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COMPARISON OF ANOVA AND KRIGING IN DETECTING ANT RESPONSES TO ENVIRONMENTAL STRESSORS
Citation:
Nash, M S., G T. Flatman, AND W G. Whitford. COMPARISON OF ANOVA AND KRIGING IN DETECTING ANT RESPONSES TO ENVIRONMENTAL STRESSORS. Presented at Southwestern EMAP Symposium, San Francisco, CA, April 12-16, 1999.
Impact/Purpose:
The primary objectives of this research are to:
Develop methodologies so that landscape indicator values generated from different sensors on different dates (but in the same areas) are comparable; differences in metric values result from landscape changes and not differences in the sensors;
Quantify relationships between landscape metrics generated from wall-to-wall spatial data and (1) specific parameters related to water resource conditions in different environmental settings across the US, including but not limited to nutrients, sediment, and benthic communities, and (2) multi-species habitat suitability;
Develop and validate multivariate models based on quantification studies;
Develop GIS/model assessment protocols and tools to characterize risk of nutrient and sediment TMDL exceedence;
Complete an initial draft (potentially web based) of a national landscape condition assessment.
This research directly supports long-term goals established in ORDs multiyear plans related to GPRA Goal 2 (Water) and GPRA Goal 4 (Healthy Communities and Ecosystems), although funding for this task comes from Goal 4. Relative to the GRPA Goal 2 multiyear plan, this research is intended to "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors." Relative to the Goal 4 Multiyear Plan this research is intended to (1) provide states and tribes with an ability to assess the condition of waterbodies in a scientifically defensible and representative way, while allowing for aggregation and assessment of trends at multiple scales, (2) assist Federal, State and Local managers in diagnosing the probable cause and forecasting future conditions in a scientifically defensible manner to protect and restore ecosystems, and (3) provide Federal, State and Local managers with a scientifically defensible way to assess current and future ecological conditions, and probable causes of impairments, and a way to evaluate alternative future management scenarios.
Description:
In an ecosystems, ants effect ecosystem functions such as water infiltration, soil nutrient distribution and composition of the soil seed bank. Ants have also been used as indicators of ecosystems health. In a study, we hypothesized that some ant species would respond to changes in vegetation characteristics by relocating their colonies, or by modifying their foraging behavior. We examined responses of ant species to environmental stressors (shrub removal and short-term intense seasonal grazing by domestic livestock) over four years period by comparing results from Analysis of Variance and kriging. The study site was located on the Jornada Experimental Range, Las Cruces, NM. Eighteen 0.5 ha plots were arranged in two rows of nine plots that were blocked along the long axis. Ants were sampled by pitfall traps arranged in 7 x 7 trap arrays with 9.14 in spacing between traps on each of the 0.5 ha plots. ANOVA results indicated that abundance of ants was significantly different among years as a result of large differences in rainfall and temperature. Three species, Conomyrma spp., Pogonomyrmex spp. and Forelius spp. did not respond significantly to shrub removal, but they responded significantly to grazing shrub removal interactions. The habitat structure changes resulting from shrub removal were hypothesized to have a larger effect on the structure and activity of the ant community than grazing by cattle.
Kriging maps demonstrated that spatial analysis can be used to detect changes on behavior of species that respond to environmental stressors. These patterns m be used in developing indicators of exposure to environmental stress.