WHITTEMORE-OLSON, A. A.*, A. MOSIER, AND JOHN C. MOORE. Department of Biological Sciences, University of Northern Colorado, Greeley, CO 80639. - Effects of elevated atmospheric carbon dioxide on micro-arthropod populations of the Shortgrass Steppe.
We studied the effects of doubled atmospheric CO2
concentration on the density and diversity of microarthropods of the
Shortgrass Steppe of the Pawnee National Grasslands in Colorado.
Samples were extracted from soil cores taken from three ambient
CO2 chambers, three doubled CO2 chambers and
three control plots. The treatments were established in the spring of
1997 and the first year's data was collected after the first full
growing season, in the fall of 1998. In all, we collected 18 soil
cores per year or two cores per chamber or plot, each of which was
separated into five depths. The total microarthropods for combined
depths, found in the first year, equaled 744 in the ambient
CO2 chambers, 523 in the control plots and 670 in the
doubled CO2 chambers. While the total microarthropod
densities were similar across treatments, the numbers of
cryptostimatid, astigmatid, mesostigmatid and prostigmatid mites began
to show differences by functional groupings. The cryptostigmatid mites
had the highest densities in the ambient chambers and control plots.
The doubled CO2 chambers had higher densities of predatory
prostigmatid mites. The populations did not demonstrate significant
treatment affects but did have significant treatment by depth
interactions. The aggregation of mite populations to lower soil
horizons was apparent.
Key words: CO2, microarthropods, mites