Forested landscapes are transformed by changing climate, fire regimes and land use as well as feedbacks among them. The unprecedented drought affecting California provides a timely natural experiment for advancing our knowledge of forest change under the effects of prolonged drought. The investigators will leverage National Ecological Observatory Network (NEON) data in synergy with their microclimate measurements, experimental data on tree species establishment, and ecosystem models to understand how forest response to drought may lead to landscape change in the drought-stricken West. It is critical to understand how regional forest dynamics, driven by global change, are moderated by the effects of local topography on climate in mountainous landscapes. For example, tree seedlings may find refuge from drought conditions on cooler, moister north-facing slopes. The current drought foreshadows the expanding drought conditions anticipated under 21st century warming and offers an excellent opportunity to answer key questions about ecosystem resilience in water-limited forests of western North America. Predictive capability is critical for anticipating and planning for global change effects on forest ecosystem services that include watershed protection. Results form this research will support adaptive management of forests by land managers and policy makers and help bridge local efforts to maintain forest biodiversity and ecosystem services to regional and global mitigation plans.

The investigators will test the hypothesis that microenvironments exert a strong influence on macroecological patterns of forest dynamics. Specifically, the research questions are: 1) How do microclimates (solar insolation, surface temperature, and soil moisture regime) vary at fine spatial and temporal scales across the southern Sierra Nevada foothills and mountains of the Pacific Southwest NEON Domain? 2) How does the relationship between local microclimate and vegetation canopy cover change across the foothills to subalpine climate gradient that occur within this region? 3) How does drought-induced tree mortality affect microenvironmental conditions, and how do patterns of mortality and canopy gap formation affect subsequent forest dynamics? Imagery acquired by the NEON Airborne Observation Platform (AOP) offers an unparalleled data source to support cross-scale observation of vegetation composition, condition, and structure that, coupled with appropriate ground data, will allow the investigators to model the connections between microclimate, vegetation, plant communities and ecosystem dynamics. NEON airborne image data will be used to develop a fine-grained map of forest composition and structure based on fusion of imaging spectroscopy and airborne laser scanning data. Mapped vegetation structure will be used as a predictor, along with climate, in seedling establishment models. Mapped forest composition will set the initial conditions for a forest community simulation model of landscape disturbance and succession, and seedling establishment probabilities under global change scenarios will be used in the simulations. The proposed research will deepen our understanding of how knowledge of local scale biophysical variation can be incorporated into models of large-scale ecosystem dynamics. This project addresses the EAGER-NEON objective of leveraging NEON data in combination with other data to extend the spatial and temporal dimensions of potentially transformative research.