喀斯特出露基岩生境两种典型乔木的树干液流特征

以西南喀斯特地区常见的出露基岩生境为研究对象,应用TDP热扩散探针技术,分析2种典型乔木菜豆树和圆叶乌桕的树干液流特征.结果表明: 2树种树干液流对干、湿季均有明显响应;同为落叶乔木,菜豆树(约1个月)无液流特征的时长远小于圆叶乌桕(约4个月);圆叶乌桕单位胸高断面积年总蒸腾耗水量高于菜豆树,生长季内(4—9月) 2树种单位胸高断面积耗水量分别约占全年的90%和66%;2树种液流密度与光合有效辐射、水汽压亏缺、温度均呈极显著正相关,与相对湿度呈极显著负相关;2树种生长季内液流密度、日蒸腾耗水不仅小于同处于亚热带季风区的非喀斯特地区,而且小于邻近的喀斯特地区,甚至低于降水稀少的干旱地区典型树种同一参数的值.喀斯特出露基岩生境2种典型植物的蒸腾耗水量因特殊的水分环境而受到限制,同为落叶乔木却对应着不同的水分利用策略.

Characteristics of sap flow of two typical trees in exposed bedrock habitat of Karst region,China

A unique but very common habitat, rocky outcrop in Karst region of southwest China was selected for this study. Sap flow patterns of two typical tree species (Radermachera sinica and Triadica rotundifolia) were analyzed by using the method of Granier’s thermal dissipation probe (TDP). The results showed that sap flow density of both species exhibited clear response to the wet and dry seasons. However, the absence of sap flow only last about 1 month for R. sinica but 4 months for T. rotundifolia, despite the same functional type of these two species. T. rotundifolia consumed relatively higher annual total amount of water per unit area at breast height than R. sinica. Moreover, water that was consumed during the growing season (from April to September) accounted for 90% and 66% of the annual total amount for T. rotundifolia and R. sinica, respectively. Sap flow densities of the two species were very significantly positively correlated with photosynthetically active radiation, water vapor pressure deficit, and temperature, while had very significant negative correlation with air relative humidity. Sap flow densities and daily water consumptions of two tree species were not only lower than the tree species distributed in the same climatic non-karst zone of the study area, but also lower than the main tree species in karst area nearby, and even lower than the typical species in dry area with extremely low precipitation. The above results suggested that water consumption of the two tree species were restricted by the specific water environment of rocky outcrop, and species of the same functional type exhibited different water use strategies.