|Whitford, Walter -|
|Steinberger, Y. -|
Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 29, 2012
Publication Date: June 2, 2012
Citation: Whitford, W.G., Steinberger, Y. 2012. Effects of seasonal grazing, drought, fire, and carbon enrichment on soil microarthropods in a desert grassland. Journal of Arid Environments. 83:10-14. Interpretive Summary: Soil microarthropods are small animals with external skeletons, including mites and inset larvae that live below ground. They play an important role in decomposing organic matter, such as plant roots, and in releasing nutrients, such as nitrogen, for plant growth. This study evaluated the impact of above ground activities such as grazing by cattle, and impacts, such a fire and drought, on the number of microarthropods in the soil. The most abundant microarthropod in this desert environment was a species of mite. The numbers of microarthropods per cubic meter of soil were not impacted by any above ground activity or impact, except for summer drought. Severe droughts during the summer growing season reduced the amount of plant roots in the soil, which, in turn, reduced the food base for microarthropods. Unless an activity or impact reduces the organic matter in the soil, the microarthropod numbers are not affected.
Technical Abstract: This study was designed to test hypotheses about the combined effects of short-term, seasonal grazing with seasonal drought, fire, and carbon enrichment on soil microarthropod communities in a Chihuahuan Desert grassland. The study was conducted in eighteen 0.5 ha plots following three consecutive years of treatment: six plots intensively grazed in summer, six in winter, and six not grazed. There was no difference in perennial grass cover on the summer-grazed and winter-grazed plots. Intensive seasonal grazing had no effect on the abundance and community composition of soil microarthropods. Within each plot there were six subplots: summer rain-out, winter rain-out, burned, glucose amendment, rainout control and burn-glucose control. Fire and carbon enrichment had no significant effect on soil microarthropod abundance or community composition. The average number of microarthropods ranged from 8915 _ 1422 m_2 in the ungrazed, unburned plots to 7175 _ 1232 m_2 in the winter-grazed, unburned plots. Microarthropod densities in the glucose-amended plots were 8917 _ 4902 m_2 in the winter-grazed plots and 10,731 _ 863 m_2 in the glucose-amended, summer-grazed subplots. The prostigamatid mite, Tydeus sp., was the most abundant microarthropod taxon in all treatment plots.