Effect Of Leaf Litter And Forest Soil On Seed Germination And Seedling Growth Of Toona Ciliate Var.Pubescens

Toona ciliata var.pubescen was listed as a second class national-level protected endangered species.At present,the destruction of resources is serious,and the situation of endangerment is becoming more and more serious.Take 3 natural communities of Jiulian-shan National Reserve in Jiangxi Province and and a plantation in Jiangxi Agricultural University as the study object,through the laboratory germination test and pot planting experiment,combined with soil physicochemical characteristics,soil fungi isolation and pathogenicity test,chemical composition analysis of litter and root exudates,studied the effects of litter and forest soil in different communities onseed germination and seedling survival of T.ciliata var.pubescens.The function and mechanism of litter and soil on seedling formation limitation was discussed.The main research results are as follows:(1)The effect of litter on seed germination and seedling establishment varies because of its differentposition and thickness.Litter thickness>2cm has,on the whole,a significant negative effect on seedling regeneration of T.ciliata var.pubescens.(2)Leaching liquor of forest litter,fallen leaves and decomposed fallen leaves of T.ciliata var.pubescens.have allelopathic effects on seed germination and seedling growth.The allelopathic effect is concentration dependent.It showed inhibitory effect on seed germination.Low concentration(10 g·L-1)leaching solution of the decaying leaves and the humus(decomposed for 3 months)had a promoting effect on seedling growth.Forest litter(?38 g·L-1),fallen leaves(?10 g·L-1),decaying leaves(1000 g·L-1)all had inhibitory effect on seedling root growth.Alcohols,phenols and ketonesin in water extracts of fallen leaves may be allelopathic constituents.Derivatives of benzoic acid may be the main allelochemicals in the humus.The weak polar components of leaching solution of the decaying leaves is mainly sterols,fatty acids and their esters.(3)Leaf litter of T.ciliata var.pubescens in decomposition process had inhibitory effect on seed germination and seedling early growth.The litter amount>30g/Basin has a significant negative impact on seedling early growth,mainly affecting the growth of roots.But with the continuous decomposition of litter and the growth of seedlings,the inhibition of leaf litter was relieved and changed to promote the growth of seedlings.(4)The root zone soil of T.ciliata var.pubescens natural forest community had no effect on seed germination,but not conducive to seedling survival.Soil physical and chemi-cal properties and enzyme activity were not significantly related to seed germination rate and seedling survival rate.Potentially pathogenic strains of T.ciliata var.pubescens seed-lings,RS2(Lecanicillium psalliotae)and RS5(Fusarium neocosmosporiellum)were separated from the root zone soil.Root exudates of T.ciliata var.pubescens could enhance their pathogenicity and cause seedling death.That is not conducive to the preservation and completion of seedlings.(5)Root exudates and root secretion of T.ciliata var.pubescens did not affect the seed germination,the effects on seedling growth and preservation is different.Root exudates of T.ciliata var.pubescens inhibited its seedling growth,decreased the seedling survival rate.While the root secretion can promote seedling growth,had no effect on seedling survival rate;Root secretion can improve the number of bacteria and fungi in the soil,improve the soil catalase and sucrase activity,has obvious effect on root zone soil fungi and root patho-gen of T.ciliata var.pubescens;Root secretion of T.ciliata var.pubescens containing arginine,palmitic acid,phthalic acid diisobutyl and so on.