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 a natural and afforested semiarid ecosystem located 70 km west of the epicenter 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 four-fold for native litter decomposition. Summary: 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中的关键组成部分，但由于其发生频次极低且难以预测，学界难以就其对生态系统的影响形成普适性结论。火山喷发便是这类自然扰动中最为典型的一类，但其对调控碳、养分周转的微生物（microbes）与地表节肢动物（ground-dwelling arthropods）的影响，目前仍知之甚少。

我们针对阿根廷巴塔哥尼亚2011年普耶韦-科尔多纳·卡列火山喷发（Puyehue-Cordón Caulle）的影响展开研究，该研究位点设于距火山震中以西70公里的天然与人工造林（afforested）半干旱生态系统（semiarid ecosystem），针对其中枯落物与土壤的微生物及动物群落开展评估。

我们提出假说：火山灰沉降会通过火山灰对节肢动物的杀虫效应，显著抑制土壤动物与微生物群落，并伴随生态系统过程的衰退。本研究的目标为：通过同一研究位点喷发前后的时间节点对比，结合近乎一致的野外实验方法，量化本次火山喷发的影响。

我们测定了土壤与枯落物的湿度、pH值、微生物生物量（microbial biomass），以及土壤与枯落物的微生物酶活性（microbial enzymatic activity）等环境变量。我们分别采用陷捕法（pitfall traps）与土壤提取法（soil extraction），对地表节肢动物与线虫（nematodes）进行采样与鉴定。此外，我们还开展了平行受控的模拟火山灰沉降（simulated ash deposition）实验，以评估火山灰对枯落物分解与酶活性的影响。

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。同时，线虫丰度与土壤微生物酶活性亦显著下降。与之相反，地表节肢动物与枯落物酶活性则显著提升。最终，在模拟火山灰沉降实验中，本土枯落物的分解速率提升了四倍。

研究摘要：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（biogeochemical cycling）中发挥关键作用，但这未必源于其灾难性影响。与我们最初的假说相悖，我们在普耶韦火山喷发后观察到生物活动与碳周转（carbon turnover）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适应能力。本研究结果有助于将这类大规模低频扰动的生态意义置于更为严谨的生态学研究框架之中。