Historical contingency in ecology and restoration: climate change, year effects, and priority effects in California grasslands

University Of California-Davis, Davis CA

Investigators

Abstract

There are two opposing models of how natural communities develop after disturbance. One theory predicts that community composition will tend to return to the pre-disturbance state, regardless of the vagaries of early establishment. Alternatively, it has been suggested that the species that make up communities are largely determined by the order of arrival of colonizers. The unresolved question is: Do different arrival times of species produce different stable communities in the long term, or do plant communities on similar sites eventually end up with similar compositions? This study seeks to answer this question while at the same time assessing whether interannual temporal variation affects the long-term outcome of these processes. Environmental variation across years (for example, variation in the amount and pattern of rainfall) can affect the results of experiments followed for multiple years, producing different results in different years. Similarly, rare climatic events may often drive long-term community structure. Despite this, most ecological studies are followed for only a single year, and the vast majority of ecological experiments are initiated in a single year. This multi-year research program will examine the plant community ecology of California grasslands, controlling for colonization order of plants in the context of year-to-year variation in rainfall. The research has practical implications for ecosystem restoration. These include developing techniques to increase species diversity on restoration projects, and improving the success of projects by focusing planting efforts on years with highest likelihood of success, decreasing the cost of restoration by decreasing replanting. This research will also test whether rare climatic events are more important for plant communities than gradual changes in average climate, with implications for how we respond to climate change. In addition, this project will enhance the long-term relationship between our lab and the Student and Landowner Education and Watershed Stewardship (SLEWS) program, which brings high school youth (often from disadvantaged groups) into rural settings to assist in restoration projects on local farms. This program benefits not only the students and the farmers, but also the graduate student mentors.