Response of soil microbial activity to grazing, nitrogen deposition, and exotic cover in a serpentine grassland
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Background and aims
Exotic species, nitrogen (N) deposition, and grazing are major drivers of change in grasslands. However little is known about the interactive effects of these factors on below-ground microbial communities.
We simulated realistic N deposition increases with low-level fertilization and manipulated grazing with fencing in a split-plot experiment in California’s largest serpentine grassland. We also monitored grazing intensity using camera traps and measured total available N to assess grazing and nutrient enrichment effects on microbial extracellular enzyme activity (EEA), microbial N mineralization, and respiration rates in soil.
Continuous measures of grazing intensity and N availability showed that increased grazing and N were correlated with increased microbial activity and were stronger predictors than the categorical grazing and fertilization measures. Exotic cover was also generally correlated with increased microbial activity resulting from exotic-driven nutrient cycling alterations. Seasonal effects, on abiotic factors and plant phenology, were also an important factor in EEA with lower activity occurring at peak plant biomass.
In combination with previous studies from this serpentine grassland, our results suggest that grazing intensity and soil N availability may affect the soil microbial community indirectly via effects on exotic cover and associated changes in nutrient cycling while grazing directly impacts soil community function.
KeywordsCalifornia Cattle Extracellular enzyme activity Fertilization Festuca perennis Invasive species
Extracellular enzyme assay
This research was supported by funding from the Kearney Foundation for Soil Science. We thank Christal Niederer for her assistance with fieldwork and Bonnie Keeler for her useful comments on this manuscript.
- Chen H, Liu J, Zhang YL, Wang Q, Ge XL, Wei YH, Wang RQ (2011) Influence of invasive plant Coreopsis grandiflora on functional diversity of soil microbial communities. J Environ Biol 32(5):567–572Google Scholar
- Elam DR, Wright DH, Goettle B (1998) Recovery plan for serpentine soil species of the San Francisco Bay area. Portland, OregonGoogle Scholar
- Fenn ME, Allen EB, Weiss SB, Jovan S, Geiser LH, Tonnesen GS, Johnson RF, Rao LE, Gimeno BS, Yuan F, Meixner T, Bytnerowicz A (2010) Nitrogen critical loads and management alternatives for N-impacted ecosystems in California. J Environ Manage 91(12):2404–2423. doi: 10.1016/J.Jenvman.2010.07.034 PubMedCrossRefGoogle Scholar
- ICF International (2010) Draft Santa Clara Valley habitat plan. Santa Clara CountyGoogle Scholar
- Pasari JR (2011) Grassland invasion, management, and multifunctionality. Dissertation, University of California, Santa Cruz, Santa Cruz, CAGoogle Scholar
- Pasari JR, Selmants PC, Young H, O'Leary J, Zavaleta ES (2011) Nitrogen enrichment. In: Rejmanek M, Simberloff D (eds) The encyclopedia of invasive species. University of California Press, pp 488–492Google Scholar
- Pinheiro J, Bates D, DebRoy S, Sarkar D, Team RDC (2011) nlme: Linear and nonlinear mixed effects models. R package version 3.1–101Google Scholar
- Sinsabaugh RL, Lauber CL, Weintraub MN, Ahmed B, Allison SD, Crenshaw C, Contosta AR, Cusack D, Frey S, Gallo ME, Gartner TB, Hobbie SE, Holland K, Keeler BL, Powers JS, Stursova M, Takacs-Vesbach C, Waldrop MP, Wallenstein MD, Zak DR, Zeglin LH (2008) Stoichiometry of soil enzyme activity at global scale. Ecol Lett 11(11):1252–1264. doi: 10.1111/j.1461-0248.2008.01245.x PubMedGoogle Scholar
- Stromberg MR, Corbin JD, D'Antonio CM (2007) California grasslands: ecology and management. University of California Press, Berkeley, CaliforniaGoogle Scholar
- Weiss SB, Wright DH, Niederer C (2007) Serpentine vegetation management project. United States Fish and Wildlife ServiceGoogle Scholar