Bond-Lamberty Ben, Bolton Harvey, Fansler Sarah, Heredia-Langner Alejandro, Liu Chongxuan, McCue Lee Ann, Smith Jeffrey, Bailey Vanessa
Pacific Northwest National Laboratory, Joint Global Change Research Institute at the University of Maryland-College Park, 5825 University Research Court #3500, College Park, MD, 20740, United States of America.
Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, WA, 99352, United States of America.
PLoS One. 2016 Mar 2;11(3):e0150599. doi: 10.1371/journal.pone.0150599. eCollection 2016.
The effects of climate change on soil organic matter-its structure, microbial community, carbon storage, and respiration response-remain uncertain and widely debated. In addition, the effects of climate changes on ecosystem structure and function are often modulated or delayed, meaning that short-term experiments are not sufficient to characterize ecosystem responses. This study capitalized on a long-term reciprocal soil transplant experiment to examine the response of dryland soils to climate change. The two transplant sites were separated by 500 m of elevation on the same mountain slope in eastern Washington state, USA, and had similar plant species and soil types. We resampled the original 1994 soil transplants and controls, measuring CO2 production, temperature response, enzyme activity, and bacterial community structure after 17 years. Over a laboratory incubation of 100 days, reciprocally transplanted soils respired roughly equal cumulative amounts of carbon as non-transplanted controls from the same site. Soils transplanted from the hot, dry, lower site to the cooler and wetter (difference of -5°C monthly maximum air temperature, +50 mm yr-1 precipitation) upper site exhibited almost no respiratory response to temperature (Q10 of 1.1), but soils originally from the upper, cooler site had generally higher respiration rates. The bacterial community structure of transplants did not differ significantly from that of untransplanted controls, however. Slight differences in local climate between the upper and lower Rattlesnake locations, simulated with environmental control chambers during the incubation, thus prompted significant differences in microbial activity, with no observed change to bacterial structure. These results support the idea that environmental shifts can influence soil C through metabolic changes, and suggest that microbial populations responsible for soil heterotrophic respiration may be constrained in surprising ways, even as shorter- and longer-term soil microbial dynamics may be significantly different under changing climate.
气候变化对土壤有机质及其结构、微生物群落、碳储存和呼吸作用的影响仍不明确，且存在广泛争议。此外，气候变化对生态系统结构和功能的影响往往受到调节或存在延迟，这意味着短期实验不足以描述生态系统的响应。本研究利用一项长期的土壤互作移植实验，来检验旱地土壤对气候变化的响应。这两个移植地点位于美国华盛顿州东部同一山坡上，海拔相差500米，具有相似的植物物种和土壤类型。我们对1994年的原始土壤移植样本和对照样本重新进行了采样，在17年后测量了二氧化碳产量、温度响应、酶活性和细菌群落结构。在100天的实验室培养期内，相互移植的土壤与来自同一场地的未移植对照土壤呼吸的碳累积量大致相等。从炎热、干燥的低海拔地点移植到凉爽、湿润（月最高气温相差-5°C，年降水量相差+50毫米）的高海拔地点的土壤，对温度几乎没有呼吸响应（Q10为1.1），但原本来自高海拔、较凉爽地点的土壤呼吸速率通常较高。然而，移植土壤的细菌群落结构与未移植对照土壤的细菌群落结构没有显著差异。在培养过程中，利用环境控制室模拟响尾蛇上下位置之间局部气候的微小差异，从而引发了微生物活性的显著差异，但未观察到细菌结构的变化。这些结果支持了环境变化可通过代谢变化影响土壤碳的观点，并表明即使在气候变化下短期和长期的土壤微生物动态可能存在显著差异，但负责土壤异养呼吸的微生物种群可能会以惊人的方式受到限制。
