喀斯特地区土壤水中溶解有机碳浓度对植被退化的响应

按退化程度在茂兰喀斯特地区选取的4种不同植被类型依次为原生性乔木森林、次生性乔灌混合林、灌木林、灌丛草坡，并对各植被退化系统中1a内的土壤水中溶解有机碳（DOC）浓度变化特征进行测试分析，并探讨其对不同退化程度的植被的响应特征。结果显示：（1）各种植被类型下土壤水DOC含量按月份均呈现出由低到高、再由高到低的变化趋势，在6月底出现峰值；（2）土壤水DOC含量对降雨量具有很好的响应关系；（3）土壤水DOC含量随植被退化程度的加剧而呈现出递增的趋势，即退化的植被系统中土壤水的DOC含量大于未退化的植被系统，说明未退化的土壤 植被系统比较稳定，不易受到外界因素的干扰，贮存能力大，流失少。研究结果表明对植被退化响应灵敏的土壤水DOC含量可以作为评价土壤和植被关联退化的一个有效指标。

RESPONSE OF DISSOLVED ORGANIC CARBON IN SOIL WATER TO THE VEGETATION DEGRADATION IN KARST AREAS

The authors choose four sample plots with different vegetation types in Maolan karst areas according to their degradation degree,namely the virgin arbor forests,secondary arbor shrub mixed forests,shrubs and shrub grassland,and then concentrations of dissolved organic carbon (DOC) in soil water at four sample plots were sampled monthly for one year and analyzed,respectively.The results indicate that:(1)DOC concentrations are higher in warm and wet seasons than those of cool and dry seasons in one year,which increase to maximum at June and then decrease.(2)DOC concentrations show a significant dependence on rainfalls.(3)DOC concentrations increase with vegetation degradation degree,and are higher in a degraded ecosystem than those of a non degraded ecosystem,indicating that a virgin soil vegetation system is stable with less runoff and more storage and is not easily interrupted from outside disturbs.These results indicate that DOC values could be served as an effective indicator for vegetation degradation.