In the coming decades, Mediterranean forests are likely to experience higher heat-wave frequency that may severely affect soil microbial functioning. Here, we studied the effects of warming intensification on soil microbial communities and tested whether certain types of Mediterranean plant residues favor soil biological resistance to frequent drying and warming events (FDW). To this aim, we set-up mesocosms in which soils originating from six Mediterranean forest stands (i.e, Quercus ilex and Q. pubescens and Pinus halepensis and P. sylvestris monospecific and mixed stands) were amended with corresponding coarse (crushed branches) and fine (crushed twigs with leaves/needles) woody debris. A quantity of residues corresponding to five-fold the equivalent of the quantity left on the floor after tree harvesting/logging (equivalent to 35 gC.kg⁻¹ soil DW) was added to each pot, and mesocosms were laid out into a split-plot design and subjected to FDW. After nineteen months, soil physico-chemical properties and changes in microbial communities' diversity and structure, biomass and extracellular enzymatic activities were measured. We showed that FDW reduced the richness of the soil fungal community by ca. 11% and functional diversity by ca. 4% and increased bacterial richness by ca. 40%. We observed a drastic down-regulation of extracellular enzyme activities related with N and C cycles (respectively -44% for protease, -54% for cellulase and -31% for tyrosinase activities). We also found that residues inputs types (fine vs. coarse) only slightly mitigate those effects, while species origin did. Our study showed that residues retention could alleviate the consequences of hydric and thermic stresses on microbial communities by modulating communities’ resistance in specific stands. These results suggest that tree residues retention, in specific stands, could contribute to sustain soil biological properties in the context of Mediterranean climate intensification.

在未来几十年中，地中海森林可能会经历更高的热浪频率，这可能会严重影响土壤微生物的功能。在这里，我们研究了变暖加剧对土壤微生物群落的影响，并测试了某些类型的地中海植物残留物是否有利于土壤生物抵抗频繁的干燥和变暖事件（FDW）。为此，我们建立了中生态系统，其中的土壤源自六种地中海森林（即冬青和毛栎、黑松和樟子松）单一和混合林）用相应的粗（压碎的树枝）和细（压碎的带有叶子/针的树枝）木质碎片进行了修正。相当于树木采伐/伐木后留在地板上的残留量的五倍（相当于 35 gC.kg ^-1土壤 DW）被添加到每个盆中，并将中生态系统布置成裂区设计并进行 FDW。十九个月后，测量了土壤理化性质以及微生物群落多样性和结构、生物量和细胞外酶活性的变化。我们发现 FDW 使土壤真菌群落的丰富度降低了约 10%。11% 和功能多样性约。4%，细菌丰富度增加约 4%。40%。我们观察到与 N 和 C 循环相关的细胞外酶活性急剧下调（蛋白酶活性分别为 -44%，纤维素酶活性为 -54%，酪氨酸酶活性为 -31%）。我们还发现，残留物输入类型（细与粗）仅略微减轻了这些影响，而物种来源则减轻了这些影响。我们的研究表明，残留物保留可以通过调节特定林分中微生物群落的抵抗力来减轻水分和热应激对微生物群落的影响。这些结果表明，特定林分中树木残留物的保留可能有助于在地中海气候强化的背景下维持土壤生物特性。