【摘要】 对民勤绿洲区不同撂荒年限农耕地0~60 cm土层土壤总有机碳(TOC)、轻组有机碳(LFC)和重组有机碳(HFC)剖面分布以及与土壤主要属性的关系进行了比较研究。结果表明:①撂荒区0~60 cm土层土壤TOC、LFC和HFC含量分别介于3.21~5.23、0.34~1.51、2.55~4.30g/kg,相对于常规耕作土壤,撂荒土壤TOC、LFC和HFC的下降主要发生在耕层(0~20 cm),撂荒40年间,TOC、LFC和HFC年均减幅分别为1.94%、5.46%和2.13%;20~60 cm土层土壤TOC和HFC含量总体呈现缓慢增长的趋势,撂荒40年TOC和HFC年增幅分别为0.31%和0.88%,LFC持续减少,年均减幅为1.18%。②撂荒地HFC对TOC的贡献大于LFC,土壤TOC和HFC含量分别与黏粒百分比和粉粒百分比呈极显著正相关,与砂粒百分比呈极显著负相关,LFC含量与粉粒、砂粒和黏粒百分比均未达到统计学上的显著相关,但LFC含量分别与土壤pH、EC和SAR(钠吸附比)呈显著或极显著相关,说明LFC对土壤盐碱化较为敏感。③逐步回归分析表明,土壤全氮、总碳氮比对土壤TOC、LFC和HFC影响较大。④随撂荒时间延长,耕层土壤逐步趋于粗质化,黏、粉粒含量不足,体积质量降低,盐碱化提高,不利于土壤有机碳的积累,随土层加深,黏、粉粒含量提高,有助于土壤有机碳的固持。更多还原

【Abstract】 This study is aimed to investigate the dynamics of total soil organic carbon(TOC),light fraction organic carbon(LFC) and heavy fraction organic carbon(HFC) concentrations,their profile distributions and influencing factors in an anthropogenic-alluvial soil in the Minqin Oasis Area under six abandonment time series.In each sampling area soil samples were collected from 4 layers within 0-60 cm depth.The results showed that 1) TOC,LFC and HFC contents were between3.21-5.23g/kg,0.34-1.51 g/kg and 2.55-4.30 g/kg in this soil profile,respectively.TOC,LFC and HFC decline mainly occurred in the tillage layer(0-20cm) after 40 years abandonment,compared to conventional tillage,the annual decline rates of TOC,LFC and HFC were 1.94%,5.46%and 2.13%,respectively.In general,TOC and HFC contents in 20-60 cm soil depth showed a slow increasing trend,compared with cropland under conventional tillage,the annual increase rate of TOC and HFC were 0.31%and0.88%,but LFC continued to decline,with an annual decrease of 1.18%.2) The HFC contribution to TOC was greater than LFC on abandoned land,soil TOC and HFC contents were significantly positively correlated with clay and silt percentages respectively,and significantly negatively correlated with the sand percentage,LFC content didn’t reach significant levels in statistics with silt,sand and clay percentages,but LFC content had significant or extremely significant relationship with pH,EC and SAR,indicating LFC was more sensitive to soil salinization.3) Stepwise regression analysis showed that soil total nitrogen(TN) and TOC/TN ratio had greater impact on soil TOC,LFC and HFC.4) With the long time abandonment,tillage layer became rough and salinity increased,which is not suitable for soil organic carbon accumulation;but with the soil horizon deepen,clay and silt percentages increased,which can increase soil organic carbon accumulation.更多还原