Study On Regeneration Characteristics Of Platycarya Longipes Population In Karst Ecologically Fragile Areas Of Guizhou

Karst ecosystem is a typical fragile ecosystem in south China.As one of the main constructive species of karst forest in guizhou,the study on natural regeneration of platycarya longipes can not only fill the gap in the research on natural regeneration ability of platycarya longipes population in karst ecologically fragile areas,but also provide scientific theoretical basis for vegetation restoration and protection in karst areas.Based on this,this study selected representative karst ecologically vulnerable areas in kaili city,libo county and shibing county,guizhou province by using the"spatio-temporal intersubstitution method".Platycarya longipes was taken as the research object,and its population renewal characteristics were studied through laboratory experiments and field surveys.The main research results are as follows:?1?Characteristics of growth and development of the platycarya longipes:the ground diameter of seedlings planted in the room of platycarya longipes increased slowly with the increase of time,and the high growth rate of seedlings was relatively slow,and the daily increment was 0.142cm/d.The DBH and tree height of the wild platycarya longipes were the fastest growing in the young age,then decreased in the young age,then increased in the middle age,and then decreased in the old age.The DBH,tree height and total growth of platycarya longipes in kaili,shibing and libo all increased with age.In different age orders,the average growth of tree height and the annual growth are different,but they basically decrease with the increase of age.?2?Reproductive characteristics of the platycarya longipes:platycarya longipes trees began to sprout in early march,and entered the leaf development stage in mid-march,and the leaf development stage in late march,and the inflorescence began to appear in early april,and the flowering stage in mid-april and the late flowering stage in early may.The flowering period ended in mid-may,the fruit began in mid-may,and the fruit was ripe in early September.The number,weight,longitudinal diameter,transverse diameter and number of seeds of the platycarya longipes were higher in the east than in the west,and higher in the south than in the north.Seeds small,average life force was 30.67%,bibulous rate is very high,seed germination condition,without any hormone,the germination rate was only 4%,with GA₃treatment could obviously promote the germination,6-BA treated seeds germination rate is still very low,IAA,NAA on platycarya longipes the germination of seeds,if you want to increase the round fruit incense seed germination rate,in a concentration of 80 mg/L best GA3 treatment.?3?Structural characteristics of the platycarya longipes:platycarya longipes population belongs to the growing population,space distribution pattern are characterized by cluster distribution,survival curve for Deevey?type curve,the population in each age mortality is basically the same.The survival function S_?i?and cumulative mortality function F_?ti?of platycarya longipeshad opposite trends,but the range of these two functions was smaller in the later stage than in the earlier stage.The change trend of the curve of death density function f_?ti?generally decreases with the increase of age level,and local fluctuation occurs.Trend of change of risk function lambda??ti?is similar to that of death rate?qx?or loss rate?Kx?.?4?Vertical structural characteristics of the platycarya longipes:the vertical structure of platycarya longipes community was clear,which could be divided into tree layer,shrub layer,herb layer and interlayer plant;On the whole,platycarya longipes was dominant in number,and the species existed in both tree layer and shrub layer,the number of shrub layer was more than that of tree layer,platycarya longipes was the dominant species in all regions.The biomass and species diversity of each vertical structure layer were as follows:the total biomass in libo limestone area was greater than that in kaili and shibing dolomite area,and the biomass in tree layer was>and the biomass in herb layer was>the biomass in shrub layer.The analysis results of species richness,Simpson index,Shannon-weiner index and evenness index showed that libo had the largest number of species,the largest diversity and the most uniform distribution of all species.Except for Carey,the number of species in shrub layer was more than that in tree layer,and the diversity was also higher than that in tree layer.?5?Regeneration characteristics of seedlings and saplings of the platycarya longipes:number of seedlings and saplings of platycarya longipes were the highest at the age of 3-4,and the number of platycarya longipes saplings decreased gradually with the growth of age.The number of seedlings and saplings of kaili and shi bing were the most in the 1-2 ages,and the number of seedlings and saplings of libo were the most in the 3-4 ages.There was a difference in the trend of seedling initiation between seedlings and saplings and seedling with open path grade and height grade.The natural regeneration initiation,ground diameter and plant height of seedling were increasing gradually with the increase of age,and the proportion of seedlings and saplings initiation was 43.7%.Germination and solid seedling trees showed a decrease with the increase of age,mainly with solid regeneration,but the germination and regeneration also accounted for a large proportion,and although there were many seedling trees,the survival rate was low,and the natural regeneration ability was poor.