Evaluation On The Effect Of Tending And Transformation Of Larix Gmelinii Natural Over-felled Forest

Affected by natural disasters and human factors for a long time,the forest resources in Daxing an Mountains have been harvested in large quantities,the stand structure tends to be single,the ecological function is low,and the forest quality has declined.Therefore,the sustainable management of natural secondary forests in Daxing an Mountains needs to be solved urgently.Taking the natural secondary forest in Chaocha Forest Farm of Daxing an Mountains in Inner Mongolia as the research object,this paper adopts different transformation methods,including artificial promotion of regeneration after selective cutting,artificial promotion of regeneration,induction of mixed forest and tending thinning,and different tending thinning intensities(10%,20%,30%,40%)after five years of natural regeneration,analyses the stand growth of Larix gmelinii secondary forest under different transformation methods.The effects of stand structure,undergrowth plant diversity and biomass,and soil physical and chemical properties are as follows:(1)Compared before and after 5 years of forest transformation,the annual growth of DBH,tree height and volume increased significantly.Among them,natural regeneration was promoted artificially,and regeneration was promoted artificially after selective cutting.The growth of sample plots was good,which was beneficial to stand growth.The annual average growth of DBH was 0.64 cm,0.11 cm,0.56 cm,0.16 cm and 0.04 cm,and the annual average growth of tree height was 1 m,0.31 m,0.66 m,0.34 m and 0.04 M.The annual growth of individual stand volume was 0.0089 m3.hm-2,0.0015 m3.hm-2,0.0050 m3.hm-2,0.0017 m3.hm-2,0.0007 m3-hm community structure.Gradually succession to Larix gmelinii as the main forest type,non-purpose tree species Populus davidiana gradually degraded;and the control plot without any transformation of natural growth in 2012 was 7 falls 3 birch+poplar,now 5 falls 4 birch+1 poplar,forest structure degradation,the proportion of Larix gmelinii decreased.(2)Forest stand improvement has improved the diversity of understory plants and increased the biomass under the forest.The Simpson species diversity index,Shannon-Wiener index,Pielou evenness index and species richness index of different undergrowth vegetations were improved after transformation,and the differences were significant under different transformation methods(P<0.05).The number of species and the number of individuals in the understory plants increased by 1,19,2,8,respectively;the shrub layer of bilberry was the dominant species,accounting for 36%of the important value of each plot,and the herbaceous layer had no prominent dominant species,and the mixed forest was induced.The impact of technology on the vegetation layer diversity index is most pronounced.(3)Forest stand improvement has improved soil quality.The bulk density of soil physical properties is significantly negatively correlated with soil porosity.The larger the porosity,the smaller the bulk density,and the other physical properties have no obvious regularity.It is necessary to continue the observation and study.The chemical properties of different soils:the total phosphorus of soil under different transformation modes(P),available phosphorus(AP),available potassium(AK),and ammonium nitrogen(NH4-)were higher than the control plots,but there was no significant relationship between the different methods.(4)The medium-strength thinning(30%)of the plots has the highest average tree height and average DBH growth,and excessive intensity thinning leads to a decrease in forest growth.The 30%tending intensity can increase the stand volume and adjust the spatial pattern of the forest to significantly reduce the forest mortality rate.The Shannon-Weiner index Simpson index increases most at 30%intensity;the undergrowth vegetation layer organism with 40%stand in the thinning intensity The amount is better;the effect of 30%tending intensity is the best in the change of soil physical and chemical properties.Based on the study and analysis of the gro,wth status,vegetation diversity and soil physical and chemical properties of Larix gmelinii secondary forest after different transformation,the effects of different transformation modes on the overall stand were obtained.According to the different effects of different transformation modes,the management measures suitable for stand growth of artificial promotion regeneration technology were selected to provide theoretical basis for the transformation of Larix gmelinii secondary forest.And the experimental basis.