Technical Note: Nitrogen and phosphorus in runoff from 2 montane riparian communities

It was hypothesized that the type and height of riparian vegetation would affect its ability to filter and retain inorganic nitrogen (nitrate-nitrogen (NO3--N), ammonium-nitrogen (NH4+-N)), and inorganic phosphorus (phosphate-phosphorus (PO4-3-P)), A rotating boom rainfall simulator was used to evaluate 2 montane riparian communities as filters for removing NO3--N, NH4+-N, and PO4-3-P nutrients from sediment laden overland flow water. One riparian community was characterized by Kentucky bluegrass (Poa pratensis L.) and tufted hairgrass (Deschampsia caespifosa (L.) Beauv,), while the second community was dominated by beaked sedge (Carex rostrata Stokes) and water sedge (Carex aquatilus Wahl.). Three vegetation height treatments were evaluated: control (natural condition), moderate treatment (clipped to IO-cm height and clipped material removed), and heavy treatment (clipped to ground level, clipped material removed, and litter vacuumed up). A 10-m wide riparian buffer zone was an efficient filter as about 84% NO3--N and 79% PO4-3-P was removed from the applied water and sediment. However, there were no consistent differences among specific vegetation height treatments or communities in the removal of N and P nutrients.