Study On Forest Ecosystem Restoration And Reconstruction Technique In Yalong River Basin

The author of this paper aims to study the vegetation restoration in the Yalong river basin.In this study,with long term located and semi-located observation in field, combining with the special environmental and resources features,verification of vegetation restoration's environmental media features was carried out;the excellent materials of vegetation restoration were selected based on the native plant under the guidance of Ecology and Forestry;the fast restoration technique for mountainous vegetation of different types were selected,integrated and optimized in view of the capricious environment in Yalong river basin;ecological function evaluation was carried through with the constructed fast restoration models and the first-hand data were got,the achievement of which will directly provide technical and theoretical support for the vegetation restoration in Yalong river basin and the areas nearby.The main content and conclusions of this study are as follows:1.According to the special ecological environment of the cutting-blank in the Yalong river basin,the soil temperature and moisture,which affect vegetation restoration greatly,were checked:find out soil temperature's changing tendency with the season, altitude and interdiumal change,which made clear the vertical distribution regularity of moisture in soil in the cutting-blank and its characteristics with the season and interdiumal change.The practice showed that:temperature of soil in the near-surface layer changes greatly;the soil temperature declines with the elevation of altitude;the thermal diffusivity of soil in the cutting-blank at the altitude of 3,900m is above that at the altitude of 3,700m;the plateau loses water from May to August while profits water after September;the profit and lose of water directly influence the preserving rate of different vegetation restoration stages.2.Choosing and equipping vegetation restoration materials are the premise and basis of ecological restoration.This paper selected many kinds of native species and established fast propagation techniques:(1) To propagate spruces fast,1 year old branches of 3～4 years old spruce should be chosen for cutting propagation,and the matrix of CombinationⅠ(peat 1/2+ carbonized rice husk 1/2 + 4‰compound fertilizer) or CombinationⅡ(peat 1/2+ bark 1/2 + 4‰compound fertilizer) should be better.And the temperature should be 20～25℃while the exogenous rooting hormone should be ABT.(2) About Populusschneiderivar tibetica,while 1～3 years old branches with length of 15cm were used for cutting propagation in middle March with the planting space 20cm×15cm,the effect is better.(3) For Populous beijengensis,branches of 18～24cm long is better for cutting propagation.2～8 years' old mother trees are in their growing peak period,with much nutrient and strong reproductive capacity.Different factors' affect on height and survival height of seedling:species＞age of branches＞field for cutting propagation＞immersing dealt＞disposal＞plastic film.(4) With regard to crabapple seed seedling,while seeds are immersed in formalin solution (concentration=0.15%) for 15～30 minutes or in potassium permanganate solution(0.3%) for 15 minutes,the germination rate is higher and the quality is better.3.This thesis observes and studies the growth of renewed seedlings systematically, and puts forward renewing techniques for spruces and firs in autumn.At the same time, through selecting plant materials in vegetation restoration,Populus schneideri var. tibetica forestation trial and crabapple vegetation renewal trial were carried through, which all acquired good effect and can provide scientific basis and practical technology for the vegetation restoration and forestation at high altitude:(1) Plant fixed tests were implemented in the five experimental plots in the Xilin area of Wengda river,Rilin area of Luohuo and Lamagoulin area of Daofu.Through observing the phonological and meteorological factors of Picea balfouriana,Abies squamata Mast.and Picea aurantiaca var.rtroflexa termly,it showed that the phonological phase and growth of every specie seedling are closely related with temperature,and the height growth law takes on an N growth model of "slow-fast-slow".The growth of total height,current year height and crown width of Picea aurantiaca var.rtroflexa termly and Picea balfouriana is as Daofu＞Luhuo＞Wengda.The renewed seedlings' annual height growth of different grades takes on a W growth model of "high-low-high-low".The preserving rate of renewal in autumn is a little lower than that in spring.The preserving rate is 46.8%after three years without replanting,testing according to effective renewing area of forestation.Tests showed the influence of each factor on preserving rate is renewal season＞renewal species＞numbers of seeding＞blank disposal＞seedling disposal.(2) Populus schneideri var.tibetica is the ideal specie for forestation in strath at high altitude.The specification of soil preparation is alpine meadow soil 50×50×50cm,foreign soil of overflow land 50×50×60cm,with each point weighing 10kg:the season for forestation is when the soil thaws,that is from April 5^th to April 20^th:Populus schneideri var.tibetica seedlings for transplantation should be of first or second grade and 2 years old,with unabridged root,1.0cm long stem and over 1.0m height;about density and method for forestation:plant seedlings in subalpine meadow soil,the initial planting density should be 74 trees per mu with the space of 3×3m by hole planting;plant seedlings on overflow land,as a result of much gravel and blown sand,the initial planting density should increase to 111 trees per mu with the space of 2×3m by hole planting.