Response of a Native Perennial Grass Stand to Disturbance in California's Coast Range Grassland

Abstract

To assess the potential for enhancing an existing stand of native perennial grasses on a California Coast Range Grassland site, we experimentally manipulated the seasonal timing and presence of grazing for 3 years (1994 through 1996) and of autumn burning for 2 years (1994 and 1995) and measured species cover for 6 years (1993 through 1998). We subjected the species matrix to classification (TWINSPAN) and ordination (CCA) and tested the ordination site scores as well as diversity indices with linear mixed effects models. Four distinct plant community groups emerged from the classification. Two of these were dominated by annual grasses and two by perennial grasses. No treatment effects were observed on diversity. For composition, temporal and spatial random effects were important mixed effects model parameters, as was the fixed effect covariate, pre-treatment CCA site score, indicating the importance of random environmental variation and initial starting conditions. Incorporation of these random effects and initial condition terms made for more powerful tests of the fixed effects, grazing season, and burning. We found no significant burning effects. Grazing removal imparted a shift in plant community from more annual-dominated toward more perennialdominated vegetation. Individual perennial grass species responded differently according to genus and species. Nassella spp. increased gradually over time regardless of grazing treatment. Nassella pulchra (purple needlegrass) increase was greatest under spring grazing and N. lepida (foothill needlegrass) was greatest with grazing removal. Danthonia californica (California oatgrass) had little response over time under seasonal grazing treatments, but increased with grazing removal. Under relatively mesic weather conditions it appears that grazing removal from Coast Range Grasslands with existing native perennial grass populations can increase their cover. However if N. pulchra is the sole existing population, spring season-restricted grazing should be equally effective at enhancing cover of the native grass species.

The ecology of restoration: historical links, emerging issues and unexplored realms

“…Even post-establishment, a number of restoration studies have shown that management treatments, such as grazing and burning, can be highly contingent upon year effects (e.g. Sarr 2002; Bartolome et al 2004;Foster & Dickson 2004). Here we discuss two additional kinds of year effects that are also particularly relevant to restoration.…”

Soil heterogeneity and the distribution of native grasses in California: Can soil properties inform restoration plans?

“…Barkworth (purple needlegrass) (Hickman 1993). These species are the targets of numerous restoration programs and evidence suggests that they were historically common in coastal woodlands and grasslands (Holstein 2001, Bartolome et al 2004, Rein et al 2007). The contribution of spatial and environmental components to bunchgrass species abundance was estimated using canonical analysis and variation partitioning, with subsequent testing of individual variables identified in ordination.…”

Eliminating Invasive Introduced Species While Preserving Native Species in Coastal Meadow Habitat, a Critically Imperiled Ecosystem

“…Increases in non-native annual forbs were a result of significant increases in Geranium dissectum (Appendix B). This weedy annual forb responds vigorously to disturbance (Bartolome et al 2004). Non-native annual grasses increased due to three species (Aira caryophyllea, Bromus hordeaceus L. ssp.…”