Drought suppresses soil predators and promotes root herbivores in mesic, but not in xeric grasslands
Drought suppresses soil predators and promotes root herbivores in mesic, but not in xeric grasslands
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DOI：
10.1073/pnas.1900572116
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发表时间：
2019-06-25
影响因子：
11.1
通讯作者：
Wall, Diana H.
中科院分区：
文献类型：
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作者：
Franco, Andre L. C.;Gherardi, Laureano A.;Wall, Diana H.
降水量随年平均降水量 (MAP) 的梯度随年份和地点变化。这些变化相互作用并影响土壤生物从干旱环境到潮湿环境的方式仍然未知。降水的时空变化可能导致土壤群落功能组成的变化，这些群落涉及生态系统功能的关键方面，例如生态系统初级生产和碳循环。我们在干旱、半干旱和中温草原的田间试验中减少和增加了生长季降水2年，以研究降水对土壤线虫丰度和群落功能组成的时空控制，土壤线虫是陆地生态系统中丰富且功能多样的后生动物。我们发现，随着生长季降水量的增加，捕食性线虫丰度增加，线虫总丰度下降，这些捕食性线虫消耗并限制了营养结构较低层（包括根食者）线虫的丰度。这些线虫对降水时间变化的反应强度沿着长期 MAP 的空间梯度而增加，并且仅在中等地点发生显着影响。与时间模式相反，从干旱草原到中温草原的空间梯度，线虫丰度随着长期MAP的增加而增加。因此，预计中温草原极端干旱年份频率的增加将削弱地下捕食压力，增加食根线虫的数量，可能导致更高水平的植物侵染和植物损害，从而加剧干旱对生态系统初级生产和碳循环的负面影响。
Precipitation changes among years and locations along gradients of mean annual precipitation (MAP). The way those changes interact and affect populations of soil organisms from arid to moist environments remains unknown. Temporal and spatial changes in precipitation could lead to shifts in functional composition of soil communities that are involved in key aspects of ecosystem functioning such as ecosystem primary production and carbon cycling. We experimentally reduced and increased growing-season precipitation for 2 y in field plots at arid, semiarid, and mesic grasslands to investigate temporal and spatial precipitation controls on the abundance and community functional composition of soil nematodes, a hyper-abundant and functionally diverse metazoan in terrestrial ecosystems. We found that total nematode abundance decreased with greater growing-season precipitation following increases in the abundance of predaceous nematodes that consumed and limited the abundance of nematodes lower in the trophic structure, including root feeders. The magnitude of these nematode responses to temporal changes in precipitation increased along the spatial gradient of long-term MAP, and significant effects only occurred at the mesic site. Contrary to the temporal pattern, nematode abundance increased with greater long-term MAP along the spatial gradient from arid to mesic grasslands. The projected increase in the frequency of extreme dry years in mesic grasslands will therefore weaken predation pressure belowground and increase populations of root-feeding nematodes, potentially leading to higher levels of plant infestation and plant damage that would exacerbate the negative effect of drought on ecosystem primary production and C cycling.