Invasion of non-native shrubs comprises a serious economic and ecological problem in North American forests. Prescribed grazing by goats may offer an effective alternative to traditional methods of control, but has received little study in forest settings. In a 5-year field experiment, we varied the stocking of goats and number of grazing periods to determine effects of prescribed grazing on both invasive shrubs and native plant species. Specifically, we examined how varied stocking levels and grazing periods affect: (1) the cover and height of invasive shrub and native woody species (2) the cover and diversity of herbaceous species, and (3) the density of native tree seedlings. Data were analyzed with linear mixed-effects models. We found that prescribed grazing by goats significantly reduced the cover and height of invasive shrubs, regardless of goat stocking or duration. Generally, the greatest reductions in invasive shrub cover occurred in treatments with two grazing periods, regardless of goat stocking. While we observed mostly neutral or positive effects on the herbaceous layer, all grazing treatments reduced the cover and height of native understory woody species. While changes were not significant, we observed a general decline in the aggregate height of native tree species regeneration. Our results suggest that prescribed grazing by goats provides an effective and environmentally friendly treatment for heavy invasions of non-native shrubs such as Rosa multiflora, but grazing needs to be followed by focused mechanical or chemical treatments to maintain control while allowing the regeneration of native tree species.

中文翻译：

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山羊规定放牧对阔叶混交林中非本地入侵灌木和本地植物物种的影响

非本地灌木的入侵在北美森林中构成了严重的经济和生态问题。山羊规定的放牧可能是传统控制方法的有效替代方法，但在森林环境中的研究很少。在为期 5 年的田间试验中，我们改变了山羊的放养量和放牧期数，以确定规定的放牧对入侵灌木和本地植物物种的影响。具体而言，我们研究了不同的放养水平和放牧期如何影响：（1）入侵灌木和本地木本物种的覆盖率和高度（2）草本物种的覆盖率和多样性，以及（3）本地树苗的密度。使用线性混合效应模型分析数据。我们发现山羊的规定放牧显着降低了侵入性灌木的覆盖度和高度，无论山羊放养或持续时间。一般来说，无论山羊放养情况如何，在两个放牧期的处理中侵入性灌木覆盖的减少最大。虽然我们观察到对草本层的大部分中性或积极影响，但所有放牧处理都减少了本地林下木本物种的覆盖率和高度。虽然变化并不显着，但我们观察到本地树种更新的总高度普遍下降。我们的结果表明，山羊的规定放牧为非本地灌木的严重入侵提供了一种有效且环保的治疗方法，例如 虽然我们观察到对草本层的大部分中性或积极影响，但所有放牧处理都减少了本地林下木本物种的覆盖率和高度。虽然变化并不显着，但我们观察到本地树种更新的总高度普遍下降。我们的结果表明，山羊的规定放牧为非本地灌木的严重入侵提供了一种有效且环保的治疗方法，例如 虽然我们观察到对草本层的大部分中性或积极影响，但所有放牧处理都减少了本地林下木本物种的覆盖率和高度。虽然变化并不显着，但我们观察到本地树种更新的总高度普遍下降。我们的结果表明，山羊的规定放牧为非本地灌木的严重入侵提供了一种有效且环保的治疗方法，例如Rosa multiflora，但放牧后需要进行集中机械或化学处理，以保持控制，同时允许本地树种再生。