鄂东南低山丘陵区枫香种群的天然更新方式与特征

鄂东南低山丘陵区是一个生态脆弱区, 枫香(Liquidamb ar formasana)林是该地区的重要森林植被类型, 对于维持该地区的生态安全和经济发展具有重要意义。为了探明枫香实生和萌芽更新对枫香种群维持的作用, 采用样方法研究了该地区枫香林和马尾松(Pinus massoniana)-枫香混交林枫香种群的天然更新方式, 并采用不同年代伐桩构建的时间序列研究了枫香伐桩的萌芽更新规律。结果表明: (1) 该地区的枫香种群由实生和萌芽更新植株组成, 但二者的比例在马尾松-枫香混交林和枫香林间存在明显差异; (2) 萌芽更新可以划分为幼苗萌芽和伐桩萌芽更新2类, 其中幼苗萌芽更新是对自然环境的适应, 伐桩萌芽更新是对人类砍伐的适应; (3) 枫香伐桩萌芽更新存在明显的自疏现象, 并最终形成1-2杆的萌代主; 与实生幼苗相比,伐桩萌条具有生长迅速的特点。上述结果表明, 枫香的实生和萌芽更新共同维持了该地区枫香种群的稳定。

Natural Regeneration of Chinese Sweet gum (Liquidambar formasana) Population in Southeast Hilly Region of Hubei Province

Chinese sweet gum (Liquidambar formasana) is a subdominant tree in the forest of a southeast hilly region in Hubei province. A stable sweet gum population is considered as a key component to the regional environment; thus, a clear understanding of its natural regeneration is important to vegetation management and regional economy. To study the role of sweet gum natural regeneration, we surveyed the Chinese sweet gum forest and the pine (Pinus massoniana)-Chinese sweet gum mixed fores t in a southeast hilly region in Hubei province; to explore the growth and dynamics of sprouting, we surveyed sprouts of sweet gum stumps that were logged 1 year, 7 and 30 years ago. The results indicated that individuals developed from seeds, and stump-sprouts coexisted in sweet gum populations, but the ratio of seedlings to sprouts differed between the two forest types. All sprouts could be classified into two groups: one was from the base of seedlings, which could be a response to natural selection, and the other was from stumps left by cutting, which was a response to disafforestation. Self-thinning played an important role during seedling survival: one or two sprout(s) could survive and eventually reach the canopy. In general, sprouts possessed a greater height growth rate than did seedlings. In conclusion, the coexistence of seedling regeneration and sprout regeneration maintained the population size of Chinese sweet gum in the southeast hilly region in Hubei province.