02885nas a2200205   4500008004100000245012000041210006900161300001300230490000700243520216800250653001302418653001602431653001202447653002102459653002602480653001202506100001502518700001802533856012802551       2001                        eng d00aSpatial and temporal patterns of nitrogen concentrations in pristine and agriculturally- influenced prairie streams0 aSpatial and temporal patterns of nitrogen concentrations in pris  a125 -1410 v533 aLong-term data on nitrogen chemistry of streams draining Konza Prairie Biological Station (Konza), Kansas were analyzed to assess spatial and temporal patterns and examine the influence of agricultural activity on these patterns. Upland watersheds of Konza are predominantly tallgrass prairies, but agricultural fields and riparian forests border the lower reaches of the streams. We have up to 11 years of data in the relatively pristine upland reaches and 4 years of data on wells and downstream reaches influenced by fertilized croplands. Seasonal and spatial patterns in total nitrogen (TN) concentrations were driven largely by changes in the nitrate (NO3 −) concentrations. A gradient of increasing NO3 − concentrations occurred from pristine upland stream reaches to the more agriculturally-influenced lowland reaches. Nitrate concentrations varied seasonally and were negatively correlated with discharge in areas influenced by row-crop agriculture (p = 0.007). The NO3 − concentrations of stream water in lowland reaches were lowest during times of high precipitation, when the relative influence of groundwater drainage is minimal and water in the channel is primarily derived from upland prairie reaches. The groundwater from cropland increased stream NO3 − concentrations about four-fold during low-discharge periods, even though significant riparian forest corridors existed along most of the lower stream channel. The minimum NO3 − concentrations in the agriculturally influenced reaches were greater than at any time in prairie reaches. Analysis of data before and after introduction of bison to four prairie watersheds revealed a 35% increase of TN concentrations (p < 0.05) in the stream water channels after the introduction of bison. These data suggest that natural processes such as bison grazing, variable discharge, and localized input of groundwater lead to variation in NO3 − concentrations less than 100-fold in prairie streams. Row-crop agriculture can increase NO3 − concentrations well over 100-fold relative to pristine systems, and the influence of this land use process over space and time overrides natural processes.10aammonium10agroundwater10aNitrate10anutrient cycling10ariparian buffer zones10astreams1 aKemp, M.J.1 aDodds, W., K.  uhttp://knz.lternet.edu/content/spatial-and-temporal-patterns-nitrogen-concentrations-pristine-and-agriculturally-influenced