Vegetation monitoring provides information on how plant communities respond to spatial and temporal abiotic variation and stressors. We collected and analyzed ten years of vegetation data collected from multiple permanent transects across Orange County, CA, to understand the fluctuating patterns of species abundance in shrub and prairie communities. We investigated regional trends through space and time over ten years. This time period coincided with a large wildfire, and extreme drought, and rapid population explosions of particularly problematic non-native species. Data were analyzed with a variety of linear models, including repeated measures ANOVAs, and with NMMDS.
The cover of native shrubs remained relatively constant over ten years, despite major abiotic variation. Annual forbs and grasses increased and decreased with inter-annual variation in precipitation, with annual forbs also responding to the previous year’s abundance of annual grasses. Shrub cover decreased dramatically following wildfire, but recovered to pre-burn levels in three years. Areas with the highest shrub cover showed dramatic decreases following severe drought, while those with initially low shrub cover increased despite drought. Coastal shrub communities had a higher proportion of native plants than inland shrub communities, and had more natives than coastal or inland prairie communities. We conclude that shrub communities are incredibly resilient, but that communities characterized by the highest native cover and biodiversity may be the most susceptible to abiotic stressors.