How Does Simulated Gopher Disturbance Affect the Establishment ofHolcus lanatusL. (Poaceae) in Calfornia Coastal Prairie?

Abstract

Abstract Disturbance often has the net effect of promoting invasive plant establishment, but the precise nature of the relationship between disturbance and invasion can depend on community context. We used simulated gopher mounds in bare and monoculture plots of three California native grasses (Bromus carinatus var. maritimus [Piper] C. L. Hitch., Festuca rubra L., and Calamagrostis nutkaensis [J. Presl] Steudel) to test the effects of mounds on seedling establishment and survival of the European perennial grass Holcus lanatus L. Soil disturbance treatments were crossed with manipulations of the plant canopy (shade cages in bare and Bromus plots vs. pinning back grass leaves in Festuca and Calamagrostis plots) to separate some of the positive and negative effects of natural mounds. Mean PAR measured in February at the soil surface varied from 11 to 969 µm/m2/s. As predicted, shade structures that decreased light availability but also increased soil moisture generally increased Holcus seedling establishmen...