Soil organisms play a major role on litter decomposition process and nutrient cycling in forest ecosystems. These organisms are extremely sensitive to environmental conditions such as soil temperature and moisture conditions which control their demographic parameters and activity. The ongoing climate change can therefore directly affect soil biota communities and the processes they drive. Besides, climate change can also indirectly affect soil biota by altering tree functional traits (e.g., N, Ca, Mg, water holding capacity) with cascading effects on the litter quality. The aim of this study was to determine the relative effects of increased drought and litter type on microbial biomass (bacteria and fungi) and mesofauna abundance (Collembola and Acari) in three experimental sites representative of the three main forests encountered in the northern part of the Mediterranean Basin (dominated by either Quercus pubescens, Quercus ilex or Pinus halepensis) where rainfall exclusion experiments were taking place. At each site, and in each precipitation treatment (natural and amplified drought plots), we collected and transplanted foliage litters (i.e., species × drought level). After two years, we reported a litter species effect: Q. pubescens litter presented consistently the higher abundance of all soil biota groups compared to Q. ilex and P. halepensis litters in each forest. Surprisingly, despite that the amplified drought treatment induced a modification of the litter quality, we did not reported an indirect reduced precipitation effect on soil biota parameters. While Oribatid Acari abundance decreased with amplified drought in all three forest types, the direct effects on the other soil biota groups were forest-dependent. In P. halepensis forest, amplified drought resulted in higher bacterial and fungal biomasses but lower Collembola abundance. In Q. ilex forest both Collembola and predatory Acari abundances decreased with amplified drought. In addition, the positive relationships between Collembola and Oribatida abundances and litter mass loss disappeared under amplified drought conditions in both Q. ilex and P. halepensis forests. These results suggest a key role played by Ca, Mg, specific leaf area (SLA) and water holding capacity (WHC) as drivers of soil biota parameters. Finally, the study highlights that within the same Mediterranean region, climate change could differently alter the soil organisms inhabiting the litter layer and their contributions to the decomposition process depending on the tree species and soil biota group considered.

土壤生物在森林生态系统的凋落物分解过程和养分循环中起着重要作用。这些生物对环境条件极为敏感，例如控制其人口统计参数和活动的土壤温度和湿度条件。因此，持续的气候变化会直接影响土壤生物群落及其驱动的过程。此外，气候变化还可以通过改变树木的功能性状（例如氮，钙，镁，持水量）而间接影响土壤生物，从而对凋落物质量产生连锁效应。进行了降雨排除实验的毛栎，栎或樟子松。在每个地点和每个降水处理中（自然干旱地区和放大干旱地区），我们收集并移植了叶子凋落物（即物种×干旱水平）。两年后，我们报告了一种凋落物的影响：毛冬青枯萎病菌始终表现出所有土壤生物群的丰富度，高于冬青枯萎病和哈利伯冬青。每个森林里乱扔垃圾。出人意料的是，尽管扩大的干旱处理导致了凋落物质量的改变，但我们没有报道降水对土壤生物区系参数的间接降低。在三种森林类型中，随着干旱的加剧，Oribatid Acari的丰度降低，而对其他土壤生物群的直接影响则取决于森林。在P. halepensis森林中，干旱加剧导致细菌和真菌生物量较高，而Collembola丰度较低。在Q. ilex森林中，Collembola和掠食性Acari的丰度都随着干旱加剧而降低。此外，在干旱条件下，冬虫夏草和冬虫夏草的丰度与凋落物丰度之间的正相关关系消失了。和哈利普山森林。这些结果表明，钙，镁，比叶面积（SLA）和持水量（WHC）作为土壤生物区系参数的驱动因素起着关键作用。最后，研究强调，在同一地中海区域内，气候变化可能会不同地改变栖息在枯枝落叶层的土壤生物及其对分解过程的贡献，具体取决于所考虑的树种和土壤生物群。