中国木本植物幼苗生长对光照强度的响应

光照是影响植物幼苗生长的重要的环境因子,定量化研究光照对木本植物不同生活型幼苗生长的影响具有重要意义。系统收集了有关光照对我国木本植物幼苗生长影响的国内外文献,采用Meta分析的方法对幼苗的生长效应进行评估。研究结果表明:(1)与全光照下幼苗生长相比,由于遮阴处理对幼苗基径增长量的抑制作用强于对株高增长量的作用,幼苗出现株高基面积比增高的形态特征变化;(2)与灌木相比,乔木树种幼苗对不同光照强度的响应更加敏感;(3)在小于20%和20%—40%全光照条件下,落叶阔叶和常绿阔叶树种幼苗基径均受到显著抑制,而常绿针叶树种的基径并没有受到遮阴的明显抑制;(4)落叶阔叶和常绿阔叶树种的株高基面积比均显著高于全光照,而常绿针叶树种的株高基面积比与全光照相比差异较小。我们的这一研究将有助于更好的理解木本植物幼苗生长对光照的响应机理。

Growth response of Chinese woody plant seedlings to different light intensities

As an important environmental factor, light has a substantial effect on plant seedling growth. The amount of light changes considerably during forest successions or micro-successions in mature forests, and therefore, it is necessary to evaluate the effects of light on the growth of woody plant seedlings of different life forms. Although much recent research has been conducted to determine shade tolerance of woody plants, most of these studies focused only on one or two plant species, and review studies across experiments are needed to elucidate plant responses to light conditions. In this meta-analysis, we collected data from experimental studies on growth responses of woody plants to shading gradients. Consequently, 106 species belonging to 42 families from 71 published papers (to 2016) were collected. Extracting data from these studies, we conducted a meta-analysis by using MetaWin 2.1 software. The growth responses of woody plant seedlings were analyzed using the mean values of seedling height, basal diameter, biomass, and height:basal area ratio in the treatments relative to those of the control (with full light) to estimate the appropriate effect size for the analysis. Our results showed that (1) Compared with seedling height, basal diameter of plant seedlings was more sensitive to shade treatments, resulting in higher height:basal area ratio for seedlings growing under shade treatments; (2) Shrub seedlings exhibited stronger tolerance to shade treatments than did tree seedlings; (3) Regarding life forms with different leaf traits, basal diameters of deciduous broadleaved and evergreen broadleaved species were significantly inhibited by shading of 0-20% and 20%-40% light intensity of unshading control, whereas the basal diameter of evergreen conifers was relatively insensitive to shade treatments; (4) The height:basal area ratios of deciduous broadleaved and evergreen broadleaved plants were significantly enhanced by shading treatments, whereas the height:basal area ratio of evergreen conifers were relatively insensitive to shading treatments, which indicated that light responses of plant seedlings may strongly depend on the leaf traits of the species. Our results increased our understanding of how seedling growth responds to different light conditions in natural forests.