不同水分和植株密度处理对牛鞭草生长及形态的影响

为了解常见湿地植物牛鞭草在不同水分和种植密度条件下的生长和形态响应,将4种不同密度的植株(每盆分别种植1,2,4或12株)均置于4种不同水分条件下对照组(CK)、水淹与干旱交替组(FD)、土壤水分饱和组(LF)、全淹组(FL)],研究其生长及形态上的变化。结果表明,不同水分及密度处理显著影响牛鞭草的生长及形态特征(P<0.05)。全淹显著抑制牛鞭草的生长(P<0.05)。非全淹条件下,除高密度组外,总生物量、地上生物量和茎生物量均保持较高水平,其中在LF条件下各密度处理间无显著差异(P>0.05)。除单独个体组外,植株的节间长和主茎长均在LF条件下达到最大值。随着水分胁迫和密度的增加,根生物量、叶片数和分枝数逐渐降低。中、高密度组的相对邻体效应值随着水分胁迫的增加而增加,植株间竞争作用逐渐减弱,但未转变为促进作用。牛鞭草在不同的水环境中可以采取不同的策略以应对,适宜在水分多变地区大量种植,在易出现深水淹地区,牛鞭草以高密度种植为佳,在浅水淹或水陆交汇处,建议以中密度方式种植。

Effects of different water levels and plant densities on the growth and morphology of Hemarthria altissima

Seasonal fluctuation of water levels is commonly found in natural and constructed wetlands and the tolerance of a plant to such fluctuation is a key factor for the composition of community and distribution of wetland species. Understanding how the growth and morphology of plant species respond to different water levels and plant densities is important to help predict their productive potential under certain environments and better manage the wetlands. In this study, Hemarthria altissima was planted at four densities (1, 2, 4 or 12 plants/pot) and four water levels were imposed (Control, CK; Wet-dry alternation group, FD; Waterlogged group, LF; Flooded group, FL) to study the morphological and growth responses. The growth and morphological characteristics of H. altissima were influenced significantly by different water levels and densities. Growth was inhibited significantly in the FL group, while in the FD and LF groups, the total biomass, aboveground biomass and stem biomass of the plants were high, except in the groups planted at higher densities and there was no significant effect of densities under LF. The length of internodes and the main stems were greatest in the LF treatment, except for the group with 1 plant/pot. With increase in plant density or in the level of water stress, the total root biomass and the number of leaves and shoots decreased gradually. Moreover, with increasing flooding stress, the relative neighbor effect and its value increased gradually, and the intensity of competition decreased, but the intraspecific interaction did not shift to facilitation. H. altissima showed the ability to adopt different strategies under different water conditions, either to escape from partial submergence by further shoot elongation or to adopt a non-elongating quiescent strategy when completely submerged. Hence, H. altissima is a suitable species for planting in the regions with varying soil water availabilities. Based on the results, higher planting densities are recommended in completely flooded areas and medium densities are suitable in the partially flooded areas or in the ecotone between terrestrial and aquatic environments.