米心水青冈种群萌条更新与高度生长

萌条是许多木本植物更新的重要方式,尤其是在干扰生境中.有种观点认为萌条需要消耗大量资源,导致其他方面投入减少,据此提出萌条数-高度的权衡假说.对该假说的检验多比较萌条和非萌条同属植物的高度,然而由于生活史以及其他生物学习性的差异,可能使这一比较的基础不成立.在米心水青冈中比较萌条现象不同的个体间高度来检验该假说,结果表明米心水青冈萌条和非萌条个体间的高度不存在显著差异(p=0.873),多茎干和少茎干成体间的高度也没有显著差异(p=0.559),并且个体的高度与茎干数存在显著的正相关,表明在米心水青冈中不存在茎干数-高度的权衡关系,其原因是由于萌条的叶片也具有光合能力,向萌条的资源运输随着萌条的长大而逐渐减少,直至中止.在调查的米心水青冈种群中,多干指数达到96.4%,几乎所有的幼苗、幼树和小树都是通过萌条形成的,表明萌条在种群的更新中起着关键作用.

Sprouting and height in a Fagus engeriana population

Resprouting plays an important role in the regeneration of many tree species, especially in disturbed habitats. It was suggested that there is a trade\|off between sprouting and height growth. This hypothesis was previously tested by comparing the heights of sprouters and its non\|sprouting congeners. However, differences in life history and other biological characteristics may invalidate such a comparison. In this paper, we try to test such a hypothesis in Fagus engleriana and to understand the effect of resprouting on demography. We investigated characteristics of Fagus engleriana individuals from a community in Tianmushan. We compared the heights of single and multi\|stem individuals with similar diameter at breast height (DBH) as well the heights of mature individuals of the similar size with few and abundant stems. We also quantified the sprouting characteristics and their relationship with height and DBH of the largest individual. Positive relationship was found between number of stems and DBH of the largest stem. No significant difference was found in height between single and multi\|stem individuals, also between mature individuals with few and abundant stems, indicating that there is no trade\|off between sprouting and height growth in F. engleriana. Positive relationship was found between height and number of stems. Negative relationship was found between variation coefficient of the largest three stem and number of stems, indicating that difference among the largest three stems decreased with increasing number of stems, due to photosynthesis of each stem. Size of the studied population was much larger at the ramet level than that at the genet level. Almost all seedling, saplings and small individuals were formed by sprouting, indicating that sprouting plays a critical role in the regeneration of the F. engleriana population in Tianmushan.