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United States Department of Agriculture

Agricultural Research Service

Title: Carbon Sequestration in a Semi-Arid Ecosystem

Authors
item Smith, Jeffrey
item Bolton, Harvey, Jr - BATTELLE PNW LABORATORY

Submitted to: Global Energy Exposition Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 1, 2000
Publication Date: N/A

Interpretive Summary: There have been many projections on the effects of climate change on soil systems, however this speculation is difficult to verify. Most studies on soils and climate change are complicated by other factors such as different soil types or changes in vegetation. At our study site in the semi-arid shrub-steppe we developed a transect over a 500m elevation gradient which has the same parent material, the same soil type and similar vegetation. We have studied the soil carbon pools and have shown that in a hotter drier climate certain active carbon pools are depleted and the organic matter decomposition cycle is changed. In addition, when soil from a wetter- cooler climate is transplanted to a hotter-drier climate carbon and nitrogen is rapidly lost from the system.

Technical Abstract: We investigated the effects of climate on C fractionation and storage over a 500m elevation transect. The transect parent material, loess, was deposited at the same time, the climate has been stable for the last 3,000 y, and the vegetation is similar. Thus, the variables over the transect are mean maximum temperature ranging from 30 degrees C at the lower slope to 24 degrees C at the upper slope, and precipitation ranging from 180 mm at the lower slope to 270 mm at the upper slope (see graph at left). Soil, sampled under grass and in bare areas, was analyzed for C in the POM (particulate organic matter) fraction and in the fine mineral fraction. In both soil types there was a significant increase in POM-C with elevation, more so in soil associated with grass. The trends for POM-N follow the POM- C with highly significant differences across the transect and between the soil type. The difference in climate from 300 m and 800 m elevation has influenced the C and N content of the soil, both in bare areas and under grass. The increase in plant biomass and decrease in decomposition is the cause of the increase in soil C and N over the transect.

Last Modified: 12/21/2014
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