State Key Laboratory of Efficient Utilization of Arid and Semi-Arid Arable Land in Northern China/Key Laboratory of Arable Land Quality Monitoring and Evaluation, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences (CAAS), Beijing 100081, China; State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi 712100, China.
State Key Laboratory of Efficient Utilization of Arid and Semi-Arid Arable Land in Northern China/Key Laboratory of Arable Land Quality Monitoring and Evaluation, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences (CAAS), Beijing 100081, China.
Sci Total Environ. 2024 Jul 15;934:173287. doi: 10.1016/j.scitotenv.2024.173287. Epub 2024 May 21.
Microbial metabolism is closely related to soil carbon dioxide emissions, which in turn is related to environmental issues such as global warming. Dissolved organic matter (DOM) affects many fundamental biogeochemical processes such as microbial metabolism involved in soil carbon cycle, not only directly by its availability, but also indirectly by its chemodiversity. However, the association between the DOM chemodiversity and bioavailability remains unclear. To address this knowledge gap, soils from two agro-ecological experimental sites subjected to various long-term fertilizations in subtropical area was collected. The chemodiversity of DOM was detected by multi-spectroscopic techniques including ultraviolet-visible spectrophotometry, Fourier transform infrared spectroscopy and excitation emission matrices fluorescence spectroscopy. Results showed that long-term manure amendments significantly decreased microbial metabolic quotient (qCO) by up to 57%. We also observed that long-term manure amendments significantly increased recalcitrant components of DOM (indicated by the aromaticity, humification index, the ratio of aromatic carbon to aliphatic carbon, and the relative abundances of humic-like components) and decreased labile components of DOM. Negatively correlation between the qCO and the proportion of recalcitrant components of DOM supported that accumulation in recalcitrant components of DOM increased microbial carbon utilization efficiency. Random forest models also showed the highest contribution of the relative abundances of humic-like components and the aromaticity of DOM in affecting qCO. Both of the redundancy analysis and structural equation modeling further indicated the decisive role of soil pH in influencing the DOM chemodiversity. Soil pH explained 56.7% of the variation in the chemodiversity of DOM. The accumulation of recalcitrant components in DOM with increasing soil pH might be attributed to the accelerated microbial consumption of bioavailability components and/or to the negative impact on the solubility of bioavailability components. Overall, this research highlights the significance of long-term manure amendments in regulating qCO by altering the chemodiversity of soil DOM.
微生物代谢与土壤二氧化碳排放密切相关，而土壤二氧化碳排放又与全球变暖等环境问题有关。溶解有机物质（DOM）通过其可利用性直接影响，也通过其化学多样性间接影响许多与土壤碳循环有关的基本生物地球化学过程，如微生物代谢。然而，DOM 的化学多样性与生物可利用性之间的关联尚不清楚。为了解决这一知识空白，本研究从亚热带地区两个经过长期不同施肥处理的农业生态实验点采集了土壤。采用多光谱技术，包括紫外可见分光光度法、傅里叶变换红外光谱法和激发发射矩阵荧光光谱法，检测 DOM 的化学多样性。结果表明，长期施用有机肥显著降低了微生物代谢商（qCO），最大降幅达 57%。我们还观察到，长期施用有机肥显著增加了 DOM 的难降解成分（以芳香度、腐殖化指数、芳香碳与脂肪碳的比值和类腐殖质成分的相对丰度来表示），降低了 DOM 的易降解成分。qCO 与 DOM 的难降解成分比例呈负相关，表明 DOM 的难降解成分积累提高了微生物对碳的利用效率。随机森林模型也显示，DOM 的类腐殖质成分相对丰度和芳香度对 qCO 的影响最大。冗余分析和结构方程模型进一步表明，土壤 pH 在影响 DOM 化学多样性方面起着决定性作用。土壤 pH 解释了 DOM 化学多样性变化的 56.7%。随着土壤 pH 的增加，DOM 中难降解成分的积累可能归因于微生物对生物可利用成分的加速消耗和/或对生物可利用成分溶解度的负面影响。总的来说，本研究强调了长期施用有机肥通过改变土壤 DOM 的化学多样性来调节 qCO 的重要性。
