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Title:   Author  item
                                            Smith, Jeffreyitem
                                            Halvorson, Jonathanitem
                                            BOLTON, HARVEY, JR. - BATTELLE PNW LABORATORY
  Submitted to: Soil Biology and Biochemistry
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 5/10/2002
                                    Publication  Date: 8/6/2002
                                    Citation: Smith, J.L., Bolton, H. Jr., Halvorson, J.J. Soil properties and microbial activity across a 500 m elevation gradient in a semi-arid environment. Soil Biology & Biochemistry. 2002. 34: 1749:1757.Interpretive Summary: Human activity is causing the Earth's climate to change to a warmer and potentially drier environment.  This change in climate may potentially cause changes in the chemistry and biology of soils and thus contribute to ecosystem changes.  To evaluate the effect of climate change on soil processes we sampled soil from an elevation transect in the semi-arid  shrub-steppe.  This transect spanned an elevation change of 500 m, thus being cooler and wetter at the top and warmer and drier at the bottom.  We measured soil chemical and microbiological parameters.  We found that the soil carbon and nitrogen decreased as we went from cooler to warmer conditions.  We also found the many measures of microbial activity decreased under warmer drier conditions.  Thus as the Earth's climate becomes warmer these decreases in soil nutrient pools and microbiology will cause areas like the shrub-steppe to become more like deserts  changing the function of this ecosystem.
                                Technical Abstract: If climate change causes the semi-arid shrub-steppe to become hotter and drier it may cause a loss of soil C and N and changes in soil processes and microbial and plant community structure. This study was conducted, using an elevation gradient as an analog of climate change, to determine the influence of climate on soil microbial activity and soil properties.  We collected soil from cryptogamic crust areas and around bunchgrass plants at 25 sites over a 500m elevation transect.  The samples were analyzed for several chemical and microbiological attributes including pH, microbial biomass and nitrification potential and the data grouped into five sites for statistical analysis. Soil pH decreased over the transect with higher pH values in the grass soil than the crust. Both total C and N increased with elevation as nitrification potential.  Due to high sample variability microbial biomass, respiration and mineralization showed non-  significant trends over the 500m elevation transect.  The climate change that is expected in this shrub-steppe ecosystem over the next 100 years will cause the pH to increase and the EC to decrease.  Plants would become more sparse, nitrification potential will decrease and ammonium will increase. Total C, N and biomass will decrease and may shift the controlling factors of the ecosystem to abiotic factors. The changes in the cycling of N and to some extent C due to climate change will alter the microbial and plant community structure and function of this ecosystem and cause it to move in the direction of desertification.


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