钙对耕地土壤有机碳的保护机制研究

Carbon sequestration of agricultural soil is one of carbon sequestration measures recognized by Kyoto Protocol. It has a win-win positive effect on stabilizing productivity and combating climate change. Calcium is not only an essential macronutrient, but it also a good binder of soil aggregate. Calcium often is used in agriculture as a structure-improving agent for the soil. As a soil organic carbon keeping place, the protection of soil aggregate is one of the main mechanisms on soil organic carbon stability. But it’s not very clear that what is the impact of calcium on soil carbon sequestration and if can adding calcium play important roles as a carbon sink in agriculture. It will be necessary to reveal the effect mechanisms of calcium on soil organic carbon sequestration. Therefore, this study will take advantage of 27 years long-term fertilization experiment for brown soil at Shenyang Agricultural University . Brown soil in different treatment will be the research object. It will explore the correlations between calcium of the soil aggregate grain group and total carbon, active soil organic carbon, calcium bond organic carbon. On this basis we will study the effect of calcium on the exogenous new carbon (13C demarcating corn stalk ) distribution in soil aggregate and organic carbon by use model experiment in laboratory method and the technology of stable isotopes δ13C. The ultimate aim of the study is to reveal protection mechanism of calcium on soil organic carbon sequestration. The results of the study will provide certain theoretical basis for the sustainable development of agriculture and solid carbon emission. At the same time, it will has important significance for enhancing the ability of agricultural climate change.

土壤固碳是《京都议定书》认可的固碳措施之一，对稳定生产力和应对气候变化具有双赢的积极效应。钙既是作物必需的中量营养元素，也是土壤团聚体的良好胶结剂，常作为土壤结构改良剂。而团聚体的保护是土壤有机碳主要的稳定机制。那么，钙对土壤有机碳固定影响如何？能否通过施钙增加土壤有机碳稳定性，达到固碳减排的目的还不十分清楚。因此，为揭示钙对耕地土壤有机碳的保护机制，本研究拟利用沈阳农业大学连续27年的棕壤长期定位试验，探讨不同施肥处理土壤团聚体粒组中各形态钙与全碳、活性有机碳、钙键合态有机碳等的相关性。并在此基础上，拟采用室内恒温模拟培养的方法，利用稳定性同位素δ13C，研究钙对外源新碳（13C标定的玉米秸秆）在耕地棕壤团聚体粒组和不同形态有机碳中分配的影响，以揭示钙对土壤中有机碳保护的作用机制。研究结果可为实现农业固碳减排提供一定理论依据，同时对增强农业应对气候变化能力具有重要意义。

土壤碳库是陆地生态系统中最大最活跃的有机碳库之一，是全球碳循环的核心内容，强烈影响着温室气体排放。钙是植物生长发育必需的中量营养元素之一，是许多重要生理生化过程的调控者。同时钙也是土壤团聚体形成过程的良好胶结剂，常被作为土壤改良剂。. 为了探讨钙素对耕地棕壤有机碳转化的影响机制，论文以长期定位施肥27年耕地棕壤为研究对象，探讨了土壤钙素与有机碳积累的相关性。同时采用室内模拟培养的方法，利用13C标定的玉米秸秆，研究了施入外源钙对耕地棕壤不同形态碳素转化的影响。. 本课题的研究结果显示长期定位施肥处理耕地棕壤钙素含量和有机碳含量的增加均有利于土壤>1mm粒级团聚体的形成。全钙与土壤总有机碳含量及1-0.25mm和0.25-0.053mm粒级团聚体总有机碳含量之间的相关性均为极显著正相关关系，相关系数分别为0.8832**、0.8632**和0.8611**。土壤及各级团聚体（1-0.25mm粒级团聚体除外）交换性钙与有机碳含量之间的相关性呈现显著正相关关系。土壤及各级团聚体酸溶性钙含量与有机碳含量之间的相关性最显著，相关系数分别为r（>1mm）=0.7303*、r(1-0.25mm)=0.8995**、r(0.25-0.053mm)=0.9616**、r(<0.053mm)=0.9251**。因此，耕地棕壤中钙对有机碳可起到一定的保护作用。当单施外源钙时，促进了对耕地棕壤有机碳的保护作用；玉米秸秆与外源钙配施，当添加CaCl2为1%时，提高了土壤及各级团聚体有机碳的含量；当添加CaCl2为2%时，则促进了耕地棕壤有机碳的矿化。因此外源钙对耕地棕壤有机碳有一定的保护作用，但对玉米秸秆有机碳的保护作用与施入外源钙量有关。. 综合上述结果，本课题的研究为揭示钙对耕地棕壤有机碳的保护作用奠定了一定的工作基础，同时对认识钙素与全球碳循环之间的关系提供了启示性线索。