From a plant-centric view, islands-of-fertility supply essential nutrients to the plant species creating the island; however, from a microbe-centric view, do islands-of-fertility also benefit microorganisms? To investigate the impact of islands-of-fertility on microbial metabolism and efficiency, we evaluated metabolic and soil characteristics in interspace and Pinus edulis and Juniperus osteosperma tree-island (i.e., soils beneath the canopy and at the edge of the canopy) surface soils in over forty cold deserts. Characteristics included: microbial quotient=microbial efficiency, basal respiration=measure of overall activity, and ratio of biomass to dissolved organic C (DOC)=the amount of biomass supported by C substrates. Also, we measured the same characteristics under coarse woody debris (CWD) additions from tree-islands in all our deserts. To stem catastrophic wildfires, whole desert trees are being mechanically masticated into CWD and deposited on soils previously exposed to decades of tree-induced changes. These CWD additions are the ultimate setting to evaluate the extent of influence tree litter has on tree-island soils and metabolic activity. We found that microorganisms were less efficient in tree-island canopy than interspace soils. Further, basal soil respiration was only 7% higher in tree-island canopy soils, and 66% less microbial biomass was supported by DOC in tree-island canopy than interspace soils. The addition of CWD only enhanced these differences and also caused all metabolic characteristics in tree-island edge to differ from interspace soils. The lower efficiency and less biomass supported per unit DOC was not due to a lack of DOC or P. DOC was 3-times and P was 1.5-times higher in tree-island than interspace soils. Low levels of inorganic N in tree-island soils may indicate that microorganisms were limited by poor litter quality. Our results suggest that, microorganisms enjoy better soil quality, lower chemical stresses, and less energy demand for metabolism in interspace soils.
Oral presentation and poster titles, abstracts, and authors from the Society for Range Management (SRM) Annual Meetings and Tradeshows, from 2013 forward.