Linking Landscape Characteristics and Stream Nitrogen in the Oregon Coast Range: Red Alder Complicates Use of Nutrient Criteria” – E
Total Page：16
File Type：pdf, Size：1020Kb
APPENDIX FOR “LINKING LANDSCAPE CHARACTERISTICS AND STREAM NITROGEN IN THE OREGON COAST RANGE: RED ALDER COMPLICATES USE OF NUTRIENT CRITERIA” – E. A. GREATHOUSE, J. E. COMPTON, AND J. VAN SICKLE Supplemental Table 1 is a comprehensive list of plot- to watershed-scale studies which indicate that alder species increase N levels in aquatic systems. The data sets we compiled include several studies which used probability-based sampling designs following the protocols of USEPA’s Environmental Monitoring and Assessment Program (EMAP) (i.e., sampling sites were randomly selected from the population of interest and therefore well represent the region’s chemistry conditions at the time of sampling). Other data sets in our compilation are from targeted monitoring, watershed experiments, and special purpose collections by individual researchers. Supplemental Table 2 lists projects with stream chemistry data from the Oregon Coast Range which we did not collate. We obtained stream N data from 761 sites in total (Fig. 1 of main paper), but only 593 of these sites were streams without evidence of estuarine and beach/dune influence, draining land within the OCR, and with data on analytes that were both widely represented across the region and had adequate detection limits. The 593 sites in Table 1 of the main paper were judged to be definitely within the OCR and representative of a freshwater stream system because: 1) at least 98% of the watershed was within the OCR; 2) the study site was judged to be upstream from the head of tide; and 3) the site was not located in the Clatsop region. Eliminating sites below the head of tide was intended to screen out lowland tidal streams and estuarine sites where relationships between watershed characteristics and chemistry are likely complex, due to tidal influence on streamflow, and difficult to tease apart from high N inputs from ocean upwelling (Brown and Ozretich, 2009). Head of tide was determined from a GIS layer of heads of tide (Sounhein, 2000), if possible. For streams lacking a head of tide in the Sounhein (2000) layer, we used GIS layers of wetlands (U.S. Fish and Wildlife Service, 2008) and elevation (30-m National Elevation Dataset, Gesch, 2007) to judge whether the site was upstream from the head of tide. Clatsop sites were similarly eliminated because the Clatsop region is a small coastal plain of ~100 km2 of unconsolidated dune and beach sand in northwest Oregon; furthermore, 1 watershed delineations are inaccurate, and complex groundwater dynamics cause uncertainty in whether stream chemistry reflects watershed attributes, in this dune/beach sand region (Sytsma, 2005). Supplemental Table 3 lists the number of freshwater stream sites we collated which had nutrient data that we did not do analyses on because they lacked adequate spatial representation or detection limits: ammonium and total dissolved nitrogen. Ammonium was analyzed by automated phenate at the Oregon Department of Environmental Quality Laboratory, and by a comparable automated colorimetry method at the Willamette Research Station, but we did not do analyses on NH4-N concentrations because those analyzed at the OR DEQ Lab were generally below a detection limit of 20 µg NH4-N/l. Likewise, TDN was analyzed by persulfate digestion at both the Willamette Research Station and the Cooperative Chemical Analytical Laboratory, but we did not do analyses on TDN because this analyte was not well represented in the database (sites with TDN data were concentrated in three small regions). The relative lack of TDN data also meant that we were not able to examine patterns in dissolved organic nitrogen (DON), because DON is determined by subtracting NH4-N and NO3-N from TDN. Sampling points from different projects in Table 1 of the main paper were considered to be the same site if stream line distance between sampling points was <1 km, there were no USGS 24K blue line tributaries entering between the two sampling points, there were no obvious changes in land use or point sources, there was not a large difference in watershed areas, and they were not in large mainstem rivers; 42 sampling points were consolidated into 21 sites, but numbers in Table 1 reflect all 42 sampling points (e.g., one site was sampled in both the REMAP Coast Range project and the OR Tillamook Kilchis project, and it is included in both projects’ number of sites in Table 1 of the main paper; one site was sampled in both the EMAP West project and the OR Salmon Plan project, and it is included in both of these projects’ number of sites in Table 1 of the main paper; etc.). Data from OCR EMAP projects were stored in the Surface Waters Information Management (SWIM) system, an internal USEPA server of EMAP data which is no longer in existence; however, we obtained most of 2 our EMAP data from a database compiled from SWIM by Herlihy and Sifneos (2008). We downloaded