Rainfall patterns in arid and semi-arid regions are characterized by a reduction in rainfall frequency. However, under this novel climatic condition, potential changes in soil nematode community among different degraded grasslands remain unclear. We conducted a mesocosm experiment to test the effects of lower precipitation frequency (decreased by 50% from the long-term mean) on nematodes in the lightly degraded (LDG), moderately degraded (MDG) and severely degraded grasslands (SDG). The decreased precipitation frequency treatment significantly reduced the total abundance of nematodes by reducing soil moisture and enhancing moisture variability. Compared with other trophic groups of nematode, bacterivores were more sensitive to the altered precipitation and were significantly suppressed by higher soil moisture variation caused by lower precipitation frequency in the degraded grasslands. The decreased precipitation frequency treatment promoted plant belowground biomass through increasing soil moisture variation, which promoted plant parasites in LDG. However, in MDG and SDG, plant parasites were mainly suppressed by higher soil moisture variation under the altered precipitation frequency treatment, and were less impacted by the aforementioned stimulation in plant belowground biomass. The nematode community structure was not affected by the altered precipitation frequency treatment. This study provides experimental data for predicting responses of ecosystem functions to the projected changes in precipitation regimes. These findings are critical for making feasible decisions for the sustainable management of degraded grasslands.

干旱和半干旱地区的降雨模式的特点是降雨频率减少。然而，在这种新的气候条件下，不同退化草地之间土壤线虫群落的潜在变化仍不清楚。我们进行了中观实验，以测试较低的降水频率（比长期平均值降低 50%）对轻度退化 (LDG)、中度退化 (MDG) 和严重退化草原 (SDG) 中线虫的影响。减少降水频率处理通过降低土壤水分和增强水分变异性显着降低了线虫的总丰度。与线虫的其他营养群相比，食菌动物对改变的降水更敏感，并被退化草原中较低的降水频率引起的较高土壤水分变化显着抑制。减少降水频率处理通过增加土壤水分变化促进植物地下生物量，从而促进 LDG 中的植物寄生虫。然而，在千年发展目标和可持续发展目标中，植物寄生虫主要受到改变降水频率处理下较高的土壤水分变化的抑制，并且受上述植物地下生物量刺激的影响较小。线虫群落结构不受降水频率变化处理的影响。本研究为预测​​生态系统功能对降水状况预测变化的响应提供了实验数据。