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United States Department of Agriculture

Agricultural Research Service

Title: Spatial Relationships of Soil Microbial Biomass and C and N Mineralization in An Arid Shrub Steppe Ecosystem

Authors
item Smith, Jeffrey
item Bolton, Harvey - BATTELLE PACIFIC NW
item Halvorson, Jonathan - BATTELLE PACIFIC NW

Submitted to: Journal of Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 25, 1994
Publication Date: N/A

Interpretive Summary: The shrub-steppe ecosystem is a vast area of the intermountain west. This system may contribute large amounts of greenhouse gases especially N2O to the atmosphere. This potential contaminant source would only be significant if the spatial proximity of nutrients and microorganisms were such that gases could be generated from normal metabolism. This study focused on where the nutrient pockets in this system were in relationship to the concentration of organisms and plants. We found that even though microorganism concentrations were high under the plants that the nitrogen was low preventing nitrogen loss from these areas. This was most likely due to competition from the plants for nitrogen. In open areas this was not the case and nitrogen had a higher potential for loss as a gas. These nutrient/organism spatial relationships were found to be very important in this type of ecosystem when trying to estimate gaseous losses.

Technical Abstract: Microbial processes such as C and N mineralization in arid ecosystems are influenced by heterogeneously spaced plants and abiotic parameters. The cycling of nutrients through mineralization processes are in turn important for plant productivity and ecosystem stability. The objective of this study was to determine the spatial relationships of C and N mineralization and microbial resource islands to plant location. We measured inorganic N pools, microbial biomass and C and N mineralization potentials from 205 soil samples positioned around five Artemisia tridentata shrub plants. Most parameters showed log normal distributions and all were significantly correlated to each other. Microbial biomass had the highest positive correlations with C mineralization and soluble C. Geostatistical analysis of spatial relationships showed that samples were spatially related with each other to a distance of 0.5 to 1.0 m. At sample locations where SIR-C was high Co was also high. In contrast, No was low in these areas. Cross correlation with plants showed that No was not related to plant location but that Co was spatially related to shrubs and not grass plants. The resource island effect in the shrub steppe ecosystem is important when estimating landscape level microbial processes.

Last Modified: 7/23/2014
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