Community Structure And Species Diversity Of Subtropical Evergreen-deciduous Mixed Broad-leaved Forest In Jinzi Mountain

Subtropical evergreen deciduous broad-leaved mixed forest is a typical zonal vegetation type in subtropical evergreen broad-leaved forest in north latitude or high elevation area,at the same latitude in the world,has the most abundant biodiversity,the most complex community structure and the highest productivity,plays an irreplaceable role in maintaining regional ecological system and global carbon balance,evergreen-deciduous broadleaved forest is one of the typical vegetation types in mountainous area of southwest Hubei.This paper relied on the establishment of the National Forest Ecosystem Research Station of Enshi,Hubei Province,based on dynamic monitoring data for the first phase of the 6 hm~2 plot in Jinzi mountain,studied the species composition and structure of community,dominant population and interspecific association,community diversity and change regularity systematically.The results show:1.There were 43 846 individuals of woody plants(DBH?1 cm),belonging to 52 families,111 genera and 196 species.Included 48 families and 101 genera of angiosperms,and about 4 genera and species of gymnosperms,2 species of endemic plants in China,4 rare and endangered plants and 4 National Key protection plants.The species composition was mainly composed of Rosaceae and Caprifoliaceae,there were many single species and multi species plants.The floristic composition showed the origins of the community species,and the primitive plants were abundant;the areal types of families showed that tropical distribution were more than temperate distribution,the areal types of genera showed that temperate distribution were more than tropical distribution,the areal types of families and genera had obvious transitional characteristics of tropical and temperate.2.There were 16433 individuals of evergreen tree spieces in the whole plots,belonging to 26 families,42 grnera and 69 species,mainly included Lauraceae,Aquifoliaceae and Rosaceae.There were 27 413 individuals of deciduous tree species,belonging to 44 families,82 genera and 127 species.mainly included Lauraceae,Aquifoliaceae and Moraceae.The species richness and individual abundance of deciduous tree species were more than 1.6 times of evergreen species.The species abundance and individual numbers of the community decreased with the increase of the diameter and height,and the species abundance and individual numbers of deciduous broad-leaved species in each diameter and height were more than evergreen broad-leaved species.Castanea henryi had the largest important value,was the constructive species in the community.It played a decisive role in the establishment of community structure and community environment.Ficus heteromorpha was the dominant species of sub-arbor layers,which had obvious control effect on community structure and environment construction.The important value of Eurya alata ranked secend,was the main dominant species in shrub layer.3.The number of species increased with the increase of the number of individuals and the sample area.The number of species increased rapidly within 10000 dividual numbers of woody plants,then increased gradually.The species abundance distribution in the whole plot was uneven,the rare species were 67,accounted for 31.18% of the total species,there were 22 single species,accounted for about 11.22% of the total number of species.The species increased repapidly Within 2 hm~2,then the growth rate of species tends to be stable at about 5 hm~2.4.In the dominant species whoes important values were in the top 10,there were 8 pairs' ecological association(x2)?6.635,accounted for 26.67% of the total species.There were 32 pairs' ecological association(x2)greater than 0.There were significant positive correlation between Carpinus fargesiana and Eurya alata,Cunninghamia lanceolata and Eurya alata,Castanea henryi and Populus lasiocarpa.Ficus heteromorpha and Cunninghamia lanceolata had significant negative association,most species presented positive correlation,species composition of the community were relatively stable.5.There were 96 trees species,81 shrubs species and 19 lianas species in the whole plot,Margalef species richness index value was 8.89,Shannon-Wiener index value was 3.87,Simpson index value was 0.96,Pielou evenness index value is 0.73.the species diversity was relatively high,The species composition was abundant and the structure was relatively complicated.Margalef species richness index and Shannon-wiener diversity index decreased with the increase of DBH class,and the species richness,abundance and frequency distribution decreased with the increase of height,and all the indexes showed a downward trend.