The climatic dependence of recruitment in western forests
The ability of species to persist under changing environmental conditions requires successful seed production and seedling establishment. These processes directly determine the environments in which species may persist in and migrate to. Seed and seedling dynamics vary substantially in response to local environmental gradients and community dynamics that are not represented in broad-scale projections of future species range dynamics. We are quantifying the impacts of local and broad-scale environmental gradients and community structure on spatial and temporal patterns of seed production, dispersal and seedling establishment in western conifer forests by monitoring seed production, seedling germination, and seedling survival across a network of long-term forest plots extending from the Oregon coast to the Cascade crest. Specifically, we are addressing questions such as: (1) What is the impact of coarse-scale climate on seed production and seedling establishment success relative to microsite conditions? (2) How does seed dispersal vary over time and space and how can this process be predicted over broad spatial extents? (3) Does the climatic dependence of recruitment vary with range position? (4) What is the role of density dependence in recruitment dynamics? This work is conducted in collaboration with the EPA Western Ecology Division.
*Seed identification resources are difficult to come by. See the link to the right for a helpful guide created by Parry Lab researcher Carmen Hixson.
Linking demography and population dynamics to tree range dynamics
Range dynamics ultimately arise from variation in demographic rates of species, and this variation may result from individual and species-specific responses to abiotic and biotic conditions. Mechanistically linking individual and population-level variation with broad-scale occurrence patterns presents complex theoretical and practical challenges, particularly for long-lived organisms such as trees which may show substantially lagged responses to environmental change. Additional challenges arise from the paucity of long-term and spatially extensive demographic data available for forest trees. We are addressing these challenges by using a variety of integrated modeling approaches to assimilate existing data on forest occurrence, population dynamics, and individual vital rates and using these models to project future and near-term climate change impacts on tree range dynamics. Specific modeling approaches include a Bayesian hierarchical metamodeling framework, inverse integral projection models, and integrated population models. We are applying these approaches to address questions such as (1) How does variation in vital rates contribute to climate-driven variation in population growth and range dynamics? (2) To what extent can forest demographic rates enable forests to track climate change? (3) Does integration of demographic information impact projections of current and future tree distributions? This work includes collaborations with Dr. Matt Talluto at the Leibniz Institute of Freshwater Ecology and Inland Fisheries, Dr. Dave Bell at the USDA Forest Service Pacific Northwest Research Station, and Dr. Kai Zhu at the University of California Santa Cruz.