不同年龄阶段胡桃楸天然更新幼树的光合生理特性

Photosynthetic Physiological Characteristics of Naturally Regenerated Juglans mandshurica Saplings at Different Ages

探究不同树龄胡桃楸(Juglans mandshurica)幼树适宜的光环境条件,为制定林下胡桃楸幼树的人工抚育措施提供理论依据。以哈尔滨市方正县转山实验林场的树龄为1~3 a(Ⅰ年龄阶段)、4~6 a(Ⅱ年龄阶段)和7~9 a(Ⅲ年龄阶段)的胡桃楸天然更新幼树为研究对象,测定其在不同光环境(林缘、林隙和林下)的生长形态和光合指标。结果表明,随着光照强度的减弱,各年龄阶段的幼树生物量、苗高和地径降低,比叶面积增大;叶片叶绿素a/b值、光补偿点(Light Compensation Point,LCP)、最大净光合速率(maximum net photosynthetic rate,P_(max))、暗呼吸速率(Dark respiration rate,R_(d))下降,叶绿素含量升高。在林下和林隙中,Ⅱ年龄阶段的幼树叶片最大净光合速率和叶绿素含量最高,叶片光补偿点、暗呼吸速率和叶绿素a/b最低;在林缘,随着树木年龄的增长叶片最大净光合速率和光补偿点逐渐增大。综上所述,林缘更适宜幼树的生长。此外,对4~6 a的胡桃楸幼树进行抚育时,可适当降低抚育强度;而对1~3 a和7~9 a的胡桃楸幼树进行人工抚育时,要加强抚育力度,及时对上层林木透光。

This study was aimed to investigate the appropriate light conditions for Juglans mandshurica saplings of different ages,and provide a theoretical basis for the development of artificial tending measures for J.mandshurica saplings in the understory.In this study,natural regeneration of J.mandshurica saplings aged 1-3 a(age stageⅠ),4-6 a(age stageⅡ)and 7-9 a(age stageⅢ)in the experimental forestry farm of Zhuan Shan,Fangzheng County,Harbin City were used as experimental subjects,determining their growth patterns and photosynthetic indicators in different light environments(forest edge,forest gap and understory).The results showed that:as light intensity diminished,the biomass,saplings height and ground diameter decreased,and the specific leaf area increased;chlorophyll a/b,light compensation point(LCP),the highest maximum net photosynthetic rate(P_(max))and dark respiration rate(R_(d))decreased,chlorophyll content increased in saplings of all ages.In the understory and the forest gap,saplings of ageⅡhad the highest maximum net photosynthetic rate and chlorophyll content and the lowest values of light compensation point,dark respiration rate and chlorophyll a/b;the highest maximum net photosynthetic rate and light compensation point of saplings increases as saplings age in the forest edge.In summary,the forest edge is more suitable for the growth of saplings.In addition,when artificially tending J.mandshurica saplings between 4 and 6 years old,tending intensity can be reduced appropriately.In contrast,when artificially tending J.mandshurica saplings of 1-3 and 7-9 years old,and light transmittance of the upper forest layer should be strengthened timely.