核桃树干液流特征及其与气象因子的关系

Study on Sap Flow of Juglans regia L.and Its Response to Meteorological Factors

运用热扩散式探针和自动气象站,对核桃树干液流密度及气象因子进行同步测定,研究不同树龄核桃树干液流密度特征以及与气象因子的关系。结果表明:核桃树干液流日变化呈单峰型,但不同树龄核桃树干液流启动、达到峰值以及夜间液流均存在差异。不同树龄核桃树干液流密度存在显著差异,中龄和老龄核桃树干平均液流密度分别为0.2042,0.5236mL/(cm2.min);最大液流密度分别为0.4909,1.5243mL/(cm2.min)。多元线性回归分析结果表明,核桃树干液流密度与水汽压饱和差、辐射之间呈显著正相关,与相对湿度呈显著负相关,气象因子对核桃树干液流存在显著影响。

Water is one of the main factors affecting plant growth in arid and semiarid areas.The 99.8% of water absorbed by roots contributes to transpiration.It is very important to analyze water use of plants in arid and semiarid areas,which constitues the theoretical basis for calculating water use of plants and for supplying the reasonable advice of planting mode.Water consumed by transpiration could be calculated by measuring the sap flow of trees.The means of thermal diffusion probe is one of the most accurate methods used to measure the sap flow of trees.Juglans regia L.trees are widely planted in arid area of south Xinjiang,and they adapt to the severe sandy conditions well.However,the understanding on the pattern of stem sap is poor.In this study,the diurnal variation of sap flow of Juglans regia L.was continuously measured every 30 minutes by means of thermal diffusion probe method.In the meantime,some meteorological factors,including solar radiation,air temperature,relative air humidity,precipitation and wind speed,were synchronously observed with measuring the sap flow fluctuation at a nearby automatic weather station.The correlations between meteorological factors and the sap flow density were analyzed with SPSS13.0.The result shows that the curve of diurnal change of sap flow density of Juglans regia L.was unimodal.There was no obvious difference of start time of the sap flow between different-aged trees.The maximum density of sap flow occurred during 12：00-14：30 for the mid-aged trees and during 10：30-16：00 for the old trees.The average period of sap flow peak of the mid-aged trees was 6.9 hours longer than that of old trees.There was a significant difference of sap flow density between the different-aged trees.The sap flow densities of the mid-age and old Juglans regia L.trees were 0.204 2 and 0.523 6 mL/（cm2·min） in average and 0.490 9 and 1.524 3 mL/（cm2·min） in maximum,respectively.The multi-linear regression analysis reveals that there is a significant positive correlation between the sap flow density of Juglans regia L.and the saturation deficit and radiation,but a significant negative correlation between the sap flow density and relative air humidity,which indicates that the meteorological factors play an important role in affecting sap flow density of Juglans regia L.