桂林岩溶试验场植被水文过程总有机碳通量垂直变化特征

摘要

该研究以广西桂林岩溶石山区的两种典型植被(香椿林和云实灌丛)为例,利用野外长期定位监测降雨、穿透雨、树干径流、钻孔和表层岩溶水中总有机碳(TOC)的变化特征,探讨不同植被林冠层TOC浓度和通量的年变化特征.结果表明:在降雨通过大气-植被-土壤/岩石的过程,TOC浓度变化趋势为树干径流＞穿透雨＞钻孔水＞泉水＞大气降雨;穿透雨和树干径流中TOC浓度呈现为雨季大旱季小的趋势,钻孔水和泉水的TOC浓度月变化则相对稳定;TOC浓度的增幅不同,穿透雨和树干径流TOC浓度的平均增量和变化幅度比钻孔水和泉水的大;香椿林树干径流TOC浓度与树干径流量呈负相关关系;TOC月平均通量为云实穿透雨＞香椿穿透雨＞降雨＞泉水＞香椿树干径流＞云实树干径流;云实灌丛林下降雨(204.86 kg·hm-2)的TOC通量是香椿林(153.48 kg·hm-2)的1.3倍;观测期间,大气降雨输入的TOC通量为63.06 kg·hm-2,表层岩溶泉水输出为48.29 kg·hm-2,TOC输入输出之差为14.77 kg·hm-2,系统TOC为正平衡;降雨进入植被内部后时,植被林冠层作为"TOC活库"具有增加TOC通量的"源"作用,而表层岩溶带的土壤/岩石系统作为"TOC死库"具有吸收、过滤和固定TOC的"汇"作用.%In order to reveal the annual variation characteristics of TOC concentration and flux in different vegetation canopies, total organic carbon (TOC) concentration and its flux in precipitation, throughfall, stemflow, borehole water and epikarst spring water were monitored in two typical vegetations (Toona sinensis and Caesalpinia decapetala) in karst rocky mountain area, Guilin, Guangxi.The results indicated that in the process of rainfall through the atmosphere-vegetation-soil/rock profile, the variation trend of TOC concentration was stemflow＞throughfall＞borehole water＞epikarst spring water＞rainfall.The TOC concentration in throughfall and stemflow was bigger in rainy season and smaller in drought season.The monthly TOC concentration in borehole water and epikarst spring water was relatively stable.The increase of TOC concentration was different, and average increment and amplitude of TOC concentration in throughfall and stemflow were larger than that in borehole water and spring water.The TOC concentration of stemflow was negatively correlated with stemflow water quantity in Toona sinensis forest.TOC average monthly flux was throughfall in Caesalpinia decapetala＞throughfall in Toona sinensis＞precipitation＞spring＞stemflow in Toona sinensis＞stemflow in Caesalpinia decapetala.The TOC flux under shrub rain (204.86 kg·hm-2) was 1.3 times that in Toona sinensis (153.48 kg·hm-2).The TOC flux from rainfall input was 63.06 kg·hm-2, with 48.29 kg·hm-2TOC flux from epikarst spring output.The TOC difference between input and output was 14.77 kg·hm-2, which indicate that TOC in system was a positive balance.When precipitation entered vegetation, vegetation canopy, as"TOC live reservoir", increased TOC flux and was a carbon"source", however, soil-rock system in epikarst zone, as"TOC dead reservoir", was carbon"sink"with absorption, filtration and fixing of TOC.