<br>微生物机制调节土壤有机碳矿化在碳下，在林线以上生态系统中，氮添加量不同,Science of the Total Environment

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微生物机制调节土壤有机碳矿化在碳下，在林线以上生态系统中，氮添加量不同
Science of the Total Environment ( IF 8.2 ) Pub Date : 2024-02-01 , DOI: 10.1016/j.scitotenv.2024.170497
Gokul Gaudel ₁ , Li Xing ₂ , Sujata Shrestha ₃ , Megharaj Poudel ₄ , Pemba Sherpa ₅ , Md Raseduzzaman ₁ , Xianfu Zhang ₆

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气候变化导致山区林线向上迁移，导致土壤中碳和氮输入发生变化。这些变化对现有土壤有机碳（SOC）库的微生物矿化的影响仍然不确定，因此很难预测它们对碳平衡的影响。为了加强我们对喜马拉雅地区由林线变化导致的原生 SOC 矿化的预测和理解，我们进行了一项研究，以量化林线生态系统上方高海拔地区的土壤启动效应（PE）。在实验室培养中，土壤用 13C-葡萄糖和不同氮用量的组合处理，以及纯碳处理和对照组，没有任何改良。具有不同氮添加速率的碳添加在天然 SOC 上表现出不同的 PE。由于高碳/氮失衡和 L-亮氨酸氨肽酶（LAP）活性增加，再加上低氮可用性和碳利用效率（CUE），在低氮输入下观察到高度阳性的 PE。相比之下，由于低碳/氮不平衡和 LAP 活性，再加上高氮可用性和 CUE，在高氮输入后，正 PE 下降。这些发现支持这样一个概念，即存在多种机制（即微生物氮开采和微生物代谢效率）在以不同氮速率添加碳的情况下调节 SOC 矿化。因此，氮可用性的增加满足了微生物氮的需求，减少了微生物碳/氮的不平衡，降低了需要氮的酶活性，并提高了微生物代谢效率。因此，这种机制减少了正 PE，从而成为在林线以上生态系统中稳定原生 SOC 的潜在工具。

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Microbial mechanisms regulate soil organic carbon mineralization under carbon with varying levels of nitrogen addition in the above-treeline ecosystem

Climate change is leading to the upward migration of treelines in mountainous regions, resulting in changes to the carbon and nitrogen inputs in soils. The impact of these alterations on the microbial mineralization of the existing soil organic carbon (SOC) pool remains uncertain, making it challenging to anticipate their effects on the carbon balance. To enhance our prediction and understanding of native SOC mineralization in Himalayan regions resulting from treeline shifts, a study was conducted to quantify soil priming effects (PEs) at high elevations above the treeline ecosystem. In laboratory incubation, soils were treated with a combination of 13C-glucose and varying nitrogen rates, along with carbon-only treatments and control groups without any amendments. The addition of carbon with varying nitrogen addition rates exhibited diverse PEs on native SOC. A highly positive PE was observed under low nitrogen input due to a high carbon/nitrogen imbalance and increased L-leucine aminopeptidase (LAP) activity, coupled with low nitrogen availability and carbon use efficiency (CUE). In contrast, a positive PE declined following high nitrogen input due to a low carbon/nitrogen imbalance and LAP activity, coupled with high nitrogen availability and CUE. These findings support the concept that multiple mechanisms (i.e., microbial nitrogen mining and microbial metabolic efficiency) exist that regulate SOC mineralization under the addition of carbon with varying nitrogen rates. Thus, an increase in nitrogen availability fulfils microbial nitrogen demand, reduces the microbial carbon/nitrogen imbalance, decreases enzyme activity that requires nitrogen and enhances microbial metabolic efficiency. Consequently, this mechanism reduces the positive PE, thereby serving as a potential tool for stabilizing native SOC in above-treeline ecosystems.

更新日期：2024-02-01

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