Is nitrogen availability, forest carbon uptake, and canopy albedo enhanced along a nitrogen deposition gradient in the central Appalachian Mountains?

Brenden E. McNeil, West Virginia University, brenden.mcneil@mail.wvu.edu (Presenter)
Richard Thomas, West Virginia University, richard.thomas@mail.wvu.edu
William Peterjohn, West Virginia University, william.peterjohn@mail.wvu.edu
Amy Hessl, West Virginia University, amy.hessl@mail.wvu.edu
Kenneth Smith, West Virginia University, kenneth.smith13@gmail.com
Bradley Breslow, West Virginia University, bbreslow15@gmail.com
Aditya Singh, University of Wisconsin, singh22@wisc.edu
Shawn Serbin, University of Wisconsin, serbin@wisc.edu
Philip Townsend, University of Wisconsin, ptownsend@wisc.edu

Recent satellite observations suggest that central Appalachian forests have among the highest rates of N availability, atmospheric C uptake and canopy albedo of all North American forested ecosystems. To begin testing whether the high rates of atmospheric nitrogen deposition to these forests could be responsible for this pattern, we have measured N deposition proxies and ecosystem responses in five tulip poplar stands and seven spruce stands within the region. Our measurements of tree-rings, soil lead, and N in throughfall all help confirm modeled deposition patterns, and suggest that a large, north to south, N deposition gradient within this region has been a persistent spatial feature from the 1960’s to the present day. Interestingly, our measurements of ecosystem responses in stands along this N deposition gradient do not conform to the hypothesis that N deposition has directly altered N availability, C uptake, and albedo. In both the spruce and tulip poplar stands, leaf-level albedo, foliar N, foliar and soil N15 isotopes, and soil C:N were unrelated to the deposition gradient. Moreover, tree-ring measured basal area growth was strongly negatively related to deposition in spruce stands and unrelated in tulip poplar stands. In the spruce stands, we also measured soil respiration, and found it had a strong positive relation to a gradient of soil N availability. Thus, our results do support a strong linkage among N and C cycling in this region, and suggest that some other driver besides deposition is more directly responsible for the elevated N availability, C uptake, and canopy albedo in the central Appalachians. We suggest that this direct driver is likely related to variability in forest species composition and associated changes to canopy architecture (e.g. leaf angle distribution). Toward this end, we present some preliminary imaging spectroscopic and forest inventory data examining how these canopy-level drivers change within the Appalachian region, including along the gradient of N deposition.

Presentation: 2011_Poster_McNeil_238_191.pdf (915k)

Presentation Type:  Poster

Session:  Global Change Impact & Vulnerability   (Tue 11:30 AM)

Associated Project(s): 

• Townsend, Phil: Characterization of forest functional types and their role in mediating ecosystem response to environmental change ...details

Poster Location ID: 238