Direct and indirect disturbance impacts in forests

Human and natural disturbances are key drivers of change in forest ecosystems. Yet, the direct and indirect mechanisms which underpin these changes remain poorly understood at the ecosystem level. Here, using structural equation modelling across a 150+ year chronosequence, we disentangle the direct and indirect effects of major disturbances in a temperate forest ecosystem. We show that wildfires, logging and post-fire (salvage) logging can affect plant and microbial communities and abiotic soil properties both directly and indirectly through plant-soil-microbial interactions. We quantified 68 direct and indirect disturbance effects across these components, with the majority resulting in ecosystem-wide adverse effects. Indirect disturbance effects accounted for 43% of total disturbance effects, with some amplifying or partially mitigating direct disturbance effects. Overall, human disturbances were associated with more negative effects than natural disturbances. Our analyses provide novel insights into the multifaceted dynamics of forest disturbances and the mechanisms which underpin their relative impacts.

Methods
Please see https://doi.org/10.1111/ele.13741 for detailed methods.

人为与自然干扰是森林生态系统变化的核心驱动因素。然而，支撑这些变化的直接与间接机制，在生态系统尺度上仍未得到充分解析。本研究基于时长超150年的演替时间序列（chronosequence），采用结构方程模型（structural equation modelling），厘清了温带森林生态系统中主要干扰的直接与间接效应。研究表明，野火、林木采伐以及火烧后补救性采伐，可通过植物-土壤-微生物互作，直接或间接影响植物与微生物群落以及土壤非生物属性。我们量化了上述组分中总计68项直接与间接干扰效应，其中绝大多数会对整个生态系统产生负面影响。间接干扰效应占总干扰效应的43%，部分效应会放大或部分缓解直接干扰效应。整体而言，人为干扰相较于自然干扰，会带来更多负面影响。本研究的分析为森林干扰的多维度动态及其相对影响的支撑机制提供了全新认知。

方法
详见https://doi.org/10.1111/ele.13741以获取详细研究方法。