太湖地区3种水稻土不同温度培养中有机碳库变化及其对升温的响应

全球变暖下土壤有机碳储存的变化是土壤与全球变化研究的热点问题.本研究选择了3种太湖地区代表性水稻土的表层土壤,分别进行20℃和25℃的室内恒温培养,监测培养过程中总有机碳、溶解性有机碳和微生物量碳的变化动态,试图了解这些土壤的有机碳分解过程对全球变暖的响应特点.结果表明,这些土壤培养中总有机碳变化可以用一级衰变动力学方程或对数衰减方程描述,但动力学特征依培养温度的不同而异.升温大大促进了铁渗水耕人为土和潜育水耕人为土中有机碳的分解与呼吸损失,而铁聚水耕人为土没有显著变化.供试土壤总有机碳损失的Q₁₀系数分别为:潜育水耕人为土(11.1～14.1)＞铁渗水耕人为土(4.4～6.4)＞铁聚水耕人为土(0.63～0.73).这一方面说明温度敏感性在同一地带的不同土壤间的差异超过文献上报道的不同气候带的差异,但另一方面揭示了水稻土可能是一类对全球升温敏感响应的人为土.溶解性有机碳和微生物量的碳的变化还提示不同温度培养下水稻土微生物群落结构可能改变,因而影响到土壤有机碳库的生物有效性在温度条件下的变化.可以认为,土壤升温下有机碳的变化不但与土壤有机碳的性质有关,而且与土壤性质控制下的生物条件的改变有关.故土壤升温下有机碳的损失不仅仅是温度对分解过程的反应速度的影响.当然,对于不同土壤间的这种差异还需从有机碳-土壤环境-土壤生物的相互关系上做进一步的工作.

Change of Organic Carbon Pools and the Responses to Soil Warming during Laboratory Incubations under Different Temperatures of 3 Kinds of Paddy Soils in Tai Lake Region, China

Change of soil organic carbon (SOC) storage under global warming scenarios was paid much attention of the soil and global change studies. To address the features of SOC loss of paddy soils in response to global warming, the authors used 3 representative paddy soils from the Tai Lake region, China to incubate at laboratory respectively under 20 degrees C and 25 degrees C and the change dynamics of total organic carbon(TOC), soluble organic carbon (DOC) and microbial biomass carbon (MBC) were monitored in time intervals. The TOC dynamics could be described with primary reaction equations with the constants varied with soil types and incubation temperature. While soil warming strengthened TOC loss of a Fe-leached Stagnic Anthrosol and a Gleyic Stagnic Anthrosol, no significant difference of TOC was detected in a Fe-accumulic Stagnic Anthosol under different temperature incubations. Q10 quotient, a measurement of soil SOC sensitivity to warming, of the studied soils decreased in the order: 11.1-14.1 for the Gleyic Stagnic Anthrosol < 4.4-4.6 for Fe-leached Stagnic Anthrosol < 0.63-0.73 for the Fe-accumulic Stagnic Anthosol. This indicated that paddy soils could be a group of human managed soils with sensitive response to global warming, whereas the inter-soil group difference in this sensitivity may be greater than that existing between the soils from different eco-zones. The different patterns of DOC and MBC change during the incubation of the 3 studied soils were indicative of different features of soil microbial community of the studied 3 types of paddy soils, which influenced the carbon bio-availability under different temperatures. Thus, change of SOC pools due to soil warming can be accounted for not only by nature of SOC of the soils but changes of microbial activity and even the community associated with soil properties. This study evidences that SOC loss due to soil warming is not a temperature-controlled kinetically decomposition process at least. Further studies should be dedicated on the SOC loss in relation to the interactions between SOC-soil minerals-soil micro-biota.