Monday, August 3, 2009

PS 2-21: Affects of grazing and removal of woody species on ant diversity

Sonny Shlomo Bleicher, Rochester Institute of Technology

Background/Question/Methods
In the LTER-Israel at Mt Meron National Reserve in Israel we studied the effects that grazing by cattle and the removal of the dominant woody species (Quercus calliprinos) on ant assemblages. The effectiveness of five trapping methods were tested (pit fall traps, baiting, timed manual searching, sweeping by canvas net and litter sampling).  We hypothesized that the removal of woody species would cause a lowering on ant diversity and that grazing would raise it. Five four dunam (1000 M3) plots were divided into four sections each managed according to a different regime testing for the different regimes and incorporating the two.  Samples were collected from the different plots three years into the management plan, during the summer of 2007. The samples were identified down to species level where possible using a key to the ants of Israel (Kugler, unpublished). This spring-summer season (2009) another LTER-Israel site (which received half the annual rainfall) will be compared to the data from 2007 and may be added to the poster/ presentation.
Results/Conclusions
Approximately 30 species of ants were found in the site in Meron (depending vouchering at Tel Aviv University’s zoological collection).  Grazing raised diversity as hypothesized in the plot, and the removal of woody species lowered the diversity slightly. The two management regimes converged caused a significant decline in diversity.  
Dry pit fall traps yielded the highest diversity and abundance in collected species from the site. Manual collection and baiting were statistically significant in collection of a diverse sample of ant species. Sweeping and litter sampling showed marginal to no statistical significance (when run through a rarefaction test for 95% confidence. Our conclusions were that a normal controlled grazing activity (as practiced in that region for thousands of years) has a beneficial effect on ant diversity while removal of woody species leads to rapid degradation in the environment causing a loss in diversity as well. We also concluded that for this region the use of pit fall traps, baiting and timed manual active searching collection methods are the most efficient at detecting less dominant ant species.