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Carbon dioxide is increasing in the atmosphere, presumably from human activities. Many soils on Walnut Gulch Experimental Watershed (WGEW) in southeastern Arizona contain carbonates that have accumulated over long periods of time. The hypothesis is that these soils are maintaining this carbon pool under present climatic conditions and are a sink for some of the increasing atmospheric carbon. Bowen ratio systems were used to measure CO2 fluxes from a brush and a grass community with different soil types on WGEW. Contradictory to the hypothesis, the two sites were found to be losing carbon annually. The brush site with higher inorganic carbon in the soil, had an average annual loss of 144 g C m-2 and the grass site...
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In the marginally productive rangelands of the semiarid, southwestern USA, the maintenance of organic C (OC) is essential to the stability of the ecosystem. This study was conducted to identify landscape factors responsible for the distribution of OC in watershed soils, its loss from upland areas and subsequent transport within the stream system of a large semiarid watershed (Walnut Gulch Experimental Watershed [WGEW], Tombstone, AZ). Samples were collected along transects from the surface 5 cm of each major soil mapping unit in six subwatersheds (SW). Data were recorded for slope class, landscape position, and aspect at each of the 435 sampling points. Soil analyses consisted of: total C and OC, particle-size distribution,...
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