[Environmental responses of four urban tree species transpiration in northern China].
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.
Chen
Li-xin
LX
Beijing Forestry University, China. myclover17@yahoo.cn
Li
Zhan-dong
ZD
Zhang
Zhi-qiang
ZQ
Zhang
Wen-juan
WJ
Zhang
Xiao-fang
XF
Dong
Ke-yu
KY
Wang
Guo-yu
GY
D028203:Cedrus / Q000254:growth & development / Q000378:metabolism; D002681:China; D002947:Cities; D029779:Cupressaceae / Q000254:growth & development / Q000378:metabolism; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods*; D029756:Euonymus / Q000254:growth & development / Q000378:metabolism; D018526:Plant Transpiration; D014197:Trees / Q000254:growth & development / Q000378:metabolism*; D034401:Ulmaceae / Q000254:growth & development / Q000378:metabolism