Plant species can differentially shape soil biota and abiotic conditions. In some grasslands, edaphic factors are more influential on microbial communities than biotic interactions. Arid grasses are intimately linked with a hyphal network that delivers substantial water and nutrients to plant roots. Examining microbial activities associated with dominant grasses determines how individual plant species shape ecosystem processes and how these processes may be affected as plant communities change. If microbial activity is consistent between different plant species, then microbial activity is largely controlled by edaphic factors, and microbial mediated ecosystem processes may not be affected if plant communities change. If microbial activity varies between plant species, it is controlled by differential plant properties and microbial mediated ecosystem processes would presumably change as plant communities change. The main research questions for this project were 1) does microbial activity vary between dominant semiarid grasses, and 2) is microbial activity driven mainly by edaphic or plant species-specific attributes?
There are five monocultures of each of seven grasses (35 plots) for total of 95 plot. There are 55 plots that have two species: Each of the five non-blue and black species will be planted with blue grama and black grama. Blue and black grama will also be planted together, for a total of 11 species interaction treatments, which will also be replicated five times. The plots will be 2 x 2.5 meters to allow the 0.5 meter strip on one side of the plot to be used in invasion future experiments.
The seven species planted:
Reseeded four species in July 2008. The species planted in each plot can be found in the plot treatment are: Sporobolus cryptandrus, sand_dropseed, Bouteloua gracilis, Blue gramaOryzopsis hymenoides, Indian_ricegrass, Hilaria jamesii, galleta, Aristida purpurea, purple_threeawn, Bouteloua eriopoda, Black gramma, Bouteloua curtipendula, Side oats grama. We reseeded four species in July of 2008.
Only monoculture plots of Bouteloua eriopoda, Bouteloua gracilis and Aristida Purpurea were utilized for this project. Soil samples were collected from the rhizosphere and interspaces between plants. Four soil cores (1cm wide, 3 cm deep) were taken across the plot and mixed together for each sample. Enzyme activity in the rhizosphere and interspace were analyzed separately. Samples were refrigerated and processed within 48 hours of collection to prevent enzyme degradation. Soils were subsampled for organic matter and water content. Field soil moisture was calculated by comparing weights of freshly collected soil and soil dried at 60 °C. A subsample was also burned at 500 °C for 4 hours to determine percent organic matter. The potential activity levels of beta-glucosidase, beta-N-acetylglucosaminidase, alanine aminopeptidase, alkaline phosphatase, and phenol oxidase were measured in the lab following the methods of Stursova et al. (2006).
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