Study On The Regeneration Characteristics And Population Diffusion Of Larix Chinensis Forest

Larix chinensis,as the main constructive species in the alpine forest area of Qinling Mountains,is an important part of the ecosystem.It plays an important role in water conservation,rock stabilization,soil and water conservation and biodiversity conservation.It is listed as the second-class rare and endangered protected tree species in China.The distribution area of L.chinensis is narrow and concentrated from 2800m to 3500m altitude in Qinling Mountains,Shaanxi Province.L.chinensis is difficult to reproduce because of its special germination environment and poor seed setting ability.Therefore,in order to understand the regeneration strategy of L.chinensis,protecting the population reasonably,promoting the regeneration,and further explore the regeneration conditions of the forest is very necessary.In this paper,the community of L.chinensis forest in Taibai Mountains is taken as the research object.Through studying and analyzing the spatial and temporal dynamics of seed rain,the regeneration characteristics in forest gaps and the spatial pattern of different development stages,the environmental factors restricting the population reproduction are sought,the characteristics of natural maintenance of the population are preliminarily revealed,and the ecological process of regeneration of L.chinensis forest is understood,so as to provide the theoretical basis and data support for the protection of L.chinensis.The main research results are as follows:?1?Spatial and temporal dynamics of seed rain in L.chinensis forest showed that the time of seed dispersal was mainly from late September to mid-November.The peak period was mid-late October,seed rain showing similar trends in different habitats.The average intensity of seed rain during peak period was 113.3 grain m^-2,74 grain m^-2 and 137.3 grain m^-2,respectively.During the period of seed drop,dry seeds are dominant in the early stage,and mature seeds are dominant in the peak stage and the end stage.But in the forest gap,the maturation time of seeds is earlier than that of under-forest and forest edge.?2?Based on the relationship between gap characteristics and seedling regeneration quantity of L.chinensis forest,the environmental factors affecting natural regeneration of L.chinensis forest were explored.The results are reported as followed:?1?In the L.chinensis forest,the areas of canopy gap?CG?and extended gap?EG?appeared to have a small-medium sized area of 100m² dominated distribution,and the formation of forest gaps is mainly affected by wind and snow,resulting stem breakage.?2?The order of correlation degree of influencing factors of natural regeneration under forest gaps was as follows:forest gaps>opening degrees>position>slope aspect>gradient>altitude>litter depth,indicating that the forest gaps area and opening degrees had the biggest influence on the natural regeneration;?3?The seedlings were mainly distributed in the medium and small forest gaps.Besides,the opening degrees is best kept between 0.6 and 0.8.Therefore,it is suggested that the seed germination rate,seedling survival rate and seedling rate of L.chinensis should be increased by improving the understory environment.In the process of forest management,we can take the opening degrees as the index and artificially create certain forest gaps to accelerate the natural regeneration of the L.chinensis forest and maintain the stability of its community.?3?In order to explore the spatial distribution characteristics and correlation of L.chinensis population in the community ecotone,the spatial distribution characteristics and correlation characteristics of different development stages of L.chinensis and A.fargesii population were analyzed by using O-ring statistics of point pattern analysis method through investigating the pure-edge ecotone and pur-mixed ecotone.The results showed that:?1?In the mixed forest with lower distribution limit,the population structure of L.chinensis was declining,while the quantitative structure of A.fargesii was typical inverted"J"type at each development stage,and the population structure was stable,which could achieve continuous renewal.Moreover,all individuals of L.chinensis and A.fargesii showed aggregation distribution as a whole,and the correlation between the two populations was positive or not.?2?There are more seedlings in the pure forest with the upper limit of distribution,but most of the adult trees are"little old"trees with poor growth.In addition,the spatial pattern of all individuals of L.chinensis is aggregated distribution,and there is a positive correlation between the adult trees and the renewed seedlings.