Thursday, August 9, 2007

PS 56-23: Influence of grazing on the spatial heterogeneity of soil-surface temperature

Ryan Limb1, Samuel D. Fuhlendorf1, and Darrel E. Townsend2. (1) Oklahoma State University, (2) Grand River Dam Authority

Ecologists are beginning to recognize the role of heterogeneity in ecological systems and acknowledging its influence on population dynamics and biodiversity. The influence of temperature on the biotic community has been widely documented, but landscape temperature patterns are reported rarely in ecological studies. To better understand the ecological importance of these relationships to conservation and restoration of our native ecosystems, we designed an experiment to document relationships between soil surface temperature, landscape heterogeneity, and grazing intensity. The range of mean temperatures among the three grazing treatments was less than 2° C, but across riparian and upland landscapes within grazing treatments, temperatures ranged 21° C. Moderate grazing produced the smallest thermal patch size (17m) while heavy grazing and no grazing produced patch sized of 24 and 27m respectively. Also, moderately grazed pastures had higher temperature variation at nearly all scales measures. Because animals selectively graze at multiple scales and because they do not graze uniformly, grazing is likely to have an influence on the spatial arrangement of vegetation resulting in thermal heterogeneity. We determined that in terms of temperature heterogeneity, heavy grazing is not the opposite of ungrazed, but rather the opposite of moderate grazing.

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