天目山柳杉古树的树干液流速率时空变化

应用热扩散式边材液流计，研究了天目山柳杉Cryptomeria fortunei树干液流速率时空变化、蒸腾耗水量及其与环境因子的关系，揭示了柳杉水分生理的内在机制。结果表明：柳杉树干液流速率的日变化呈单峰曲线．春季于6：20左右启动，12：30左右达到峰值，18：50左右开始迅速下降。夏季于7：00左右启动，13：20左右达到峰值．19：40左右开始迅速下降。春季液流启动比夏季早，达到高峰和迅速下降时间均比夏季提前。春季液流峰值、日均液流速率和液流量均显著大于夏季，且胸径越大的柳杉液流速率越大：在柳杉不同方位上．春季柳杉南向液流速率最大，为平均值的187．3％，西向最小仅为平均值的15．4％。夏季东向液流速率最大，为平均值的226．2％．北向最小为平均值的33．1％。同一季节不同测点的液流速率目变化有明显差异．但具有较好的一致性．不同季节液流变化节律表现不同；在柳杉垂直高度上，柳杉春季日均液流速率大小排序为中位（61．71g．min-1）〉上位（48．36g．min-1）〉下位（35．10g·min-1），夏季则为上位（20．65g·min-1）〉下位（14．81g·min-1）〉中位（10．43g·min-1），不同高度的树干液流速率差异明显，且上位液流的波动节律明显早于中位和下位．上位液流峰值出现的时间比下位要早。图5表3参30

Temporal and spatial changes for sap flow velocity of Cryptomeria fortunei stems in National Nature Reserve of Mount Tianmu

To protect the Cryptomeriafortunei plant community in National Nature Reserve of Mount Tianmu, the temporal and spatial changes of stem sap flow velocity and transpiration as well as their relationship to meteorological factors were studied using a thermal dissipation probe （TDP）. Also, internal mechanisms of water physiology were explained. Results showed that the diurnal change of sap flow velocity was a single peak curve. In spring, sap flow started at 06：20, peaked at 12：30, and fell quickly at 18：50. However in summer, it started at 07：00, peaked at 13：20, and fell quickly at 19：40. The peak value, average daily velocity, and sap flow flux in spring were larger than in summer with a larger diameter stem having a greater sap flow velocity. For stem orientation, compared with the average sap flow, in spring flow velocity in the southern section was largest （187.3%） and in the western part lowest （15.4%）; however, in summer sap flow velocity in the east was largest （226.2%） and lowest in the north （33.1%）. Sap flow for vertical height of the stem by season, showed that in spring the order of average daily sap flow velocity for the middle （61.7l g·rain-1） 〉 the top （48.36 g·min-1） 〉 the bottom （35.10 g·min-1）, but in summer revealed the top （20.65 g·min-1） 〉 the bottom （14.81 g·min-1） 〉 the middle （10.43 g·min-1）. Ch, 5 fig. 3 tab. 30 ref.]