长江下游沿江平原土壤发育过程中碳库分配动态

Soil Carbon Pool Allocation Dynamics During Soil Development in the Lower Yangtze River Alluvial Plain

土壤发育和土地利用过程中土壤碳库的分配动态是揭示碳循环过程的关键.为了明晰土壤碳库分配及其变化趋势,在长江下游沿江平原典型区建立土壤围垦时间序列(围垦0、60、160、280、1000和1500 a),对不同土地利用方式下表层土壤有机碳(SOC)、无机碳(SIC)、颗粒态(POC)和矿物结合态有机碳(MAOC)的含量、密度及土壤固碳潜力(CSP)等指标进行测定和估算.结果表明,围垦1500 a后,由长江冲积物母质发育的SOC含量经过围垦初期的下降后上升4.9%,而SIC经过快速的淋失,含量已由初期占总碳含量的25.8%普遍降至0.2%.MAOC含量总体上高于POC,对SOC积累贡献率达48.0%~79.7%.区内有机碳密度(SOCD)占总碳密度的57.4%~100%,土壤碳饱和水平(CSL)为18.6%~56.1%,水旱轮作的CSP相较于光滩增长了20.8%.碳氮比和全氮含量是解释土壤碳积累过程的关键因素,围垦年限对评价土壤碳饱和水平有重要作用.沿江平原区土壤经长期利用后必须注重保持养分平衡,以维持土壤生产能力并促进SOC积累,避免土壤固碳能力下降.

The allocation dynamics of soil carbon pools during soil development and land use are the key to revealing the carbon cycle process.To clarify the distribution of the soil carbon pool and its change trend,a soil reclamation chronosequence(0 a,60 a,160 a,280 a,1000 a,and 1500 a reclamation)was established in a typical alluvial plain in the Lower Yangtze River,and the content and density of soil organic carbon(SOC),soil inorganic carbon(SIC),particulate organic carbon(POC),and mineral-associated organic carbon(MAOC),along with carbon sequestration potential(CSP)indicators of topsoil under different land use types were measured and analyzed.The results showed that after approximately 1500 a reclamation,the SOC content developed from the Yangtze River alluvial deposits generally increased by 4.9% after the initial decline,whereas the SIC content decreased to 0.2% from 25.8% of the total carbon content due to its rapid leaching.The MAOC content was normally higher than that of POC,and MAOC was contributing 48.0%-79.7% of the SOC accumulation.In this region,the soil organic carbon density(SOCD)accounted for 57.4%-100% of the total carbon density,the soil carbon sequestration levels(CSL)ranged from 18.6% to 56.1%,and CSP under paddy-dryland rotation increased by 20.8%compared to that under dryland.The C/N ratio and total nitrogen content are key factors in explaining soil carbon accumulation processes,and the reclamation year plays an important role in evaluating soil carbon sequestration levels.After long-term utilization,the cultivated soil in the Yangtze River floodplain must be carefully managed through balanced fertilization to maintain soil productivity,promote the accumulation of SOC,and avoid the decline in soil carbon sequestration capacity.