南湖新聞訊（通訊員 蘇榮琳）8月23日，華中農業大學資源與環境學院生態過程與環境效應團隊在水稻土有機碳礦化機制方面的最新研究成果以“Warming promotes the decomposition of oligotrophic bacterial-driven organic matter in paddy soil”為題在Soil Biology and Biochemistry上發表。 　　全球變暖對土壤碳氮循環造成了難以估量的影響。土壤有機碳周轉快慢取決于微生物的活動，研究微生物介導的土壤有機碳分解對溫度的響應過程，可為預測全球土壤碳動態變化提供科學依據。氣候變化的典型表現形式暖冬，會加速冬閑期稻田土壤有機碳的分解損失。長期耕作會使稻田表層和底層的有機碳特性及微生物組成產生差異，但學術界對于它們對大氣溫度升高的響應、對溫度變化的敏感性是否存在差異仍存在認知缺陷。 　　基于此背景，團隊以原狀土柱為研究對象，在室內設定溫度下培養117天。研究結果表明，0-15 cm表層土壤富含不穩定的溶解性有機碳，表現出高水平的微生物生物量和富營養菌豐度；15-30 cm底層土壤以有機碳含量低且結構復雜為特征，微生物生物量低，其中寡營養菌占據優勢。 　　盡管表層土壤是主要的CO2排放區域，但底層土壤有機碳礦化的溫度敏感性更高，促進了頑固性土壤有機質的分解，降低了可溶性有機質的熒光強度。溫度升高沒有顯著改變微生物生物量，但提高了寡營養菌的相對豐度。由于寡營養菌驅動的頑抗性有機質的分解對增溫更敏感，全球變暖更易引起底層土壤的碳損失。 　　圖1 增溫條件下土壤有機質的周轉模式圖 　　圖1 增溫條件下土壤有機質的周轉模式圖 　　本研究從有機質化學性質和微生物代謝策略的角度對稻田土壤有機質礦化的溫度敏感性機制提供了新見解，強調在預測未來氣候變化與土壤碳的反饋模式時，應加強對深層土壤有機質動態的關注。 　　研究得到湖北省重點研發項目的資助。我校資源與環境學院博士研究生蘇榮琳為論文第一作者，胡榮桂教授為論文通訊作者。資環院趙勁松副教授，吳限博士，博士研究生胡金麗、李華彬、肖恒斌也參與了研究工作。 　　【英文摘要】 　　The ongoing global warming is causing paddy soil to come under threat by hitherto unseen levels of carbon and nitrogen loss. The mechanism of soil organic matter （SOM） components and microbial metabolism responding to increased temperature is complicated; for example, the temperature sensitivity （Q10） of SOM decomposition in rice topsoil and subsoil remains poorly understood. In this study, 0–30 cm columns of undisturbed paddy soil were collected and incubated at 5, 15, or 25 ℃ for 117 days to investigate the effect of temperature on SOM decomposition and microbial characteristics in different soil layers. Results showed that Q10 of subsoil （15–30 cm） was more than twice that of topsoil （0–15 cm）， indicating that SOM mineralisation in subsoil was facilitated more by temperature than that in topsoil. Warming promoted the decomposition of recalcitrant SOM and reduced the fluorescent intensity of dissolved organic matter. Increased temperature exerted no significant effect on microbial biomass, but it did enhance the relative abundance of oligotrophic bacteria and promote anabolism. Therefore, recalcitrant SOM decomposition driven by oligotrophic bacteria was more sensitive to warming than labile organic matter consumption mediated by copiotrophic bacteria. Our findings revealed the underlying mechanisms by which elevating temperature promoted SOM mineralisation, thereby emphasising the need to remain vigilant regarding the threat to carbon dynamics in deep soil poised by global climate changes. 　　論文鏈接：/file/upload/2023-10-04/qpr5q4jbqyd 　　審核人：胡榮桂