An increase in tree mortality rates as a consequence of biotic disturbances has been detected worldwide. Biotic disturbances in forests might cause significant impacts at ecosystem-level, with strong effects on soil biological activity and organic matter transformation. However, very few empirical studies have explored to date the consequences of biotic disturbances for soil microbial communities and C and N cycles. Here, we assessed the effects of Quercus suber dieback, caused by the exotic root pathogen Phytophthora cinnamomi, on the soil microbial community and key components of the C and N cycle. We used a spatially explicit neighborhood approach to analyze the effects of Q. suber trees with different health status and non-declining coexistent species on soil variables. The study was replicated in the two main Q. suber forest types of the region (closed forests and open woodlands) with contrasting soil texture characteristics. Pathogen-induced tree dieback did not affect microbial functional diversity or biomass, but translated into lower soil microbial respiration. Tree mortality induced changes in several variables of the C and N cycle, but the sign and magnitude of these effects varied depending on the local characteristics of soil texture. Coexistent species differed strongly from Q. suber in their effects on the C and N cycle. Overall, our results show that tree dieback due to invasive pathogens translates into complex short- and long-term effects on different components of the C and N cycles, despite no effects on microbial functional diversity and biomass.

在世界范围内已经发现由于生物干扰而导致的树木死亡率增加。森林的生物干扰可能会对生态系统造成重大影响，对土壤生物活性和有机质转化产生重大影响。然而，迄今为止很少有经验研究探索生物干扰对土壤微生物群落以及碳和氮循环的影响。在这里，我们评估了由外来根病原菌疫霉（Phytophthora cinnamomi）引起的枯死栎（Quercus suber dieback）对土壤微生物群落以及碳和氮循环的关键成分的影响。我们使用空间显式邻域方法来分析Q.suber的影响健康状况不同且树木变量并没有共同减少的树木。这项研究在该地区的两种主要Q.suber森林类型（封闭森林和开阔林地）中进行了重复，具有不同的土壤质地特征。病原体诱导的树木枯萎不会影响微生物的功能多样性或生物量，但会转化为较低的土壤微生物呼吸作用。树木死亡率导致C和N循环的几个变量发生变化，但是这些影响的迹象和程度取决于土壤质地的局部特征。共存物种与苏博克差异很大对碳和氮循环的影响。总体而言，我们的研究结果表明，尽管对微生物功能多样性和生物量没有影响，但由于侵入性病原体导致的树木枯死会转化为对C和N循环不同组成部分的短期和长期影响。