculture study was established in old-growth stands at the Dukes Experimental Forest. In response to social demands for more “natur...
متن کاملLong-term changes in forest carbon under temperature and nitrogen amendments in a temperate northern hardwood forest.
Currently, forests in the northeastern United States are net sinks of atmospheric carbon. Under future climate change scenarios, the combined effects of climate change and nitrogen deposition on soil decomposition, aboveground processes, and the forest carbon balance remain unclear. We applied carbon stock, flux, and isotope data from field studies at the Harvard forest, Massachusetts, to the F...
متن کامل