Better explicating the strengths and shortcomings of these models will help refine projections and improve transparency in the years ahead.
Image credit: Witsawat.S.
Edited by Sarah E. Hobbie, University of Minnesota, Saint Paul, Saint Paul, MN, and approved February 23, 2016 (received for review August 4, 2015)
Article Figures & SI
Figures
- Fig. 1.
Herbaceous plant species richness relationships with N deposition. Raw data points (n = 15,136 sites) are gray. Surface plots represent 0.1 (red), 0.5 (median; black), and 0.9 (blue) quantile regression models (median parameters in Table 1) fitted to 3,317 open sites (combined grassland, shrubland, and woodland) (A) and 11,819 closed canopy sites (combined deciduous, evergreen, and mixed forests) (B), as influenced by soil pH. Asterisks indicate significant interactions (P < 0.05).
- Fig. S1.
Herbaceous plant species richness relationships with N deposition, as moderated by temperature and precipitation. Raw data points (n = 15,136 sites) are gray. Surface plots represent 0.1 (red), 0.5 (median; black), and 0.9 (blue) quantile regression models (median parameters in Table 1) fitted to 3,317 open sites (combined grassland, shrubland, and woodland) (A and B) and 11,819 closed canopy sites (combined deciduous, evergreen, and mixed forests) (C and D), as influenced by temperature (A and C) and precipitation (B and D). Asterisks indicate significant interactions (P < 0.05). This figure is the counterpart to the pH panels in Fig. 1.
- Fig. 2.
Nitrogen deposition (gray-scale) and critical loads for nitrogen deposition based on total graminoid plus forb species richness (colored symbols). The 3,317 open sites (combined grassland, shrubland, and woodland vegetation types) are portrayed with triangles, and the 11,819 closed canopy sites (deciduous, evergreen, and mixed forests) are portrayed with circles. Background deposition values are the average of 27 y of wet deposition (NADP 1985–2011) plus the average of 10 y of dry deposition (CMAQ 2002–2011). Other variation in critical loads is due to the other predictor variables (soil pH, temperature, and precipitation).
- Fig. S2.
Critical loads for N deposition at open vegetation sites only, based on total graminoid plus forb species richness. This figure is the same as Fig. 2, except that only the 3,317 open vegetation sites (combined grassland, shrubland, and woodland vegetation types) are portrayed here, so that those sites and the underlying N deposition can be seen more clearly. Background deposition values are the average of 27 y of wet deposition (NADP 1985–2011) plus the average of 10 y of dry deposition (CMAQ 2002–2011).
- Fig. S3.
Uncertainty in the critical loads for nitrogen deposition. The percent error in the critical load for each site in Fig. 2 is calculated at each site as the average of the absolute values of the lower and upper endpoints (equivalent to a plus/minus percent error for a symmetric CI) of the 95% confidence interval of 10,000 Monte Carlo simulations of coefficient uncertainty at each site. Background deposition values are the average of 27 y of wet deposition (NADP 1985–2011) plus the average of 10 y of dry deposition (CMAQ 2002–2011).
- Fig. S4.
Critical loads (and their 95% confidence interval) of N deposition as a function of soil pH. The 11,819 closed canopy sites (deciduous, evergreen, and mixed forests) are in A, and the 3,317 open sites (combined grassland, shrubland, and woodland vegetation types) are in B.
- Fig. S5.
Exceedances of critical loads for nitrogen deposition based on total graminoid plus forb species richness. Exceedances were calculated by subtracting critical loads (of median point estimates) from N deposition values at each site, so negative values indicate that N deposition has been below the critical load and positive values indicate that N deposition has exceeded the critical load. The 3,317 open sites (combined grassland, shrubland, and woodland vegetation types) are portrayed with triangles, and the 11,819 closed canopy sites (deciduous, evergreen, and mixed forests) are portrayed with circles. Background deposition values are the average of 27 y of wet deposition (NADP 1985–2011) plus the average of 10 y of dry deposition (CMAQ 2002–2011).
- Fig. 3.
Summary of relationships between plant species richness and N deposition in 46 gradients. Gradients (uniquely defined by vegetation type and data source) contain 6,807 sites, conditional on soil pH, average annual temperature, annual precipitation, and N deposition interactions with each of the other three predictors. In conditionally negative or positive gradients, the relationship was either negative or positive, respectively, for more than half of the range of the moderating variable(s).
