Impacts of short-rotation hybrid poplar plantations on regional water yield

Abstract

Hybrid poplar plantations are being established on northwestern Minnesota farmlands in response to demands for timber, pulp and paper, and as a potential source of biomass energy. The Minnesota Department of Natural Resources estimates that between 30 000 and 40 000 ha of former cropland, and former conservation reserve program (CRP) land that was primarily herbaceous cover, will be converted to tree plantations by 2005. This paper reports the results of a 2-year study of the effects of such land use conversions on water yield for plots within tributary watersheds of the Red River of the North, in northwestern Minnesota. Three 8- and 9-year-old hybrid poplar plantations and three 22- to 34-year-old natural mixed hardwood stands were instrumented to measure precipitation, soil moisture, and soil water chemistry. Climatological observations at these sites were used to estimate potential evapotranspiration. These data were used to apply the GLEAMS model (Knisel, W.G. (Ed.), 1993. GLEAMS: groundwater loading effects of agricultural management systems. UGA-CPES-BAED Publication No. 5, University of Georgia. Coastal Plain Experimental Station, Tifton, GA, 259 pp.) to predict water yield from the two cover types. No significant differences in water yield were detected between hybrid poplar plantations and natural forest stands ( α=0.05). The similarities between the hydrology of these two cover types suggest that increasing the acreage of short-rotation hybrid poplar plantations may influence average peak flows in streams, stormflow during average events, snowmelt runoff and spring flooding in the region.