Integrating climate and air pollutant effects on coastal redwood population dynamics

Climate and air pollution are stressors that profoundly alter forest tree diversity and abundance. Understanding the ecological impacts of these stressors, and their interactions, is critical for developing effective forest management under changing climate and air pollution conditions. Specifically, disentangling how future climate change will modify tree species’ responses to changes in atmospheric nitrogen (N), sulfur (S), and ozone (O3) exposure is an important step towards predicting biodiversity impacts. As recent work in the western United States has found that climate (precipitation and temperature) plays a significant role in predicted population growth rates of trees, one of the next steps is to integrate projected climate change and atmospheric exposure of air pollutants. Here, we used publicly available data to determine how population growth rate of a culturally and economically important tree species, the coastal redwood (Sequoia sempervirens), is affected by current and future projected climate change and air pollution (i.e., N, S, and O3 exposure and changes in fire frequency). The goal of this work is to combine growth, survival, and recruitment relationships to determine overall responses of tree populations to climate and air pollution effects. We used tree growth, survival, and recruitment data (USDA Forest Inventory Analysis) with N and S deposition (National Atmospheric Deposition Program), O3 exposure data (U.S. EPA’s Air Quality System), and climate date (PRISM) to determine how sensitive tree growth, survival, and recruitment are under current levels of atmospheric N, S, and O3 exposure. In our preliminary analyses, we found that tree growth is affected by precipitation, while survival and recruitment are most influenced by the presence of other live trees. We are still working towards integrating the effects of N, S, and O3 on vital rates. We will combine these rates into population growth models to estimate future growth rates using downscaled climate models and varying levels of atmospheric pollutant exposure. This research will further advance our understanding of how N and S deposition and O3 exposure affects growth and survival of trees species across the U.S.

Impact/Purpose

Environmental problem: Climate change and atmospheric deposition of pollutants impact tree abundance and distribution. These in turn can profoundly affect biodiversity, carbon sequestration, and many other ecosystem services. Thus, understanding the combined effects of climate, deposition, and disturbance on tree dynamics is critical for predicting changes to future ecosystem structure and function. As coastal redwoods are a long-lived, culturally important species facing warmer temperatures and changes in precipitation, we evaluated the effects of atmospheric deposition, climate, and disturbance on growth, survival, and canopy recruitment.  We used tree data from the USFS Forest Inventory and Analysis, climate data from PRISM climate group, and N and S deposition data from the National Atmospheric Deposition Program. In our preliminary analysis, we found that growth rate of coastal redwoods are affected by N and S deposition, vapor pressure deficit, and fire impacts. This work is ongoing, and we next plan to incorporate ozone into our analyses.  In order to understand long-term impacts of climate and deposition on coastal redwood ecosystems, we will project how changes in climate and deposition regimes will impact future population growth rate.  These findings could help land managers and stakeholders make informed decisions about management plans and policies protecting these ecosystems. Additionally, the results from this study could be used to inform how climate change might impact the economy (specifically tourism) surrounding an iconic species.

Citation

Dalton, R., S. Kaylor, T. Greaver, C. Clark, AND S. Leduc. Integrating climate and air pollutant effects on coastal redwood population dynamics. Ecological Society of America, Long Beach, CA, August 04 - 09, 2024.