不同径级的西伯利亚红松树干液流及蒸腾耗水特征的差异

基于热扩散技术,采用TDP法连续监测了新疆喀纳斯国家自然保护区内不同径级西伯利亚红松的树干液流,分析其在生长季内(6~9月)的液流变化及蒸腾耗水特性,为阐明喀纳斯保护区优势树种水分循环机理,以及理解区域尺度上森林生态系统水分循环及其过程应对未来气候变化的响应机制提供依据。结果显示:(1)不同径级西伯利亚红松在晴、阴、雨3种天气条件下的树干液流日动态变化均呈昼高夜低的多峰型曲线,但变化频率和变化幅度差异明显,日最大液流值的排序为晴天阴天雨天。(2)树干液流的发生较光合有效辐射的变化存在明显的滞后效应,不同径级西伯利亚红松的最大液流峰值滞后时间在30~207min。(3)西伯利亚红松的月平均树干液流的大小顺序为7月8月9月6月,且相同径级树干阳生面的液流速率均大于阴生面。(4)西伯利亚红松全株的蒸腾耗水量为7月份的最大,其值占整个生长季的61.8%;且大径级阳生面的蒸腾耗水总量(6 716.79g)和阴生面蒸腾耗水总量(4 649.08g)分别是相应小径级阳生面和阴生面的2.00和2.45倍。(5)气温、空气相对湿度和光合有效辐射是影响西伯利亚树干液流的主要因素,同时0~5cm和20~30cm土壤温度对其影响也较大。研究表明,西伯利亚红松在生长过程中,大径级树干的液流和蒸腾耗水量大于小径级,主要发生部位为树干的阳生面,且在7月份的变化最明显。

Sap Flow and Transpiring Water-consumption of Pinus sibirica in Differernt Diameter Classes

In order to know the different capacity of water cycle in the forest ecosystem,we monitored the trunk sap flow in different diameter at breast height (DBH) of Pinus sibirica which in sunny side and shady side using TDP (thermal dissipation method) constantly in the Kanas National Nature Reserve,northwest of Xinjiang.The aims were to explain the relationship between water cycle of tree and environment,and provide basis on forest ecosystem water cycle responding to the climate change in the regional scale.The results showed that:(1)the diurnal variation of sap flow in sunny day,rainy day,and cloudy day were all multi-peak type.There were significant changes on frequency and range among these three weather conditions.The sequence of daily maximum sap flow value was sunny day>cloudy day>rainy day.(2)There was the hysteresis effect between sap flow and photosynthetically active radiation,hysteresis time of the maximum sap flow was about 30-207 min,respectively.(3)From June to September,the sap flow of P.sibirica in the sunny side were greater than those in the shady side,and the sequence of monthly mean sap flow was July>August>September>June.(4)The maximum transpiring water-consumption of P.sibirica was in July,and the value of it was 61.8% of the total value of whole growing season.Total transpiring water-consumption of P.sibirica with big diameter was 6 716.79 g in sunny side,while 4 649.08 g in the shady side.It was the 2.00 times and 2.45 times small diameter of P.sibirica,respectively.(5)Air temperature,air relative humidity,and photosynthetically active radiation were significant factors that affected the sap flow.Otherwise,the soil temperature in the layer of 0-5 cm and 20-30 cm were highly impacted on the sap flow too.This research showed that both sap flow and transpiring water-consumption of P.sibirica with big diameter were higher than that of P.sibirica with small diameter in the process of growth;these changes mainly happened in the sunny side of the trunk,especially in July.