Evaluation Of Pinus Tabuliformiss And Robinia Pseudoacacia Thinning Effect

Forest thinning is a kind of cultivation measures on the stand density larger,its purpose is to improve the stand growth environment,accelerate the growth speed of forest trees,shorten the process maturity,improve the yield and quality of forest.It is important to study the disturbance of different tending methods and time on forest ecosystem,and to reconstruct and restore the inherent function of forest ecosystem and to realize sustainable forest management.In this study,the growth of Pinus tabuliformiss(thinning 3 years,5 years,7 years),Robinia pseudoacacia(thinning for at least 3 years,5 years and 7 years)were studied.This paper uses the CI-110 canopy analyzer obtained stand closed in time in the course of the study,to understand the spatial structure of the stand,field measurement of tree growth,species and quantity of understory shrubs and herbs of the investigation,analysis and determination of soil samples from the interior,Pinus tabuliformiss,Robinia pseudoacacia,growth and understory vegetation diversity and forest land soil quality,analysis of key indicators of different thinning stage and thinning effect,found thinning cycle.It was found that the tending effect of Pinus tabuliformiss and Robinia pseudoacacia was different in different tending thinning stage.The results are as follows:1.The effect of thinning on canopyAfter thinning,the leaf area index of Pinus tabuliformiss in fifth years decreased obviously,and showed a rising trend in the past seventh years.But on the contrary,the value of leaf area index of fifth years was the highest in the middle thinning.The transmission coefficient for radiation penetration and scattering radiation penetration coefficient reflects the stand transmittance,thinning after 5 years of Pinus tabuliformiss of DBH and crown are increasing,lead to direct radiation and scattered radiation through the permeability coefficient decreases and the transmittance decreased,so the Chinese pine forest thinning,5 years as one of the best thinning period.Comparison of Robinia pseudoacacia forest thinning stage of Robinia pseudoacacia in thinning data obtained 3 years and 7 years in the case of effective radiation can reach the maximum.The leaf angle of Pinus tabuliformiss and Robinia pseudoacacia was significantly i ncreased in fifth years,and decreased in the past seventh years.2.Correlation analysis of canopy parametersThe determination results of Pinus tabuliformiss,Robinia pseudoacacia canopy parameters by correlation analysis,found has a significant positive correlation between leaf area index of Pinus tabuliformiss,Robinia pseudoacacia and average leaf angle,direct radiation coefficient and scattering coefficient of radiation,R2 proved more significant correlation between these two species,but the correlation is more obvious,showing black locust.The correlation between leaf area index and photosynthetically active radiation was analyzed.It was found that with the increase of leaf area index,photosynthetically active radiation decreased,showing a negative correlation.3.Effects of thinning on stand growthAt the early stage of thinning,the growth rate of tree height and DBH of Pinus tabuliformiss and Robinia pseudoacacia was more obvious than that of the control stand,and the growth was more significant.After thinning of Pinus tabuliformiss,Robinia pseudoacacia under branch height,crown width,volume growth and control stand compared to no obvious growth trend,poor effect.On the basis of the average number of each stage,each growth tending growth,Pinus tabuliformiss,Robinia pseudoacacia forest tending to determine and control forest effect difference,found the best occurs during tending forest fifth years to seventh years,the worst is the control forest third years to fifth years.4.The effect of thinning on BiodiversityThe spatial structure of forest stands of Pinus tabuliformiss and Robinia pseudoacacia in different time periods will change,which will affect the species and quantity of shrubs and herbs.Pine forest in 3 years tending thinning to 5 years,only the Vitex negundo shrub species diversity index is low,seventh years,to have more species.The diversity of shrubs increased continuously during the period from 3 to 7 years,and the diversity of herbaceous species continued to rise.The diversity index of Pinus tabuliformiss forest thinning 7 years of shrub layer and herb layer,locust forest thi nning in diversity index of shrub layer 3 years maximum,the largest in the diversity index of the herbaceous layer thinning 7 years.5.The effect of thinning on soil physical and chemical propertiesThe total porosity and field capacity of Pinus tabuliformiss and Robinia pseudoacacia plantation were higher than that of ck.The p H value decreased,the contents of organic matter,total nitrogen and total phosphorus increased.