耕作年限对鄱阳湖围垦区稻田土壤有机碳组分的影响

Effects of Tillage Years on Soil Organic Carbon Fractions in the Poyang Lake Reclaimed Paddy Fields

在鄱阳湖围垦区选取6个不同耕作年限的稻田,分析测定了土壤总有机碳(SOC)、重组有机碳(HFOC)、轻组有机碳(LFOC)和微生物生物量碳(MBC)含量,以阐明耕作年限对土壤有机碳组分的影响。结果表明:(1)鄱阳湖围垦区稻田0~30 cm土层土壤HFOC、LFOC和MBC含量分别为5.89~24.01 mg·g^(-1)、0.47~4.14 mg·g^(-1)和12.43~850.53 mg·kg^(-1),3种有机碳组分均与SOC含量呈显著正相关关系(P<0.01)。(2)耕作年限显著影响HFOC、LFOC和MBC含量,随着耕作年限的增加,3种有机碳组分含量均呈不同程度的增加趋势,但其占SOC的比例随有机碳组分及土层呈不同的变化规律。(3)鄱阳湖区围垦稻田与垦殖前的湿地相比,HFOC占SOC的比例在耕作50 a后呈相对稳定状态,但较天然湿地小,表明围垦在一定程度上降低了土壤碳库的稳定性。

Wetland conversion to paddy field is a typical land use change in the middle and lower reaches of the Yangtze River.Poyang Lake is the largest fresh water lake in China.There were total 1 466.9 km 2 Poyang Lake wetlands that were converted to croplands,and most of them were used as paddy cultivation.Soil samples were collected from Poyang Lake reclaimed paddy fields with different tillage years.Subsequently,soil total organic carbon(SOC),heavy fraction organic carbon(HFOC),light fraction organic carbon(LFOC)and microbial biomass carbon(MBC)were measured.The objective was to clarify the effect of tillage years on soil organic carbon fractions in the Poyang Lake reclaimed paddy fields.Results indicate that the top 30 cm soil HFOC and LFOC ranged from 5.89 to 24.01 and 0.47 to 4.14 mg·g-1,respectively,whereas MBC varied from 12.43 to 850.53 mg·kg-1.All three organic carbon fractions were significantly positively correlated with soil total organic carbon.HFOC,LFOC and MBC were significantly affected by tillage years.The contents of all three organic carbon fractions increased with tillage years.However,the ratios of various organic carbon fractions to soil total organic carbon differed among the three components and varied with soil depth.After 50 years tillage,HFOC in the reclaimed paddy fields was relatively stable,however,the ratio of HFOC to SOC declined in comparison to natural wetlands.Hence,to some extent,reclamation declined the stability of soil carbon pool.