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土地利用变化是驱动陆地与大气之间碳迁移变化的主要因素,为正确评估土地利用方式变化后土壤有机碳固持和稳定性,对南方双季稻田(RR)改为玉米-玉米(MM)和大豆-花生(SP)2年后土壤化学性质、有机碳矿化及微生物群落结构的变化进行研究.结果表明,RR改为MM和SP后,土壤p H值显著降低(0.50-0.52,P=0.002),而可溶性有机碳显著提高(23%-35%,P=0.016).土壤有机碳的矿化速率没有显著变化,但在培养13 d后SP累积矿化量显著降低(P=0.019).稻田改旱地后,土壤微生物总磷脂脂肪酸(PLFAs)、细菌、革兰氏阳性菌(G+)、革兰氏阴性菌(G-)和放线菌PLFAs显著降低(P<0.05),而真菌PLFAs/细菌PLFAs(F/B)显著增加(P=0.006),但改MM和SP没有显著差异.培养初期,土壤放线菌PLFAs与累积碳矿化显著相关(P=0.034),土壤F/B与培养13 d累积碳矿化显著相关(P=0.004),而土壤微生物群落主成分分析的PC1(P=0.014)和总的PLFAs(P=0.033)与培养108 d累积碳矿化显著相关.本研究发现稻田改旱地后土壤p H和总氮含量是影响土壤微生物群落结构和生物量进而影响土壤有机碳矿化的关键因素.
Land use change is the main factor driving the change of carbon migration between land and atmosphere. In order to properly evaluate the soil organic carbon fixation and stability after land use change, the paper changed the double cropping paddy (RR) in southern China to maize-maize (MM) and Soybean-peanut (SP) soil chemical properties, organic carbon mineralization and microbial community structure were studied after 2 years.The results showed that after RR was changed to MM and SP, soil p H decreased significantly (0.50-0.52, P = 0.002), while the content of soluble organic carbon increased significantly (23% -35%, P = 0.016). There was no significant change in the mineralization rate of soil organic carbon, but significantly decreased after 13 days of culture (P = 0.019) After changing dry land in paddy field, PLFAs, bacteria, Gram - positive bacteria (G +), Gram - negative bacteria (G -) and actinomycetes PLFAs were significantly decreased (P <0.05) PLFAs / bacterial PLFAs (F / B) increased significantly (P = 0.006), but no significant difference was found between MM and SP. In the early culture stage, PLFAs of soil actinomycetes were significantly correlated with cumulative carbon mineralization (P = 0.004), while PC1 (P = 0.014) and total PLFAs (P = 0.033) in the soil microbial community were significantly correlated with the cumulative carbon mineralization 108 d raising significant correlation cumulative carbon mineralization. The present study found that total nitrogen content of the soil p H paddy fields and upland change is the key factor community structure and microbial biomass and further on soil organic carbon mineralization.