Evidence for shifts in plant species diversity along N deposition gradients: a first synthesis for the United States

The impacts of nitrogen (N) deposition on plant diversity loss have been well documented across N deposition gradients in Europe, but much less so in the U.S. Published N fertilizer studies suggest losses will occur in the US, but many of these were done at levels of N input that were higher than modeled and measured N deposition, and higher than presumed N critical loads. The recent availability of modeled N deposition across the U.S. (e.g. using CMAQ) has provided a high‐resolution tool to identify regions where steep N deposition gradients facilitate detection of ecological shifts. A number of plant diversity (richness plus abundance) data sets across the U.S. have explained diversity shifts based on anthropogenic drivers such as distance from urban and agricultural areas. In many cases investigators were unaware that they were collecting data across N deposition gradients, and in most cases they did not have access to the recent CMAQ modeled N inputs. We have assembled multiple data sets, and will seek others, to re‐analyze plant diversity data across nitrogen gradients within similar plant communities. While the analyses will of necessity be correlative, we will analyze mechanistic reasons for the responses by including available properties of soils, microclimate, plant nutrient ecophysiology, ecological traits, plant‐microbial interactions, and plant‐plant interactions.



Publications:
BBelnap J, Webb RH, Esque T, DeFalco L, Brooks M. Mojave Desert. 2016. In: Ecosystems of California Mooney H, Zavaleta E (eds) Island Press, San Francisco, CA Pgs. 635-668.
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Clark, C.M., Simkin, S.M., Allen, E.B., Bowman, W.D., Belnap, J., Brooks, M.L., Collins, S.L., Geiser, L.H., Gilliam, F.S., Jovan, S.E., Pardo, L.H., Schulz, S.K., Stevens, C.J., Suding, K.N., Throop, H.L., & Waller, D.M. “Potential Vulnerability of 348 Herbaceous Species to Atmospheric Deposition of Nitrogen and Sulfur in the United States.” Nature Plants 5, no. 7 (July 1, 2019): 697–705. https://doi.org/10.1038/s41477-019-0442-8.
Rao, L.E., Matchett, J.R., Brooks, M.L., Johnson, R.F., Minnich, R. A., Allen, E.B. (2014). Relationships between annual plant productivity, nitrogen deposition and fire size in low elevation California desert scrub. International Journal of Wildland Fire. doi: 10.1071/WF13152
Simkin, S.M., Allen, E.B., Bowman, W.D., Clark, C.M., Belnap, J., Brooks, M.L., Cade, B.S., Collins, S.L., Geiser, L.H., Gilliam, F.S., Jovan, S.E., Pardo, L.H., Schulz, B.K., Stevens, C.J., Suding, K.N., Throop, H.L., and Waller, D.M. (2016), Conditional vulnerability of plant diversity to atmospheric nitrogen deposition across the United States, PNAS, doi:10.1073/pnas.1515241113.