Sources of C and N contributing to the flush in mineralization upon freeze-thaw cycles in soils
Sources of C and N contributing to the flush in mineralization upon freeze-thaw cycles in soils
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DOI：
10.1016/s0038-0717(02)00121-9
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发表时间：
2002-10-01
影响因子：
9.7
通讯作者：
Witter, E
中科院分区：
文献类型：
--
作者：
Herrmann, A;Witter, E
在中纬度气候区（35- 65度），土壤可能会经历冻融循环（FTC），这可能在冬末和早春频繁发生。FTC通常导致C和N矿化的冲洗，因此可能是控制C和N矿化速率的重要因素。进行了实验室实验，以表征在FTC后可用的有机物质的来源。土壤，不同的数量和质量的有机物质投入，他们收到自1956年以来，取样，预培养，以减少不稳定的有机物质的量，随后暴露于重复的FTC。每个FTC包括在-2 ℃下6 h，在-5 ℃下16 h，在+2 ℃下4 h和在+5 ℃下22 h，每个IFTC总共48 h。通过用少量的C-14标记的葡萄糖标记天然微生物生物量，并比较IFTC与氯仿熏蒸后的C冲洗的比活性，来确定微生物生物量C对FTC后的C冲洗的贡献。温度校正量的C和N矿化在恒温培养的土壤中作为控制的计算冲洗。FTC使C和N矿化量增加2-3倍。冲洗是短暂的，最高的前四个FTC，这表明，容易分解的材料成为FTC后可用，冻融敏感池的大小是有限的。土壤碳排放量与土壤有机碳、水溶性有机碳、微生物生物量碳和基础呼吸呈线性相关，但仅与后两者成正比。用少量葡萄糖标记天然微生物生物量表明，微生物生物量C贡献了约100%。65%的微生物生物量C，而仅占微生物生物量C的约5%。我们没有直接的证据来证明剩余的35%的C冲洗的来源或其释放的机制。在土壤中进行氯仿熏蒸前被暴露于FTC有机物质熏蒸释放的冲洗比微生物生物量成为一个更重要的来源，这表明不稳定的有机物质是非常敏感的FTC。从我们的研究结果来看，FTC的影响对年度C和N预算的影响很小，但在中纬度气候区冬末春初的C和N矿化建模时可能需要考虑。(C)2002爱思唯尔科技有限公司版权所有。
In mid-latitude climatic regions (35-65degrees) soils may be subjected to freeze-thaw cycles (FTC) which can occur frequently in late winter and early spring. FTC often results in flushes in C and N mineralization and could therefore be an important factor controlling C and N mineralization rates. Laboratory experiments were carried out to characterize the source of organic matter that becomes available upon FTC. Soils, differing in the quantity and quality of organic matter inputs they had received since 1956, were sampled, pre-incubated to reduce amounts of labile organic matter and subsequently exposed to repeated FTC. Each FTC consisted of 6 h at -2 degreesC, 16 h at -5 degreesC, 4 h at +2 degreesC and 22 h at +5 degreesC, giving a total of 48 h for each IFTC. The contribution of microbial biomass C to the C flush upon FTC was determined by labeling the native microbial biomass with a small amount of C-14-labeled glucose and comparing the specific activity of the C flush upon IFTC with that upon chloroform fumigation. Temperature corrected amounts of C and N mineralized in soil incubated at constant temperatures acted as control in the calculation of the flush. FTC increased the amounts of C and N mineralized 2-3 fold. The flush was short-lived and highest in the first four FTC, suggesting that easily decomposable material became available upon FTC and that the size of the freeze-thaw susceptible pool was limited. The C flush was linearly related to organic C, water-soluble organic C, microbial biomass C and basal respiration, but only proportional to the latter two. Labeling the native microbial biomass with a small amount of glucose suggested that microbial biomass C contributed ca. 65% to the C flush upon FTC, while representing only about 5% of microbial biomass C. We have no direct evidence for the source of the remaining 35% of the C flush or for the mechanism of its release. In soils subjected to chloroform fumigation prior to being exposed to FTC organic matter released by fumigation became a more important source to the flush than the microbial biomass, suggesting that labile organic matter is highly susceptible to FTC. From our results, effects of FTC have little consequence for annual C and N budgets, but may need to be taken into account when modeling C and N mineralization during the late winter and early spring period in mid-latitude climatic regions. (C) 2002 Elsevier Science Ltd. All rights reserved.