马占相思林冠层气孔导度对环境驱动因子的响应

利用Granier热消散探针在2003年10月测定了广东鹤山丘陵地马占相思林14株样树的树干液流,同时监测林冠上方的光合有效辐射、空气湿度和气温,结合树木的形态和林分的结构特征,计算马占相思的整树蒸腾(E)、林分总蒸腾(E_t)以及冠层平均气孔导度(g_c),分析树形特征与整树水分利用的关系、冠层气孔导度对光合有效辐射(PAR)和空气水汽压亏缺(D)的响应.结果表明,整树蒸腾与胸径(P＜0.0001)、边材面积(P＜0.0001)和冠幅(P=0.0007)以自然对数的形式、与树高(P=0.014)以幂函数的形式呈现显著正相关.冠层气孔导度最大值(g_cmax)随D的上升呈对数函数下降(P＜0.0001),对光合有效辐射的响应则呈双曲线函数增加(P＜0.0001).液流测定系统能提供连续和准确的整树和林分蒸腾速率值,经严格数学推导公式计算,最终可求出冠层气孔导度,是研究森林水分利用与环境因子相互关系的有效方法.

Responses of canopy stomatal conductance of Acacia mangium forest to environmental driving factors

Employing Granier's probes,this paper measured the sap flow of 14 sample trees in an Acacia mangium forest on the Heshan hilly lands of Guangdong Province,and recorded the photosynthetic active radiation(PAR),air relative humidity(RH),and air temperature(T) above the forest canopy.The whole-tree transpiration(E),stand transpiration(E_t),and mean canopy stomatal conductance(g_c) were calculated,and the relationships between tree morphological characters and whole-tree water use as well as the responses of g_c to PAR and vapor pressure deficit(D) were analyzed.The results showed that the whole-tree transpiration had logarithmical positive correlations with tree diameter at breast height(DBH)(P<0.0001),sapwood area (P<0.0001) and canopy size(P=0.0007),and an exponential positive correlation with tree height(P=0.014).The maximum g_c(g_(c max)) changed with PAR hyperbolically(P<0.0001),and with D logarithmically(P<0.0001).The sap flow measurement system used in this study was reliable and accurate in estimating the transpiration of whole-tree and stand and the canopy stomatal conductance,being an effective tool in studying the relationships between forest water use and environmental factors.