全球變暖對(duì)土壤碳氮循環(huán)造成了難以估量的影響。土壤有機(jī)碳周轉(zhuǎn)快慢取決于微生物的活動(dòng)，研究微生物介導(dǎo)的土壤有機(jī)碳分解對(duì)溫度的響應(yīng)過程，可為預(yù)測(cè)全球土壤碳動(dòng)態(tài)變化提供科學(xué)依據(jù)。氣候變化的典型表現(xiàn)形式暖冬，會(huì)加速冬閑期稻田土壤有機(jī)碳的分解損失。長(zhǎng)期耕作會(huì)使稻田表層和底層的有機(jī)碳特性及微生物組成產(chǎn)生差異，但學(xué)術(shù)界對(duì)于它們對(duì)大氣溫度升高的響應(yīng)、對(duì)溫度變化的敏感性是否存在差異仍存在認(rèn)知缺陷。

 

　　基于此背景，團(tuán)隊(duì)以原狀土柱為研究對(duì)象，在室內(nèi)設(shè)定溫度下培養(yǎng)117天。研究結(jié)果表明，0-15 cm表層土壤富含不穩(wěn)定的溶解性有機(jī)碳，表現(xiàn)出高水平的微生物生物量和富營(yíng)養(yǎng)菌豐度；15-30 cm底層土壤以有機(jī)碳含量低且結(jié)構(gòu)復(fù)雜為特征，微生物生物量低，其中寡營(yíng)養(yǎng)菌占據(jù)優(yōu)勢(shì)。

 

　　盡管表層土壤是主要的CO2排放區(qū)域，但底層土壤有機(jī)碳礦化的溫度敏感性更高，促進(jìn)了頑固性土壤有機(jī)質(zhì)的分解，降低了可溶性有機(jī)質(zhì)的熒光強(qiáng)度。溫度升高沒有顯著改變微生物生物量，但提高了寡營(yíng)養(yǎng)菌的相對(duì)豐度。由于寡營(yíng)養(yǎng)菌驅(qū)動(dòng)的頑抗性有機(jī)質(zhì)的分解對(duì)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(jī)質(zhì)的周轉(zhuǎn)模式圖

 

　　圖1 增溫條件下土壤有機(jī)質(zhì)的周轉(zhuǎn)模式圖

 

　　本研究從有機(jī)質(zhì)化學(xué)性質(zhì)和微生物代謝策略的角度對(duì)稻田土壤有機(jī)質(zhì)礦化的溫度敏感性機(jī)制提供了新見解，強(qiáng)調(diào)在預(yù)測(cè)未來氣候變化與土壤碳的反饋模式時(shí)，應(yīng)加強(qiáng)對(duì)深層土壤有機(jī)質(zhì)動(dòng)態(tài)的關(guān)注。

 

　　研究得到湖北省重點(diǎn)研發(fā)項(xiàng)目的資助。我校資源與環(huán)境學(xué)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(huán)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：https://doi.org/10.1016/j.soilbio.2023.109156

 

　　審核人：胡榮桂