OR DEQ data from LASAR (Laboratory Analytical Storage and Retrieval, http://deq12.deq.state.or.us/lasar2), an online database of OR DEQ air and water quality monitoring data (search criteria are listed below). After downloading, LASAR data required additional quality control specific to the data set: sites characterized as sloughs were eliminated; sites with descriptions related to point sources and landfills were eliminated, unless verified to be stream sites; duplicate samples for laboratory quality control analyses were eliminated after recoding samples which were mislabeled as duplicates; multiple parameter names for analytes were confirmed to be equivalent with DEQ Laboratory personnel (e.g., all nitrate analytes listed in search criteria are nitrate/nitrite-N in mg N/l); and many sites' latitude/longitude coordinates were corrected based on stream names, site descriptions, and personal communications with OR DEQ personnel. LASAR search criteria: Type of Data = Grab and Continuous Sampling Location Filter = EPA Coast Range Ecoregion Station type = Stream or River System = LASAR Sample Matrix = Aqueous – Surface Water Sample Date Range = 1/1/1990 – 10/25/2007 QC Status = A+ or A Analytes 1345 Ammonia mg/L 2586 Ammonia as N mg/L as N 2335 Ammonia as N mg/L 2043 Nitrate mg/L 1061 Nitrate as N mg/L 2264 Nitrate/nitrite mg/L as N 1168 Nitrate/nitrite mg/L 1868 Nitrate/nitrite as N mg/L 1303 Total Kjeldahl Nitrogen mg/L 1397 Total Kjeldahl Nitrogen mg/L as N 2868 Total Total Kjeldahl Nitrogen mg/L as N As described in the main text, we grouped direct measurements and estimates of TN (i.e., direct measurements from persulfate digestion and estimates from TKN and NO3-N). Such grouping of TN 3 data measured/estimated by different methods is a standard and long-term practice in freshwater biogeochemistry (e.g., Herlihy and Sifneos, 2008; Stanley and Maxted, 2008). Furthermore, adding TKN and NO3-N was the standard method for determining TN for decades prior to the development of the persulfate digestion method (Patton and Kryskalla, 2003). However, we further validated our grouping of direct measurements and estimates of TN by fitting separate models for the two types of TN data. These models showed similar forms and coefficients; thus, our analysis of all measured and estimated summer TN data combined is supported by both the literature and our own data. Natural non-forested land cover categories from the 2000 GNN/IMAP layer (LEMMA 2008) included in our estimates of watershed-level percent natural land cover were ESLF codes 3155, 3158, 3165, 3177, 5311, 5409, 5457, 7013, 7161, 7162, 9106, 9166, 9221, 9260, and 9281. CAFO locations in the 2007 OR Department of Agriculture CAFO layer were from GPS coordinates taken at the center of the main area where animals are located (Diana Walker, Oregon Department of Agriculture, personal communication, September 18, 2008). SUPPLEMENTAL TABLE 1. Plot- and Watershed-Scale Studies Indicating Relationships Between Alder (Alnus) Species and N in Aquatic Systems. Location Citations Evidence or indication of effect of alder on aquatic N Alaska Stottlemyer, 1992 Longitudinal patterns in streamwater N matched longitudinal patterns in A. viridis cover along Rock Creek in Denali National Park Hu et al., 2001 Based on pollen and sediment records, alder expansion during the Holocene increased dissolved N in Grandfather Lake Johnson and Edwards, 2002 Relative area of A. rubra explained 60% of the variation in nitrate among streams on Prince of Wales Island O’Keefe and Edwards, 2002 Watershed cover of A. crispa explained 75% of the variation in dissolved N among streams in the Lynx Creek watershed region 4 British Columbia Coast Binkley et al., 1982 Over a 9-month period, both in-stream nitrate, and soil water nitrate at various depths, were greater in a watershed with high levels of A. rubra compared to a watershed with little A. rubra California Goldman, 1961 Springs along the east shore of Castle Lake, which was dominated by A. incana stands, had twice the amount of ammonium and 10x the amount of nitrate than did springs along the west shore where there was little alder; east shore spring water N from alder was estimated to be ~15% of the lake's inorganic N budget Leonard et al., 1979 In Lake Tahoe's Ward Valley watershed, sub-basins with substantial cover of A. incana had high nitrate concentrations compared to sub-basins without A. incana stands Triska et al., 1989 Injected nitrate in return flow (water returning to the channel that had entered the hyporheos at an upstream location) under an abandoned alder-lined channel was higher than expected compared to a conservative tracer, whereas injected nitrate in another return flow with no alder present was less than expected Michigan Stottlemyer and Toczydlowski, Mean monthly nitrate beneath alder stands was 1999 strongly correlated to streamwater nitrate in the Wallace Lake watershed over a 4-year period New York Hurd and Raynal, 2004 Channel water and groundwater nitrate in a riparian wetland dominated by A.