Geophysical Evidence to Link Terrestrial Insect Diversity and Groundwater Availability in Non-Riparian Ecosystems

Abstract:

Wyoming, the third driest state in the United States, is home to a high level of biodiversity. In many cases, ecosystems are dependent on the vast systems of water resting just below the surface. This groundwater supports a variety of organisms that live far from surface water and its surrounding riparian zone, where more than 70% of species reside. In order to observe the correlation of groundwater presence and biodiversity in non-riparian ecosystems, a study was conducted to look specifically at terrestrial insect species linked to groundwater in Bighorn National Forest, WY. It was hypothesized that the more groundwater present, the greater the diversity of insects would be. Sample areas were randomly selected in non-riparian zones and groundwater was evaluated using a transient electromagnetic (TEM) geophysical instrument. Electrical pulses were transmitted through a 40m by 40m square of wire to measure levels of resistivity from near the surface to several hundred meters below ground. Pulses are echoed back to the surface and received by a smaller 10m by 10m square of wire, and an even smaller 1m by 1m square of wire set inside the larger transmitting wire. An insect population and species count was then conducted within the perimeter set by the outer transmitting wire. The results were not as hypothesized. More inferred groundwater below the surface resulted in a smaller diversity of species. Inversely, the areas with a smaller diversity held a larger total population of terrestrial insects.