The microbe-mediated mechanisms affecting topsoil carbon stock in Tibetan grasslands.
The microbe-mediated mechanisms affecting topsoil carbon stock in Tibetan grasslands.
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微生物介导的西藏草原表土碳储量影响机制
DOI：
10.1038/ismej.2015.19
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发表时间：
2015-09
期刊：
影响因子：
--
通讯作者：
Yang Y
中科院分区：
文献类型：
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作者：
Yue H;Wang M;Wang S;Gilbert JA;Sun X;Wu L;Lin Q;Hu Y;Li X;He Z;Zhou J;Yang Y
研究表明，由于微生物分解加速抵消了草地生产力的提高，变暖导致北方草原土壤碳（C）流失。然而，一项长达数十年的调查显示，西藏高寒草原表层土壤碳储量相对稳定。为了探究这种不一致性，我们通过在西藏草原进行土壤移植来分析土壤微生物群落对模拟变暖的反馈响应。微生物功能多样性因变暖而降低，但微生物群落结构与温度变化无关。与氮（N）和碳循环相关的分解代谢基因的相对丰度随变暖而降低，在编码与更难分解的碳底物相关的酶的基因中表现得最为明显。相比之下，与碳固定相关的基因相对丰度增加。与脲酶、谷氨酸脱氢酶和氨单加氧酶（ureC、gdh和amoA）相关的基因相对丰度与N₂O排放显著相关。这些结果表明，与干旱/半干旱草原不同，西藏草原维持着保护陆地碳和氮库的负反馈机制。为了检验这些趋势是否适用于整个高原，我们将这些测量结果纳入一个模型，并验证了表层土壤碳储量相对稳定。因此，通过建立微生物代谢潜力与土壤生物地球化学过程之间的联系，我们得出结论：西藏草原中难分解碳底物的微生物分解减少，缓解了长期的碳流失。
Warming has been shown to cause soil carbon (C) loss in northern grasslands owing to accelerated microbial decomposition that offsets increased grass productivity. Yet, a multi-decadal survey indicated that the surface soil C stock in Tibetan alpine grasslands remained relatively stable. To investigate this inconsistency, we analyzed the feedback responses of soil microbial communities to simulated warming by soil transplant in Tibetan grasslands. Whereas microbial functional diversity decreased in response to warming, microbial community structure did not correlate with changes in temperature. The relative abundance of catabolic genes associated with nitrogen (N) and C cycling decreased with warming, most notably in genes encoding enzymes associated with more recalcitrant C substrates. By contrast, genes associated with C fixation increased in relative abundance. The relative abundance of genes associated with urease, glutamate dehydrogenase and ammonia monoxygenase (ureC, gdhandamoA) were significantly correlated with N2O efflux. These results suggest that unlike arid/semiarid grasslands, Tibetan grasslands maintain negative feedback mechanisms that preserve terrestrial C and N pools. To examine whether these trends were applicable to the whole plateau, we included these measurements in a model and verified that topsoil C stocks remained relatively stable. Thus, by establishing linkages between microbial metabolic potential and soil biogeochemical processes, we conclude that long-term C loss in Tibetan grasslands is ameliorated by a reduction in microbial decomposition of recalcitrant C substrates.