The Natural Regeneration Status And Influencing Factors Of The Fir Forest In Minjiang River In Tangjiahe Nature Reserve

Natural regeneration plays an important role in the reproduction of forest ecosystem.Forest regeneration characteristics include the regeneration of trees,the understory woody plant seedlings and saplings density,and the regeneration methods.Those not only reflect the current situation of forest,but also imply the future trend of forest succession.Evaluating of natural regeneration in the forest community and analyzing the reason that hinder forest regeneration will provide scientific basis for forest protection and management.In this paper,we surveyed and evaluated the natural regeneration status of the dominant species of coniferous forest,Abies faxoniana population located at Tangjiahe natural reserve in Sichuan.We conducted two times plants’community investigation,three times soil seed bank survey and 1 year monitoring of seed rain.We tried to to analyze the reason of natural regeneration barriers in Tangjiahe Nature Reserve by considering both growth environment and provenance,the results are as follows:1.The coniferous forest community structure is relatively simple in Tangjiahe Natural Reserve.Abies faxoniana was the dominant species in arborous layer accounting for 98.57%.In shrub layer Fargesia rufa,Fargesia denudata are the dominant species.In 15 plots,We found 38 families,73 genera,and 77 species located at the elevation of 2310-3194 m.2.The A.faxoniana populations in Tangjiahe Natural Reserve in recession stages and exists serious natural regeneration barriers.The A.faxoniana populations in Tangjiahe Natural Reserve were dominated by medium trees and mature trees.DBH0-7.5cm young trees were accounted for only 4.57%.We found a heavy situation of death trees(192 death trees in 15 plots).In the plants’community,there was a significant difference in the seedling density of A.faxoniana.The seedling density was about 916.67 trees/ha with a large spatial distribution difference,which was mainly found at the altitude 2482-2578 m.3.In the environmental factors,the soil physical and chemical properties has a great influence on the germination and growth of the A.faxoniana seedling.Correlation analysis showed,the thickness of litter,natural water holding capacity,maximum water holding capacity were not significantly related to A.faxoniana seedling density.The soil water content,pH,total phosphorus,total potassium,available nitrogen,available potassium,organic carbon,total nitrogen content were also not significantly related to A.faxoniana seedling density.Leaf area index,shrub cover,herbaceous cover had no significant relation to A.faxoniana seedling number.From the results of RDA,organic carbon,total nitrogen,available nitrogen and available potassium had great effect on the germination of A.faxoniana and their seedling growth.4.Lack of seeds is one of main factors in regeneration barriers of A.faxoniana.The seed rain and soil seed bank were significantly correlated with the density of A.faxoniana seedlings.In the survey area,the spatial distribution of seeds rain,soil seed bank and seeds set of A.faxoniana were different,and the seeds number was lower.The average intensity of seed rain was 10.57±5.79/m~2 particle,and there is a huge difference in the spatial distribution,which mainly distributed in the altitude of2482-2578 m(90.81%).A.faxoniana average seed bank density was 28.08±9.31/m~2,mainly distributed at the upper soil(0-2cm,48.09%),the lower soil(7-12cm)distribution was lowest(15.29%);the seeds setting rate was low and had different spatial distribution.No A.faxoniana seeds was found above the altitude of 2600m.The seeds setting rate was 22.62%,0 and 23.46%at three sample lines,respectively.To sum up,there are serious natural regeneration barriers in the A.faxoniana forest in Tangjiahe Natural Reserve.Lack of seeds is one of the dominant factors in the regeneration of A.faxoniana forest.The content of organic carbon,total nitrogen and alkali hydrolyzable nitrogen of soil had great influence on the germination and growth of A.faxoniana seedlings.The influence of shrub cover on the regeneration might be mainly concentrated in the over stages of seedlings to young trees.