The current increase of severe droughts associated with climate change is one of the main causes of the observed dieback in Mediterranean holm-oak (Quercus Ilex subs ballota) forests. Effects of forest dieback in soils are greatly variable and depend on a number of local factors, but generally include increased soil organic C due to increased litter inputs, alterations in soil nutrient contents, changes in the nitrogen cycle, and detrimental effects on soil microbial communities and their functioning. There is little evidence, however, of the effects of forest dieback on soil faunal diversity. In this study, we assessed the effects of holm-oak dieback and induced nutrient shifts on soil microfaunal communities and their relationships with soil properties and functioning. We studied 13 Holm oak forest sites affected by tree dieback in the Iberian Peninsula and assessed the relationship between soil properties, microbial functions, and nematode diversity under healthy, defoliated, and dead trees at each site. We found that nematode abundances were variable and significantly patchy across sites. Bacterivore and herbivore nematodes were the most abundant nematode trophic groups. Nematode abundance increased with increasing levels of soil C only if soil P was available, indicating that nematode abundances might be P-limited in these semi-arid systems. Bacterivore nematodes were especially affected by tree death, since tree dieback switched the relationship between bacterivore abundance and soil nutrient contents. Opportunistic bacterivores, able to exploit ephemeral bacterial resources blooming after soil organic enrichment, seemed more resilient to tree death than generalist ones, while fungivores did not clearly respond to forest dieback. We found complex and unexpected effects of tree dieback on soil microfaunal communities, which should receive further attention.

目前与气候变化相关的严重干旱的增加是观察到的地中海圣栎 ( Quercus Ilex subs ballota ) 枯死的主要原因之一) 森林。森林枯死对土壤的影响变化很大，取决于许多当地因素，但通常包括由于凋落物输入增加而导致的土壤有机碳增加、土壤养分含量的改变、氮循环的变化以及对土壤微生物群落的不利影响以及它们的功能。然而，几乎没有证据表明森林枯萎对土壤动物多样性的影响。在这项研究中，我们评估了圣栎树枯萎和诱导的养分变化对土壤微型动物群落的影响及其与土壤特性和功能的关系。我们研究了伊比利亚半岛受树木枯死影响的 13 个圣栎林场地，并评估了每个场地健康、落叶和死树下的土壤特性、微生物功能和线虫多样性之间的关系。我们发现线虫的丰度是可变的，并且跨站点显着不完整。细菌食性线虫和草食性线虫是最丰富的线虫营养群。只有当土壤 P 可用时，线虫丰度才会随着土壤 C 水平的增加而增加，这表明在这些半干旱系统中线虫丰度可能受到 P 限制。食菌线虫尤其受到树木死亡的影响，因为树木枯死改变了食菌线虫丰度和土壤养分含量之间的关系。机会性食菌动物能够利用土壤有机物富集后开花的短暂细菌资源，似乎比一般的食菌动物更能抵御树木死亡，而食真菌动物对森林枯死没有明显反应。我们发现树木枯死对土壤微型动物群落的复杂和意想不到的影响，