O'Neill Kevin M, Olson Bret E, Wallander Roseann, Rolston Marni G, Seibert Catherine E
Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT 59717, USA.
Environ Entomol. 2010 Jun;39(3):775-86. doi: 10.1603/EN09173.
Livestock grazing can affect habitat quality for grasshoppers through effects on food and oviposition site availability, microclimate, and other factors. Because of this, some authors have suggested that grazing programs can be used to help manage pest grasshopper populations. In a 6-yr study, we controlled access of cattle to replicated experimental plots on an Agropyron spicatum/Poa sandbergii pasture to create consistent year-to-year differences in postgrazing plant cover, with resultant affects on microclimate. After sampling grasshoppers multiple times after grazing treatments each summer, we found evidence of between-treatment differences in grasshopper abundance for the entire assemblage during 4 of the 6 yr. Some species, including Melanoplus sanguinipes (perhaps the worse rangeland grasshopper pest in the western United States), tended to be more abundant on ungrazed plots, whereas Melanoplus gladstoni often had greater densities on heavily-grazed plots. The effect of grazing on grasshopper densities in this study was lower in magnitude and less consistent among years than in a study we conducted simultaneously at a nearby site where the vegetation was dominated by the exotic species crested wheatgrass (Agropyron cristatum). Our results generally support proposals that grazing could be used to reduce pest grasshopper densities, although the effectiveness of a particular grazing scheme may vary among sites, years, and grasshopper and vegetation assemblages.
牲畜放牧会通过影响食物、产卵场所的可用性、小气候及其他因素来影响蝗虫的栖息地质量。因此，一些作者建议可以利用放牧计划来帮助控制蝗虫害虫种群数量。在一项为期6年的研究中，我们控制牛群进入以穗状冰草/桑德伯格早熟禾为牧草的重复实验地块，以使放牧后植被覆盖度每年保持一致的差异，从而对小气候产生影响。每年夏天在放牧处理后对蝗虫进行多次采样后，我们发现6年中有4年整个蝗虫群落的处理间丰度存在差异。一些物种，包括红胫戟纹蝗（可能是美国西部最严重的牧场蝗虫害虫），在未放牧地块上往往数量更多，而格拉德斯通戟纹蝗在重度放牧地块上的密度通常更高。与我们同时在附近一个以外来物种扁穗冰草为主导植被的地点进行的研究相比，本研究中放牧对蝗虫密度的影响在幅度上较小，且年份间的一致性较差。我们的结果总体上支持了放牧可用于降低蝗虫害虫密度这一建议，尽管特定放牧方案的有效性可能因地点、年份、蝗虫和植被群落而异。
