Granivores and the Composition of Experimental Grass and Forb Communities

[9420860]本研究将探讨食籽鸟类和食籽食叶啮齿动物是否影响高草草原的群落结构。目的是确定可预测的觅食行为是否对模型高草群落的组成和优势有可预测的后果。为此，研究人员将根据种子大小、形态和物候特征建立可控的植物物种群落。受脊椎动物保护的地块应显示出大种子物种和双种子物种的优势。啮齿类动物可及的样地具有啮齿类动物喜爱的种子的植物幼苗的覆盖度应降低，而鸟类可及的样地具有种子在其最佳处理范围内的植物的覆盖度和幼苗应降低。暴露于两者的地块将由具有最小，最不理想种子的物种占主导地位。为了完善预测，pi将对试验区内外的脊椎动物种群进行普查，并对12种植物的种子或叶子进行普通鸟类、老鼠和田鼠的选择性试验。选择的排序将决定种子偏好是否符合基于种子大小和/或相遇率的觅食理论的预测。种子和叶片选择性的排名还将提供具体的预测，说明关键动物物种可能如何影响该领域的植物群落。对现场和场外脊椎动物种群的一致性评估将允许评估处理的影响，并将其与鸟类和哺乳动物的场外影响进行比较。

9420860 Howe This study will examine whether seed-eating birds, and seed-eating and foliage-eating rodents influence community structure of tallgrass prairie. The objective is to determine whether predictable foraging behaviors have predictable consequences for composition and dominance in model tallgrass communities. To do so, the investigators will establish controlled communities of plant species stratified by seed size, form, and phenology. Plots protected from vertebrates should show dominance of large-seeded species and dicots. Plots accessible to rodents should show a depression in cover of seedlings of plant with seeds favored by rodents, while plots accessible to birds should show a depression in cover and seedlings of plant with seeds in their optimal handling range. Plots exposed to both will be dominated by species with the smallest, least desirable seeds. To refine predictions, the PIs will integrate censuses of vertebrate populations on and off the treatment plots with selectivity trials of common birds, mice, and voles on seeds or foliage of 12 plant species. Ranking of selectivities will determine whether seed preferences conform to predictions of foraging theory based on seed size and/or encounter rate. Rankings of seed and foliage selectivities will also provide specific predictions of how key animal species are likely to influence plant communities in the field. Concordant evaluation of on-site and off-site vertebrate populations will permit assessment of influences of treatments as compared with off-site effects of birds and mammals.