Investigating the controls on soil organic matter decomposition in tussock tundra soil and permafrost after fire
Investigating the controls on soil organic matter decomposition in tussock tundra soil and permafrost after fire
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DOI：
10.1016/j.soilbio.2016.04.020
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发表时间：
2016-08
影响因子：
9.7
通讯作者：
S. Baets;M. J. V. D. Weg;R. Lewis;N. Steinberg;J. Meersmans;T. Quine;G. Shaver;I. Hartley
中科院分区：
文献类型：
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作者：
S. Baets;M. J. V. D. Weg;R. Lewis;N. Steinberg;J. Meersmans;T. Quine;G. Shaver;I. Hartley
北极生态系统的迅速变暖导致火灾等干扰的频率增加，不同植物群落的分布和生产力发生变化，永久冻土的融化深度增加，养分供应增加，特别是氮。单独和集体，这些因素有可能强烈影响土壤碳的分解速率，在这个地区的全球重要的碳储量的影响。然而，相当大的不确定性仍然是关于如何控制北极土壤中的碳分解率。在这项研究中，我们调查了温度，氮的可用性和不稳定的C除了影响CO2生产率在短期（10天的不稳定C）和长期（1.5年的温度和N）孵化的样品收集燃烧和未燃烧的网站在阿拉斯加北坡的Anaktuvuk河烧伤从不同深度（有机层，矿物层和上部永冻土）。这一地区的火灾导致了几厘米的有机层的损失，也增加了活性层的深度，使四年的解冻对更深的土壤层的影响进行调查。呼吸速率并没有大幅下降，在长期培养，虽然每单位有机物的分解率更大的有机层。在矿物和上部冻土层的土壤层，CO2的生产是更温度敏感，而N除了抑制呼吸的矿物和上部冻土层，特别是在低温下。在短期孵化，不稳定的C添加促进矿物和上部永冻土样品中的土壤有机质的分解，但不是在有机样品，这种效果失去了以下N添加在更深的层。这些结果突出表明，（i）有大量的不稳定的有机质在这些土壤中（ii），存储在矿物和上部永久冻土中的草丛苔原的有机质是不容易分解比有机层，但（iii）其分解是更敏感的温度变化和（iv）在较深的土壤层中的微生物活性是有限的不稳定的C的可用性，而不是N。总的来说，这些结果表明，除了碳的有机物燃烧的损失，增加火灾频率也有可能间接促进土壤碳释放到大气中的干扰后的几年。
Rapid warming in Arctic ecosystems is resulting in increased frequency of disturbances such as fires, changes in the distribution and productivity of different plant communities, increasing thaw depths in permafrost soils and greater nutrient availability, especially nitrogen. Individually and collectively, these factors have the potential to strongly affect soil C decomposition rates, with implications for the globally significant stores of carbon in this region. However, considerable uncertainty remains regarding how C decomposition rates are controlled in Arctic soils. In this study we investigated how temperature, nitrogen availability and labile C addition affected rates of CO2production in short (10-day for labile C) and long-term (1.5 year for temperature and N) incubations of samples collected from burned and unburned sites in the Anaktuvuk river burn on the North Slope of Alaska from different depths (organic horizon, mineral horizon and upper permafrost). The fire in this region resulted in the loss of several cms of the organic horizon and also increased active layer depth allowing the impacts of four years of thaw on deeper soil layers to be investigated. Respiration rates did not decline substantially during the long-term incubation, although decomposition rates per unit organic matter were greater in the organic horizon. In the mineral and upper permafrost soil horizons, CO2production was more temperature sensitive, while N addition inhibited respiration in the mineral and upper permafrost layers, especially at low temperatures. In the short-term incubations, labile C additions promoted the decomposition of soil organic matter in the mineral and upper permafrost samples, but not in the organic samples, with this effect being lost following N addition in the deeper layers. These results highlight that (i) there are substantial amounts of labile organic matter in these soils (ii), the organic matter stored in mineral and upper permafrost in the tussock tundra is less readily decomposable than in the organic horizon, but that (iii) its decomposition is more sensitive to changes in temperature and that (iv) microbial activity in deeper soil layers is limited by labile C availability rather than N. Collectively, these results indicate that in addition to the loss of C by combustion of organic matter, increasing fire frequency also has the potential to indirectly promote the release of soil C to the atmosphere in the years following the disturbance.