{1B0B5221-C726-4E7D-93FD-23F7A4FF8930} eng; USA utf8 dataset EnviroAtlas Coordinator U.S. Environmental Protection Agency, Office of Research and Development-Sustainable and Healthy Communities Research Program, EnviroAtlas Geospatial Data Owner (919) 541-3832 109 T.W. Alexander Drive Research Triangle Park NC 27709 EnviroAtlas@epa.gov https://www.epa.gov/enviroatlas pointOfContact 2025-07-23 ISO 19115 Geographic Information - Metadata ISO 19115:2003/Cor.1:2006(E) EnviroAtlas - Biological nitrogen fixation in natural/semi-natural ecosystems by 12-digit HUC for the Conterminous United States, 2006 2015-05-07 publication U.S. EPA Office of Research & Development (ORD) - National Exposure Research Laboratory (NERL) Research Triangle Park NC publisher US Environmental Protection Agency (US EPA) originator This EnviroAtlas dataset contains data on the mean biological nitrogen fixation in natural/semi-natural ecosystems per 12-digit Hydrologic Unit (HUC) in 2006. Biological N fixation (BNF) in natural/semi-natural ecosystems was estimated using a correlation with actual evapotranspiration (AET). This correlation is based on a global meta-analysis of BNF in natural/semi-natural ecosystems (Cleveland et al. 1999). AET estimates for 2006 were calculated using a regression equation describing the correlation of AET with climate (average annual daily temperature, average annual minimum daily temperature, average annual maximum daily temperature, and annual precipitation) and land use/land cover variables in the conterminous US (Sanford and Selnick 2013). Data describing annual average minimum and maximum daily temperatures and total precipitation for 2006 were acquired from the PRISM climate dataset (http://prism.oregonstate.edu). Average annual climate data were then calculated for individual 12-digit USGS Hydrologic Unit Codes (HUC12s; https://water.usgs.gov/GIS/huc.html; 22 March 2011 release) using the Zonal Statistics tool in ArcMap 10.0. AET for individual HUC12s was estimated using equations described in Sanford and Selnick (2013). BNF in natural/semi-natural ecosystems within individual HUC12s was modeled with an equation describing the statistical relationship between BNF (kg N ha-1 yr-1) and actual evapotranspiration (AET; cm yr-1) and scaled to the proportion of non-developed and non-agricultural land in the HUC12. The first half of the equation represents the most conservative estimate in a meta-analysis of BNF in natural/semi-natural ecosystems (Cleveland et al. 1999), and was chosen over the central and high estimates because recent, top-down global mass balances that suggest that natural BNF rates are less than previous estimates based on scaled-up estimates from individual plots (Vitousek et al. 2013). The land use/land cover modifier is not included in the original Cleveland et al. (1999) analysis. We believe it is appropriate to include so as not to overestimate BNF in HUC12s with large proportions of urban or agricultural development. These data represent an average N input to individual HUC12s, i.e., they are not specific to an individual land use type within the HUC12. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets). The purpose of this data set is to provide information that can be used to estimate landscape-level loading of biological nitrogen fixation (BNF) in natural/semi-natural ecosystems to water resources management units, and to other management- or ecosystem-relevant spatial units. BNF is a natural supply of reactive nitrogen to ecosystems that helps sustain biological productivity, and information describing natural rates can help frame the degree to which humans have altered the loading of N to terrestrial and aquatic ecosystems. These data can be used to examine correlations with air and water quality characteristics or be fed into terrestrial and aquatic biogeochemical models. The overall goal of EnviroAtlas is to employ and develop the best available science to map indicators of ecosystem services production, demand, and drivers for the