杉木不同形态特征对水力结构的影响

Effects of different morphological characteristics on hydraulic architecture of Chinese fir

水力结构是植物长期进化过程中所形成的不同形态结构和水分运输策略。以我国南方重要的商品林树种杉木为研究对象,开展不同分枝级、冠层高度及分枝方向的水力结构特征研究。结果表明:杉木水力结构参数变化具有明显的等级效应,导水率和比导率表现为主茎>1级侧枝>2级侧枝,叶比导率和胡伯尔值表现为1级侧枝>2级侧枝。不同分枝级的水力结构参数受冠层高度的影响明显,主茎的导水率和比导率随冠层高度增加而显著下降,主茎的胡伯尔值则随冠层高度增加而显著升高,1、2级侧枝的导水率和比导率表现为中部冠层最高,1级侧枝的叶比导率随冠层高度的增加而显著下降,2级侧枝的叶比导率表现为中部冠层最高。在不同分枝方向中,1、2级侧枝的导水率、比导率和叶比导率总体表现为南向、西向高于北向和东向。相关分析表明,不同分枝级的导水率与总直径、边材横截面积、叶干重呈极显著正相关(P<0.01),主茎的比导率与上述指标显著正相关(P<0.05),1、2级侧枝的比导率与上述指标呈负相关关系。可见,杉木高级别的枝条直径越小、水分输导能力越差,这种水力等级效应有利于杉木在遭受干旱胁迫时牺牲劣势枝条而优先保障优势枝条的水分供给,是杉木长期进化过程中适应干旱逆境的重要生存策略。

Hydraulic architecture refers to the different morphological structures and water transport strategies acquired during the long-term evolution of plants. In this study, Chinese fir, an important commercial forest species in southern China, was examined, and hydraulic architecture characteristics with respect to ramification rate, canopy height, and ramification direction were studied. The results showed that changes in hydraulic architecture parameters of Chinese fir had pronounced rank effects;the hydraulic conductivity and leaf-specific conductivity were in the following order: main stem>primary lateral branches>secondary lateral branches;leaf-specific conductivity and Huber values were higher in primary than in secondary lateral branches.Hydraulic architecture parameters at different ramification rates were significantly affected by canopy height. Hydraulic conductivity and specific conductivity of the main stem decreased significantly with increasing canopy height, and the Huber value of the main stem increased significantly with increasing canopy height. Hydraulic conductivity and specific conductivity of primary and secondary lateral branches were the highest in the middle canopy, leaf-specific conductivity of the primary lateral branches decreased significantly with increasing canopy height, and leaf-specific conductivity of secondary lateral branches was the highest in the middle canopy. With regard to different ramification directions, hydraulic conductivity, specific conductivity, and leaf-specific conductivity of primary and secondary lateral branches were generally higher in the south and west directions than in the north and east directions. Correlation analyses showed that hydraulic conductivity at different ramification rates was significantly positively(P<0.01) correlated with the total diameter, sapwood cross-sectional area, and leaf dry weight;specific conductivity of the main stem was significantly positively(P<0.05) correlated with these factors, whereas the specific conductivity of primary and secondary lateral branches produced a negative correlation with them. Thus, the smaller the diameter of high-level branches of Chinese fir, the lower is the water transport ability. This hydraulic grade effect is beneficial to sacrificing inferior branches in order to maintain the water supply of superior branches when Chinese fir experience drought stress, which is an important adaption to drought acquired during long-term evolution. This study is of great significance for the breeding of drought-tolerant Chinese fir and sustainable plantation management.