Wild Birgit, Schnecker Jörg, Alves Ricardo J Eloy, Barsukov Pavel, Bárta Jiří, Capek Petr, Gentsch Norman, Gittel Antje, Guggenberger Georg, Lashchinskiy Nikolay, Mikutta Robert, Rusalimova Olga, Santrůčková Hana, Shibistova Olga, Urich Tim, Watzka Margarete, Zrazhevskaya Galina, Richter Andreas
University of Vienna, Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, Vienna, Austria ; Austrian Polar Research Institute, Vienna, Austria.
Austrian Polar Research Institute, Vienna, Austria ; University of Vienna, Department of Ecogenomics and Systems Biology, Division of Archaea Biology and Ecogenomics, Vienna, Austria.
Soil Biol Biochem. 2014 Aug;75(100):143-151. doi: 10.1016/j.soilbio.2014.04.014.
Rising temperatures in the Arctic can affect soil organic matter (SOM) decomposition directly and indirectly, by increasing plant primary production and thus the allocation of plant-derived organic compounds into the soil. Such compounds, for example root exudates or decaying fine roots, are easily available for microorganisms, and can alter the decomposition of older SOM ("priming effect"). We here report on a SOM priming experiment in the active layer of a permafrost soil from the central Siberian Arctic, comparing responses of organic topsoil, mineral subsoil, and cryoturbated subsoil material (i.e., poorly decomposed topsoil material subducted into the subsoil by freeze-thaw processes) to additions of C-labeled glucose, cellulose, a mixture of amino acids, and protein (added at levels corresponding to approximately 1% of soil organic carbon). SOM decomposition in the topsoil was barely affected by higher availability of organic compounds, whereas SOM decomposition in both subsoil horizons responded strongly. In the mineral subsoil, SOM decomposition increased by a factor of two to three after any substrate addition (glucose, cellulose, amino acids, protein), suggesting that the microbial decomposer community was limited in energy to break down more complex components of SOM. In the cryoturbated horizon, SOM decomposition increased by a factor of two after addition of amino acids or protein, but was not significantly affected by glucose or cellulose, indicating nitrogen rather than energy limitation. Since the stimulation of SOM decomposition in cryoturbated material was not connected to microbial growth or to a change in microbial community composition, the additional nitrogen was likely invested in the production of extracellular enzymes required for SOM decomposition. Our findings provide a first mechanistic understanding of priming in permafrost soils and suggest that an increase in the availability of organic carbon or nitrogen, e.g., by increased plant productivity, can change the decomposition of SOM stored in deeper layers of permafrost soils, with possible repercussions on the global climate.
北极地区气温上升会直接或间接地影响土壤有机质（SOM）的分解，其途径是增加植物初级生产力，进而使植物源有机化合物向土壤中的分配增加。这类化合物，例如根系分泌物或腐烂的细根，很容易被微生物利用，并能改变较老的土壤有机质的分解（“激发效应”）。我们在此报告了一项在西伯利亚北极中部永久冻土土壤活动层进行的土壤有机质激发实验，比较了有机表土、矿质底土和冻融扰动底土物质（即通过冻融过程被卷入底土的分解程度较差的表土物质）对添加的碳标记葡萄糖、纤维素、氨基酸混合物和蛋白质（添加量相当于土壤有机碳的约1%）的反应。表土中土壤有机质的分解几乎不受有机化合物有效性提高的影响，而两个底土层中土壤有机质的分解反应强烈。在矿质底土中，添加任何一种底物（葡萄糖、纤维素、氨基酸、蛋白质）后，土壤有机质分解增加了两到三倍，这表明微生物分解者群落分解土壤有机质更复杂成分的能量有限。在冻融扰动层中，添加氨基酸或蛋白质后土壤有机质分解增加了两倍，但葡萄糖或纤维素对其没有显著影响，这表明是氮限制而非能量限制。由于冻融扰动物质中土壤有机质分解的刺激与微生物生长或微生物群落组成的变化无关，额外的氮可能被用于土壤有机质分解所需的胞外酶的产生。我们的研究结果首次对永久冻土土壤中的激发效应有了机理上的理解，并表明有机碳或氮有效性的增加，例如通过提高植物生产力，可能会改变永久冻土土壤深层储存的土壤有机质的分解，对全球气候可能产生影响。