- Fig. 4.
Magnitude of plant species richness changes associated with N deposition, as moderated individually by (A) soil pH, (B) average temperature, or (C) annual precipitation. Each point, symbolized by the mean N deposition of that gradient (kg⋅ha−1⋅y−1), represents an individual gradient with a single narrow vegetation type. Species richness change is calculated as the simple slope of nitrogen deposition from multiple regression coefficients: βN + (βN*M × Mi), where βN is the parameter for N deposition, βN*M is the parameter for the interaction of N deposition and the moderating variable M, and Mi are the mean (symbol) and range (lines) of the moderating variable M across the gradient. Unlike in Fig. 3, each predictor variable is considered separately.
Tables
Data name Location Source Sites Alvar Northeastern US Peet RK, Lee MT, Jennings MD, Faber-Langendoen D. Long database report: VegBank—A permanent, open-access archive for vegetation-plot data. Pages 233–241 in ref. 37. Downloaded from VegBank. 36 CO Western plains of US (Pawnee Nat. Grassland) Peet RK, Lee MT, Jennings MD, Faber-Langendoen D. Long Database Report: VegBank—A permanent, open-access archive for vegetation-plot data. Pages 233–241 in ref. 37. Downloaded from VegBank. 17 CVS Southeastern US Peet RK, Lee MT, Boyle MF, Wentworth, TR, Schafale, MP, Weakley AS. Long database report: Vegetation-plot database of the Carolina Vegetation Survey. Pages 243–253 in ref. 37. Provided by R. K. Peet and M. T. Lee in 2013 and now available in the Ecological Society of America VegBank. 2,611 FIA Contiguous US Schulz BK, Dobelbower K. Short database report: FIADB vegetation diversity and structure indicator (VEG). Page 436 in ref. 37. Provided by B. K. Schulz. Available from apps.fs.fed.us/fiadb-downloads/datamart.html. 1,280 Knutson Intermountain West of US sagemap.wr.usgs.gov/ESR_Chrono.aspx and ref. 38. Provided by K. C. Knutson. 160 MN Upper Midwest US Provided by Minnesota Biological Survey. Copyright 2013 State of Minnesota, Department of Natural Resources. 2,896 NY Northeastern US (NY Natural Heritage Program) Peet RK, Lee MT, Jennings MD, Faber-Langendoen D. Long database report: VegBank—A permanent, open-access archive for vegetation-plot data. Pages 233–241 in ref. 37. Downloaded from VegBank. 75 PNW Pacific Northwest of US Peet RK, Lee MT, Jennings MD, Faber-Langendoen D. Long database report: VegBank—A permanent, open-access archive for vegetation-plot data. Pages 233–241 in ref. 37. Downloaded from VegBank. 3,570 SW Southwestern US Provided by the Southern Colorado Plateau Network of the US National Park Service and the laboratory of W. D. Bowman. 106 VA Southeastern US Provided by the Virginia Department of Conservation and Recreation, Division of Natural Heritage, VA Plots, the DCR-DNH Vegetation Plots Database. Data exported on March 8, 2013. Now available in VegBank. 2,777 WI Upper Midwest US Waller DM, Amatangelo KL, Johnson S, Rogers DA. Long database report: Wisconsin Vegetation Database—Plant community survey and resurvey data from the Wisconsin Plant Ecology Laboratory. Pages 255–264 in ref. 37. Provided by D. M. Waller. 112 WV Southeastern US Vanderhorst JP, Byers EA, Streets BP. Short database report: Natural Heritage Vegetation Database for West Virginia. Page 440 in ref. 37. Provided by the West Virginia Natural Heritage Program. Now available in VegBank. 