Data from: Litter microbial and soil faunal communities stimulated in the wake of a volcanic eruption in a semi-arid woodland in Patagonia, Argentina

Large-scale disturbances can be important components of the temporal landscape of natural ecosystems, but generalities regarding ecosystem impacts are difficult due to their infrequent and unpredictable nature. Volcanic eruptions figure as one of the most prominent of these natural disturbances, but the effects on microbes and ground-dwelling arthropods, which modulate carbon and nutrient turnover, are relatively unknown.

We evaluated the effects of the 2011 Puyehue-Cordón Caulle eruption in Patagonia, Argentina, on the litter and soil microbial and faunal communities in natural and afforested semi-arid ecosystems located 70 km west of the epicentre of the eruption. We hypothesized that volcanic ash deposition would strongly reduce soil faunal and microbial communities due to insecticidal effects of ash on arthropods, with a concomitant reduction in ecosystem processes.

Our objective was to quantify the impact of the volcanic eruption by comparing pre- and post-eruption time points in the same study site, with nearly identical field methodology. We measured environmental variables of soil and litter moisture, pH, microbial biomass, and soil and litter microbial enzymatic activity. We evaluated ground-dwelling arthropods and nematodes using pitfall traps and soil extraction, respectively. Additionally, a parallel, controlled-condition experiment of simulated ash deposition was conducted to evaluate ash effects on litter decomposition and enzymatic activity.

In the field, post-eruption soils had lower soil water content, pH and soil organic matter. Additionally, nematode abundance and soil microbial enzyme activity were significantly reduced. In contrast, ground-dwelling arthropods and litter enzymatic activity increased significantly. Finally, with simulated ash deposition, litter decomposition increased fourfold for native litter decomposition.

Large-scale disturbances may play a key role in biogeochemical cycling in affected natural ecosystems, but not necessarily due to their catastrophic effects. In contrast to our original predictions, we observed a marked stimulation of biotic activity and carbon turnover in the aftermath of the Puyehue volcanic eruption, which demonstrates that the biotic component of these ecosystems has a substantial capacity to respond to these disturbances in short time frames. These results can contribute to placing the role of these large-scale infrequent disturbances in a more robust ecological context.

大规模扰动是自然生态系统时间动态格局的重要组成部分，但由于其发生频率低且难以预测，学界难以就其对生态系统的影响形成普适性结论。火山喷发是这类自然扰动中最为突出的类型之一，但目前针对其对调控碳与养分周转的微生物及地表栖息节肢动物的影响的研究仍相对匮乏。

我们以阿根廷巴塔哥尼亚地区、距普耶韦-科登·考列（Puyehue-Cordón Caulle）火山喷发震中以西70公里处的自然半干旱生态系统与人工造林半干旱生态系统为研究对象，评估了此次2011年火山喷发对其枯落物与土壤中的微生物及动物群落的影响。我们提出假说：火山灰沉降会通过其对节肢动物的杀虫作用，大幅降低土壤动物与微生物群落，进而伴随生态系统过程的减弱。

本研究的核心目标为：通过在同一研究样地内对比喷发前后的时间节点，并采用近乎一致的野外研究方法，量化此次火山喷发的生态影响。我们测定了土壤与枯落物的含水量、pH值、微生物生物量，以及土壤和枯落物中的微生物酶活性；分别利用陷阱法与土壤萃取法调查了地表栖息节肢动物与线虫群落。此外，本研究还开展了一项平行受控模拟灰沉降实验，以评估火山灰对枯落物分解及酶活性的影响。

野外调查结果显示，喷发后的土壤含水量、pH值与土壤有机质含量均显著降低；线虫丰度与土壤微生物酶活性也同步下降。与之形成鲜明对比的是，地表栖息节肢动物的数量与枯落物酶活性均显著提升。此外，在模拟灰沉降处理下，原生枯落物的分解速率提升了四倍。

大规模扰动或可在受影响自然生态系统的生物地球化学循环中发挥关键作用，但这未必源于其灾难性破坏效应。与本研究最初的假说相悖，普耶韦火山喷发后，我们观测到生物活动与碳周转过程均得到显著增强，这表明此类生态系统的生物组分具备在短时间尺度内响应这类扰动的强大能力。本研究结果有助于将这类大规模低频扰动的生态功能置于更严谨的生态学框架中进行阐释。