西双版纳楝径向生长和木质部发生季节动态及其对环境因子的响应

Seasonal radial growth and xylogenesis of Melia azedarach and its response to environmental factors in Xishuangbanna,Southwest China

热带森林在全球碳循环过程中起着重要的作用,研究热带树木的生长动态及其对环境因子的响应,有助于预测全球变化下热带森林固碳能力的变化。目前对热带树木径向生长以及木质部发生季节动态的研究相对较少。利用微树芯和生长环法对西双版纳热带植物园内的落叶树种楝(Melia azedarach)2021年的年内径向生长和木质部发生季节动态进行监测,结合环境因子的监测,分析了楝的径向生长过程的驱动因子。结果表明:2021年楝的扩大细胞在3月1日(年积日(DOY):60.2±1.6)开始出现,细胞壁加厚在12月11日(DOY:345.4±3.1)结束,年生长量为7.76 mm,最大生长速率为0.039 mm/d。生长环监测显示,楝在3月18日(DOY:76.6±8.6)左右开始生长,10月13日(DOY:286.4±6.8)生长结束,年径向生长量为(6.25±2.35)mm,最大生长速率为(0.056±0.02)mm/d。楝的径向生长速率与降水(r=0.77,P<0.001)、平均温度(r=0.61,P<0.05)和最低温度(r=0.67,P<0.001)均呈显著正相关,与风速(r=-0.45,P<0.05)呈显著的负相关。本研究有助于认识热带树木的径向生长季节动态以及热带树木生长-气候关系。

The tropical forests play an important role in global carbon cycling,so the investigation of the growth dynamics of tropical trees and their relationships with climate factors are important for predicting the impact of climate change on the carbon fixation capacity of tropical forests.There is still limited knowledge for the seasonal radial growth dynamics and xylogenesis of tropical tree species.In this study,we used microcoring and band dendrometer to monitor the seasonal radial growth variations and xylogenesis of a tropical deciduous tree species Melia azedarach in Xishuangbanna Tropical Botanical Garden during 2021.Combined with the monitoring of environmental factors,the relationships between radial growth rate of M.azedarach and environmental factors were also analyzed.The results showed that the enlarged cells of M.azedarach in 2021 began to appear on March 1(Day of year(DOY):60.2±1.6),and cell wall thickening of M.azedarach ended on December 11(DOY:345.4±3.1),the annual xylem growth of M.azedarach was 7.76 mm,and the maximum growth rate was 0.039 mm/d.The results of band dendrometer showed that growth of M.azedarach started on March 18(DOY:76.6±8.6),and ended on October 13(DOY:286.4±6.8),and the annual radial growth was(6.25±2.35)mm.The maximum growth rate was(0.056±0.02)mm/d.The radial growth of Melia azedarach was positively correlated with precipitation(r=0.77,P<0.001),mean temperature(r=0.61,P<0.05)and the minimum temperature(r=0.67,P<0.001),and negatively correlated with wind speed(r=-0.45,P<0.05).The study will be helpful to understand the seasonal growth pattern and growth-climate relationships for tropical tree species.