毛乌素沙地旱柳和小叶杨树干液流密度及其与气象因子的关系

研究毛乌素沙地旱柳(Salix matsudana)和小叶杨(Populus simonii)树干液流密度的变化特征及其与气象因子的关系,是实现该地区水与生态和谐发展的基础。利用Granier热消散探针法测量了旱柳和小叶杨不同方向和不同深度的树干液流密度。监测结果表明:不同方位间的树干液流密度日变化特征相似并具有较强的相关性,但监测结果相差较大;不同深度的监测结果也具有类似的特征。如果忽略这种方位间和深度上的变化,整树耗水计算结果的误差最大可达104%。树干液流密度与气象因子的相关分析表明,旱柳和小叶杨的树干液流密度与大气辐射相关性最好,其次为气温。时滞分析表明,旱柳和小叶杨的树干液流密度与净辐射没有时滞,与水汽压亏缺间存在1 h的滞后。由此可见,以树干径流结果为基础在推算单株耗水量时,必须考虑方位及探头深度并合理校正。

Relationships between Sap Flow Densities in Tree Trunks of Salix matsudana and Populus simonii and Meteorological Factors in the Mu Us Sandland

In this study,the spatiotemporal variations of sap flow densities in tree trunks of Salix matsudana and Populus simonii and their relationships with meteorological factors in the Mu Us Sandland were explored so as to achieve a harmonic development of water and ecology.The Granier's thermal dissipation probe method was used to measure the azimuthal and radial sap flow densities in tree trunks of S.matsudana and P.simonii.The results indicated that the daily variation of sap flow densities in the tree trunks at different directions was similar with a good correlation,but the values were quite different.The measured results at different depths were alsor similar.If the variations of such directions and depths were ignored,the maximum error of the calculated whole-tree water consumption could be up to 104％.The correlation analysis between the sap flow density and the metrological factors revealed that the correlation of sap flow densities in tree trunks of S.matsudana and P.simonii with the net radiation was the best,and then with the air temperature.The analyzed results showed that there was no time lag between the sap flow density and the net radiation,but there was one-hour time lag between the sap flow density and vapor pressure deficit.Thus the direction and the depth of probe must be considered when estimating the plant water consumption based on the results of sap flow density.