Does Long-term Grazing by Pack Stock in Subalpine Wet Meadows Result in Lasting Effects on Arthropod Assemblages?

Pack stock are often used in mountain environments and are grazed in uplands and wetlands, particularly subalpine wet meadows. Effects of pack stock on wetland invertebrates are unknown. Sequoia National Park, (Sierra Nevada, USA), was an ideal location for the study of lasting stock impacts on fauna, because a) there was an 18-year database of stock usage, b) there were meadows with little grazing that could be contrasted with grazed meadows, c) there is a long winter with no stock use, and d) the start of grazing for each meadow is controlled, so we could sample after greenup but just before stock arrived. We could thus address persistent conditions produced by many years of stock use in isolation from any potential short term impacts. We sampled terrestrial arthropods in paired "grazed" and "ungrazed" meadows across the Park and collected associated vegetation data. We found some negative effects of grazing on vegetation structure, but few lasting negative or positive effects of long-term stock grazing on arthropods in these wetlands. Although it appears that pack stock do not cause lasting damage to this arthropod assemblage, the extent of impact at the height of the grazing season remains unknown.