1,496 Overall 15,136 Variable Source Wet N deposition NADP (2013) Annual National Trends Network (NTN) Maps by Analyte. Available at nadp.sws.uiuc.edu/ntn/maps.aspx (National Atmospheric Deposition Program, Illinois State Water Survey). Dry N deposition CMAQ (Community Multiscale Air Quality) model. Provided by R. L. Dennis in 2014 (39). Precipitation, mm PRISM (2013) 30-year normals. Parameter-elevation relationships on independent slopes model. Available at prism.nacse.org/normals/ (Northwest Alliance for Computational Science & Engineering at Oregon State University) (1981–2010 normals) (40). Temperature, °C PRISM (2013) 30-year normals. Parameter-elevation relationships on independent slopes model. Available at prism.nacse.org/normals/ (Northwest Alliance for Computational Science & Engineering at Oregon State University) (1981–2010 normals) (40). Soil pH Provided with vegetation data; otherwise from USDA SSURGO soil dataset. SSURGO (2014) Geospatial Data Gateway. Available at https://gdg.sc.egov.usda.gov/GDGOrder.aspx?order=QuickState (USDA Natural Resources Conservation Service). Vegetation Alliance (33) (from National Vegetation Classification) N deposition, kg⋅ha−1⋅y−1 Sites Min. Max. Abies lasiocarpa-Picea engelmannii forest (ABLA) 1.7 5.0 355 Acer saccharum-Betula alleghaniensis-(Fagus grandifolia) forest (ACSA) 4.1 15.2 399 Acer saccharum-Tilia americana-(Quercus rubra) forest (ACETIL) 4.7 17.0 479 Andropogon gerardii-(Sorghastrum nutans) herbaceous (ANGE) 8.7 14.0 64 Artemisia tridentata shrubland (ARTR) 1.3 4.6 314 Betula papyrifera forest (BEPA) 3.4 11.4 25 Fagus grandifolia-Quercus rubra-Quercus alba forest (FAGR) 7.0 14.9 26 Festuca idahoensis alpine herbaceous (FEID) 1.8 4.6 330 Liriodendron tulipifera forest (LITU) 8.4 15.6 20 Pinus contorta forest (PICO) 1.7 4.8 603 Pinus palustris woodland (PIPA) 5.6 15.1 199 Pinus ponderosa forest (PIPO) 1.5 6.0 238 Pinus strobus forest (PIST) 4.1 13.9 50 Pinus taeda forest (PITA) 6.6 14.4 206 Populus tremuloides forest (POTR) 1.3 12.3 362 Pseudotsuga menziesii forest (PSME) 1.4 7.5 333 Pseudotsuga menziesii giant forest (PSME) 1.4 3.6 106 Pseudotsuga menziesii woodland (PSME) 1.5 4.4 656 Quercus alba-(Quercus rubra, Carya spp.) forest (QUAL) 6.6 17.8 1,362 Quercus prinus-Quercus (alba, falcata, rubra, velutina) forest (QUPR) 9.3 15.2 23 Quercus spp.-Pinus (rigida, echinata) forest (QUEPIN) 7.9 17.9 233 Quercus virginiana-(Sabal palmetto) forest (QUEVIR) 6.0 12.8 21 Schizachyrium scoparium-Bouteloua curtipendula herbaceous (SCSC) 8.4 14.3 267 Symphoricarpos albus shrubland (SYAL) 1.6 4.1 31 Thuja occidentalis forest (THOC) 4.2 9.1 24 Tilia americana-Fraxinus americana-(Acer saccharum) woodland (TIAM) 4.7 14.1 81 Overall 1.3 17.9 6,807 Name Open canopy (±1 SE) Closed canopy (±1 SE) Intercept 14.9 (3.42)* 13.6 (2.55)* N 4.69 (0.60)* 0.449 (0.33)n N2 −0.494 (0.02)* −0.125 (0.01)* pH −2.17 (0.46)* −1.49 (0.37)* Precip −0.011 (0.002)* −0.003 (0.001)* Temp −0.059 (0.18)n −0.321 (0.04)* N:pH 0.475 (0.07)* 0.543 (0.04)* N:precip 0.002 (0.001)* NA N:temp −0.073 (0.03)+ NA Regressions represent herbaceous plant species richness response to N deposition (kg⋅ha−1⋅y−1; quadratic), soil pH, total annual precipitation (mm), average annual temperature (°C), and interactions of N (deposition) with pH, precipitation, and temperature. An NA (not applicable) indicates that term didn't appear in best model. Sample size is 11,819 sites for closed canopy (deciduous forest, evergreen forest, and mixed forest) and 3,317 sites for open canopy (grassland, shrubland, and woodland). Level of significance is indicated as follows: nP ≥ 0.05, +P < 0.05, or *P < 0.001.
