Bioavailability of soil organic matter and microbial community dynamics upon permafrost thaw
Bioavailability of soil organic matter and microbial community dynamics upon permafrost thaw
复制标题
DOI：
10.1111/j.1462-2920.2011.02489.x
复制
发表时间：
2011-08-01
影响因子：
5.1
通讯作者：
Wuchter, Cornelia
中科院分区：
文献类型：
--
作者：
Coolen, Marco J. L.;van de Giessen, Jeroen;Wuchter, Cornelia
到2100年，放大的北极变暖可能会使25%的永久冻土地区融化，使大量目前固定的有机碳暴露在微生物介导的分解和通过土壤有机质(SOM)呼吸释放的温室气体中。我们对全新世多年冻土在4℃下进行了长达11天的时间序列培养实验，以确定胞外酶活性(EEAs)(即磷酸酶、β-葡萄糖苷酶、氨基肽酶)的变化，以此来衡量有机质在冻土融化过程中的生物有效性。我们还对SSU rRNA转录本进行了分析，以跟踪存活的原核生物和真核生物在孵化过程中的质量和数量变化。EEA、rRNA转录本数量和微生物群落结构在不同土层之间对解冻的响应有很大差异：在11天的孵化后，活动层的C和P略有耗尽，并含有指示更多寡营养条件(酸性细菌)的细菌门。解冻时磷酸酶和β-葡萄糖苷酶的快速反应，以及活性共养类杆菌的优势，表明在夏季，冻土板上部是来自上覆解冻活动层的易降解碳的储存。EEA剖面和微生物群落动态进一步表明，较深和较老的冻土层主要含有顽固的SOM，细胞外土壤结合的外源酶在生物聚合物的初始切割中发挥作用，这可能在融化后启动微生物的生长。担子菌属真菌和OP5亚科候选细菌在冻土层深度解冻后最先做出反应，可能在顽固的土壤有机质分解过程中发挥重要作用，释放出更多不稳定的底物来支持主要的细菌门(β-变形杆菌、放线杆菌、细菌)，并在此之后占主导地位。
Amplified Arctic warming could thaw 25% of the permafrost area by 2100, exposing vast amounts of currently fixed organic carbon to microbially mediated decomposition and release of greenhouse gasses through soil organic matter (SOM) respiration. We performed time-series incubation experiments with Holocene permafrost soils at 4 C for up to 11 days to determine changes in exoenzyme activities (EEAs) (i.e. phosphatase, beta-glucosidase, aminopeptidase) as a measure for the bioavailability of SOM in response to permafrost thaw. We also profiled SSU rRNA transcripts to follow the qualitative and quantitative changes in viable prokaryotes and eukaryotes during incubation. EEA, amount of rRNA transcripts and microbial community structures differed substantially between the various soil intervals in response to thaw: after 11 days of incubation, the active layer became slightly depleted in C and P and harboured bacterial phyla indicative of more oligotrophic conditions (Acidobacteria). A fast response in phosphatase and b-glucosidase upon thaw, and a predominance of active copiotrophic Bacteroidetes, showed that the upper permafrost plate serves as storage of easily degradable carbon derived from the overlying thawed active layer during summer. EEA profiles and microbial community dynamics furthermore suggest that the deeper and older permafrost intervals mainly contain recalcitrant SOM, and that extracellular soil-bound exoenzymes play a role in the initial cleavage of biopolymers, which could kick-start microbial growth upon thaw. Basidiomycetous fungi and Candidate Subdivision OP5 bacteria were the first to respond in freshly thawed deeper permafrost intervals, and might play an important role in the decomposition of recalcitrant SOM to release more labile substrates to support the major bacterial phyla (beta-Proteobacteria, Actinobacteria, Firmicutes), which predominated thereafter.