Community Characteristics Of 8 Hm~2 Permanent Plots Across10 Years In Picea Shrenkiana Forest At The Middle Zone Of The Northern Slope Of Tianshan Mountains

Picea schrenkiana forest plays an important ecological role in regulating climate,water conservation,carbon fixation and oxygen release,and biodiversity conservation.Picea schrenkiana is the single dominant species in Tianshan forest community.To reveal the problems of forest community construction and dynamic characteristics,it has become a mainstream trend to establish forest dynamic monitoring sample plots(large fixed sample plots)and continuously carry out monitoring and analysis.This research is based on data obtained from three surveys for 2009-2019 years of 8 hm~2long-term dynamic monitoring plots of Picea schrenkiana forest,the characteristic of species composition and structure,spatial distribution pattern,tree volume and carbon storage in the study area over the past 10 years were analyzed.The main results are as follows:(1)From 2009 to 2019,there was no significant change in species composition,diameter and tree height,but species renewal was slow,and the community would not change significantly in the short term.The number of individuals with DBH≥1 cm decreased from 11835(8 species,8 genera,6 families)to 10301(8 species,8 genera,5families).The average diameter,basal area of diameter and tree height increased by 2.35cm,4.55 m~2/hm~2and 2.27 m,respectively.In every five years of review,1044 and 851dead individuals and 259 and 102 new individuals were found,respectively.The average annual mortality rate was high(3.41%)and the average annual recruitment rate was low(0.65%).(2)The number of individuals decreased with the increase of diameter class,and the frequency of tree height decreased with the increase of height in Picea schrenkiana forest.The survival and death individuals in small and medium diameter class(diameter class 1-20 cm)was more than that in large diameter class(diameter class greater than 20cm);The number of dead individuals was the most within 1-5 cm of the small diameter class,while the number of middle and large diameter class individuals was less;Most of the new individuals were within 1-2.5 cm in diameter.In every five years of review,the proportion of individuals with diameter 1-20 cm decreased,while that of individuals with diameter greater than 20 cm increased.The total tree frequency decreased with the increase of height,and the proportion of individuals with tree height greater than 10 m increased with the increase of time.(3)The overall spatial distribution pattern of Picea schrenkiana forest sample plot showed aggregation distribution in the scale of 0-40 m,but the aggregation intensity gradually decreased with the increase of scale.The distribution of dead individuals was aggregated in the scale of 0-35 m,and then turned to random distribution;The survival and death individuals showed aggregation distribution at different diameter stages,and the aggregation degree decreased with the increase of size.There was a positive correlation between the middle and small diameter classes,and a negative correlation or no correlation between the large diameter class and the small and medium diameter class.(4)In the past 10 years,the volume,biomass and carbon storage of the dominant species in the sample plot increased,but the distribution of different diameter classes was different.Every five years,the volume increased by 29.17 m~3/hm~2and 39.99m~3/hm~2respectively,the biomass increased by 24.47 t and 22.34 t respectively,and the carbon storage increased by 11.99 t and 10.95 t respectively.The largest volume was in20-30 cm diameter class,accounting for 34.56%-35.17%,and the smallest volume was in 1-10 cm diameter class,accounting for 1.61%-2.55%;The biomass and carbon storage were the largest within 40-80 cm,accounting for 75.50%-78.53%of the total,and the smallest within 1-10 cm,accounting for 0.02%of the total,the carbon sequestration potential of Picea schrenkiana is high.In conclusion,the analysis of the community dynamic characteristics and carbon storage capacity of dominant species of Picea schrenkiana under the condition of global climate change in 8 hm~2dynamic monitoring plot of Picea schrenkiana forest will contribute to the protection and sustainable management of Picea schrenkiana forest in Tianshan Mountains,and accurately assess the contribution of Picea schrenkiana forest to the carbon cycle of Xinjiang ecosystem,It provides a theoretical reference for the study of carbon cycle of forest ecosystem in Xinjiang.