Vegetation CL expression (partial derivative of species richness equation) CL (kg N⋅ha−1⋅y−1) CL error§ Mean† Range† Range of 95% CI‡ Open canopy vegetation [4.690 + (0.475 · (soil pH)) + (0.0018 · (mm of precip.)) + (−0.073 · (temp. (°C)))]/(−2 · −0.494) 8.7 7.4–10.3 6.4–11.3 −4.5%, 4.8% Closed canopy vegetation [0.449 + (0.543 · (soil pH))]/(−2 · −0.125) 13.4 7.9–19.6 6.8–22.2 −6.2%, 7.7% The critical load (CL) expression is derived using the partial derivative with respect to nitrogen of the species richness equation in Table 1, and then evaluated locally with site-specific soil pH, precipitation, and temperature values.
↵† Mean and range of CLs across sites, reflecting variation in soil pH, precipitation, and temperature variables across sites but not uncertainty in coefficient estimates.
↵‡ Range of CL 95% confidence interval endpoints across sites (Fig. S3), reflecting both ecological variability (soil pH and climate variables) and uncertainty in coefficient estimates, with the latter calculated from the 2.5th and 97.5th percentiles of 10,000 Monte Carlo simulations of coefficient uncertainty.
↵§ Average of the site-specific CL % errors, calculated from the lower and upper endpoints of the 95% confidence interval of Monte Carlo simulations of coefficient uncertainty repeated at each site.
- Table S4.
Critical loads (CLs) of N deposition for level 1 ecoregions in the present study compared with previously cited estimates in Pardo et al. (18)
Level 1 ecoregion CL of N dep. cited in table 5 of ref. 18 (Pardo et al.), kg⋅ha−1⋅y−1 CL of N dep. (total herbaceous richness) from present study, kg⋅ha−1⋅y−1 Compared with Pardo et al. (18) Northern forests 7–21 (hardwood forest alteration of herbaceous understory) Open: 8.0–9.8 (mean = 8.9, n = 75) New Closed: 8.0–18.9 (mean = 13.8, n = 1,955) Similar Northwestern forested mountains 4–10 (alpine grassland species composition change) Open: 8.0–10.2 (mean = 9.1, n = 1,429) Similar Closed: 10.8–19.6 (mean = 15.3, n = 2,113) New Marine west coast forests No vascular plant CL Open: No data Closed: 10.4–15.0 (mean = 12.8, n = 24) New Eastern temperate forests <17.5 (hardwood forest declines in species-rich genera) Open: 6.6–9.7 (mean = 7.9, n = 947) New Closed: 7.8–19.3 (mean = 12.5, n = 7,378) Lower Great plains 5–15 (tallgrass prairie community shifts) Open: 8.3–9.8 (mean = 9.3, n = 618) Similar Closed: 11.3–19.6 (mean = 16.6, n = 274) New North American desert 3–8.4 (warm desert decrease of native forbs) Open: 8.3–9.9 (mean = 9.2, n = 240) Higher Closed: 13.5–17.0 (mean = 16.5, n = 32) New Temperate Sierras No vascular plant CL Open: 8.6–8.7 (mean = 8.65, n = 3) New Closed: 14.8–14.8 (mean = 14.8, n = 42) New Critical load estimates in the present study are calculated using the two equations in Table 2. “Open” refers to open canopy vegetation whereas “Closed” refers to closed canopy forest vegetation. We did not have any vegetation sites with critical loads to summarize for the remaining two ecoregions: namely the wet tropical forest and the Mediterranean California ecoregions.
- Table S5.
