IMHE OpenIR  > 山地表生过程与生态调控重点实验室
紫色土坡耕地土壤固碳机制研究
Alternative TitleMechanisms of soil organic carbon sequestration on sloping cropland of purple soil
Language中文
花可可
Thesis Advisor朱波
2013
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name博士
Degree Discipline土壤学
Keyword土壤异养呼吸 泥沙有机碳 壤中流doc 模型 紫色土 固碳机制
Abstract气候变暖是全球性环境问题,主要因大气中CO2浓度不断增加所导致的地球温室效应加剧。农田土壤固碳可抵消部分CO2排放,因此,农田土壤固碳是陆地生态系统固碳机制、潜力研究的热点领域,也是应对全球气候变化的前沿科学命题。农田土壤固碳过程是土壤有机碳、土壤水分运动和大气碳水循环紧密联系的复杂链式生物物理和生物化学耦合过程。但农田土壤固碳过程研究多注重于农田温室气体排放和土壤有机碳随泥沙流失的单独研究,割裂了有机碳气态与径流损失的客观联系,忽略了土壤有机碳气体排放与径流损失的协同作用。因此,加强农田土壤有机碳的气?水循环过程的综合研究,查明土壤有机碳气态排放和径流、泥沙协同损失过程、通量及其相互作用关系,进一步阐明农田土壤固碳机制,为全面评估陆地生态系统固碳潜力与效应具有重要的理论和现实意义。 本文选择紫色土坡地农田为研究对象,依托中科院盐亭紫色土农业生态试验站,利用可同步观测坡耕地有机碳的气态排放和径流迁移的大型排水采集器(Free-drain-lysimeter),通过3年的连续野外定位观测和采样分析,结合Hydro-DNDC模型模拟,拟查明紫色土坡耕地有机碳随气态、径流途径损失过程、通量、协同损失特征及其施肥的影响。利用实测数据对Hydro-DNDC模型进行参数标定与验证,探讨计量紫色土坡地农田土壤固碳潜力和速率的方法,阐释紫色土坡耕地土壤有机碳气态与径流损失的协同减排机制。论文主要研究结果和结论如下: (1) 施肥可对土壤异养呼吸速率产生强烈的激发效应,单施猪厩肥(OM)处理激发效应最强,显著高于秸秆配施氮磷钾(RSDNPK)和常规施肥(NPK)处理;有机物料的投入是紫色土土壤异养呼吸速率的主要调控措施,低碳氮比的有机物料能促进土壤异养呼吸速率和CO2排放量。土壤异养呼吸的温度敏感性系数Q10值受气象条件和有机物料碳氮比的双重影响。低温少雨的秋冬小麦季的土壤异养呼吸Q10值大于高温多雨的玉米季,施用猪厩肥处理的土壤异养呼吸Q10值高于秸秆配施氮磷钾肥处理,说明碳氮比值低的有机物料能够提高土壤异养呼吸Q10值,使土壤异养呼吸速率对温度变化更加敏感。 (2) 降雨、径流过程对紫色土坡耕地有机碳迁移的形态与浓度有显著影响。地表径流过程中可溶性有机碳(DOC)浓度随降雨历时逐渐降低,表现为初始浓度高,而后逐渐降低最后趋于稳定。泥沙有机碳(TOC)含量的变化与产沙速率同步,随产沙量的增加而增加。壤中流过程DOC浓度则呈现出先升后降而后趋于稳定的趋势,表现为壤中流产流初期的DOC浓度较低,而后持续上升至最大值,后期持续下降至稳定;暴雨和大雨地表径流过程DOC初始浓度高,衰减快,壤中流DOC浓度高、峰值出现较早。中雨和小雨条件下,壤中流过程DOC初始浓度低,变化幅度大,峰值出现时间较迟。 (3) 常规施肥(NPK)条件下,泥沙TOC、地表径流DOC和壤中流DOC年平均迁移通量分别为2188.99、173.02和990.50 mg C m-2 a-1,分别占全年有机碳迁移总量的65.29%、5.16%和29.55%,说明紫色土坡耕地有机碳流失主要以泥沙为主,其次是壤中流携带的DOC淋失;泥沙有机碳的流失以矿物结合态有机碳(MSOC)为主要形态,其年平均迁移通量为1805.29 mg C m-2 a-1,占泥沙有机碳迁移总量的82.5%,其次是颗粒态有机碳(POC)为374.34 mg C m-2 a-1,比例为17.1%,泥沙的DOC年迁移通量为9.36 mg C m-2 a-1,比例为0.4%;次降雨事件泥沙的MSOC和POC含量均随降雨量增大而增大,而泥沙的DOC含量随降雨量增大而逐渐减小。土壤温度是影响壤中流中DOC浓度季节性变化的重要因素,土壤温度越高,随壤中流淋失的DOC浓度越低。 (4) 与常规施肥相比,秸秆配合氮磷钾施肥(RSDNPK)处理的泥沙TOC年迁移量减少了84.6%,地表径流DOC迁移量减少了51.7%,而壤中流DOC淋失量增加了39.7%,壤中流DOC淋失量占全年有机碳迁移总量的76.7%,增施秸秆有利于减少地表径流和泥沙有机碳迁移量,但壤中流DOC淋失量有增大的趋势,壤中流DOC淋失是秸秆还田农田管理模式下有机碳流失的主要方式,不同于常规施肥;与常规施肥相比,猪厩肥配合氮磷钾施肥(OMNPK)的泥沙TOC年迁移量增加了0.1%,地表径流DOC迁移量增加了19.1%,壤中流DOC淋失量增加了6.81%,说明有机肥-无机肥配施有增大有机碳迁移的趋势。 (5) 紫色土坡耕地水文过程特色鲜明,壤中流发育,壤中流携带的DOC淋失可显著降低土壤中DOC含量,因此可能影响气态碳排放。研究发现,气态碳排放与径流碳迁移之间存在明显的关联效应,土壤异养呼吸速率与壤中流的DOC淋失呈现时间同步,通量消涨的变化特征,其通量关系符合指数衰减方程:y=110.09e-0.003x(y为CO2排放通量,x为DOC淋失通量,R2=0.46,P=0.001),二者的关联机制在于壤中流携带的DOC淋失降低了土壤活性底物DOC的含量。 (6) 玉米秸秆累积腐解速率为47.2%,有机碳累积腐解速率为77.6%。小麦秸秆累积腐解速率为65.8%,有机碳累积腐解速率为86.7%,小麦秸秆累积腐解速率和秸秆有机碳累积腐解率均高于玉米秸秆,这与秸秆的碳氮比值有关,秸秆(C/N)值越低,累积腐解速率越快。 (7) Hydro-DNDC模型可有效模拟有机物料腐解、土壤异养呼吸速率、泥沙有机碳流失和壤中流的DOC淋失。模拟精度为土壤异养呼吸速率>有机物料腐解>壤中流的DOC淋失>泥沙有机碳流失;Hydro-DNDC模型嵌入了SCS和MUSLE水文模块后,所模拟的土壤固碳潜力和速率分别比原DNDC模型降低了68%和33%;外源有机物料的添加能够增大土壤有机碳饱和值并提高土壤固碳速率,秸秆配施氮磷钾和猪厩肥配施氮磷钾处理的未来土壤的固碳潜力和速率分别为16.4和8.07g kg-1,速率分别为0.041和0.025g kg-1 a-1,秸秆配施氮磷钾处理的固碳潜力与速率最高。 (8) 紫色土坡耕地土壤有机碳固定主要通过增加土壤粉粘团聚体和大团聚体内矿物结合态有机碳含量,秸秆还田和农家肥的管理方式均有利于增加粉粘团聚体和大团聚体内矿物结合态有机碳累积。外源有机物料的投入对紫色土坡耕地土壤有机碳库的累积实质为增加土壤中的惰性凋落物和活性腐殖质组分。秸秆还田和施用农家肥管理方式均有利于增加土壤有机碳的累积,秸秆还田与氮磷钾混施的农田管理模式最优。农田土壤固碳机制在于有机物料投入与土壤异养呼吸和有机碳流失的平衡,农田土壤CO2排放与有机碳流失的协同减排机制是紫色土固碳潜力发挥的关键。
