石漠化治理对岩溶作用强度的影响及其碳汇效应

Impact of Rocky Desertification Treatment on Kast Carbonate Rock Dissolution Rates and Its Carbon Sink Effect

以贵州关岭-贞丰花江岩溶石漠化综合治理区代表石漠化治理的退耕还林地和未进行石漠化治理的耕地及对应的B泉和A泉为研究对象,分析退耕还林地、耕地的土壤CO_2浓度变化、土下溶蚀量及碳汇差异,以及对应泉水Ca^(2+)、HCO_3^-的变化,并计算岩溶碳汇效应,揭示石漠化治理对岩溶作用强度的影响及其碳汇效应。研究结果表明,研究区土壤CO_2浓度变化范围为417~10 000ml/m^3以上,表现为夏秋高、冬春低的季节变化。土壤CO_2浓度表现为土层60cm>40cm>20cm,在一定深度范围内随土层的增加呈现升高的趋势。相对耕地,退耕还林地能够明显增加土壤CO_2浓度,表明植被恢复有利于土壤CO_2积累。A泉和B泉的Ca^(2+)、HCO_3^-变化范围分别为78~98mg/L,207.4~280.6mg/L和118~133mg/L,323.3~396.5mg/L,B泉的Ca^(2+)和HCO_3^-含量明显高于A泉,其消耗的CO_2量也相对较大,表明植被恢复有利于岩溶作用的进行。在雨季时,泉水中HCO_3^-含量变化相对土壤CO_2滞后大约1~2个月,而在旱季时,其变化趋势一致,表明泉水中HCO_3^-敏感地响应土壤CO_2的变化。退耕还林地土下溶蚀量及碳汇量约为耕地的7倍,受土壤有机质和土壤CO_2浓度及土壤水分等理化性质的影响,退耕还林地土下溶蚀量和碳汇量表现为土下40cm处最高,土下20cm处和60cm处相当。而耕地土下溶蚀量和碳汇量主要受CO_2浓度控制,其变化趋势与土壤CO_2浓度一致。综上表明,岩溶地区石漠化治理能明显增强岩溶作用强度及岩溶碳汇效应。

In order to analyze the variations of soil CO2 concentration, dissolution rates, the differences in carbon sink I and the features of Ca^2＋ , HCO3^- in epikarst A and epikarst B, returning farmland to forest, cultivated land and their corresponding epikarst A and B were chosen in Huajiang karst rocky desertification treatment demonstration site in Guanling-Zhenfeng counties in Guizhou. This study could reveal the effect of rocky desertification treatment on karst carbonate rock dissolution rates and carbon sink. The results showed that the concentration of soil CO2 varied from 417 ml/m^3 to above 10 000 ml/m^3 , it was high in the summer and autumn, and low in spring and winter. The soil CO2 concentration presented in different soil layer was 60 cm〉40 cm〉20 cm, which meant that soil CO2 concentration increased with the increasing of soil depth in a certain rage of depth. Compared with cultivated land, returning farmland to forest could obviously increase the concentration of soil CO2 which meant that vegetation restoration was benefit for soil CO2 accumulation. The concentration of Ca^2＋ ,HCO3^- in epikarst B （118-133 mg/L, 323.3-396.5 mg/L respectively） were higher than that in epikarst A （78-98 mg/L, 207. 4-280. 6 mg/L respectively）, resulted in higher con-sumption of CO2 in epikarst B, which indicated that vegetation restoration promoted karst process. The variation of HCO3- in epikarst was 1-2 months lagged behind the variation of soil CO2 in rainy season. However, it had the same variation trend with soil CO2 in dry season. These suggested that HCO3- variation in epikarst was sensitive response to the change of soil CO2. Soil dissolution rates and carbon sink quantities in returning farmland to forest were 7 times as cultivated land, the highest value of soil dissolution rates and carbon sink was under 40 cm in soil, and the value under 20 cm in soil was equal to that under 60 cm in soil. These could be contributed to the different impact factors included soil organic matter, soil CO2, soil water and other soil properties. However, soil dissolution rates and carbon sink quantities in cultivated land were controlled by soil CO2. All above indicated that rocky desertification treatment could obviously increase the intensity of karst process and karst carbon sink effect.