Summary of herbaceous plant species richness responses to N deposition in gradients
Gradient code N deposition response Data source NVC Alliance Major vegetation type Model R2 Weight Sites N_dep min N_dep mean N_dep max Precip mm min Precip mm mean Precip mm max Temp °C min Temp °C mean Temp °C max pH min pH mean pH max ACSA2 Spp decline unconditionally with N dep CVS Acer saccharum-Betula alleghaniensis-(Fagus grandifolia) forest Broad-leaved forest N_dep + pH + temp_C + 1 0.269 0.73 34 9.12 11.98 13.77 1,203 1,640 2,383 9.0 11.0 15.2 4.23 4.87 5.80 ACSA3 No N dep response FIA Acer saccharum-Betula alleghaniensis-(Fagus grandifolia) forest Broad-leaved forest pH + 1 0.107 0.62 176 4.12 8.30 14.53 680 1,034 1,613 2.9 5.6 8.9 3.42 4.49 6.54 ACSA4 No N dep response MN Acer saccharum-Betula alleghaniensis-(Fagus grandifolia) forest Broad-leaved forest 1 0.000 0.42 23 4.68 6.92 8.75 625 681 790 3.8 4.3 5.1 5.00 6.02 6.70 ACSA5 Spp decline conditional on precip WV Acer saccharum-Betula alleghaniensis-(Fagus grandifolia) forest Broad-leaved forest N_dep + N:precip + pH + precip_mm + temp_C + 1 0.426 0.65 166 9.08 11.79 15.23 886 1,217 1,718 6.3 8.8 12.9 3.20 4.48 7.90 ACETIL1 No N dep response FIA Acer saccharum-Tilia americana-(Quercus rubra) forest Broad-leaved forest 1 0.000 0.38 32 4.93 9.27 12.55 710 963 1,339 4.1 6.1 8.6 3.83 4.96 6.46 ACETIL2 Spp decline conditional on precip and temp MN Acer saccharum-Tilia americana-(Quercus rubra) forest Broad-leaved forest N_dep + N:precip + N:temp + pH + precip_mm + temp_C + 1 0.317 0.31 352 4.69 8.92 14.40 607 741 895 3.1 5.5 8.2 4.90 6.16 7.90 ACETIL3 Spp increase conditional on temp WI Acer saccharum-Tilia americana-(Quercus rubra) forest Broad-leaved forest N_dep + N:temp + temp_C + 1 0.300 1.00 95 6.02 10.75 17.04 728 848 945 4.2 7.1 8.9 4.30 5.90 7.40 BEPA No N dep response FIA Betula papyrifera forest Broad-leaved forest pH + precip_mm + 1 0.211 0.41 25 3.37 6.33 11.42 664 963 1,501 3.0 4.8 7.9 3.41 4.92 6.49 FAGR No N dep response VA Fagus grandifolia-Quercus rubra-Quercus alba forest Broad-leaved forest pH + 1 0.265 0.42 26 6.98 11.61 14.94 1,054 1,142 1,243 13.2 14.4 15.8 3.80 4.45 5.40 LITU Spp decline unconditionally with N dep FIA Liriodendron tulipifera forest Broad-leaved forest N_dep + precip_mm + 1 0.489 1.00 20 8.40 12.72 15.62 985 1,134 1,330 8.7 11.4 14.4 3.94 5.05 6.00 POTR1 No N dep response FIA Populus tremuloides forest Broad-leaved forest pH + temp_C + 1 0.218 0.25 85 4.89 7.45 12.31 627 779 1,159 2.8 4.9 7.6 3.88 5.04 7.04 POTR2 Spp decline conditional on precip MN Populus tremuloides forest Broad-leaved forest N_dep + N:precip + precip_mm + 1 0.077 0.31 227 4.69 6.97 9.29 549 655 782 3.0 4.1 5.3 4.80 6.28 7.90 POTR3 No N dep response PNW Populus tremuloides forest Broad-leaved forest precip_mm + temp_C + 1 0.446 0.67 50 1.30 2.51 4.07 325 623 1,359 1.1 4.4 7.8 5.50 6.54 7.40 QUAL1 Spp decline conditional on pH CVS Quercus alba-(Quercus rubra, Carya