Effects Of Dwarf Bamboo Density On Trees Seedling Regeneration And Community Structure In Deciduous Broad-leaved Forest

During the development of forest community succession,dwarf bamboo as a dominant species in undergrowth shrubs,its distribution in the forest is closely related to community structure composition and population dynamics,and renewal of seedlings of dominant tree species.With their strong underground stems and their rapid clonal growth ability,dwarf bamboo can easily form contiguous coverage and become the dominant species of the shrub layer.Its densely clustered stems and plenty of roots affect other species in the community,witch affect the use of illumination,water and resources.In addition,the bamboo in the environment produce large amounts of litter and not easily decomposed,affecting the thickness of the litter layer,which directly or indirectly affect the regeneration of tree species and the growth of seedlings,young trees.Studying the influence of dwarf bamboo on the structure of forest community and the dynamic of the dominant species,and the update of dominant species,which will help to correctly evaluate the impact of dwarf bamboo on the regeneration and development of forest communities and provide scientific theoretical basis for forest management and protection.In this paper,evergreen and deciduous broad-leaved mixed forests with dwarf bamboo distribution was selected as the research object,and set up three parts:?1?10 strips of 160 m in length and 8 m in width were randomly arranged in the forest community.In each strip there were 20arbor squares with 8 m×8 m,4 m×4 m shrub squares,and 1 m×1 m herbaceous squares and bamboo squares nested,a community investigate was conducted for each sample,the bamboo density and environment factors in each sample were measured.Divided into five groups of density gradients according to the number of bamboo ramets?Density 1:0 ramet/m²;Density 2:16.75±7.27 ramet/m²;Density 3:42.89±7.93 ramet/m²;Density 4:70.56±7.46 ramet/m²;Density 5:101.35±10.97 ramet/m²?,the relationship of community composition,species diversity and bamboo density with environmental factors was analyzed.?2?Based on the same survey method described above,the differences in population dynamics of dominant species in communities with different densities of bamboo tussock were analyzed.?3?In order to further understand the effects of dwarf bamboo growth on early regeneration of seedlings,we controlled four group bamboo densities?0%:3.83±0.53 ramet/m²;25%:16.00±1.80 ramet/m²;50%;39.00±1.69 ramet/m²;100%:69.00±2.15 ramet/m²?,from 2014 to 2017,annual maintenance maintains the bamboo density constant,after the environment stable,to measure the micro-environments?soil temperature,soil humidity,soil conductivity and litter thickness?under different bamboo densities,thus discussed the influences of bamboo density on seedling number,seedling survival and growth of dominant species Carpinus viminea Wall.The results showed that:?1?Community composition and species diversity in different density of bamboo tussock:Changes in environmental factors caused by bamboo plexuses of different densities,resulting in different levels of species diversity in the community.At the density of 3?42.89±7.93 ramet/m²?,the highest level of species diversity and richer vegetation composition was observed.As the density of bamboo tussocks increased,the level of species diversity decreased.The species diversity of irrigated vegetation was found at all levels of the community,the species diversity of shrub vegetation is the highest,while the herb species has the lowest species diversity.?2?Population structure and dynamic changes of arbor dominant populations in dwarf bamboo environments with different densities:The percentages of individuals of different age classes in the density of 2?16.75±7.27 ramet/m²?bamboo cluster environment were the largest among the dominant populations?Carpinus viminea Wall.Sorbus folgneri?Schneid.?Rehd.?,which have higher survival rate of individuals and more stable population structure.As the density of bamboo tussock increase,individual mortality increased and its structural stability weakened.While the dominant population of Eurya nitida showed the highest percentage of individuals of all ages in the density of5?101.35±10.97 ramet/m²?,and the individual survival rate was higher,and the population structure was more stable.And further calculate the overall age structure dynamic index(V_pi)of dominant populations in bamboo environment with different densities?without considering external interference?,and dynamic indexV_pi^'?disturbed by external random interference?,the results showed thatV_piandV_pi^'are positive values,andV_pi>V_pi^',indicated that the overall performance of concentrated dominant populations in the five groups of density bamboo environment for the growth type,the population is more sensitive to external disturbances.?3?Early renewal of seedlings of dominant tree species in bamboo clusters of different densities:Through control experiments,it was found that the environmental factors were different in bamboo clusters of different densities.With the increase of bamboo density,litter thickness,soil temperature,and soil moisture showed a trend of increasing;There was a significant difference in the occurrence of seedlings of the dominant species?Carpinus viminea Wall.?in different bamboo densities,with the dwarf bamboo density increase,the number of seedling of Carpinus viminea was Significantly reduced.The relationship between bamboo environment and the number of seedling initiation was analyzed,it showed that the bamboo density,bamboo height,bamboo cover,litter thickness,soil temperature,soil moisture and seedling germination were significantly negatively correlated;we analyzed the dynamic life table of seedling,and found that after the age of 6 years,the effect of the dwarf bamboo on seedling mortality has increased,the mortality of seedlings in 0%was significantly less than the other three groups;There were no significant differences in the effects of different densities of bamboo tussock on seedling height and leaf development.Overall,the dense growth of undergrowth bamboo is not conducive to the occurrence of seedlings,and has a negative impact on the early renewal of seedlings.