The Climate Adapted Seed Tool: Using Provenance Tests to Inform Oak Seed Transfer in a Changing Climate

Joseph Stewart, Department of Environmental Science and Policy, UC Davis

Jessica Wright, Pacific Southwest Research Station, USDA Forest Service; James Thone, Department of Environmental Science and Policy, UC Davis; Victoria Sork, Department of Ecology and Evolutionary Biology, UC Los Angeles

Legacy guidelines for seed transfer in California were based on a system of seed zones and elevation bands, and meant to constrain seed transfer to relatively local sources. By judiciously moving seeds to track the climatic adaptations of their source populations, we can take a proactive step to better adapt ecosystems to climate change. Provisional guidelines to incorporate climate-adaptation into seed transfer are contained in the Climate Adapted Seed Tool (CAST) and based on data from seed transfer experiments (provenance tests). CAST estimates of the performance (e.g., growth and survival) of candidate seed sources in units relevant to management (e.g., carbon sequestration) and allows users to examine how performance is projected to change over time, as the climate continues to warm. Robust provenance-test datasets for conifers indicate that populations tend to be adapted to the historical climate where they are found and that relatively small differences in climate—commensurate with the magnitude of recent and/or anticipated anthropogenic climate change—can result in substantial declines in growth and survival. Compared with conifers, provenance data for oaks are relatively sparse. Recently published analyses of provenance test data for 5-yr-old Quercus lobata suggest populations may be adapted to climates at least 4°C colder than local historical climate conditions, suggesting that populations may be adapted to long-past climate conditions approaching the last glacial maximum. In light of available evidence, we will discuss and analyze potential climate-based seed transfer approaches for California oaks. How much inference can be gained from early measurements of provenance tests? Should climate-based seed transfer guidelines optimize trees for growth and survival, or should they attempt to place trees in conditions that approximate what their parents grew in prior to rapid anthropogenic climate change?