spp.) forest Broad-leaved forest N_dep + N:pH + pH + precip_mm + temp_C + 1 0.420 0.34 182 9.54 11.12 15.57 1,115 1,365 2,171 9.2 13.1 17.3 3.50 4.91 6.54 QUAL2 No N dep response FIA Quercus alba-(Quercus rubra, Carya spp.) forest Broad-leaved forest pH + 1 0.012 0.25 202 6.63 11.26 17.84 715 1,066 1,448 3.8 10.7 14.6 3.49 5.15 7.82 QUAL3 No N dep response MN Quercus alba-(Quercus rubra, Carya spp.) forest Broad-leaved forest pH + 1 0.085 0.33 57 6.83 11.04 13.31 625 817 892 4.0 6.9 8.3 5.40 6.45 7.50 QUAL4 No N dep response VA Quercus alba-(Quercus rubra, Carya spp.) forest Broad-leaved forest pH + temp_C + 1 0.290 0.44 355 7.08 10.76 15.38 944 1,175 1,711 7.1 12.0 15.7 3.00 4.71 7.90 QUAL5 Spp decline unconditionally with N dep WI Quercus alba-(Quercus rubra, Carya spp.) forest Broad-leaved forest N_dep + precip_mm + temp_C + 1 0.298 0.19 45 10.19 12.27 16.20 789 885 926 7.0 8.0 8.8 4.70 6.02 7.10 QUAL6 No N dep response WV Quercus alba-(Quercus rubra, Carya spp.) forest Broad-leaved forest pH + precip_mm + 1 0.273 0.45 521 8.45 11.30 15.23 874 1,163 1,725 6.5 10.5 13.0 3.30 4.47 7.50 QUPR Spp decline unconditionally with N dep FIA Quercus prinus-Quercus (alba, falcata, rubra, velutina) forest Broad-leaved forest N_dep + 1 0.214 0.25 23 9.27 11.82 15.19 911 1,129 1,338 7.9 10.4 13.9 3.23 4.21 5.36 QUEPIN2 Spp decline conditional on temp precip and pH CVS Quercus spp.-Pinus (rigida, echinata) forest Mixed forest N_dep + N:pH + N:precip + N:temp + pH + precip_mm + temp_C + 1 0.535 1.00 120 7.88 11.14 17.90 1,085 1,298 1,501 9.7 14.2 19.7 3.18 4.48 5.74 QUEPIN1 No N dep response VA Quercus spp.-Pinus (rigida, echinata) forest Mixed forest pH + temp_C + 1 0.331 0.56 113 8.40 10.95 13.73 980 1,154 1,657 7.4 12.6 15.5 3.30 4.60 8.00 QUEVIR No N dep response CVS Quercus virginiana-(Sabal palmetto) forest Mixed forest 1 0.000 0.63 21 6.01 9.35 12.75 1,185 1,265 1,451 17.3 18.6 19.2 4.56 5.70 7.85 ABLA Spp increase conditional on precip and temp PNW Abies lasiocarpa-Picea engelmannii forest Conifer forest N_dep + N:precip + N:temp + precip_mm + temp_C + 1 0.331 0.42 355 1.68 2.99 5.00 417 1,119 2,133 −1.5 2.7 7.4 4.80 6.09 7.60 PICO Spp increase conditional on temp and pH PNW Pinus contorta forest Conifer forest N_dep + N:pH + N:temp + pH + precip_mm + temp_C + 1 0.226 0.72 603 1.69 2.97 4.77 338 773 1,565 −1.4 2.9 7.4 4.80 6.23 8.20 PIPO1 No N dep response FIA Pinus ponderosa forest Conifer forest temp_C + 1 0.095 0.33 28 1.60 2.93 6.00 335 690 2,131 3.6 6.5 9.2 4.60 6.11 7.61 PIPO2 No N dep response PNW Pinus ponderosa forest Conifer forest temp_C + 1 0.109 0.54 210 1.46 2.36 4.35 328 640 1,554 0.8 6.5 9.1 5.00 6.40 7.60 PIST1 No N dep response FIA Pinus strobus forest Conifer forest pH + temp_C + 1 0.360 0.45 25 4.09 7.09 10.69 670 924 1,257 3.1 5.5 7.5 3.78 4.70 5.82 PIST2 No N dep response WV Pinus strobus forest Conifer forest pH + 1 0.235 1.00 25 8.94 10.59 13.90 970 1,143 1,464 7.0 10.2 12.2 3.70 4.60 6.50 PITA1 Spp