钩梢强度对麻竹生物量分配和生理特性的影响

以不钩梢为对照,对笋期内麻竹进行轻度、中度、重度钩梢处理,研究各钩梢处理立竹构件生物量分配、当年生枝条和商品叶生长,以及净光合速率(P_n)、蒸腾速率(T_r)、水分利用效率(WUE)和叶片水势(LWP)等的变化,分析麻竹对营林措施中钩梢强度的适应机制和生存策略.结果表明: 与对照相比,钩梢处理对麻竹生物量及分配影响显著,3个处理麻竹立竹的叶/枝、叶/秆、枝/秆生物量比均显著高于对照.轻度钩梢和中度钩梢处理当年生枝条数量、基径、长度均显著大于对照,其中,中度钩梢处理当年生枝条基径、数量、长度和商品叶数量分别比对照增加43.0%、53.3%、29.8%和39.5%.各钩梢处理麻竹P_n、T_r、WUE、LWP在笋期内大小为出笋盛期>末期>初期;钩梢后麻竹的P_n、T_r和WUE显著提高,其中,各处理出笋盛期和末期的P_n大小为中度钩梢>轻度钩梢>重度钩梢>对照,且出笋盛期和末期的P_n分别是对照的1.4和1.3倍.各处理出笋初期、盛期和末期的T_r均为重度钩梢>中度钩梢>轻度钩梢>对照.中度钩梢处理对麻竹立竹的生物量分配、商品叶产量和生理特性均有明显优势,并能有效提高麻竹立竹的水分可获得性.

Effects of truncation intensity on the biomass allocation and physiological characteristics of Dendrocalamus latiflorus

The effects of three different truncation treatments, i.e., light, medium and heavy truncation treatments on biomass allocation, current-year twig indexes, and quantity of commodity lea-ves, net photosynthetic rate (P_n), transpiration rate (T_r), water use efficiency (WUE), and leaf water potential (LWP) values of Dendrocalamus latiflorus were studied, and the adaptation mechanisms and survival strategy of D. latiflorus under these silvicultural truncation treatments were discussed. Results showed that the biomass of D. latiflorus and its allocation rates were significantly affected by truncation treatments, compared with the untruncated control. Leaf to branch, leaf to stem, and branch to stem biomass ratios under all truncation treatments were significantly higher than under the untruncated control. The diameter, number, and length of current-year twigs, and the quantity of commodity leaves in light truncation and medium truncation treatments were markedly higher than in the control, and were increased by 43.0%, 53.3%, 29.8% and 39.5%, respectively, in medium truncation treatment compared with the control. After truncation treatments, the overall trend of the physiological characteristics of D. latiflorus, including P_n, T_r, WUE, LWP values, were displayed in the order of the peak stage > the telophase stage > the initial stage. The P_n, T_r and WUE values of D. latiflorus were significantly improved in the truncation treatments. The P_n va-lues were greatest in the medium truncation treatment followed by the light truncation treatment, heavy truncation treatment, and were the lowest in the control at the peak and telophase stages. At the peak and telophase stage the P_n values in the medium truncation treatment were 1.4 and 1.3 times as much as the control. The T_r values at the initial, peak and telophase stages were the greatest in the heavy truncation treatment, followed by the middle truncation treatment and the light truncation treatment, and were the lowest in the control. In this study, the medium truncation treatment showed a significant advantage in improving plant biomass allocation, quantity of commodity leaves, and other physiological indices, and could effectively improve the ability of moisture acquisition for D. latiflorus.