nation. completed EnviroAtlas Coordinator U.S. Environmental Protection Agency, Office of Research and Development-Sustainable and Healthy Communities Research Program, EnviroAtlas Geospatial Data Owner (919) 541-3832 109 T.W. Alexander Drive Research Triangle Park NC 27709 EnviroAtlas@epa.gov https://www.epa.gov/enviroatlas pointOfContact asNeeded Ecosystem Environment theme EPA GIS Keyword Thesaurus 12-digit HUCs Ecosystem Ecosystem Services EnviroAtlas Environment Environmental Atlas theme EnviroAtlas Alabama Arizona Arkansas California Colorado Connecticut Delaware Florida Georgia Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Texas United States Utah Vermont Virginia Washington Washington DC West Virginia Wisconsin Wyoming place None https://edg.epa.gov/EPA_Data_License.html otherRestrictions Use Constraints: None. Please check sources, scale, accuracy, currency and other available information. Please confirm that you are using the most recent copy of both data and metadata. Acknowledgement of the EPA would be appreciated. otherRestrictions Access Constraints: None PUBLIC https://project-open-data.github.io/schema/#accessLevel Standard Technical Controls eng; USA environment -128.02839229 -65.20336449 22.7348894 51.6773602 2013-09-27 Citations: Cleveland, C. C., A. R. Townsend, D. S. Schimel, H. Fisher, R. W. Howarth, L. O. Hedin, S. S. Perakis, E. F. Latty, J. C. Von Fischer, A. Elseroad, and M. F. Wasson. 1999. Global patterns of terrestrial biological nitrogen (N2) fixation in natural ecosystems. Global Biogeochemical Cycles 13:623-645; Sanford, W. E., and D. L. Selnick. 2013. Estimation of evapotranspiration across the conterminous United States using regression with climate and land-cover data. Journal of the American Water Resources Association 49:217-230; Vitousek, P.M., D. N. L. Menge, S. C. Reed, and C. C. Cleveland. 2013. Biological nitrogen fixation: rates, patterns and ecological controls in terrestrial ecosystems. Philosophical Transactions of the British Royal Society 368:1471-2970. This EnviroAtlas dataset is based on data originally developed using a version of the Watershed Boundary Dataset (WBD 2011) extracted for EnviroAtlas on March 22, 2011. In 2015, EnviroAtlas transitioned from the WBD 2011 to a newer version - the National Hydrography Dataset Plus (NHDPlus) V2 WBD Snapshot, EnviroAtlas version - which includes updated 12-digit HUC boundaries for the Conterminous United States. This EnviroAtlas dataset was created by reallocating the original WBD 2011 dataset to the NHDPlus V2 WBD Snapshot using area-weighted reallocation. The area weighting process assumes that values are distributed evenly across HUCs. In cases where values are unevenly distributed within a HUC, this can result in misallocated values in the new dataset. Therefore, users should exercise caution when interpreting this data, especially in regions where there are significant changes to the 12-digit HUCs. The majority of spatial changes between the two 12-digit HUC versions took place along the California coast, in Minnesota, and along the US-Canada border, especially in New England. Metric values for most of the rest of the United States are essentially unchanged. If the user is interested in data for a specific small area, especially in areas that were modified, using the original WBD 2011 version of this dataset joined with the WBD 2011 boundary feature class should provide accurate metric values. As new versions of the dataset are developed using the 2015 HUCs, these will replace the reallocated datasets in EnviroAtlas. Before reallocating the metrics, edits were made to the area of some 12-digit HUCs. For example, along the coast of California some 12-digit HUCs had stopped at the coastline in the WBD 2011 dataset but were extended into the ocean in the NHDPlus V2 dataset. Instead of reallocating the metrics using the total area of the NHDPlus V2 HUCs, the land area based on National Land Cover Database (NLCD) 2011 was used to update the land area values. This ensured the land area of