不同园林树种叶片N·P·K养分内吸收作用

目的]研究8种亚热带常见园林树种叶片N、P、K内吸收率及其季节变化.方法]分别采用扩散法、钼锑抗比色法和火焰光度计法对采集叶片N、P、K含量进行测定.结果]各树种成熟叶养分含量都高于新鲜凋落叶,且大部分呈显著性差异,N、P、K的内吸收率（平均值±标准差）分别为（9.11±3.89）％～ （68.42±2.44）％、（9.94±5.31）％～（60.54±13.74）％和（24.66±12.14）％ ～ （77.15±5.21）％.N和K的内吸收率有显著性差异（P＜0.05）,N和P以及P和K之间差异并不显著;N和P的内吸收率春季低于秋季,K的内吸收率春季高于秋季;常绿树种和落叶树种的养分内吸收率无显著差异;固氮树种（羊蹄甲和黄槐）与非固氮树种的N内吸收率也未出现显著差异.结论]植物叶片在凋落前发生内吸收作用是一种比较普遍的现象,季节变化只是影响植物叶片养分内吸收的主要因素之一,不同的生活型并没有显著影响植物的内吸收率,固氮作用对植物在N养分供给上作用并不明显.

Leaf Nutrient Resorption Research of N,P and K in Different Garden Trees

Objective] Leaf N,P and K nutrient resorption rates were investigated in spring and autumn for eight species of subtropical garden trees.Method] N,P and K contents were determined by diffusion method,colormetric method and flame photometer method,respectively.Result] The results showed that the contents of three nutrients in mature leaves were higher than those in fresh littered leaves for all species of trees among which the content differences between mature leaves and fresh littered leaves for the three nutrients were mostly significant,and the resorption rates（mean ± standard deviation） of N,P and K were （9.11 ± 3.89） ％-（68.42 ± 2.44） ％,（9.94 ± 5.31） ％-（60.54 ± 13.74） ％ and （24.66 ± 12.14） ％-（77.15 ± 5.21） ％,respectively; there were significant differences between N and K in term of resorption rates,while no significant differences existed between N and P or P and K; the resorption rates of N and P in spring were less than those in autumn,meanwhile the resorption rates of K in spring were higher than those in autumn ; there were no significant differences in the rcsorption rates for three nutrients between the evergreen and the deciduous trees and there were also no significant differences in N resorption rate between nitrogen-fixing tree species（Cassia surattemis and Bauhinia blakeana） and non-nitrogen-fixing species.Conclusion] Leaf nutrient resorption before leaf falling for garden trees is a relatively common phenomenon,and that seasonal variation is one of the main factors influencing the plant leaf nutrient resorption.Different life forms have no significant effect on plant nutrient resorption rates,the role of nitrogen is not obvious in nitrogen nutrient supply for nitrogen-fixing tree species.