Restoration of dryland ecosystems is often limited by low seedling establishment and survival. Defoliation caused by insects and small mammals could be an overlooked cause of seedling mortality. In the sagebrush steppe, we examined the effect of seedling defoliation on the survival of perennial grasses commonly used as restoration materials. Under field conditions, seedlings of three perennial bunchgrass species (non-native Agropyron cristatum, and native grasses Poa secunda and Pseudoroegneria spicata) were defoliated at two intensities (30 % and 70 % leaf length removal) and frequencies (one or two clippings) and compared to a non-defoliated control. Following emergence the first year, clippings occurred at the two-leaf stage; a second clipping occurred 1 month later for repeated defoliation treatments. We monitored seedling survival and tillering for 2 years. We expected higher defoliation intensity and frequency to reduce survival for all species, but only a few treatments reduced Po. secunda survival. Conversely, larger-statured Triticeae (wheatgrasses) benefited from some defoliation treatments. In both years, A. cristatum survival increased with repeated defoliation at both intensities. Defoliation did not affect Ps. spicata survival in the first year, but a single defoliation in the second year resulted in increased survival. In both A. cristatum and Ps. spicata, higher-intensity defoliation reduced the boost to survival resulting from defoliation frequency. Seedlings with more tillers had greater survival probabilities, but tiller number was unaffected by defoliation. Further research may elucidate mechanisms seedlings use to compensate for or benefit from defoliation. In the meantime, managers should aim to select defoliation-tolerant species if they anticipate herbivory will be problematic for restoration sites.

中文翻译：

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在北大盆地的山艾树草原中，幼苗落叶可能会提高优势小麦草的存活率，但不会提高播种用于恢复的早熟禾的存活率

旱地生态系统的恢复通常受到幼苗建立和存活率低的限制。昆虫和小型哺乳动物引起的落叶可能是幼苗死亡的一个被忽视的原因。在山艾树草原，我们研究了幼苗落叶对常用作修复材料的多年生草本生存的影响。在田间条件下，以两种强度（30% 和 70% 的叶片长度去除）和频率（一次或两次剪报）对三种多年生草本植物（非本地 Agropyron cristatum 和本地禾本科 Poa secunda 和 Pseudoroegneria spicata）的幼苗进行落叶，然后与非落叶对照相比。出苗后第一年，剪枝发生在二叶期；1个月后进行第二次修剪，以进行重复脱叶处理。我们监测了 2 年的幼苗存活和分蘖情况。我们预计更高的落叶强度和频率会降低所有物种的存活率，但只有少数处理降低了 Po。第二个生存。相反，较大的小麦科（小麦草）受益于一些落叶处理。在这两年中，A. cristatum 的存活率随着两种强度下的反复落叶而增加。落叶不影响 Ps。spicata 在第一年存活，但在第二年单次落叶导致存活率增加。在 A. cristatum 和 Ps 中。spicata，较高强度的落叶降低了落叶频率对生存的促进作用。分蘖多的幼苗成活率较高，但分蘖数不受落叶影响。进一步的研究可能会阐明幼苗用于补偿或受益于落叶的机制。与此同时，如果管理人员预计食草会对恢复地点造成问题，他们应该着眼于选择耐落叶的物种。