the NHDPlus V2 HUCs roughly matched the land area of the WBD 2011 HUCs. This method helped avoid incorrectly distributing terrestrial metrics, such as including the new ocean-extended area in the denominator of values that were originally calculated using land-only area as the denominator, which would result in artificially lowering the values of per-unit area metrics in the ocean-extended HUCs. true Entity and Attribute Information Entity and Attribute Overview: These data provide per area reactive nitrogen inputs (kg N/ha/yr) to individual 12-digit HUCs across the conterminous United States. A comprehensive list of metric creation steps is included in the Processing Steps. Biological N fixation (BNF) in natural/semi-natural ecosystems was estimated using a correlation with actual evapotranspiration (AET). This correlation is based on a global meta-analysis of BNF in natural/semi-natural ecosystems (Cleveland et al. 1999). AET estimates for 2006 were calculated using a regression equation describing the correlation of AET with climate and land use/land cover variables in the conterminous US (Sanford and Selnick 2013). Data describing annual average minimum and maximum daily temperatures and total precipitation at the 2.5 arcmin (~4 km) scale for 2006 were acquired from the PRISM climate dataset (http://prism.oregonstate.edu). The AET regression equation requires annual average daily temperature; we thus calculated annual average temperature as the mean value of the minimum and maximum temperature on a cell-by-cell basis using the Zonal Statistics tool in ArcMap 10.0 (ESRI, Inc. Redlands, CA). Average annual daily temperature, average annual minimum daily temperature, average annual maximum daily temperature, and annual precipitation were then calculated for individual 12-digit USGS Hydrologic Unit Codes (HUC12s; https://water.usgs.gov/GIS/huc.html; 22 March 2011 release) using the Zonal Statistics tool in ArcMap 10.0. The National Land Cover Database (NLCD) for 2006 were acquired from the USGS at the scale of 30 x 30 m (http://www.mrlc.gov/nlcd06_data.php). Percent covers of developed lands (d; low + medium + high intensities), agricultural land (a; cultivated crops + hay/pasture), forest (f; conifer + deciduous + mixed), shrubland (s; dwarf + shrub/scrub), grassland/herbaceous, and wetland (w; woody + emergent herbaceous) were calculated for individual HUC12s using the Zonal Statistics tool in ArcMap 10.0. AET for individual HUC12s was estimated with the following equations (Sanford and Selnick 2013): (1) AET = PΛ(τ∆/(τ∆+Π)) (2) Λ=1+cLd+eLf+hLs+jLg+kLa+rLw (3) τ = ((Tm+T0)^m)/(((Tm+T0)^m)+a) (4) ∆=(Tx-Tn)/((Tx-Tn)+b) (5) Π=(P/P0)^n Where P is annual precipitation (cm yr-1), Tm is mean annual daily temperature ( ℃), Tx is mean annual minimum daily temperature ( ℃), Tn is mean annual maximum daily temperature ( ℃), and Li is the fraction of land cover type i within an individual HUC12. The remaining fixed parameter values for equations 2 - 5 are listed in Table 1. BNF in natural/semi-natural ecosystems within individual HUC12s was modeled with an equation describing the statistical relationship between BNF (kg N ha-1 yr-1) and actual evapotranspiration (AET; cm yr-1) and scaled to the proportion of non-developed and non-agricultural land in the HUC12: (6) BNF = (0.102 * AET + 0.524)*(1-(Ld+La)). The first half of the equation represents the most conservative estimate in a meta-analysis of BNF in natural/semi-natural ecosystems (Cleveland et al. 1999), and was chosen over the central and high estimates because recent, top-down global mass balances that suggest that natural BNF rates are less than previous estimates based on scaled-up estimates from individual plots (Vitousek et al. 2013). The land use/land cover modifier is not included in the original Cleveland et al. (1999) analysis. We believe it is appropriate to include so as not to overestimate BNF in HUC12s with large proportions of urban or agricultural development. Table 1. Fixed parameter values for the regression equations (equations 1 - 5) describing the correlation of actual evapotranspiration with climate and land use/land cover variables. Parameter Value T0 17.737 P0 938.89 m 1.9897 n 2.4721 a 10,000 b 18.457 c 0.173 e 0.297 h 0.094 j 0.236 k 0.382 r 0.400 Cleveland, C. C., A. R. Townsend, D. S. Schimel, H. Fisher, R. W. Howarth, L. O. Hedin, S. S. Perakis, E. F. Latty, J. C. Von Fischer, A. Elseroad, and M. F. Wasson. 