不同群落冠层环境下紫耳箭竹笋期生长发育研究

对金佛山国家级自然保护区内3个不同类型群落(落叶阔叶林、常绿落叶阔叶混交林、常绿阔叶林)下紫耳箭竹(Fargesia decurvata J. L. Lu)幼笋的生长发育进行研究。结果显示:(1)落叶阔叶林和常绿落叶阔叶混交林下的紫耳箭竹出笋期早而长,历时110 d,出笋量大,出笋率高;常绿阔叶林下的出笋期晚而短,历时88 d,出笋量少,出笋率低;常绿落叶阔叶混交林中出笋量最大。(2)出笋期分为3个阶段:初期、盛期和末期,各群落中的紫耳箭竹进入每个时期的时间有所差异,常绿落叶阔叶混交林中最早进入出笋盛期,落叶阔叶林次之,常绿阔叶林最迟。出笋盛期也是退笋的高峰期,退笋率的大小为:常绿落叶阔叶混交林落叶阔叶林常绿阔叶林。(3)同一群落冠层环境下,紫耳箭竹不同时期出土的幼笋地径无显著差异。在落叶阔叶林和常绿落叶阔叶混交林林冠环境中,各时期出土的幼笋地径间无显著差异,但均显著大于常绿阔叶林(P 0.05)。(4)紫耳箭竹幼笋出土后80 d左右完成高生长过程,且符合Logistic方程,呈"慢-快-慢"的生长趋势。高生长速率为:常绿落叶阔叶混交林落叶阔叶林常绿阔叶林,且差异显著(P 0.05)。(5)紫耳箭竹的克隆繁殖与分株密度间有密切关系。随着分株密度的增加,出笋数量增加,成竹数量降低。本研究表明不同群落冠层环境下紫耳箭竹生长发育存在显著差异,在常绿落叶阔叶混交林中发育最好,常绿阔叶林中发育最差,种群密度对竹类的更新发展起重要调节作用。

Study on shooting rhythm of Fargesia decurvata under different canopy conditions

We studied the shooting rhythm of Fargesia decurvata J. L. Lu under three different forest canopies (i.e., deciduous broad-leaved forest, evergreen-deciduous broad-leaved mixed forest, and evergreen broad-leaved forest) in Jinfo Mountain National Nature Reserve. Results showed that (1) the deciduous broad-leaved forest and evergreen-deciduous broad-leaved mixed forest exhibited an early shooting time, long shooting period (~110 days), high shooting number, and high shooting rate. In contrast, the evergreen broad-leaved forest exhibited a late shooting time, short shooting period (~88 days), low shooting number, and low shooting rate. The highest shooting number was observed in the evergreen-deciduous broad-leaved mixed forest. (2) The F. decurvata shooting period could be divided into three stages (i.e., early, peak, and late) and differed for each forest type. In evergreen-deciduous broad-leaved mixed forest, F. decurvata entered the peak stage earliest, followed by the deciduous broad-leaved forest and evergreen broad-leaved forest. The peak stage of bamboo shooting was also the peak period of shoot degradation. The rate of shoot degradation was highest in the evergreen-deciduous broad-leaved mixed forest, followed by the deciduous broad-leaved forest and evergreen broad-leaved forest. (3) In the same canopy environment, there were no significant differences in the basal diameter of bamboo shoots during the different periods. The basal diameters of the bamboo shoots in the deciduous broad-leaved forest and evergreen-deciduous broad-leaved mixed forest showed no significant differences in the shooting period but were significantly larger than that in the evergreen broad-leaved forest (P < 0.05). (4) The height growth process for bamboo shoots was completed after ~80 days and followed a logistic curve with a "slow-fast-slow" growth trend. Furthermore, the height growth rate of the bamboo shoots exhibited significant differences under the different canopy conditions and followed the pattern of evergreen-deciduous broad-leaved mixed forest > deciduous broad-leaved forest > evergreen broad-leaved forest. (5) Clonal propagation and bamboo density were closely correlated. With the increase in bamboo density in the forest canopy, the shooting number increased, and the rate of mature bamboo shoots decreased. Thus, this study suggests that F. decurvata development was best in the evergreen-deciduous broad-leaved mixed forest and worst in the evergreen broad-leaved forest. In addition, population density played an important role in regulating bamboo regeneration and development.