HR: 08:50h
AN: B31A-04 INVITED     [PDF]
TI: Spatially Distributed Effects of Woody Encroachment on Soil NO emissions From a North Texas Rangeland.
AU: * Martin, R E
EM: robin@globalecology.stanford.edu
AF: Carnegie Institution of Washington Department of Global Ecology, Stanford University, Stanford, CA 94305 United States
AU: Asner, G P
EM: greg@globalecology.stanford.edu
AF: Carnegie Institution of Washington Department of Global Ecology, Stanford University, Stanford, CA 94305 United States
AB: Woody encroachment, a spatially-explicit process of land-cover change, has produced documented changes to the biophysical and biogeochemical properties of ecosystems. However, little information (none that is spatially distributed) is available on the impacts of woody encroachment on N oxide emissions from savanna regions. We combined hyperspectral remote sensing and field measurements to quantify spatial patterns and estimate regional fluxes of soil N oxide emissions as they co-vary with vegetation cover and soil type across a semi-arid rangeland in North Texas. Soil nitric oxide (NO) emissions were highly correlated with {it Prosopis} canopy cover, allowing the extrapolation of NO fluxes from hyperspectral observations of woody cover. NO emissions were highly variable, ranging from 0-550 NO-N kg km$^{ 2}$y$^{-1}$, across the region, with the lowest emissions from shallow clay soils and highest from deeper upland clay loams. A remotely-derived annual NO emission estimate was 122 kg NO-N $^{ 2}$y$^{-1}$, almost 40% greater than that of the value derived from traditional averaging of field measurements. We conclude that relationships between NO emissions and remotely sensed structure and composition are advantageous for quantifying NO emissions at the regional scale. This study also provides new insight into the role of woody encroachment on biogeochemical processes that are highly variable and otherwise difficult to measure at the regional scale.
DE: 0400 Biogeosciences
DE: 1640 Remote sensing
DE: 4805 Biogeochemical cycles (1615)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting