西南典型岩溶区石漠化治理生态修复对土壤有机碳的影响及其保护机制

The reduction of greenhouse gas emissions and increasing carbon sinks have been become the primary task of mitigating climate change. Soil organic carbon sequestration has been played a key role on global carbon cycle and mitigating climate change. A scientific question that how the ecological restoration of karst rocky desertification control measures affect the soil organic carbon sequestration and its protection mechanism should be emergent to be researched. The work will be important significance to enhance soil carbon sequestration of karst and karst carbon sink. Two typical karst rocky desertification control site, Huajiang in Zhenfeng Country-Guanling Country and SaLaXi in Bejie in Guizhou Province are selected as the study area in this scientific program. Stable isotope 13C and cultivation experiment of mineralization will be used in this research. Aim to reveal the source, transformation and stability characteristics of soil organic and its fractions, as well as their sensitivity to ecological restoration. Variation characteristics of soil organic carbon and its fractions, as well as their stable isotope 13C will be measured. Distribution of soil organic carbon and its fractions, Ca-bound organic carbon, Fe/Al- bound organic carbon in different aggregate particles group and the relationship between soil organic carbon, soil organic fractions, Ca-bound organic carbon, Fe/Al- bound organic carbon and aggregate particles, soil organic carbon in bulk soil will be measured, as well as soil organic carbon mineralization characteristics and influence of calcium form on soil organic carbon, to reveal the mechanism of physically protected soil organic carbon chemical binding and protection in aggregates. And then the optimal mode of ecological restoration of rocky desertification control and the comprehensive control strategy of carbon sequestration and emission reduction of rocky desertification control will be proposed. The study will provide theoretical bases for recognizing the mechanism of soil organic carbon sequestration of karst rocky desertification control model.

土壤有机碳的固定在全球碳循环与缓解气候变化中发挥关键作用。岩溶石漠化治理的生态修复对土壤有机碳影响及其保护机制如何，对增强岩溶土壤碳汇和岩溶碳汇具有重要意义，需要亟待解决。以贵州喀斯特石漠化综合治理示范区关岭——贞丰花江和毕节撒拉溪为例，利用稳定性同位素13C技术和矿化培养实验等方法，研究不同生态修复模式土壤有机碳不同组分及其稳定性同位素13C变化特征，揭示土壤有机碳不同组分的来源、转化和稳定特征及其对生态修复模式的敏感性。进一步研究土壤有机碳及组分、钙键合态和铁铝键合态有机碳在不同团聚体颗粒组的分配及其与土壤团聚体颗粒和全土有机碳的相互关系，团聚体颗粒组有机碳矿化特征以及土壤钙素形态对土壤有机碳的影响，揭示土壤有机碳的团聚体物理保护和化学保护机制。进而提出石漠化治理的最优生态修复模式及其固碳减排综合调控策略，为正确认识岩溶石漠化治理模式下土壤有机碳固定机制提供理论依据。

土壤有机碳的固定在全球碳循环与缓解气候变化中发挥关键作用。岩溶石漠化治理的生态修复对土壤有机碳影响及其保护机制如何，对增强岩溶土壤碳汇和岩溶碳汇具有重要意义，需要亟待解决。本项目针对上述问题获得了以下认识：揭示了土壤 EOC、POC、LFOC 等组分对生态修复的响应较为敏感；石漠化治理生态修复增加了新碳的输入，改善了土壤结构，促进土壤有机碳及其组分的积累；土壤有机碳储量的增加主要归功于粗大团聚体有机碳储量的增加；生态修复后土壤有机碳的积累主要取决于粗大团聚体含量增加的贡献，植被恢复后期团聚体有机碳含量的贡献逐渐增大；土壤颗粒有机质可能在团聚体物理保护中发挥重要作用；稳定同位素13C技术和矿化实验表明，不同团聚体有机碳具有相似的微生物过程，生态修复增加了新碳输入，减缓了粗大团聚体有机碳矿化速率，促进了有机碳的稳定；土壤交换态Ca可能通过促进团聚体的形成和稳定，进而影响土壤有机碳积累和固定。仅从固碳增汇的角度，自然退耕还林模式比人工造林模式较优，而石漠化治理兼顾社会经济效益和生态效益，因此需要调整种植结构和产业结构，筛选具有较强物理保护和化学稳定有机碳能力的管理措施和技术体系，提升区域固碳减排能力。通过该项目研究，项目组共发表论文5篇 (SCI检索论文2篇，中文核心期刊论文3篇)，完成项目计划书任务。该研究揭示了石漠化治理生态修复模式对土壤有机碳的影响及保护机制，为正确认识岩溶石漠化治理模式下土壤有机碳固定机制提供理论依据。