Grazing impacts on infiltration rates at Vernal Pools in the Modoc Plateau

Authors: MIRTE, LUBELT - University Of Nevada; SAITO, LAUREL - University Of Nevada; MONTRONE, ASHTON - University Of Nevada; WEISBERG, PETER - University Of Nevada; Blank, Robert - Bob

Submitted to: Journal of the Nevada Water Resources Association (JNWRA)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2016
Publication Date: 12/1/2016
Citation: Mirte, L., Saito, L., Montrone, A., Weisberg, P., Blank, R.R. 2016. Grazing impacts on infiltration rates at Vernal Pools in the Modoc Plateau. Journal of the Nevada Water Resources Association (JNWRA). doi:10.22542/JNWRA.1.

Interpretive Summary: Vernal pools are small depressions on the landscape that are seasonally inundated with water and support rare and endemic plant and animal species that are potentially sensitive to livestock grazing and climate change. Livestock grazing in vernal pools has the potential to alter hydrologic conditions by compacting the soil. We used disk permeameters to study grazing impacts on infiltration rates in Modoc Plateau vernal pool ecosystems. Results show no significant differences in observed infiltration rates between grazed and ungrazed plots suggesting that grazing impacts on vernal pool hydrology may be small.

Technical Abstract: Vernal pools are depressions of land that are seasonally inundated with water. They host rare and endemic plant and animal species and are sensitive to livestock grazing management and climate change impacts on hydrology and vegetation. Climate change forecasts predicting a hotter, drier climate suggest that the seasonal period of inundation may be reduced. This could allow generalist wetland species to invade and become dominant over species with unique vernal pool adaptations. However, there is potential for management practices such as livestock grazing to amplify or mitigate climate change impacts by altering infiltration rates at vernal pools. Livestock frequently graze in vernal pools and can change hydrologic conditions by consuming plant material and compacting soil with their hooves. We used large disk permeameters to study grazing impacts on infiltration rates in Modoc Plateau vernal pool ecosystems, through measurements in paired plots located inside and outside of fenced grazing exclosures. We predicted that infiltration rates would be lower in grazed plots because livestock hoof compaction can reduce soil pore sizes and hydraulic conductivity rates. Results show no significant differences in observed infiltration rates between grazed and ungrazed plots. Overall, measured infiltration rates were much higher than expected for study site soil textures. Results suggest that grazing impacts on vernal pool hydrology in the volcanic soils of northern California may be small, so there may be limited potential for grazing management to mitigate impacts of climate change on vernal pool hydrology in the Modoc Plateau.