Study On Land-Cover Change In Wind-stricken Area Of Changbai Mountain

On August 28,1986,the strong typhoon 15 struck the Changbai Mountain Nature Reserve.The original forest at 750-2,000m elevation on the west and south slopes of Changbai Mountain was severely damaged,resulting in a large area of wind collapse,with an area of 11,386hm~2.It is the first time that this strong typhoon has been observed and recorded of the humid forest area in the middle latitude in China,and there is little research on the mechanism of land cover change after typhoon disturbance.The formation of Wind-stricken area transformed the original forestland into grassland,and the natural environment and biodiversity also changed.According to the general succession law,the pioneer tree species,such as Larch and Birch,were first grown in Wind-stricken area.But through reading the literature and field investigation,it was found that the Wind-stricken area was first successed to meadow,and then the successional to shrub meadow,which was not consistent with the general succession law.In view of the multiplicity of plant community succession direction and the local characteristics of succession law,there is also uncertainty in land cover change.This study takes the Wind-stricken area on the southwest slope of Changbai Mountain as the research object.First of all,based on the vegetation survey data of long-term sample land,the remote sensing data of 7 periods before and after the wind disaster,through visual interpretation,we explore the land cover change in the Wind-stricken area of 30 years after the typhoon.Then we use the forest landscape model LANDIS PRO to simulate the succession dynamics of vegetation on different landtypes in the next 300 years,and reveal the changing law of landtypes during the natural recovery process in the Wind-stricken area of Changbai Mountain,and get the following main conclusions:(1)Results of 30 years Land cover change in Wind-stricken area of Changbai Mountain:Using ENVI5.0 software,according to certain classification system and classification principle,we perform visual interpretation on the 7 periods remote sensing images before and after the typhoon to obtain the land cover classification map.The land cover changes are mainly herbaceous and shrub,Birch forest,coniferous forest,broad-leaved forest,water body.By using ArcGIS10.2 statistical analysis,the general trend of recovery over the past 30 years is as follows:The area of herbaceous shrub decreases,the area of arbor increases,and the recovery rate of broad-leaved forest is faster than that of coniferous forest and birch forest.The entire study area is gradually formed by small and fragmented patches,and the recovery sequence is first herbaceous shrub,followed by Arbors.(2)Results of the trend of the land cover change in the next 300 years in wind-stricken area of Changbai Mountain:Using LANDIS 6.0 model,based on field survey data,through initialization and parameterization settings,we predicte the direction of vegetation succession and land cover change in the Wind-stricken area of Changbai Mountain in the next 300 years.The analysis results show that the Basal Area(BA)of tree species first increases and then decreases,and the Tree Density(TD)shows a continuous downward trend,and there are differences among different tree species and different landtypes.By using LANDIS PRO statistical analysis,it is found that the time of different tree species to reach the top of succession is different,ABIESNEP,BETULARM,LARIXOLG and PICEAJEZ reaching the top of the succession time is 200 years,200 years,250 years and 300 years.(3)Tests of the simulation results of the model:The BA of tree species in field investigation is compared with that simulated by LANDIS model in 2015,and the result is P>0.05.That means there is no significant difference which indicates that the simulation results are reliable and can be used to predict the vegetation succession and land cover change in the next 300 years.(4)Countermeasures and suggestions on rational Land use Planning in Wind-stricken area of Changbai Mountain:As a result of the existence of disturbance factors,the effect of natural recovery in the study area is not ideal,on this basis,through artificial afforestation,we can promote the land use in the research area to be more rational.According to different types of land use,we should adopt corresponding measures and methods according to local conditions.The herbaceous area should be strictly ground,regularly clear,to provide survival space for seedlings;a fire isolation zone should be established in coniferous forest area;as for the broad-leaved forest area,we should pay attention to the protection of the secondary forest and follow the principle of"planting the conifers and protect broad-leaved trees";Because of its abundant provenance,Betula forest area can protect provenances and rely on natural recovery with mountain closed to cultivate forests.In the short and long term recovery process,land use should be rationalized to promote forest ecosystem stability.