Soil aggregate-mediated microbial responses to long-term warming
Soil aggregate-mediated microbial responses to long-term warming
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DOI：
10.1016/j.soilbio.2020.108055
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发表时间：
2021
影响因子：
9.7
通讯作者：
Xiao‐Jun Allen Liu;G. Pold;L. Domeignoz-Horta;K. Geyer;H. Caris;Hannah Nicolson;K. Kemner;S. Frey;J. Melillo;Kristen M. DeAngelis
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文献类型：
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作者：
Xiao‐Jun Allen Liu;G. Pold;L. Domeignoz-Horta;K. Geyer;H. Caris;Hannah Nicolson;K. Kemner;S. Frey;J. Melillo;Kristen M. DeAngelis
土壤微生物碳利用效率（CUE）是生长和呼吸的结合，根据土壤碳（C）的物理保护及其对微生物的可用性，它对气候变化的反应可能不同。在马萨诸塞州中部的中纬度阔叶林中，27年的土壤变暖（+5 °C）导致了碳的流失和土壤有机质（SOM）质量的改变，但其潜在机制仍不清楚。在这里，我们假设长期变暖减少了SOM，微生物CUE的物理聚集保护，及其温度敏感性。将土壤分为大团聚体（250-2000 μm）和小团聚体（<250 μm）两部分，并在15和25 °C下培养24 h，用18 O富集水（H218 O）测定CUE。我们发现，长期变暖降低土壤C和N浓度和大团聚体中的胞外酶活性，但不影响SOM的物理保护。长期变暖对CUE或微生物生物量周转时间的影响不大，因为它降低了生长和呼吸。然而，CUE的温度敏感性较低的大团聚体从温暖相比，控制地块。我们的研究结果表明，微生物对长期变暖的热反应主要发生在土壤中，SOM的物理保护较少，因此更容易受到微生物降解。
Soil microbial carbon use efficiency (CUE) is a combination of growth and respiration, which may respond differently to climate change depending on physical protection of soil carbon (C) and its availability to microbes. In a mid-latitude hardwood forest in central Massachusetts, 27 years of soil warming (+5 °C) has resulted in C loss and altered soil organic matter (SOM) quality, yet the underlying mechanisms remain unclear. Here, we hypothesized that long-term warming reduces physical aggregate protection of SOM, microbial CUE, and its temperature sensitivity. Soil was separated into macroaggregate (250–2000 μm) and microaggregate (<250 μm) fractions, and CUE was measured with18O enriched water (H218O) in samples incubated at 15 and 25 °C for 24 h. We found that long-term warming reduced soil C and nitrogen concentrations and extracellular enzyme activity in macroaggregates, but did not affect physical protection of SOM. Long-term warming showed little effect on CUE or microbial biomass turnover time because it reduced both growth and respiration. However, CUE was less temperature sensitive in macroaggregates from the warmed compared to the control plots. Our findings suggest that microbial thermal responses to long-term warming occur mostly in soil compartments where SOM is less physically protected and thus more vulnerable to microbial degradation.