Impact Analysis On Geological Condition Of Grassland Distribution In The Three Parallel Rivers Region

The Three Parallel Rivers Region(TPRR)is located on the southern margin of the Qinghai-Tibet Plateau so that it has complicated geological environment and fragile ecollogical environment,and grassland is an important part of its ecological environment,and the study of grassland distribution has great significance for understanding the ecological environment and its evolution.In view of the previous research,the distribution of grassland are mostly involved,and the geological background of carrying herb grassland growth and development is less concerned so that the mechanism of geological background impact of grassland distribution is unknown.Based on the remote sensing information of grassland in 2009 and 2017,this paper takes TPRR as the research object to analyze the impact of geological backgrounds such as stratum lithology,soil type,geochemical elements,topography(land undulation,elevation,slope and aspect)for grassland distribution by GIS and RS technology.The impact mechanism of geological background conditions for grassland distribution in TPRR was preliminarily revealed,and the results also provided technical support for grassland protection and treatment.The results are as follows:(1)Grassland distribution current situation and change characteristics in TPRR are summarizedIn 2017,the grassland in TPRR(eight counties of one city and two states)reached 6385.98 km2,mainly involving Deqin County,Shanpri-La County and Gongshan Dulong Nationality Autonomous County.During the period from 2009 to 2017,the grassland had the largest increase and the fastest increase in Gongshan Dulong Nationality Autonomous County;the grassland had the largest reduction and the fastest degradation rate in Ninglang Autonomous County and Lanping Bai Pumi Autonomous County in TPRR.(2)Impact of geological conditions on grassland distributionDifferent from the parent rock,the physical and chemical properties of the soil formed are also very different,which restricts the distribution and growth of a certain type of planting to a certain extent.The relationship between the three can be lithologic-soil-plant system.It is stated that the diagenetic parent rock has different soils and different mineral nutrient contents,which in turn affects the growth and development of vegetation.The grassland in TPRR is mainly developed in sandstone(quartz sandstone,siltstone,fine sandstone,etc.),slate and basalt and granite,and sandstone grassland is mostly developed.The sandstone often has a sand-like structure,mainly containing SiO2,Al2O3,FeO,CaO,P2O5,and the soil is fine,texture soft,structure loose,good ventilation and water permeability by the soil formation,and contains nutrients such as Ca,Fe,and P required for plant growth.The slate mainly contains SiO2,Al2O3,K2O,MgO,CaO,TFe2O3,and the loam of soil is generally loam that the clay,silt and sand are moderate by the soil formation,and has the advantages of well ventilated,water-retaining and water-insulating of clay and sand and also contains nutrients such as K,Mg,Ca and Fe.The basalt mainly contains SiO2,K2O,Na2O,CaO,Fe2O3,FeO,MgO,and has a stomatal structure and is easy to weather,and the soil has nutrients such as K,Na,Ca,Fe and Mg required for plant growth by the soil formation;Granite mainly contains SiO2,Al2O3,K2O,Na2O,CaO,FeO,Fe2O3,MgO,which can be described as rich in plant nutrients.Different soil types lead to differences in grassland development.Grassland in TPRR is mainly developed in dry cinnamon soil,alpine cold desert soil,alpine meadow soil,subalpine meadow soil,brown coniferous forest soil,new soil and marsh soil.The reasons for the analysis are:These soils are characterized by good gas permeability,good loam properties,humus accumulation,high organic matter content,and good soil fertility so suitable for herb growth.Geochemical elements are enriched to varying degrees for grassland development also has a significant impact.In TPRR,Au,K2,?CaO showed a significant linear positive correlation with grassland development;Co,Hg,Li,Mn,Nb,Ti,SiO2 showed a significant linear negative correlation with grassland development;Bi,Cd,Pb,V,and Fe2O3 were significantly parabolically related to grassland development.The reasons for the analysis are:K and Ca,which are rich in K2O and CaO,are essential nutrients for plant growth,which are beneficial to photosynthesis,enzyme action and plant tissue composition in plants,and can promote herb growth.Hg and Li are toxic metal elements,which strongly inhibit herb growth,while Co and Mn are micronutrients required for plants,and Co(excess)and Mn(excess)also inhibit herb growth.Cd and Pb are also toxic metal elements,and it may promote herb growth when their enrichment is low,but its toxicity significantly inhibits herb growth when they are enriched to a certain extent.V and Fe in Fe2O3 are the micronutrients needed for plant growth,and it can promote the growth and development of the herb when a small amount is ingested,but too much will lead to imbalance of nutrients such as K,Ca and P,and inhibit the growth of herbs.The enrichment of Au,Bi,Nb,Ti,and Si02 may cause soil nutrient,texture change,and imbalance of other nutrients,which may affect grassland development.The impact of topography on grassland development is:Grassland significant development in the undulating mountain,the altitude of 3500(inclusive)?5000m,the aspect of the east slope,the southeast slope,the south slope and the southwest slope,but the slope is less obvious than the topography,elevation and aspect.The reasons for the analysis are:There are more precipitation in mountainous areas,good hydrothermal conditions,and less impact on human activities in mountainous areas,so it is suitable for the growth of herbaceous plants that are resistant to poorness,cold,drought,wind and radiation.