Identifying riparian sinks for watershed nitrate using soil surveys.
The capacity of riparian zones to serve as critical control locations for watershed nitrogen flux varies with site characteristics. Without a means to stratify riparian zones into different levels of ground water nitrate removal capacity, this variability will confound spatially explicit source-sink models of watershed nitrate flux and limit efforts to target riparian restoration and management. We examined the capability of SSURGO (1:15 840 Soil Survey Geographic database) map classifications (slope class, geomorphology, and/or hydric soil designation) to identify riparian sites with high capacity for ground water nitrate removal. The study focused on 100 randomly selected riparian locations in a variety of forested and glaciated settings within Rhode Island. Geomorphic settings included till, outwash, and organic/alluvial deposits. We defined riparian zones with "high ground water nitrate removal capacity" as field sites possessing both >10 m of hydric soil width and an absence of ground water surface seeps. SSURGO classification based on a combination of geomorphology and hydric soil status created two functionally distinct sets of riparian sites. More than 75% of riparian sites classified by SSURGO as organic/alluviumhydric or as outwash-hydric had field attributes that suggest a high capacity for ground water nitrate removal. In contrast, >85% of all till sites and nonhydric outwash sites had field characteristics that minimize the capacity for ground water nitrate removal. Comparing the STATSGO and SSURGO databases for a 64000-ha watershed, STATSGO grossly under-represented critical riparian features. We conclude that the SSURGO database can provide modelers and managers with important insights into riparian zone nitrogen removal potential.
Rosenblatt
A E
AE
Dep. of Natural Resources Science, Univ. of Rhode Island, Kingston 02881, USA.
Gold
A J
AJ
Stolt
M H
MH
Groffman
P M
PM
Kellogg
D Q
DQ
D003625:Data Collection; D017753:Ecosystem; D004784:Environmental Monitoring; D008962:Models, Theoretical; D009566:Nitrates / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis*; D011891:Rain; D012989:Soil Pollutants; D014197:Trees; D014872:Water Movements; D014873:Water Pollutants
D009566:Nitrates; D012989:Soil Pollutants; D014873:Water Pollutants; D009584:Nitrogen