对天目山不同海拔(1 067、698 和419 m)样点柳杉(Cryptomeria fortunei Hooibrenk ex Otto et Dietr.)不同冠层(分别离地面高1. 3、4 和8 m)的叶水势日变化特征进行了研究,并对柳杉叶水势与空气温度、空气相对湿度及光合有效辐射(PAR)的相关性进行了分析。结果表明:不同海拔样点柳杉不同冠层叶水势日变化曲线均呈典型的“V”型,但谷值及其出现的时间有差异;随树冠高度增加叶水势日均值均逐渐降低;不同海拔柳杉同一冠层叶水势日均值有明显差异,其中,海拔419 m 处柳杉叶水势日均值为-1. 11 ~ -1. 22 MPa,海拔698 和1 067 m 处柳杉叶水势日均值为-0. 78 ~ -0. 98 MPa,差异极显著(P<0. 01)。相关性分析结果表明:柳杉叶水势与空气相对湿度均呈显著正相关(P<0. 05)、与空气温度和光合有效辐射均呈负相关。逐步回归分析结果表明:在海拔419 m 处影响柳杉叶水势日变化的主导因子是空气温度,而在海拔1 067 和698 m 处影响柳杉叶水势日变化的主导因子是空气相对湿度。研究结果显示:随海拔升高柳杉叶水势增大且导致叶水势变化的主导因子也有所改变。

Diurnal change characteristics of leaf water potential in different crown layers (height off the ground of 1. 3, 4 and 8 m, respectively) of Cryptomeria fortunei Hooibrenk ex Otto et Dietr. at sampling plots with altitudes 1 067, 698 and 419 m in Tianmu Mountain were researched, and also, correlation of leaf water potential with air temperature, air relative humidity and photosynthetically active radiation (PAR) was analyzed. Results show that diurnal change curve of leaf water potential in different crown layers of C. fortunei at sampling plots with different altitudes all are typical “V”type, but there are certain differences in valley value and its appearance time. Daily average value of leaf water potential gradually reduces with increasing of crown height, with obvious difference in same crown layer at sampling plots with different altitudes. In which, daily average value of leaf water potential at altitude 419 m is from -1. 11 MPa to -1. 22 MPa and that at altitude 698 and 1 067 m is from -0. 78 MPa to -0. 98 MPa, respectively, with extremely significant difference (P<0. 01). Correlation analysis result shows that leaf water potential possesses a significantly positive correlation (P<0. 05) with air relative humidity and a negative correlation with air temperature and PAR. Result of stepwise regression analysis shows that the dominant factor influencing on diurnal change of leaf water potential at sampling plot with altitude 419 m is air temperature, however, that is air relative humidity at other two sampling plots with altitude 698 and 1 067 m. It is suggested that with elevating of altitude, leaf water potential increases and the dominant factor of leading to change of leaf water potential of C. fortunei also is various.