Li Na, Wang Baorong, Zhou Yue, Li Huijun, Zhu Zhaolong, Dou Yanxing, Huang Yimei, Jiao Feng, An Shaoshan
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling, 712100, China.
College of Grassland Agriculture, Northwest A &F University, Yangling, 712100, China.
J Environ Manage. 2024 Mar;354:120289. doi: 10.1016/j.jenvman.2024.120289. Epub 2024 Feb 16.
Climate change-induced warming has the potential to intensify drought conditions in certain regions, resulting in uneven precipitation patterns. However, the impact of precipitation-induced changes on soil C-fixing bacterial community composition to changes and their subsequent effect on the accumulation of microbial necromass in the soil remains unclear. To address this knowledge gap, we conducted an in-situ simulated precipitation control experiment in semi-arid grasslands, encompassing five primary precipitation gradients: ambient precipitation as a control (contr), decreased precipitation by 80% and 40% (DP80, DP40), and increased precipitation by 40% and 80% (IP80, IP40). Our findings indicate that while an increase in precipitation promotes greater total bacterial diversity, it reduces the diversity of cbbM-harboring bacteria. The dominance of drought-tolerant Proteobacteria within the cbbM-harboring bacterial community was responsible for the observed increase in their relative abundance, ranging from 8.9% to 15.6%, under conditions of decreased precipitation. In arid environments characterized by limited soil moisture and nutrient availability, certain dominant genera such as Thiobacillus, Sulfuritalea, and Halothiobacillus, which possess cbbM genes, exhibit strong synergistic effects with other bacteria, thereby leading to a high nutrient use efficiency. Linear regression analysis shows that bacterial necromass C was significantly negatively correlated with cbbM-harboring bacterial diversity but positively correlated with cbbM-harboring bacterial community composition. Consequently, in the extreme drought environment of DP80, the contribution of bacterial necromass C to SOC was dramatically reduced by 75% relative to the control. Although bacterial necromass C was preferentially consumed as nutrients and energy for microorganisms, C-fixing microorganisms supplemented the soil C pool by assimilating atmospheric CO. Bacterial necromass was primarily controlled by accessible C and N rather than by the total bacterial community composition and relative abundance. Our results provide compelling evidence for the critical role of the composition of the bacterial community and its necromass in the accumulation of SOC in semiarid grassland ecosystems.
气候变化导致的变暖有可能加剧某些地区的干旱状况，导致降水模式不均。然而，降水引起的变化对土壤固碳细菌群落组成的影响及其随后对土壤中微生物残体积累的影响仍不清楚。为了填补这一知识空白，我们在半干旱草原进行了一项原位模拟降水控制实验，涵盖五个主要降水梯度：以 ambient precipitation 作为对照（contr）、降水减少 80% 和 40%（DP80、DP40）以及降水增加 40% 和 80%（IP80、IP40）。我们的研究结果表明，虽然降水增加促进了细菌总多样性的提高，但它降低了携带 cbbM 的细菌的多样性。在降水减少的条件下，携带 cbbM 的细菌群落中耐旱变形菌的优势导致了它们相对丰度的增加，范围从 8.9% 到 15.6%。在土壤水分和养分可用性有限的干旱环境中，某些拥有 cbbM 基因的优势属，如硫杆菌属、硫硫杆菌属和嗜盐硫杆菌属，与其他细菌表现出强烈的协同效应，从而导致高养分利用效率。线性回归分析表明，细菌残体碳与携带 cbbM 的细菌多样性显著负相关，但与携带 cbbM 的细菌群落组成正相关。因此，在 DP80 的极端干旱环境中，细菌残体碳对土壤有机碳的贡献相对于对照显著降低了 75%。虽然细菌残体碳被优先作为微生物的养分和能量消耗，但固碳微生物通过同化大气中的 CO 补充了土壤碳库。细菌残体主要受可利用的碳和氮控制，而不是受细菌群落的总组成和相对丰度控制。我们的结果为细菌群落组成及其残体在半干旱草原生态系统土壤有机碳积累中的关键作用提供了有力证据。
