Distribution of northern pocket gopher burrows, and effects on earthworms and infiltration in a prairie landscape in Alberta, Canada

The prairie pothole region of North America is characterized by hydrologically closed depressions that seasonally fill with water and provide critical early season habitat for migratory waterfowl. Infiltration of snowmelt and rainfall in the uplands and under these depressions, controls the lateral input of water to the depressions. Relationships between soil infiltrability and land use, topography, northern pocket gopher burrowing, and endogeic earthworm abundances were studied in a prairie pothole region near Calgary, Alberta. An alfalfa field and an adjacent grassland area were divided into upland, transitional, and depressional zones. Gopher mound distribution and area was measured in each land-use area and each topographic zone, earthworm abundance was estimated by excavation, and infiltration was measured by a ring infiltrometer. Depressional areas in the grassland contained fewest mounds, averaging 0.2 mounds per 25 m2. Conversely, the depressional areas in the alfalfa contained 9.2 mounds per 25 m2. Transitional zones in the alfalfa and grassland averaged 4.6 and 6.9 mounds per 25 m2, respectively. In the transition zones in the two land-use areas, earthworms were Aporrectodea trapezoides and Aporrectodea tuberculata. Worm density in soil not under gopher mounds averaged 250 worms m−3 in the grassland and 82 worms m−3 in the alfalfa. Under gopher mounds, there were 860 worms m−3 in the grassland and 49 worms m−3 in the alfalfa. However, the effects of gopher and earthworm burrowing on water infiltration rates were unclear. Gopher burrowing activity appeared to have no effect on infiltration rates in either area.