为揭示北亚热带次生栎林树干液流特征, 运用Granier 热消散式探针法对栎树的树干液流进行了连续测定，同时同步测定样树周围环境因子如光合有效辐射、总辐射、空气温度、空气湿度、土壤湿度等。分析了树干液流与环境因子的相关关系。树干液流与光合有效辐射、总辐射、温度、水蒸气压亏缺在不同时间尺度上均具有显著相关关系；栓皮栎和麻栎树干液流有明显的日变化特征，基本上呈单峰型分布，树干液流速率最强一般出现在正午，最弱一般出现在早晨和凌晨；栓皮栎最大树干液流速率为0.034cm s-1比麻栎最大树干液流速率为0.032cm s-1大。栓皮栎平均液流速率为0.051cm s-1比麻栎平均液流速率为0.053cm s-1小。栓皮栎和麻栎树干液流速率对气温变化和土壤含水量比较敏感， 晴天树干液流速率明显大于阴天；阴雨天树干液流开始急剧下降时间比晴天早近4个小时。晴天栓皮栎平均液流速率为0.066cm s-1，麻栎平均液流速率为0.068cm s-1；阴天栓皮栎平均液流速率为0.008cm s-1，麻栎平均液流速率为0.012cm s-1。夏季的树干液流随天气的变化而变化，变化幅度也比较大；秋季树干液流速率显著减少。 夏季栓皮栎平均液流速率为3.625cm s-1，麻栎平均液流速率为3.917cm s-1；秋季栓皮栎平均液流速率为2.037cm s-1，麻栎平均液流速率为2.353cm s-1。
Sap flow characteristics of secondary oak forest in north subtropical zone
In order to reveal the characteristics of the sap flow in the subtropical secondary oak forest in North subtropics, the stem flow of the oak tree was continuously measured by Granier heat dissipation probe method. At the same time, the environmental factors such as photosynthetically active radiation, total radiation, Air temperature, air humidity, soil moisture, etc. The results showed that there were significant differences in the sap flow from the Quercus variabilis and Quercus acutissima, There was a significant diurnal variation of the effects of stem flow and photosynthetically active radiation, total radiation, temperature and water vapor pressure on different time scales. Quercus variabilis and Quercus acutissima had obvious diurnal variation characteristics, The strongest flow rate usually appears at noon, the weakest in the morning and early morning; the cypress oak and quercus acutissima sap flow rate is larger than that of quercus. Quercus variabilis and Quercus acutissima were the most sensitive to the temperature and water content. Rainy days of the trunk stream began to fall sharply earlier than the sunny day 3 hours. The summer sap flow goes up and down with the weather changes. Provincial decline is also relatively large. The flow rate of shrubs and oak trees decreased significantly in autumn. In the autumn, the change of the average flow rate of the internal flow of Quercus variabilis and Quercus acutissima was decreased.
In order to reveal the north subtropical secondary oak forest sap sap flow characteristics, using Granier thermal dissipation probe method to measure the oak flow continuously and simultaneous determining the environment factors surrounding the sample trees such as photosynthetically active radiation, total radiation, air temperature, air humidity, soil moisture etc. The relationship between sap flow and environmental factors was analyzed. The sap flow and photosynthetically active radiation, radiation, temperature, water vapor pressure deficit in different time scales were significantly correlated; Quercus variabilis and Quercus acutissima stem sap flow has obvious diurnal variation, basically a unimodal distribution, generally the strongest sap flow rate appear in the noon, the weakest in the the morning and the early morning; for 0.034cm S-1 than the maximum sap flow rate for q.acutissima 0.032cm S-1 variabilis maximum sap flow rate. The average flow rate of Quercus 0.051cm S-1 than the average flow rate of Quercus acutissima S-1 small 0.053cm. The rate of change of temperature and soil moisture sensitivity of Quercus variabilis and Quercus acutissima stem sap flow was significantly greater than the cloudy sunny sap flow rate; the rainy day sap flow plummeted nearly 4 hours earlier than sunny day. A sunny day the average flow rate of Quercus is 0.066cm s-1, the average flow rate of 0.068cm oak Quercus S-1; cloudy average liquid flow rate is 0.008cm s-1, and the average flow rate is 0.012cm s-1. The sap flow in summer varies with the weather. The sap flow rate decreases significantly in autumn. In summer the average flow rate of Quercus acutissima is 3.625cm s-1, average flow rate is 3.917cm S-1; the average flow rate of Quercus variabilis in autumn is 2.037cm s-1, the average flow rate is 2.353cm s-1.
Key words: northern subtropical；secondary oak forest；trunk flow；environmental factor
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