Evaluating the impact of tree species diversity on resilience of forest growth and survival to acidic deposition
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Temperate forest ecosystems throughout the globe are a major sink for carbon and provide other essential ecosystem services, but these services have been partly compromised by chronic exposure to acidic deposition, stemming historically from NOX and SOX emissions from fossil fuel combustion, for over a century. While increased rates of atmospheric N deposition, also stemming from agricultural NH3 emissions, have also been found to contribute to selective greater growth rates in trees; it is unclear if net primary production is enhanced since these studies do not account for survival. Oftentimes, the negative impacts of S deposition on growth and survival have also not been explicitly incorporated into modeled responses to atmospheric deposition. Proper accounting of species sensitivities to atmospheric S and N deposition are imperative for evaluating the impacts of NH3-N + NOx-N and SOx emissions on forest growth and survival responses. We are currently applying recently published empirical, species specific growth and survival models (n=94 species) to predict the response of 1.4 million trees observed in forest inventory analysis plots (FIA) across the contiguous United States for the year 2012. We expect forest growth and survival to be enhanced by atmospheric N deposition, but this fertilization effect is substantially offset by atmospheric S deposition and other negative effects of N deposition. In addition, we will quantify species diversity in 121,000 FIA plots and compared it to survival and growth responses across regional and national scales. We expect more diverse forests to be more resilient to higher rates of atmospheric N and S deposition. This analysis will provide pertinent information to decision makers developing management strategies to make forests more resilient to future environmental change.