凋落叶分解过程对毛红椿种子发芽和幼苗生长的影响

Effects of Decomposing Leaf Litter on the Seed Germination and Seedling Growth of Toona ciliata var. pubescens

通过盆栽试验,模拟毛红椿(Toona ciliata var. pubescens)凋落叶在土壤中的分解过程对毛红椿种子发芽和幼苗生长的影响。试验设置沙壤土和林地土两种不同的土壤条件,每种土壤条件下设置L15(15 g/盆)、L30(30 g/盆)、L60(60 g/盆)3个凋落叶添加水平,对照组(CK)不添加凋落叶L0(0 g/盆)。将各处理的凋落叶分别与1 kg林地土或沙壤土混合后装盆,播种毛红椿种子进行盆栽实验,分析不同的凋落叶含量可能对毛红椿种子萌发及幼苗生长的影响。试验结果表明:(1)在沙壤土中,高量的凋落叶(L60)显著降低种子的发芽势、发芽指数和发芽率,凋落叶分解100 d时,中量的凋落叶(L30)显著降低幼苗叶片的叶绿素,高量的凋落叶显著降低幼苗的根长,中、高量的凋落叶极显著降低幼苗的生物量;凋落叶分解170 d时,低、中量的凋落叶显著降低幼苗叶片的叶绿素和地上部分生物量,低、中、高量的凋落叶均显著降低幼苗的地下部分生物量;(2)在林地土中,凋落叶有降低种子活力的趋势,但是影响不显著;凋落叶分解100 d时,高量的凋落叶显著降低幼苗的根长,中、高量的凋落叶极显著降低幼苗的生物量;凋落叶分解170 d时,高量的凋落叶显著增加幼苗叶片的叶绿素含量和地上部分生物量,高量的凋落叶极显著增加幼苗的地下部分生物量;(3)综合凋落叶分解在2种土壤条件下的效应可见,毛红椿凋落叶对自身种子的发芽具有抑制作用,分解初期对幼苗的生长和生物量增加也具有抑制作用,主要表现为对根部的抑制作用,且随添加量的增加而增强,对幼苗的光合作用也会产生一定的影响,毛红椿凋落叶在沙壤土中的自毒作用强于林地土。

A pot experiment was conducted to investigate the effects of decomposing leaf litter on the seed germination and seedling growth of Toona ciliata var. pubescens.Two different soil conditions,T. var. pubescens canopy woodland soil and sandy loam and three levels of leaf litter addition,L15(15 g/pot),L30(30 g/pot),L60(60 g/pot),and no leaf litter as a control(CK)were set.The litter of each treatment was mixed with 1 kg of woodland soil or sandy loam,and the seeds were sowed.The effects of different litter levels on the seed germination and seedling growth of T. ciliata var. pubescens were observed.The results were as follows.(1)In sandy loam,high level leaf litter(L60)significantly decreased seed germination potential,germination index and germination rate.When litter decomposed for 100 d,the middle level leaf litter(L30)significantly decreased the chlorophyll content of seedling leaves.High level leaf litter significantly decreased the root length of seedlings,middle and high levels of leaf litter declined the seedling biomass extremely significantly.When leaf litter decomposed for 170 d,low and medium levels of leaf litter significantly reduced the chlorophyll content of leaves and above ground biomass of seedlings.Low,medium and high levels of leaf litter reduced the subsurface biomass of the seedlings significantly.(2)In woodland soil,litter had a tendency to decrease seed vigor,but the effect was not significant.When the litter decomposed for 100 d,the high level leaf litter significantly reduces the root length of the seedlings,while the middle and high level litter leaves significantly reduce the biomass of seedlings.When the litter decomposed for 170 d,the chlorophyll content and the above ground biomass of the seedlings were significantly increased by the high amount litter,and the high amount litter increased the subsurface parts of the seedlings extremely significantly.(3)A comprehensive analysis of the effects of litter decomposition under two soil conditions showed that the leaves of T. ciliata var. pubescens had inhibitory effects on the germination of their own seeds,also inhibited the growth and biomass increase of their own seedlings in the early stages of decomposition.These results also suggest that the autotoxicity effect of fallen leaves in sandy loam was stronger than that in woodland soil.