Climate change impacts on California vegetation: physiology, life history, and ecosystem change.

Dominant plant species mediate many ecosystem services, including carbon storage, soilretention, and water cycling. One of the uncertainties with climate change effects on terrestrialecosystems is understanding where transitions in dominant vegetation, often termed statechange, will occur. The complex nature of state change requires multiple lines of evidence. Here,we present four lines of inquiry into climate change effects on dominant vegetation, focusing onthe likelihood and nature of climate change–driven state change. This study combinedphysiological measurements, geographic models, historical documented cases of state change,and statewide plot sampling networks together with interpolated climate grids. Together theseapproaches suggest that the vulnerability to state change will be driven by the proximity ofclimatic conditions to biological thresholds for dominant species. The sensitivity of the dominantspecies is a much greater driver of climate vulnerability compared to the degree of climatechange seen by a particular place (Section 1). Furthermore, in some cases, physiologicalmeasurements on those species can inform the nature of these thresholds (Section 3). The studyteam’s review of past state change events suggests connections between particular state changes(e.g., forest to shrubland) and particular triggers (e.g., fire; Section 2). The effect of fire isparticularly important, as it will likely interact with climatic change with implications for thesuccess of different life history strategies among woody plants (Section 4). Our work suggeststhat the biological thresholds of dominant species will play a crucial role in the vulnerability ofCalifornia terrestrial ecosystems. Understanding where climate change will push dominantspecies past these thresholds should be a major focus of future research