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Response Of Natural Secondary Forests Structure And Soil Nutrients Dynamics To Thinning In The Qinling Mountains

Posted on:2023-10-14Degree:MasterType:Thesis
Country:ChinaCandidate:L X LiuFull Text:PDF
GTID:2543306776486974Subject:Ecology
Abstract/Summary:PDF Full Text Request
The Qinling Mountains is an important ecological barrier in Central China,with superior natural environment and abundant plant resources.However,since the logging interference in the 1970 s,a large area of low-quality and low-efficiency secondary forests have been formed,and the stand stability is poor.In order to improve the stand quality,the thinning experiment was conducted in the selected management area in 2013,in order to deeply understand the effect of thinning on the natural secondary forest in the Qinling Mountains and its dynamic change characteristics with time,so as to provide a scientific basis for the formulation of natural secondary forests thinning measures and the improvement of stand quality.Taking the typical natural secondary forest in Huoditang Forest Area of the Qinling Mountains as the research object,this study set up standard plots with five thinning intensities(CK,Thinning0%;T1,Thinning 15%;T2,Thinning 30%;T3,Thinning 45%;T4,Thinning 60%),and analyzed the community survey data and soil measurement data of three periods before thinning(2013),4 years after thinning(2017)and 8 years after thinning(2021).The thinning effect and time dynamic change law of the natural secondary forest in the Qinling Mountains after different thinning intensity treatment were studied from four aspects: the stand structure,understory plant diversity,understory regeneration diversity and soil nutrients.The results show that:(1)Light thinning(15%)can promote the growth of natural secondary forests,improve the horizontal distribution pattern,make the forest grow to the dominant state,increase the spatial isolation of tree species,and effectively improve the quality of the forest.The growth rate of average DBH and average height of the stand was the highest at the time of light thinning.Light thinning can make the stand tend to be evenly distributed.With the increase of thinning intensity,the trend of stand growth to inferior state weakened after 4 years of thinning,and the trend of stand growth to sub dominant state increased after 8 years of thinning.The increasing trend of spatial isolation degree of stand species was the strongest in light thinning.(2)Light thinning is beneficial to improve the diversity of understory shrub,herb and tree regeneration,and plays an important role in strengthening the stability of natural secondary forests community and realizing the sustainable use of forests.Thinning can increase the number of shrub and herb species under the forest,and the number of species increases first and then decreases with the thinning time.After 4 years of thinning,all thinning treatments improved Margalef richness index,Simpson dominance index,Shannon-Wiener diversity index and Pielou evenness index of understory shrubs,and light thinning had the greatest effect.The above four species diversity indexes of herbs also increased at light thinning.Light thinning can improve Margalef richness index and Shannon-Wiener diversity index of understory tree regeneration.(3)Moderate thinning(30%)is helpful to maintain soil fertility and improve soil quality of natural secondary forests.Thinning significantly reduced the contents of soil organic carbon,soil total nitrogen,soil total phosphorus,soil available nitrogen and soil available phosphorus in each soil layer of the stand,and the nutrients content decreased with the increase of thinning intensity.Moderate thinning can significantly improve the availability of soil phosphorus mineralization in 0 cm~40 cm soil layer and soil nitrogen mineralization in 40 cm~60 cm soil layer after 4 years of thinning.The stand productivity of natural secondary forests in Qinling Mountains is mainly limited by nitrogen,and moderate thinning can slow down the limitation of nitrogen.
Keywords/Search Tags:Thinning intensity, Stand structure, Plant diversity, Regeneration, Soil nutrients, Dynamic effect
PDF Full Text Request
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