小五台山森林落叶层对天然青杨种群更新方式的影响

doi:10.3724/SP.J.1258.2012.00109

摘要/Abstract

摘要：

通过野外样方调查和室内种子萌发实验两种方法, 对河北小五台山天然青杨(Populus cathayana)种群的更新方式进行了研究, 以揭示落叶层的化感作用和机械阻挡作用对青杨种子萌发的干扰机理。结果显示: 1)种群样方中的幼苗都为无性繁殖的克隆分株, 种子繁殖的幼苗年自然存活率为0%; 2)落叶层对种子幼苗的存活率有显著影响。50 mg·mL^-1浓度的落叶水浸液可使青杨种子发芽率降低41%, 使主根长度减少95%, 100 mg·mL^-1浓度的落叶水浸液则完全抑制种子萌发; 单层和多层落叶对种子萌发产生的影响差异不显著, 都能完全阻碍种子的根系正常生长, 导致幼苗脱水干枯死亡。结果表明, 在高海拔山区的青杨天然林中, 由于不断积累的落叶层通过化感作用和机械阻挡作用严重影响种子的萌发、定根以及正常生长, 从而导致种子更新的途径受阻, 而只能通过无性繁殖来完成正常的种群更新。

关键词: 化感作用, 落叶层, 机械阻挡, 青杨种群, 更新方式

Abstract:

Aims Populus cathayana, a typical riparian tree in northern China, can produce substantial seeds and numerous clones. Several studies in the last few years indicated that the proportion of seedlings and clones in the population was correlated with factors such as river flooding, soil substrates and slope gradient. Our objective was to investigate the regeneration mode of Populus cathayana located in high-elevation woodland of Xiaowutai Mountains, revealing why there was such a phenomenon.
Methods From 2010 to 2011, we excavated 1 284 small P. cathayana saplings along an elevational gradient in high-elevation woodland of Xiaowutai Mountains to determine their method of origin. The influence of allelopathy and mechanical effects of litter layer on seedling regeneration was investigated by a series of controlled experiments.
Important findings Regeneration was overwhelmingly from clonal propagation. Litter layer had a negative effect on recruitment from seed. Under treatment of different concentrations of litter layer aqueous extracts, seed germination exhibited significant differences. Compared with the control treatment, 50 mg·mL^-1 solution decreased seed germination by 41% and root length by 95%, and 100 mg·mL^-1 solution completely inhibited germination. Furthermore, litter layer inhibited roots of seedlings from absorbing water and rapidly caused seedling death. Therefore, litter layer prevents seedling recruitment, and clonal propagation was the only effective regeneration mode of P. cathayana in the population.

Key words: allelopathy, litter layer, mechanical hinder, Populus cathayana population, regeneration mode

李霄峰, 胥晓, 王碧霞, 黄尤优, 王志峰, 李俊钰. 小五台山森林落叶层对天然青杨种群更新方式的影响. 植物生态学报, 2012, 36(2): 109-116. DOI: 10.3724/SP.J.1258.2012.00109

LI Xiao-Feng, XU Xiao, WANG Bi-Xia, HUANG You-You, WANG Zhi-Feng, LI Jun-Yu. Effects of forest litter layer on regeneration of Populus cathayana natural population in Xiaowutai Mountains in China. Chinese Journal of Plant Ecology, 2012, 36(2): 109-116. DOI: 10.3724/SP.J.1258.2012.00109

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链接本文: https://www.plant-ecology.com/CN/10.3724/SP.J.1258.2012.00109

https://www.plant-ecology.com/CN/Y2012/V36/I2/109

图/表 5

表1 不同海拔各样方中青杨的克隆幼苗与种子幼苗的数量对比

Table 1 Number comparison of Populus cathayana seedlings and clones in each plot at different elevations

样地 Sample plot	海拔高度 Elevation
	1 400 m					1 500 m					1 600 m					1 700 m
		No. 1	No. 2	No. 3	No. 4		No. 1	No. 2	No. 3	No. 4		No. 1	No. 2	No. 3	No. 4		No. 1	No. 2	No. 3	No. 4
克隆植株数(株) No. of clone plants	154	80	87	26		13	128	27	102		151	113	57	39		42	50	89	126
幼苗数(株) No. of seedlings	0	0	0	0		0	0	0	0		0	0	0	0		0	0	0	0

图1 各海拔梯度青杨种苗的存活率(平均值±标准误差, p = 0.05)。

Fig. 1 Survival rate of Populus cathayana seedlings after germination peak at each elevation (mean ± SE, p = 0.05).

图2 林内与林外两种光照条件下幼苗的存活率差异(平均值±标准误差, p = 0.05)。

Fig. 2 Difference of seedling survival rate between two illumination conditions within and outside the woodlands (mean ± SE, p = 0.05).

图3 不同浓度的青杨落叶水浸液对青杨种子发芽率和幼苗根、茎长度的影响。条块上的字母表示经邓肯检验后p = 0.05的差异水平。字母只在同类字符中相互比较, 图示平均值±标准误差。

Fig. 3 Effects of different concentrations of aqueous extract in Populus cathayana leaffall on seed germination and length of stem and root of P. cathayana seedlings. Different letters above the bars represent significant differences at p = 0.05 according to Duncan’s test. The different letters comparison was restricted by the same alphanumeric classification system. Each value is the mean ± SE.

图4 在户外条件不同处理下6 h内的幼苗存活率变化(平均值±标准误差, p = 0.05)。

Fig. 4 Survival rate variance of seedlings in outdoor condition within six hours under different treatments (mean ± SE, p = 0.05).

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