影响关帝山华北落叶松天然更新与幼苗存活的微生境变量分析

采用野外典型样线调查法并结合室内实验对关帝山华北落叶松1年生幼苗更新和2～3年生幼苗存活的微生境变量进行分析。结果表明:微生境变量幼苗距大树距离、草本层盖度、土壤铵态氮两两间成极显著正相关,这3个变量与枯落物厚度和土壤硝态氮分别成极显著负相关,枯落物厚度与土壤硝态氮的正相关达到了极显著水平;通径分析表明,草本层盖度和土壤铵态氮对1年生幼苗的更新产生极显著直接负效应,幼苗距大树距离对幼苗的发生产生显著直接负效应,这3个变量的间接负效应使其对幼苗发生的阻碍作用进一步加强。枯落物厚度和土壤硝态氮对幼苗的发生产生极显著直接正效应,二者的间接效应促进了1年生幼苗的更新;枯落物厚度和幼苗距大树距离对2～3年生幼苗的存活产生极显著直接负效应,但其总间接正效应弱化了对幼苗存活的阻碍作用。草本层盖度对幼苗存活的直接负效应和间接负效应均不显著,但两效应叠加使其与2～3年生幼苗存活的负相关性增强,达极显著水平。

Analysis on Micro-habitat Variables Affecting Natural Regeneration and Survial of Larix principis-rupprechtii Seedlings in Guandi Mountain

In the Larix principis-rupprechtii stand of Guandi Mountain,micro-habitat variables affecting regeneration of one-year seedlings and survival of two-year seedlings were studied by using typical line transects method and indoor experiment.The relationships between coverage of herbage and the distance between seedlings and adjacent tree,between soil NH4+-N and the distance between seedlings and adjacent tree,between coverage of herbage and soil NH4+-N were significantly positive correlated,and those between the above three variables and thickness of litter,soil NO3——N significantly negative correlated;The path analysis suggested that coverage of herbage and soil NH4+-N had extremely remarkable direct negative effect on the regeneration of Larix principis-rupprechtii seedlings.The distance between seedlings and adjacent tree had a remarkable direct negative effect on occurrence of seedlings.Indirect negative effect of the above three variables enhanced their limitation to natural regeneration of one-year seedlings.Thickness of litter and soil NO3——N had extremely remarkable direct positive effect on occurrence of seedlings,and their indirect effect promoted the regeneration of one-year seedlings;Thickness of litter and the distance between seedlings and adjacent tree had extremely remarkable direct negative effect on the survival of two or three-year seedlings,but their total indirect negative effect attenuated their limitation to the survival of seedlings.The direct and indirect negative effect of coverage of herbage both were not remarkable,but the accumulation of the two kinds of effects made the correlation between coverage of herbage and the number of 2～3 year seedlings up to a extremely remarkable level.