应用热扩散式探针法对南方红壤丘陵区湿地松人工林耗水量的研究

运用Granier热扩散式探针法对湿地松(Pinus elliottii)树干液流密度进行长期连续测定,并对其周围多个气象要素和土壤要素进行同步测定。湿地松生长旺季不同月份晴天液流密度日变化规律基本一致,但液流启动、到达峰值的时间以及开始升高、开始下降的时间间隔存在差异。样木解析结果表明,处于低龄期的湿地松,整个木质部都可看作边材,边材面积和胸径可用二次函数很好地拟合。方差分析结果表明:不同胸径湿地松树干液流密度不存在显著性差异,与胸径无紧密关系。回归分析结果表明:湿地松日累计液流量与边材面积呈显著的线性相关关系,相关关系的判定系数达0.99。另外,单位边材面积日累计液流量与入选各气象因素的相关性显著,相关程度大小顺序为光合有效辐射>冠层相对湿度>冠层温度。结合边材面积-胸径回归方程和样木胸径调查资料,分别采用2种方法推算整个标准地的耗水量。经比较,2种方法所得结果差别不大,各自适用于一定的范围。

A study on water consumption of Pinus elliottii plantations in red earth hilly area in southern China by TDP

Whole-tree sap flow density(SFD) in Pinus elliottii plantaions was measured on 6 trees continuously using Granier's thermal dissipation probe method.Several environmental factors including meteorological variables and soil variables were also measured simultaneously.Diurnal changes of sap flow in sunny days in different months during rapid growth season were basically similar.For P.elliottii in early growth stage,a significant correlation between sapwood area(SWA) and diameter at breast height(DBH) was found and well fitted by a quadratic model.Variance analysis results showed that no significant difference existed among trees with different DBH.And there was no correlation between SFD and DBH.A significant linear correlation was found between daily cumulative sap flow and SWA with r2 value reaching 0.99.There were also remarkable correlation between daily cumulative sap flow and three factors including canopy temperature(CT),canopy relative humidity(CRH) and photo-synthetically active radiation(PAR).The sequence of correlated degrees was as follows: CRH>PAR>CT.Combined with SWA-DBH regression equation and DBH inventories of sample plots,two methods were utilized to extrapolate water use of whole-tree to the standard stand.The two methods produced similar results and each was applicable in a certain range.