Study On Effects Of Forest Vegetation Recovery Of The Spiraea Pubescens Shrub In North Region Of Yanshan Mountain

The Spiraea pubescens shrub is a major plant community type in north region ofYanshan Mountain, which is a degraded ecosystem type formed by the interference oflong-term human activities such as deforestation, grazing and so on. Scientific andreasonable management measures can not only inhibits the further degradation of shrub,but also initiate a progressive succession and vegetation restoration. Taking the Spiraeapubescens shrub in north region of Yanshan Mountain as test object, this paper studiedeffect of different vegetation restoration measures on the spiraea pubescens shrub,including closure and arbor species introduction. The results were as follows:(1)The closure imposed more influence on the species composition of herbage thanshrub. It caused the rate of annual herbs to decrease and that of perennial herbs toincreased.Closure led to a decrease in important values and quantity of dominant speciesand sub-dominant species. The Jaccard similarity index among stages of closure was low.With the increasing of the closure period, the richness index of herb species increased, andthere were no distinct change in the Simpson index, the Shannon-Wiener index and thePielou index. Moreover, the biomass of shrub layer and herb layer had increasedsignificantly after closure had been implemented.(2)The introduction of arbor species promoted the formation of arbor layer. Thesurvival rate of Pinus sylvestris var. mongolica, Pinus tabulaeformis Carr, Quercusmongolica reached87.98%,93.79%,66.69%. DBH and height of7year Pinus sylvestrisvar. mongolica, pinus tabulaeformis Carr were respecting0.98-6.36cm,0.42-2.1m. Theindividual biomass for Pinus sylvestris var. mongolica, Pinus tabulaeformis Carr, Quercusmongolica was234.35g,2018.3g,1857.36g. The canopy density of arbor shelter forestwas0.1-0.36.(3)In the horizontal direction, the root length, root surface area, root volume, rootbiomass and average root diameter of four species was gradually decreased with theincrease of horizontal distance. The root horizontal extension of Pinus sylvestris var.mongolica and Larix principis-rupprechtii were the biggest. The biomass of Quercusmongolica root system distributed in0-20cm, the biomass of Pinus sylvestris var.mongolica, Pinus tabulaeformis Carr and Larix principis-rupprechtii root system distributed in0-50cm. In the vertical direction, the root length of all soil depth for Quercusmongolica was lower than others. The root length, root surface area of Quercus mongolica,Pinus sylvestris var. mongolica and Pinus tabulaeformis Carr showed the tendency ofincrease then reduce. The root biomass for Larix principis-rupprechtii was concentrated insoil of in0-20cm. The others were concentrated in soil of0-40cm. The root length androot surface area with diameter of≤3mm accounted for the greatest propotition, whilethe root volume with diameter of＞3mm accounted for the greatest propotition aboutfour tree species. With the increase of root diameter, the proportion of main root surfacearea and volume increased.(4)Closure had significant effects on species composition and productivity of herbvegetation in Spiraea pubescens shrub and initiated a progressive succession. It gives us acertain amount of reference on appropriate tree replacement. Afforestation Measurespromoted to the ideal community structure which could be achieved and had importantsignificance for forest vegetation recovery.