Relationships between net primary production, soil moisture and topography in semi-arid grassland environments

This research studies one small basin within Grasslands National Park, Saskatchewan, Canada with a focus on net primary production (NPP), soil moisture and topography. Its purpose is to examine the distribution of soil moisture with respect to topography, and to examine any relationships between NPP and soil moisture or topography. Measures of soil moisture and vegetation biomass were taken along ten transects crossing a test basin during the summer of 2005 and correlated with detailed topographic data. Results showed that the topographic index (TI) and slope were better predictors of soil moisture than upslope area, that NPP and soil moisture do not correlate well, and that TI is a stronger predictor of NPP when the data is segregated by dominant vegetation cover. The strongest predictor of NPP is upslope area, with a threshold of approximately 5.0 m² resulting in a noticeable increase in the range of NPP.