【作者】 李涛；

【导师】 曹建华； 张美良；

【作者基本信息】 广西师范大学 ， 生态学， 2011， 硕士

【摘要】 当前,大气CO2浓度不断升高,温室效应加剧,使得碳循环研究成为全球关注的热点问题。其中,土壤碳库在全球碳循环中起着至关重要的作用,其变化直接影响全球的碳平衡。而占全球陆地面积12%、占中国国土面积1/3的碳酸盐岩分布区,是地球表层系统的重要组成部分。所以对岩溶区土壤CO2的迁移、变化进行研究有助于弄清岩溶地区的碳循环模式,尤其对岩溶动力系统有重要作用；另外,土壤碳通过土壤呼吸释放CO2到大气中,对大气CO2的源汇效应具有重要调节作用,这使得土壤CO2为该系统中主要的碳流通途径。因此,在揭示岩溶生态系统土壤碳循环规律和机理研究中,对典型岩溶区土壤CO2迁移、变化规律及岩溶效应的研究意义重大。自2009年12月至2010年12月以桂林盘龙洞岩溶实验场为例,选择岩溶洼地里的坡地灌木丛和洼地灌木丛2个样地,通过长期定时(半个月一次,连续-年多)监测土壤CO2浓度的空间分布规律和季节变化,以及土壤CO2释放速率的空间变化和日动态变化,分析表层带岩溶系统中碳的迁移、变化规律,从而揭示土壤CO2对表层岩溶作用的动力机制以及岩溶土壤CO2对大气CO2的源、汇效应。通过长期定时监测研究,研究结果如下：(1)无论是坡地还是洼地,春季和夏季时土壤CO2释放速率表层土大于深层土,秋季和冬季时深层土大于表层土,且坡地大于洼地；土壤CO2的释放速率具有明显的季节性变化特征,夏秋季(6-9月)土壤CO2释放速率是其它时期的1-3倍,并显示与土温、土壤含水率和生物活动密切相关。(2)土壤CO2的浓度具有明显的季节性变化特征,夏季最高,冬季最低,夏季(6-8月)土壤CO2的浓度是其它季节的2-3倍,并显示与气温、降水和生物活动密切相关；且深层土大于表层土,洼地高于坡地,尤其夏季时洼地比坡地高出近1000 mg/m2。(3)在垂直的土壤剖面上,大多数的情况下土壤CO2浓度随土壤深度的递增而升高,但在雨季时坡地(-50 cm与-80 cm处)和洼地(-80 cm与-100 cm处)的土壤CO2浓度又随深度的增加而降低,即双向变化。(4)石灰岩试片的溶蚀量与土壤CO2浓度呈密切正相关关系,也具有明显的季节性变化特征,春夏季溶蚀量大,秋冬季溶蚀量小；溶蚀强度随不同深度的土壤CO2浓度的变化基本是一致的,总体上CO2浓度的升高,溶蚀率增大,说明土壤CO2和土壤水的滞留时间是驱动岩溶作用的两个关键因子。(5)土壤总有机碳的613C值具有明显的季节性变化特征,但坡地灌木丛、洼地灌木丛和洼地灌草地三者的变化规律不一致；自地表向下,土壤613C值随土层深度的增加而逐渐偏正,且深层土的δ13C值较为稳定；优势种黄荆和檵木其各部位有机质平均δ13C值范围为-25.15O‰～-28.23‰；而土壤中有机碳的δ13C值范围为-19.00‰～-22.32‰,表明土壤的有机碳的δ13C值明显高于当地植物的有机碳的613C值。更多还原

【Abstract】 At present, with the situation of atmospheric CO2 concentration elevating and the greenhouse effect intensifying, carbon cycle has been one of hot topics in the world. One of the soil carbon pool is an important component of the global carbon cycle, and it has directly effects on the global carbon balance. And that karst area is occupied 12% the area of all lands in the world and 1/3 land of China, karst area is an important part of the earth surface system. Therefore, studying the migration and chang regularity of the soil CO2, and karst effects in karst region can contribute to find out the carbon cycle model, and it was helpful to karst dynamic system. In addition, soil released CO2 to the atmosphere through soil respiration, and it plays an important role in of atmospheric CO2 source and absorb effect, so soil respiration was the main way in carbon flow ways. So, in order to reveal the soil carbon cycle in karst ecological system and the mechanism research, study the migration and chang regularity of the soil CO2, and karst effects in typical karst region was significant on the research of soil carbon cycle.Since December 2009 to December 2010, using the karst experimental site Panlong Cave in Guilin as the example and chosing two plots in the scrub brush of slope and depression in karst areas, this research had tested the spatial distribution and seasonal variation of CO2 concentration, and slao the daily variation and the changes by different spaces of soil CO2 emission had been monitored in a long time (half a month time, more than a year). Analyzing the migration and change rule of soil CO2 in Epikarst, so as to reveals the karst dynamic mechanism of soil CO2 with Epikarst karstification, and the source, absorbing effect of karst-soil CO2 with atmospheric CO2. The results showed that: (1) In the two plots, the soil CO2 emission rate is greater in the deep soil than that in the top soil in spring and summer, and it’s opponent in autumn and winter and also the emission rate is greater in hillside than that in the karst depression; the soil CO2 emission rate had related with the soil temperature and soil water content; The soil CO2 emission rate had seasonal variation obviously, in summer(June to September), the soil CO2 concentration is one or three times than that in the other periods, and it showed a close relation with the temperature, soil moisture content and biological activities.(2) The soil CO2 concentration had seasonal variation obviously with a trend of highest in summer and lowest in winter, in summer (May to August), the soil CO2 concentration is two or three times than that in the other periods, and it showed a close relation with the temperature, precipitation and biological activities. And it was higher in the deep soil than that in the surface and the depressions than the slope, especially in summer the soil CO2 concentration of the depression had high nearly 1000 mg/m2 than slope.(3) In the vertical soil profile, the soil CO2 concentration was increasing with soil depth increases in most cases, but the CO2 concentration of slope (-50 cm and 80 cm) and depression (-80 cm and -100 cm) all were reducing with soil depth increases during the rainy season, so named it two-way change.(4) The rate of limestone dissolution was positively correlated with the soil CO2 concentration, and also had seasonal variation obviously for spring and summer the erosion was huge and small in autumn and winter; the trend of dissolution intensity had the soil CO2 concentration was almost uniform in different soil depths, overall when CO2 concentration increased, the dissolution rate increased, it indicated that the soil CO2 concentration and time of soil water residence was the two key factors that the driving the karstification.(5) Theδ13C value of soil organic carbon has obvious change in different seasons, but the change rule of slope, depression and grassland has inconsistent; From surface to downward, the soilδ13C value has more positive with the increase of soil depth, and theδ13C value of depth soil has stable; the two kind of advantage plant,both Vitex negundo and Loropetalum chinense their average 813C value of every parts have range for -25.15‰～-28.23‰; And Theδ13C value of soil organic carbon has soil organic carbon range for -19.00‰～-22.32‰, indicated that the 813C value of soil the organic carbon has obviously higher than theδ13C value of local plants.更多还原