Effect of ground squirrel burrows on plant productivity in a cool desert environment

Abstract

Previous work demonstrated that burrows of Townsend's ground squirrels (Spermophilus townsendii Merriam) in cool deserts increased the amount of spring recharge of soil moisture compared to areas without burrows. The objective of this study was to test the hypothesis that this additional soil moisture would enhance plant productivity. I compared productivity of western wheatgrass (Agropyron smithii Rydb.) and big sagebrush (Artemisia tridentata Nutt.) plants adjacent to burrows to plants in areas lacking burrows. Grass productivity was estimated within an experimental grid containing cells of either 0, 2, 4, or 6 artificial burrows and was based on measures of annual above ground biomass production and number of seed heads produced. For sagebrush, productivity was estimated from bushes without burrows (controls) and ones having a natural burrow near their base. Sagebrush productivity was based on average length of new annual terminal growth of vegetative stems. The mean annual estimates of grass biomass (50.0 g m-2 year-1, SE = 11.8) was significantly higher in test grid cells with the highest number of artificial burrows than controls (42.6 g m-2 year-1, SE = 11.4). The mean of annual estimates of sagebrush stem growth for bushes adjacent to burrows was a significant 0.6 cm (SE = 0.11) longer than bushes without burrows. I conclude that the added moisture from spring recharge at ground squirrel burrows can increase plant productivity in a cool desert environment.