Summer warming accelerates sub‐arctic peatland nitrogen cycling without changing enzyme pools or microbial community structure
Summer warming accelerates sub‐arctic peatland nitrogen cycling without changing enzyme pools or microbial community structure
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DOI：
10.1111/j.1365-2486.2011.02548.x
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发表时间：
2012-01
影响因子：
11.6
通讯作者：
James T. Weedon;George A. Kowalchuk;R. Aerts;J. V. van Hal;R. V. van Logtestijn;N. Taş;Wilfred F. M. Röling-Wilf
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文献类型：
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作者：
James T. Weedon;George A. Kowalchuk;R. Aerts;J. V. van Hal;R. V. van Logtestijn;N. Taş;Wilfred F. M. Röling-Wilf
北部泥炭地初级生产和分解的平衡可能会因气候变化而发生变化，并可能对大气CO2浓度产生反馈。氮的可用性将调节这种转变，但对这些环境中土壤氮动力学的驱动因素知之甚少。我们在瑞典亚北极的一个沼沼泥炭沼中进行了一项长期（9年）的开放式顶室（OTC）实验，以测试春季增温、夏季增温和冬季加雪对土壤氮通量、氮循环酶的潜在活性和土壤微生物群落组成的相互作用。这些同时进行的测量使我们能够确定气候变化影响明显的组织水平，这是发展真正的机械理解的重要要求。有机氮库和通量比无机氮库和通量高一个数量级。夏季变暖使土壤有机氮和氨的通量在生长季节增加了近一倍。在升温1°C的情况下，如此大幅度的增加不太可能是由于动力学效应，我们认为这与观测到的微生物生物量的季节性减少有关，这表明氮通量是由大量的微生物在季末枯死所驱动的。这种N循环动力学的变化没有反映在任何测量的潜在肽酶活性中。此外，不同处理的土壤微生物群落结构明显稳定，表明存在非特异性微生物枯死。我们的研究结果表明，在这些广泛分布的泥炭沼泽中，许多植物物种能够吸收有机氮，有机土壤氮动态在数量上比通常研究的无机氮动态重要得多。气候变化对有机土壤氮循环的影响将通过对微生物生物量的季节动态和维持它的基质输入进行更深入的研究来推进。
The balance of primary production and decomposition in northern peatlands may shift due to climate change, with potential feedbacks to atmospheric CO2 concentrations. Nitrogen availability will modulate this shift, but little is known about the drivers of soil nitrogen dynamics in these environments. We used a long‐term (9 years) open top chamber (OTC) experiment in an ombrotrophic Sphagnum peat bog in sub‐arctic Sweden, to test for the interactive effects of spring warming, summer warming and winter snow addition on soil nitrogen fluxes, potential activities of nitrogen cycle enzymes, and soil microbial community composition. These simultaneous measurements allowed us to identify the level of organization at which climate change impacts are apparent, an important requirement for developing truly mechanistic understanding. Organic‐N pools and fluxes were an order of magnitude higher than inorganic‐N pools and fluxes. Summer warming approximately doubled fluxes of soil organic nitrogen and ammonia over the growing season. Such a large increase under 1 °C warming is unlikely to be due to kinetic effects, and we propose that it is linked to an observed seasonal decrease in microbial biomass, suggesting that N flux is driven by a substantial late‐season dieback of microbes. This change in N cycle dynamics was not reflected in any of the measured potential peptidase activities. Moreover, the soil microbial community structure was apparently stable across treatments, suggesting a non‐specific microbial dieback. Our results show that in these widespread peat bogs, where many plant species are capable of organic‐N uptake, organic soil N dynamics are quantitatively far more important than the commonly studied inorganic‐N dynamics. Understanding of climate change effects on organic soil N cycling in this system will be advanced by closer investigation of the seasonal dynamics of the microbial biomass and the input of substrates that maintain it.