西南典型岩溶区石漠化综合治理对岩溶作用的影响机制及其碳汇效应-以贵州花江为例

The global warming and green house gas mitigation have become a common focus of the whole world. More and more attention has been paid to the karst carbon sequestration effect. It is also identified that the karst rocky desertification control will make great contribution to the carbon sequestration and green house gas mitigation. There are some scientific questions that are emergent to be researched and resolved including how the karst rocky desertification and the control measures affect the karst process and how much carbon can be sequestrated through the karst process after the rocky desertification control measures are taken. The Huajiang karst rocky desertification control site in in Guizhou Province is selected as the study area in the scientific program. Limestone tablets method, hydro-chemical runoff method and the maximal potential dissolution method are chosen for using comprehensively for the study. Typical springs and monitoring sites are determined representing different grades of karst rocky desertification and different type of controlling measures. Through dynamic monitoring on the hydrology and hydro-chemical features of the rain and underground water, and the dynamic monitoring on the carbon dioxide and the organic carbon of the soil, the influential mechanisms and carbon sequestration mechanisms of the rocky desertification and the controlling measures on the karst process and the karstification intensity will be studied and revealed. Isotope technology will be used to trace the way for the carbon transferring tracers including δ13C, D and δ18O. Finally, in a small catchment scale, typical indexes will be defined and key parameters be determined to establish a carbon calculation model for a karst rocky desertification control small catchment. The study will provide theory bases for recognizing the influential mechenisms of karst rocky desertification control on the karst process and the accurate calculation for the karst carbon sequestration.

全球气候变暖和温室气体减排成为各国共同关注的焦点，岩溶碳汇效应逐渐受到重视，岩溶区石漠化治理将为全球增汇减排做出重要贡献。石漠化土地及石漠化治理工程措施如何影响岩溶作用过程、带来多大的岩溶碳汇效应等科学问题亟待解决。本项目拟以贵州花江石漠化综合治理区为研究区，综合运用溶蚀试片法、水化学径流法和入渗-平衡化学法，选择典型不同等级石漠化土地、不同类型石漠化综合治理工程区泉点及样地进行动态观测，通过高分辨率雨水和地下水水文、水化学、土壤二氧化碳及有机碳的动态监测，研究不同等级石漠化土地及不同类型石漠化治理工程措施对岩溶作用过程及强度的影响机制和碳汇机制；利用碳-13、氧-18、氘等同位素技术，追踪碳运移途径；以小流域为单元，提取典型指标，确定参数，构建石漠化综合治理小流域岩溶碳汇估算模型并估算岩溶碳汇，为揭示石漠化治理对岩溶作用过程及强度的影响机制和准确评估石漠化治理区岩溶碳汇效应提供理论依据。

人类活动造成的以CO2为主的温室气体排放是造成全球温度升高的主要原因，岩石的化学风化作用成为大气CO2消耗的重要途径，石漠化综合治理对岩溶作用将产生重要影响，因此，该项目以贵州花江石漠化治理示范区为主要研究区，围绕不同等级石漠化土地及不同类型石漠化综合治理工程措施对岩溶作用过程及作用强度的影响机制和石漠化综合治理的碳汇估算开展研究。研究发现：第一、岩溶地区石漠化治理能明显增强岩溶作用强度，其影响机制主要体现在：(1)石漠化治理后，植被和土壤得到恢复，明显增加土壤CO2浓度和土壤湿度，石漠化治理后土壤CO2浓度可增加10000 mL/m3以上；(2)地下水水化学特征迅速响应，表现出明显差异，未进行石漠化治理的耕地A泉和石漠化治理后的退耕还林地B泉的Ca2+、HCO3-变化范围分别为78~98 mg/L，207.4~280.6 mg/L和118~133 mg/L，323.3~396.5 mg/L，B泉的Ca2+和HCO3-含量明显高于A泉；(3)不同泉水中δ13CDIC对此也响应明显，平均值大小顺序为吊井(-12.79‰)<水井湾(-12.48‰)<戈贝(-10.76‰)<毛家湾(-10.30‰)<谭家寨(-6.70‰)，反映了石漠化和农业施肥影响下的地下水的δ13CDIC值偏重，石漠化治理后泉水的δ13CDIC值则偏轻。第二、石漠化治理能明显增强岩溶碳汇效应。A泉和B泉碳酸盐岩溶蚀过程中消耗CO2的量平均值分别为1.6 mmol/L和2.5 mmol/L，B泉每月消耗CO2量均明显大于A泉。花江示范区的单位面积土下溶蚀量为强度石漠化(2.21 t/km2/a)<中度石漠化为(2.39t/km2/a)<轻度石漠化为(6.33 t/km2/a)<潜在石漠化为(15.76t/km2/a)。第三、白云石因具有较高的溶解度可能使得白云岩流域岩溶碳汇通量高于石灰岩流域，白云岩地区的石漠化治理可能能更大的促进岩溶碳汇增加。通过该项目研究，项目组共完成学术论文9篇，其中已经在发表7篇(SCI检索论文1篇、EI检索论文1篇、中文核心期刊论文4篇)，已经被中文核心期刊录用待发表学术论文2篇，申请发明专利1项，超额完成项目计划书任务。该研究揭示了不同等级石漠化及不同类型石漠化治理工程措施对岩溶作用过程及作用强度的影响机制，为今后更精确估算石漠化综合治理的碳汇效应提供理论依据。