Chen Li-xin, Li Zhan-dong, Zhang Zhi-qiang, Zhang Wen-juan, Zhang Xiao-fang, Dong Ke-yu, Wang Guo-yu
Beijing Forestry University, China.
Ying Yong Sheng Tai Xue Bao. 2009 Dec;20(12):2861-70.
By using thermal dissipation probes (TDP), this paper monitored the sap flow of four tree species (Cedrus deodara, Zelkova schneideriana, Euonymus bungeanus, and Metasequoia glyptostroboides) at the Laodong Park in Dalian City from June to August 2008, and the soil moisture content and micrometeorological variables were mehsured simultaneously. Due to the absence of water-stress in the habitat, the sap flow of all sampled trees had no significant correlation with soil moisture content (R2 < 0.050, P > 0.211, n=1296). The correlation coefficient between solar radiation and sap flow reached 0.624-0.773 (P = 0.00, n=1296) despite the existing hysteresis. Solar radiation had major effect (R2 > 0.700, P < 0.05) during early morning (5:00-8:00) and late afternoon (18:00-20:00) when undergoing dramatic changes. As the main factor determining nighttime sap flow (R2 > 0.660, P < 0.05, n=1872), vapor pressure deficit (VPD) had a correlation coefficient as high as 0.650-0.823 (P = 0.00, n=1296) with the sap flow in whole-day scale. Meanwhile, the models constructed on the basis of VPD were able to explain 90% of daily sap flow change (P = 0.00). The correlation coefficient between sap flow and wind speed was relatively smaller than the previous two (R2 < 0.380, P = 0.00, n=1296), though showing significant correlation in affecting sap flow. Observations also detected the saturation phenomenon of sap flow to the environmental demands.
本文利用热扩散探针（TDP），于2008年6月至8月对大连市劳动公园内的四种树木（雪松、榉树、丝棉木和水杉）的液流进行了监测，并同步测定了土壤含水量和微气象变量。由于研究地点不存在水分胁迫，所有采样树木的液流与土壤含水量均无显著相关性（R2 < 0.050, P > 0.211, n = 1296）。尽管存在滞后现象，但太阳辐射与液流之间的相关系数仍达到0.624 - 0.773（P = 0.00, n = 1296）。在清晨（5:00 - 8:00）和傍晚（18:00 - 20:00）太阳辐射剧烈变化时，其对液流影响显著（R2 > 0.700, P < 0.05）。作为决定夜间液流的主要因素（R2 > 0.660, P < 0.05, n = 1872），水汽压差（VPD）与全天尺度的液流相关系数高达0.650 - 0.823（P = 0.00, n = 1296）。同时，基于VPD构建的模型能够解释90%的日液流变化（P = 0.00）。液流与风速之间的相关系数相对前两者较小（R2 < 0.380, P = 0.00, n = 1296），但在影响液流方面仍表现出显著相关性。观测还发现了液流对环境需求的饱和现象。
