摘要
本文以广西桂林丫吉试验场的实际观测资料为基础，应用同位素示踪方法，探索了整个系统中碳的输入、输出和转移问题，并分析了表层岩溶生态系统中泉水水化学、土壤 ＣＯ２浓度及近地表植被层空气中ＣＯ２浓度的变化特征。结果显示，泉水水化学主要组分的日变化不明显，而土壤中ＣＯ２浓度则明显受日气候变化的影响，两者存在明显的滞后关系。用碳同位素示踪方法，重点对桂林观测站表层生态系统各碳库间碳的转移过程进行了定量研究，认为在有土壤层和植被覆盖的表层岩溶生态系统中，参与岩溶作用的碳有一半以上来源于与生物作用有关的碳。
Based on the observed data at the Guilin Experimental Site, and using carbon isotope tracing method, we have probed into the transportation of the carbon in karst ecological systems, and analyzed the change features of the hydrochemistry of an epikarst spring water and CO2 concentrations in soil gas and vegetation air. The researches included (1) measuring the hydrochemical indexes of rainfall, spring water and soil water by using some potable equipment; (2) collecting samples of 13C by codepostion method; (3) collecting 13C samples of plants and calculating the pure annual productivity of vegetation; (4) measuring the releasing rate of CO2 coming from soil surface by using alkaline absorbing method, (5) measuring CO2 concentration in soil air and vegetation air by using CO2 measuring instruments; (6) calculating the dissolution rates of limestone rocks by using denudation test of limestone tablets. The research results are as follows: (1) Based on the calculation of the carbon cycle balance in S54 spring system, the total carbon input in this spring system is 4.8t/ (ha. a). The total carbon output is 5.2t/ (ha. a), and the carbon output through spring water only makes up 15% of the total carbon output. Therefore, we hold that the carbon transportation in this system is closely related to the soil respiration processes and the decomposition of the organic matter in soil. (2) The daily change of the main hydrochemical components of spring water is not obvious, which shows that the hydrochemical change lags behind the change of CO2 in soil air, namely, the soil water moves slowly in soil layer. On the contrary, the seasonal change of hydrochemistry is great for instance, the HCO3 of S54 spring reaches the highest in autumn and the lowest in spring, but the CO2 concentration of soil air reaches the highest in summer and the lowest in winter. There is one season delay between these two indexes. (3) The CO2 fluctuation in vegetation air consists of the following four parts: the background (about 350 × 10^-6) of the atmosphere, which is relatively stable, the CO2 released from soil surface, the consumed CO2 during the photosynthesis of vegetation, and the CO2 released from the respiration processes of vegetation. As a result the spatial and temporal change characteristics of the CO2 concentration in the vegetation air are as follows f Firstly, the close environment at the bottom of depression, where the air circulation is relatively slow, is favorable for the assemblement of CO2. Moreover, the vegetation in depression grows very well, and the photosynthesis and respiration is intensive. Therefore, both the CO2 concentration and the daily fluctuation of CO2 are the highest at the same testing bine. On the contrary, the situation at the saddle is reverse. Secondly, the results along the testing profile (0cm to 240cm from the ground) at different testing time show that almost all the maximum of the CO2 concentration of vegetation air appears at 0cm(one or two at 240cm) and at 4 o'clock to 6 o'clock in the morning. Thirdly, almost all the minimum of CO2 concentration appears at 200cm to 240cm and at 12 o' clock to 15 o'clock when the photosynthesis of vegetation is most intensive. (4) The results of δ13C show that about 60% of CO2 in vegetation air comes from soil air, the other 40% comes from the atmosphere; and 67% of carbon in HCO3 forms of spring water comes from soil air, and 33% comes from carbonate rocks.
出处
《第四纪研究》
CAS
CSCD
北大核心
2000年第4期383-390,共8页
Quaternary Sciences
基金
国家自然科学基金!(批准号:49632100)
国土资源部重点科技项目!(批准号:9501104)
国土资源部科技司"十五"预
