木荷树干夜间水分补充的季节动态及其与树形特征和叶片生物量的关系

利用热消散探针(TDP)法对位于中国科学院华南植物园的木荷(Schima superba)人工纯林的15株样树进行了树干液流监测, 并结合光合有效辐射(PAR)和土壤含水量的测定, 探讨了不同季节的夜间水分补充量与树形特征和叶片生物量的关系。结果表明: 1)夜间液流活动时间与PAR同步, 但其结束时间不受PAR影响; 春、夏季夜间液流明显比秋冬季活跃。2)春、夏、秋季的夜间水分补充量与样树的胸径、冠幅、边材面积、叶片生物量呈极显著线性关系, 与树高仅在春季呈显著线性关系。3)春、夏季的夜间水分补充量主要受样树冠幅影响, 成正相关; 秋季主要受胸径影响, 成正相关; 冬季仅受树高影响。该试验说明木荷夜间水分补充与树形特征、叶片生物量关系密切, 但起主要作用的树形特征和具体关系具有季节差别。

Seasonal dynamics of night-time stem water recharge of Schima superba and its relation to tree architecture and leaf biomass

Aims Our objectives are to study the effects of tree architecture and leaf biomass of Schima superba on seasonal variations of nocturnal stem water recharge and to elucidate the compensation mechanism for hydraulic limitation and response to the hydraulic limitation hypothesis proposed by Roan and Yoder.
Methods Night-time sap flow of 15 trees in a S. superba plantation was measured with Granier-type sensors installed in the sapwood at a height of 1.3 m for calculating night-time stem water recharge. Single and multiple linear regressions were performed in data analysis.
Important findings The ending time of nocturnal sap flow was not followed by photosynthetically active radiation (PAR) but was the active time, which was unrelated to diameter at breast height (DBH). Night-time stem water recharge (W) was strongly linearly related with DBH, canopy size, sapwood area and leaf biomass (r = 0.596 to 0.895), except in winter. The linear relationship between W and tree height was found only in spring. W was positively affected by canopy in spring and summer, but by DBH in autumn and by tree height in winter. The results show that tree architecture and leaf biomass had significant effects on W and the degree changed with seasons.