This work was supported by the Coweeta LTER (Long Term Ecological Research) Program (National Science Foundation [NSF] grants BSR 90 11661 and DEB 96 32854) and partially funded by the USDA, Forest Service, Southern Research Station.
Watershed management -- Southern Appalachian Region -- Water quality
We investigated the effects of removing near-stream Rhododendron and of the natural blowdown of canopy trees on nutrient export to streams in the southern Appalachians. Transects were instrumented on adjacent hillslopes in a first-order watershed at the Coweeta Hydrologic Laboratory (35°03′N, 83°25′W). Dissolved organic carbon (DOC), K+, Na+, Ca2+, Mg2+, NO3-- -N, NH4+ -N, PO43---P, and SO42- were measured for 2 years prior to disturbance. In August 1995, riparian Rhododendron on one hillslope was cut, removing 30% of total woody biomass. In October 1995, Hurricane Opal uprooted nine canopy trees on the other hillslope, downing 81% of the total woody biomass. Over the 3 years following the disturbance, soilwater concentrations of NO3-- -N tripled on the cut hillslope. There were also small changes in soilwater DOC, SO42-, Ca2+, and Mg2+. However, no significant changes occurred in groundwater nutrient concentrations following Rhododendron removal. In contrast, soilwater NO3-- -N on the storm-affected hillslope showed persistent 500-fold increases, groundwater NO3-- -N increased four fold, and streamwater NO3-- -N doubled. Significant changes also occurred in soilwater pH, DOC, SO42-, Ca2+, and Mg2+. There were no significant changes in microbial immobilization of soil nutrients or water outflow on the storm-affected hillslope. Our results suggest that Rhododendron thickets play a relatively minor role in controlling nutrient export to headwater streams. They further suggest that nutrient uptake by canopy trees is a key control on NO3-- -N export in upland riparian zones, and that disruption of the root–soil connection in canopy trees via uprooting promotes significant nutrient loss to streams.
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The published article is copyrighted by Springer and can be found at: https://doi.org/10.1007/s10021-002-0116-6
Yeakley, J., Coleman, D. C., Haines, B. L., Kloeppel, B. D., Meyer, J. L., Swank, W. T., & ... Taylor, S. F. (2003). Hillslope Nutrient Dynamics Following Upland Riparian Vegetation Disturbance. Ecosystems, 6(2), 0154-0167.