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Appendix A. Site coordinates and soil characteristics at Lobelia siphilitica population sites.

Site coordinates and names are shown in Table A1, and soil characteristics are shown in Tables A2 and A3. Many soil characteristics measured were correlated (Table A4), so we chose variables for further analysis that (1) would be representative of the entire dataset, (2) have been shown to be important controls on microbial community composition in previous studies, and (3) that would not saturate a predictive model using the environmental variables as explanatory factors. The nine variables used in analyses described below include % C, % N, C:N ratio, pH, % clay, % gravel, and three principal components (PCs) derived from the twelve elements measured by Mehlich 3 extraction. The first three Mehlich 3 dataset PCs summarized 80% of the variation in LP soil, and 75% in IS soil (Table A5). The first axis primarily summarized variation in P, K, Ca, Mg, S, B, and Fe, all of which were positively correlated. The second axis primarily summarized variation in Al and Mn, which were negatively correlated. The third axis primarily summarized variation in Cu. Anaerobic mineralizable nitrogen, hot-water soluble carbon, and volumetric water content were not used in the analysis because they were correlated with total N (R = 0.87, 0.89, and 0.85, respectively). Among soil texture variables, % sand and % silt were excluded because they were correlated with % clay (R = -0.69 and 0.70, respectively). CEC was correlated with % gravel (R = 0.68).

TABLE A1. Names, abbreviations, and geographic coordinates of each site.

TABLE A2. Environmental variables (soil characteristics) of LP soil at each site.� �ICPPrin� variables are the first three principal components of the nutrients measured by Mehlich 3 extraction and ICP analysis.� VWC = Volumetric Water Content; AMN = Anaerobic Mineralizable Nitrogen; HWSC = Hot Water Soluble Carbon; CEC = Cation Exchange Capacity.

TABLE A3.�Environmental variables (soil characteristics) of IS soil at each site.� �ICPPrin� variables are the first three principal components of the nutrients measured by Mehlich 3 extraction and ICP analysis.

TABLE A4. Correlation matrix of environmental variables (soil characteristics).� VWC volumetric water content; AMN = Anaerobic Mineralizable Nitrogen; HWSC = Hot Water Soluble Carbon; CEC = Cation Exchange Capacity.

TABLE A5.�Eigenvector loading factors for principal components analysis of Mehlich 3 data, separated by habitat type.