The Study Of Natural Population Regeneration Of Decayed Seabuckthorn Forests In Loess Area Of North Shaanxi Province,Northwest China

The study was to illustrate the environment condition of natural renewal of decayed Sea-buckthorn forests in northern Shaanxi Province based on an investigation of natural regenerative condition of Sea-buckthorn forests after having large-area death in Wuqi County,Shaanxi Province,using renewal rate,reforestation percentage and sprouting rate as standards to measure the value of recovery ability,by using one-way Anova method of square-deviation(SD),regression fitting,static life table,survival analysis,systematical clustering and rendundency analysis methods.The research results of regenation characteristic,population structure and dynamic,the effects and the response mechanism of environments of decayed sea-buckthorn forests in loess plateau of northern Shaanxi Province:(1)Plant height,basal diameter and death rate of decyed seabuckthorn population were significant difference in three distrubutional modes,population in scattered type and medium type died naturally while the majorty of dead population occurred when they are in early succession and later succession in conventrative type.The best regenaraion conditions of medium density was the best while high density was poor.(2)Renewal rate of sea-buckthorn was significant difference in different slopes(P<0.05).The condition with a high survival rate and a huge amount of renewal young trees were in semi-shady slope.Gradient has no significant effect on renewal rate.The renewal rate of sea-buckthorn showed the first peak(gentle slope)and the second peak(extremely steep slope)on shady slope,while the renewal rate showed gradually decrease with the grade increase of slope on sunny slope.Micro-relief has a significant impact on natural renewal of declining Sea-buckthorn forests(P<0.05),the best condition of asexual reproduction potentiality of seabuckthom is platform.(3)The seabuckthorn population can be divided into different regeneration types by the standards of renewal rate and renewal density.Soil moisture in forest may be ranked in order nonrenewal,slightly and moderately renewal,severely renewal.Soli nutrient in forest including siol organic matter,total nitrogen,available nitrogen,may be ranked in order slightly renewal,moderately and severely renewal,nonrenewal,which draw a conclusion that the seabuckthorn regeneration consumed soil moisture,while soil nutrient improved soil quality.(4)The results of RDA indicaterd the cumulative information kept in two ordination axes was 56.9%in the total information,the first ordinate axis expressed the hydrothermal condition,the second ordinate axis expressed the comprehensive influence of spatial pattern and soil nutrient.All environment fators,siol organic matter,total nitrogen,available nitrogen,soil moisture and slopes have great influence on vegetation distribution while altitude,grandient and micro-topography have little influence.(5)The topographic conditions of natural renewal of declining Sea-buckthorn forests were platform,shady slope and semi-shady slope,firstly,it required the good soil moisture condition and soil nutrient condition.