Responses Of Understory Vegetation And Regeneration To Changes In Stand Density Of Pinus Tabulaeformis Natural Forest

The response of forest ecosystem to the environment and internal factors is all-round and multi-channel.The forest density is the artificially controllable internal factors of the forest ecosystem,which is closely related to the small environment within the forest,the stand structure,the succession process of the forest ecosystem and the renewal changes.Reasonable forest density is a key element in the structure and function of forest ecosystems,and it has practical guiding significance for the determination of technical indicators of near-natural forest management.This study takes the natural secondary forest of Pinus tabulaeformis in Xiaowenshan Farm of Guandishan Forest Region as the research object.The typical plot survey method is used to analyze the influence of stand density on understory vegetation and regeneration,also explore the regulation mechanism of forest community building species on the overall composition of forests.The results showed that:(1)As the stand density decreased,the plant composition of the undergrowth and shrub layer showed significant changes,the shaded plant species decreased and the positive plant species increased.The high-density stands are distributed under the shade plants,and the low-density stands are distributed under the positive plants.The medium-density forests are beneficial to the growth of many functional plants.(2)The stand density has a significant impact on the undergrowth species diversity index.The diversity index is low at high density forest.The diversity index is higher but the uniformity index is tend to decrease in low stand density forest.In the medium density forest undergrowth species diversity index and uniformity index are higher,and it can maintain species diversity.(3)The effect of stand density on the regeneration of forests is not only the change the density of the seedlings,but also the change the age structure of the seedlings.As the stands density decreased,the density of understory regeneration gradually increased.However,the high-density and low-density perennial regeneration seedlings have lower density and lower survival rate.The medium-density can maintain the renewal density and multi-age structure of Pinus tabulaeformis and Quercus liaotungensis,which is conducive to the formation of multi-generational forests and needle-wide Mixed forest.(4)Stand density has a significant effect on the growth,biomass and distribution of under-forest regeneration seedlings.Low forest density can maintain high biomassaccumulation and ground diameter growth,and high-density forest biomass distribution tends to leaves,low-density forest biomass distribution tends to roots.(5)For high-density forest stands,we should take reasonable tending measures to increase species diversity,promote forest stand renewal,and build multi-aged forests and coniferous and broad-leaved mixed forests.