三维土壤异质性对种子萌发影响的实验研究

三维土壤异质性对种子萌发影响的实验研究 种子萌发受其生长环境的影响,但土壤异质性对种子萌发的作用还不太清楚。本文通过控制实验研究了三维土壤异质性对草本植物种子萌发的影响,实验设置了两种水平的土壤异质性,即通过在花盆内的三维空间上相间填充营养丰富和贫瘠两种土壤来构建不同的土壤异质性水平。两种水平土壤异质性的斑块大小分别为7.5和15.0 cm。实验采用两种草本植物(黑麦草Lolium perenne和垂穗披碱草Elymus nutans),每种植物选择大小一致的种子50粒,这些种子要么放在异质性土壤中萌发,要么放在培养皿中萌发。实验过程中,每天统计这些种子的萌发率。实验发现,斑块小的花盆内种子萌发率较低,这个结果与我们的预期相符,我们认为斑块小的花盆内,两种土壤斑块之间的间距较小,植物遭遇不同土壤斑块资源变动的几率较大,植物为了减小这种变动带来的不利影响,会倾向于降低萌发率和延迟萌发。我们的研究还发现,斑块小的花盆内种子萌发的变异性也较大,即与大斑块内的种子萌发率相比,小斑块内的种子萌发率在各重复间的差异性较大。与二维土壤异质性相比,三维土壤异质性更接近于真实情况,这样的土壤设置能够促进我们更好地理解土壤空间异质性对种子萌发等动态过程的影响.

Effects of three-dimensional soil heterogeneity on seed germination in controlled experiments

Aims Seed germinations react to their local growing conditions,but the impacts of soil heterogeneity on seed germinations are not well known.Methods Effects of three-dimensional soil heterogeneity on seed germinations of grasses species were explored,where two levels of such soil heterogeneity were created via alternatively filling nutrient-poor and nutrientrich substrate in pot in all directions.Patch sizes of the two heterogeneity levels are around 7.5 and 15 cm,respectively.Fifty seeds of each of the grasses species(Lolium perenne and Elymus nutans)were set either in these heterogeneous soils or in petri dishes with distilled water.Seed germinations of these species were daily recorded.Important Findings We found that pots with smaller patches had relatively lower germination rate,which is con sistent with our expectati on that shorter distance between nutrient-rich and nu trient-poor patches in pots with smaller patches allows plants to reduce their germination rates and delay their germination,in order to reduce the negative impacts of the strong variation of soil resources in these pots.Our results also revealed that pots with smaller patches yielded more heterogeneous seed germination,i.e.seed germinations highly diverged among these pots.These findings highlight that the realistic three-dimensional design can improve our understanding of seed germination as driven by soil spatial heterogeneity.