基于MDC方法评价林下劣地碳氮提升对短期恢复措施的响应

Assessment of the Response of Soil Organic Carbon and Nitrogen Enhancement in Erosion-Degraded Land to Short-Term Restoration Measures Based On Minimum Detectable Change Method

为了评价林下侵蚀劣地碳氮提升对短期恢复管理措施的响应,选择基于最小可检测变化(minimum detectable change,MDC)设计的土壤有机碳(SOC)、全氮(TN)和碱解氮(AN)随时间变化的随机分层采样方法,用以消除林下土壤碳氮的空间变异性。以南方红壤低山丘陵区马尾松林下侵蚀劣地为对象,共设置7个处理:无恢复措施(CT)、乔草+鱼鳞坑(FG)、乔灌+鱼鳞坑(FS)、乔灌草+鱼鳞坑(FGS)、乔草+小水平沟(FGP)、乔灌+小水平沟(FSP)、乔灌草+小水平沟(FGSP)。结果表明:试验进行1.5年后,各处理的总植被盖度较试验前显著增加,增加幅度为7%~50%,其中草灌植被盖度增加尤为明显。基于MDC结果,除FG、FS处理外,其余处理均可以检测到SOC的变化;除FG外,其余处理均可以检测到TN的变化,而所有处理均可以检测到AN的变化。与试验前相比,各恢复措施下SOC、TN和AN含量的增量分别为0.10~2.08 g/kg、0.02~0.13 g/kg和8.54~25.06 mg/kg。SOC、TN和AN的净增量百分数分别为34%~101%,35%~83%和14%~82%;SOC的净增量大小排序为FGSP>FG>FGP>FGS>FSP>FS;而TN的净增量表现为FS>FGS>FGSP>FGP>FSP>FG。小水平沟区组对SOC、TN和AN的增加明显高于鱼鳞坑区组。近地表草灌植被盖度是SOC、TN和AN提升的关键因素。本土先锋草灌植被与小水平沟复合配置措施是林下侵蚀劣地快速增碳固氮的有效措施,研究结果可为红壤林下侵蚀劣地恢复治理提供技术支撑。

In order to evaluate the enhanced effect of soil organic carbon(SOC),total nitrogen(TN)and available nitrogen(AN)concentration under short-term restoration measures in erosion-degraded lands,we adopted the random stratified sampling strategy based on the theory of minimum detectable change(MDC),to eliminate spatial variability of SOC and nitrogen overtime.A typical erosion degraded forestland was selected,which located in the hilly red soil region of south China.7 treatments were set up in this trial:No restoration measures(CT),tree and grass+fish scale pit(FG),tree and shrub+fish scale pit(FS),tree,shrub and grass+fish scale pit(FGS),tree and grass+small horizontal ditch(FGP),tree and shrub+small horizontal ditch(FSP),tree,shrub and grass+small horizontal ditch(FGSP).The results suggested that the vegetation coverage of each treatment increased significantly compared with those before the experiment,and the increase range was 7%to 50%after 18 months.Especially,the grass and shrub coverage significantly increased under each restoration measures.Except for FG and FS treatments,changes in SOC can be detected in all other treatments;except for FG treatment,changes in TN can be detected in all other treatments,while changes in AN can be detected in all treatments.The increase ranges of SOC,TN and AN content under each restoration measure were 0.10 to 2.08 g/kg,0.02 to 0.13 g/kg and 8.54 to 25.06 mg/kg,when compared with those before the experiment.The ranges of net increment of SOC,TN and AN were 34%to 101%,35%to 83%and 14%to 82%.The net increment of SOC in different treatments were in decreasing order of FGSP>FG>FGP>FGS>FSP>FS,while the net increment of TN showed as FS>FGS>FGSP>FGP>FSP>FG.The increment of SOC,TN and AN content in small horizontal ditch groups were significantly higher than those in fish scale pit groups.Near-surface grass and shrub vegetation coverage,is a key factor affecting changes in contents of SOC,TN and AN under erosion degraded forestland of red soil region.Local pioneer shrub plus grass with soil conservation engineering practices were the effective restoration measures for red soil erosion-degraded forest hillslope land and the improvement of SOC and nitrogen in the short term.