Other AbstractGlobal warming is one of the most important environmental issues. Increasing of carbon dioxide concentration in the atmosphere is believed to contribute a lot for increasing air temperature. CO2 concentration in atmosphere is partly offseted by soil organic carbon (SOC) sequestration in cropland. SOC sequestration is an integrated process consisted of soil biochemical and biophysical processes. Up to date, numbers of studies have focused on CO2 emissions or SOC loss in associate with soil and water, separately, resulting in poor understanding of integrated process of SOC loss via gaseous and hydrological pathways. Therefore, it is crucial important to integrate both gaseous and hydrological pathways together to understand mechanisms of SOC sequestration furtherly. A study was conducted to monitor SOC loss via both gaseous and hydrological pathways on sloping cropland of purple soil by free-drain lysimeters at Yanting Agro-ecological Experimental Station of purple soil, Chinese Academy of Sciences. The experimental plots were conducted with fertilization rates at 130 kg N/hm2, 90 kg P2O5/hm2, 36 kg K2O/hm2 and 150 kg N/hm2, 90 kg P2O5/hm2, 36 kg K2O/hm2 for wheat and maize growing seasons respectively. Carbon dioxide emission and dissolved organic carbon (DOC) loss via overland flow and interflow, and SOC loss via sediment had been monitored from 2010 to 2012. A mechanistic based model of Hydro-DNDC had been revised and validated by the observed data. Meanwhile, Hydro-DNDC model had been utilized for integrated process simulation of CO2 emission and hydrological loss of SOC. Finally, soil organic carbon cycling and balance under different fertilization treatments had been simulated and calculated to propose the best management practices on SOC sequestration on hillslope cropland of purple soil. The main results and conclusions were as follows: (1) Pulse emission of CO2 via soil heterotrophic respiration was observed on the fifth day after fertilization. The peak heterotrophic respiration rate for OM regime is significantly higher than that for both RSDNPK and NPK treatments (P<0.01). The results implied that the applied organic material with lower C/N ratio was the primary driving force for increasing soil heterotrophic rate and cumulative soil CO2 emissions. In addition, the values of Q10 for heterotrophic respiration in the wheat season were greater than that in the maize season. Furthermore, Q10 for OM was the highest and that for RSDNPK was the lowest among the fertilization treatments. The results indicated that Q10 was more sensitive in the fertilization regimes with lower C/N organic materials. (2) Dissolved organic carbon (DOC) concentration and fluxes were greatly impacted by rainfall characteristics and hydrological processes.
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/7063
Collection山地表生过程与生态调控重点实验室
Recommended Citation
GB/T 7714
花可可. 紫色土坡耕地土壤固碳机制研究[D]. 北京. 中国科学院研究生院,2013.
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