Ecological Archives E094-154-A1

Elsa E. Cleland, Scott L. Collins, Timothy L. Dickson, Emily C. Farrer, Katherine L. Gross, Laureano A. Gherardi, Lauren M. Hallett, Richard J. Hobbs, Joanna S. Hsu, Laura Turnbull, Katharine N. Suding. 2013. Sensitivity of grassland plant community composition to spatial vs. temporal variation in precipitation. Ecology 94:1687–1696.

Appendix A. Supplementary analysis of the relationships among mean annual precipitation, nitrogen deposition, and species richness at our focal sites.


Fig. A1. Panel A is identical to Fig. 2A in the main text, showing that mean annual precipitation (MAP) is a significant predictor of species richness at the 1-m² scale across our focal sites. We performed supplementary analyses to evaluate whether this pattern might be driven by another variable, such as N deposition, that also varied across our spatial gradient. Data for nitrogen (N) deposition at each site were obtained from the closest monitoring station in the National Atmospheric Deposition Program (NAPD,, measured as kg N/ha wet deposition. Many of the LTER sites have NADP monitoring stations, for the remaining sites we chose the following NADP stations: for JRG we used Davis, California (CA 88), for JRN we used Mayhill, New Mexico (NM08),for SEV we used Gila Cliff Dwellings National Monument (NM01). We used only matching years of precipitation and N deposition data for this analysis. MON and HAY are historical data sets for which we do not have an estimate of N deposition and they are not included in this supplementary analysis. While MAP is a significant predictor of nitrogen (N) deposition (Fig. A1 B, r² = 0.088, p = 0.0006), species richness at the 1 m² scale is not predicted by N deposition (Fig. A1 C, r² = 0.25, p = 0.20).

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