(3) Tibetan crabapple belongs to the native broadleaf species in the test plots,with multipurpose, strong stress resistance,early germination characteristics.The soil preparation method for vegetation restoration is point preparation before the rainy season one year ahead the forestation,and the specification of soil preparation is subalpine meadow soil 50×50×50cm or foreign soil of overflow land 50×50×60cm;April 5 to April 20 each year is good time for forestation;Populus schneideri var.tibetica seedlings for transplantation should be of first or second grade and 2 years old,with unabridged root,1.0cm long stem and over 1.0m height;on subalpine meadow land,the initial forestation density should be 167 trees per mu with the planting space 2×2m;on flow land,the initial forestation density can increase to 167 trees per mu with the planting space 2×2m,due to the condition of much gravel and blown soil.Point planting should be adopted for plantation, acquiring keeping the seedlings straight,the soil solid,the soil extended,no air flow, burying soil over the root soil print of the seedlings by 2～3cm.4.The natural environment is bad in the hilly area of the plateau of the Yalong river basin,so that technique for vegetation restoration is of great difficulty,with expensive cost but obvious ecological benefit.Therefore,it is very important to analyze and assess the ecological function and benefit of vegetation restoration models.This research studies the species diversity and ecological function of artificial spruce forests,the ecological benefit of vegetation restoration in burned blank,the ecological benefit of Populus schneideri var.tibetica forestation and its cost:(1) Ecological function and benefit evaluation of artificial spruce forests:the biodiversity index of the tree layer, shrub layer and herb layer in 7 years old artificial Picea balfouriana forests is 0,0.73, 1.06 respectively,and the species richness index is 0.22,1.52,2.61 respectively.The biodiversity index of the tree layer,shrub layer and herb layer in 17 years old artificial Picea balfouriana forests is 0,0.85,1.20 respectively,and the species richness index is 0.22,2.17,and 4.99 respectively.The total biodiversity index and species index increases 14.53%and 70.05%respectively.It also has obvious increase in soil improvement,with soil organic matter increased by 40.52%,nitrogen by 40.32%,phosphor by 40.50%, potassium by 32.57%,forestland soil water storage by 5.09%;through artificial simulation of rainfall,the interception amount by layers increases evidently,especially in the early rainfall,when rainfall reaches 3mm,the interception amount by litters in Picea balfouriana forests is 1.8mm,accounting for 60%of the precipitation,while that in mixed forests is only 0.8mm,accounting for 26.7%:the soil water storage is quite different according to different forest vegetation,the adult Picea balfouriana forests＞the young artificial Picea balfouriana forests(17 years old)＞mixed forests of Picea balfouriana and birch＞the young artificial Pieea balfouriana forests(7 years old)＞birch forests.(2) Ecological benefit assessment of vegetation restoration in burned blanks:the annual average surface temperature is 5.0℃in burned blanks,1.2℃higher than that in the inner forest,and its annual range of surface temperature is 5.0℃over that in forest: the annual average temperature of air and annual range of burned blanks is 0.2℃and 0.6℃higher than that of inner forest resp ctively:in aspect of soil temperature,within 0～20cm surface layer,the annual average temperature in burned blanks is 1.2℃～1.3℃higher than that in inner forest,but 0.6～2.4℃lower in the coldest month in winter,the change and difference tendency of which is consistent to that of soil surface temperature and ail temperature:the average relative humidity at the height of 1.5m in burned blanks is 69.0%,5.0%lower than that in inner forest,while at the height of 0.2m,that is 75%, 4%higher than that in inner forest:comparing from the aspect of rainfall,the annual rainfall in burned blanks is 934.5mm,422.4mm more than that in inner forest,and the evaporation in burned blanks is 1050.2mm,493.5mm more than that in inner forest, which indicates that the interception function of canopy is distinct,reaching 45.2%of the rainfall,and the evaporation in burned blanks is far more than that in inner forest,going against the seedlings' water surplus or deficit:in view of soil's physical and chemical properties,the organic matter get lost,the soil water storage capacity and fertilizer sustainable serving ability decline in the blanks,which goes against greatly for the growth of renewed seedlings:among the enzymes in soil,activity of the urease,protease, peroxide,amylase and phosphatase weakens,catalase is enabled in black soil layer and weakened in inner soil layer,cellulose and polyphenol oxidase keep their original activity basically.Among the soil enzymes in the whole blanks,protease and peroxide have the greatest change.(3) Biological productivity and forestation effectiveness evaluation of Populus schneideri var.tibetica:the total biomass of 9 years old stand is 61.371t·hm^-2, 425.468 t·hm^-2 lower than that of thick shell cherry bay forests in Dinghu mountain, 357.976 t·hm^-2 lower than that of evergreen broad-leaved forests in Heishiding, Guangdong,578 t·hm^-2,325t·hm^-2 and 328.8 t·hm^-2 lower than that of temperate zone adult forests,close with that of semitropical secondary cypress-oak mixed forests and alder-cypress mixed forests 75.869 t·hm^-2,61.409 t·hm^-2 respectively.The stand biomass of trunk,branch,leaf and root is 32.383 t·hm^-2,6.792 t·hm^-2,3.163 t·hm^-2,19.033 t·hm^-2 respectively,taking on an change tendency of trunk＞root＞branch＞leaf.The root biomass of Populus schneideri var.tibetica is 16.84 t·hm^-2,in which root crown and big root account for 87.7%,fine root and middle root account for only 12.3%,indicating that the main root is more developed than the lateral root,and the environment improvement effectiveness is good after vegetation restoration.In view of productivity,it is 0.9511 t·hm^-2.a^-1 of 5 years old Populus schneideri var.tibetica,increasing to 6.477t·hm^-2.a^-1 of 9 years old Populus schneideri var.tibetica by 6.8 times,indicating that Populus schneideri var.tibetica enter their fast growth period when they are 7 years old,and their biomass and biological productivity multiple.After planting Populus schneideri var. tibetica,not only the vegetation restoration is accelerated,but also the forest coverage increases in the basin,consequently,obvious ecological,social and economic benefit are produced.