1999. Global patterns of terrestrial biological nitrogen (N2) fixation in natural ecosystems. Global Biogeochemical Cycles 13:623-645. Sanford, W. E., and D. L. Selnick. 2013. Estimation of evapotranspiration across the conterminous United States using regression with climate and land-cover data. Journal of the American Water Resources Association 49:217-230. Sobota, DJ, JE Compton, and JA Harrison. 2013. Reactive nitrogen inputs to US lands and waterways: How certain are we about sources and fluxes? Frontiers in Ecology and the Environment 11:82-90. Vitousek, P.M., D. N. L. Menge, S. C. Reed, and C. C. Cleveland. 2013. Biological nitrogen fixation: rates, patterns and ecological controls in terrestrial ecosystems. Philosophical Transactions of the British Royal Society 368:1471-2970. Entity and Attribute Detail Citation: https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets EnviroAtlas Coordinator U.S. Environmental Protection Agency, Office of Research and Development-Sustainable and Healthy Communities Research Program, EnviroAtlas Geospatial Data Owner (919) 541-3832 109 T.W. Alexander Drive Research Triangle Park NC 27709 EnviroAtlas@epa.gov https://www.epa.gov/enviroatlas distributor https://enviroatlas.epa.gov/download/CONUS_metrics_FGDB.zip download Download The URL providing direct access to the downloadable dataset. download https://enviroatlas.epa.gov/download/CONUS_metrics_CSV.zip ESRI:ArcGIS API The endpoint of a web service to access the dataset (REST endpoint, WMS GetCapabilities URL, or a SOAP WSDL endpoint). webMapService https://www.epa.gov/enviroatlas/enviroatlas-data information Documentation URL for accessing related documents such as data dictionary, technical information about a dataset, developer documentation, etc. information https://www.epa.gov/enviroatlas information Home Page Alternative landing page used to redirect user to a contextual, Agency-hosted "homepage" for the Dataset or API information dataset Horizontal Positional Accuracy Report Data were collected using methods that have unknown accuracy (EPA National Geospatial Data Policy [NGDP] Accuracy Tier 10). For more information, please see EPA's NGDP at https://epa.gov/geospatial/policies.html Features represented have not been tested for completeness Features represented have not been tested for completeness Tests for integrity have not been performed. This lineage was generated by the FGDC CSDGM to 19139 transformation Estimates of actual evapotranspiration (AET) were calculated from HUC12-summarized data on temperature and precipitation 2013-01-01T00:00:00 Estimates of biological nitrogen fixation (BNF) for each HUC12 were calculated using a statistical relationship between BNF and AET. BNF was scaled according to the proportion of non-developed (1 - (proportion agriculture + proportion urban)) in the HUC12. 2013-01-01T00:00:00 Reallocated values from the original March 22 2011 WBD to the NHDPlus V2 WBD Snapshot, EnviroAtlas version for the Conterminous United States using area-weighted redistribution. 2015-03-19T00:00:00 unknown 2029-07-23 This metadata was automatically generated from the FGDC Content Standard for Digital Geospatial Metadata standard (version FGDC-STD-001-1998) using the 2024-02-09T11:11:00 version of the FGDC CSDGM to ISO 19139 transform. EnviroAtlas Coordinator U.S. Environmental Protection Agency, Office of Research and Development-Sustainable and Healthy Communities Research Program, EnviroAtlas Geospatial Data Owner (919) 541-3832 109 T.W. Alexander Drive Research Triangle Park NC 27709 EnviroAtlas@epa.gov https://www.epa.gov/enviroatlas pointOfContact