decline conditional on temp and pH CVS Pinus taeda forest Conifer forest N_dep + N:pH + N:temp + pH + temp_C + 1 0.584 0.71 182 6.56 10.99 14.35 1,083 1,281 1,489 13.7 16.8 22.6 3.00 4.44 7.20 PITA2 No N dep response VA Pinus taeda forest Conifer forest precip_mm + temp_C + 1 0.268 0.26 24 7.38 11.54 14.41 1,064 1,092 1,124 14.5 14.8 15.3 4.60 4.88 5.30 PSME1 Spp decline unconditionally with N dep FIA Pseudotsuga menziesii forest Conifer forest N_dep + 1 0.088 0.71 62 1.42 3.55 7.51 397 1,609 4,346 4.7 8.8 12.6 4.00 5.56 7.43 PSME2 Spp increase conditional on temp and pH PNW Pseudotsuga menziesii forest Conifer forest N_dep + N:pH + N:temp + pH + precip_mm + temp_C + 1 0.159 0.48 271 1.61 2.78 4.57 305 611 1,988 −1.3 3.9 8.7 4.80 6.49 8.20 PSME3 Spp increase unconditionally with N dep PNW Pseudotsuga menziesii giant forest Conifer forest N_dep + N:pH + pH + 1 0.250 0.36 106 1.43 1.97 3.62 379 557 919 3.6 6.3 9.6 5.00 6.50 7.00 THOC No N dep response FIA Thuja occidentalis forest Conifer forest pH + 1 0.320 0.38 24 4.17 6.81 9.08 617 832 1,235 2.7 4.8 7.2 3.69 5.46 7.90 TIAM Spp decline conditional on temp MN Tilia americana-Fraxinus americana-(Acer saccharum) woodland Broad-leaved woodland N_dep + N:temp + precip_mm + temp_C + 1 0.600 0.40 81 4.69 10.33 14.06 583 743 886 3.8 6.3 7.7 5.00 6.71 7.90 PIPA2 Spp decline conditional on temp and pH CVS Pinus palustris woodland Conifer woodland N_dep + N:pH + N:temp + pH + precip_mm + temp_C + 1 0.614 0.57 199 5.59 8.99 15.06 1,103 1,356 1,697 15.2 18.8 22.8 3.40 4.59 5.98 PSME4 Spp increase unconditionally with N dep PNW Pseudotsuga menziesii woodland Conifer woodland N_dep + N:temp + precip_mm + temp_C + 1 0.289 0.55 656 1.45 2.43 4.40 244 617 1,544 0.3 4.4 8.8 5.00 6.39 8.20 ARTR1 Spp decline unconditionally with N dep Knutson Artemisia tridentata shrubland Shrubland N_dep + precip_mm + 1 0.150 0.13 143 1.26 2.09 3.79 205 265 331 6.8 9.0 10.7 7.00 7.98 9.10 ARTR2 Spp increase conditional on pH PNW Artemisia tridentata shrubland Shrubland N_dep + N:pH + pH + precip_mm + temp_C + 1 0.229 0.50 171 1.60 2.74 4.57 243 543 985 0.9 3.9 9.6 5.20 6.64 8.20 SYAL No N dep response PNW Symphoricarpos albus shrubland Shrubland pH + precip_mm + temp_C + 1 0.546 1.00 31 1.60 2.53 4.07 330 513 877 2.5 5.3 8.1 5.20 6.72 8.20 ANGE1 Spp decline conditional on temp MN Andropogon gerardii-(Sorghastrum nutans) herbaceous Grassland N_dep + N:temp + precip_mm + temp_C + 1 0.351 0.67 64 8.71 12.06 14.01 616 749 882 6.3 7.0 7.8 5.50 7.13 8.20 FEID Spp increase conditional on temp PNW Festuca idahoensis Alpine herbaceous Grassland N_dep + N:temp + pH + precip_mm + temp_C + 1 0.173 0.71 330 1.81 2.90 4.57 363 612 1,088 −0.8 3.3 8.8 5.30 6.60 8.20 SCSC Spp decline unconditionally with N dep MN Schizachyrium scoparium-Bouteloua curtipendula herbaceous Grassland N_dep + temp_C + 1 0.093 0.22 267 8.37 11.70 14.28 604 751 895 5.2 7.0 8.3 5.40 7.22 7.90
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