Sharp Bowman Tiffanny R, McMillan Brock R, St Clair Samuel B
Department of Plant and Wildlife Sciences, Brigham Young University, Provo, UT, 84602, USA.
Oecologia. 2017 Nov;185(3):465-473. doi: 10.1007/s00442-017-3944-y. Epub 2017 Sep 8.
Ecosystems are transformed by changes in disturbance regimes including wildfire and herbivory. Rodent consumers can have strong top-down effects on plant community assembly through seed predation, but their impacts on post-germination seedling establishment via seedling herbivory need better characterization, particularly in deserts. To test the legacy effects of fire history, and native rodent consumers on seedling establishment, we evaluated factorial combinations of experimental exclusion of rodents and fire history (burned vs. unburned) on seedling survival of 14 native plant species that vary in their life history strategies and growth form in the Mojave Desert. Seedlings were placed into the experimental plots, and seedling survival was monitored daily for 8 days. The legacy effects of fire history had minimal effects on seedling survival, but rodent exclusion, year, and their interaction were strongly significant. Seedling survival rates were nearly sixfold greater in rodent exclusion plots compared to control plots in 2012 (53 vs. 9%) and 17-fold greater in 2013 (17 vs. 1%). The dramatic increase in seedling mortality from 2012 to 2013 was likely driven by an increase in rodent abundance and an outbreak of grasshoppers that appears to have intensified the rodent effect. There was strong variability in plant species survival in response to rodent herbivory with annual plants and forb species showing lower survival than perennial plants and shrub species. These results indicate that rodent consumers can strongly regulate seedling survival of native plant species with potentially strong regulatory effects on plant community development.
生态系统会因包括野火和食草动物在内的干扰 regime 的变化而发生转变。啮齿动物消费者可通过种子捕食对植物群落组装产生强大的自上而下的影响，但其通过幼苗食草作用对种子萌发后幼苗建立的影响需要更好地加以描述，尤其是在沙漠地区。为了测试火灾历史和本地啮齿动物消费者对幼苗建立的遗留效应，我们评估了在莫哈韦沙漠中对 14 种具有不同生活史策略和生长形式的本地植物物种的幼苗存活情况，进行啮齿动物实验排除和火灾历史（火烧与未火烧）的析因组合。将幼苗放置在实验地块中，并每天监测 8 天的幼苗存活情况。火灾历史的遗留效应对幼苗存活的影响最小，但啮齿动物排除、年份及其相互作用具有很强的显著性。与对照地块相比，2012 年啮齿动物排除地块的幼苗存活率几乎高出六倍（53% 对 9%），2013 年高出 17 倍（17% 对 1%）。2012 年至 2013 年幼苗死亡率的急剧增加可能是由于啮齿动物数量增加以及蝗虫爆发，这似乎加剧了啮齿动物的影响。植物物种对啮齿动物食草作用的存活反应存在很大差异，一年生植物和草本物种的存活率低于多年生植物和灌木物种。这些结果表明，啮齿动物消费者可强烈调节本地植物物种的幼苗存活，对植物群落发展可能具有强大的调节作用。
