The Bearing Of Biomass And Its Spatial Distribution Evaluation In Yanhe Basin

Biomass is the key variable of characterization vegetation ecosystem, the formation and spatial distribution of biomass is an important controlling role for regional ecosystem processes and functions of the system. In natural conditions, the biomass that the specific site environment can carry has certain threshold. To study potential biomass and space distribution, and analyse the biomass bearing capacity of the environment,can help the further research for regularity of vegetation restoration. The study based on the existing research, chooses Yanhe River catchment as a case study and choose natural ecosystem as a reference, to analyze the relationship between natural vegetation biomass and environmental factors in catchment, a prediction model is developed for the natural vegetation potential biomass and is used to predict the spatial distribution of potential biomass in the catchment. In addition, By using remote sensing data to predict the actual biomass and its spatial distribution in the catchment. Then the potential biomass is taken as a reference and compared with the reality biomass to evaluate environmental biomass carrying condition of catchment by spatial analysis. The results are as follows:(1) In this study, the vegetation investigation and biomass sampling to collect biomass of natural vegetation by using environmental stratification sampling techniques. Then using generalized additive model (GAM) and in combining with GIS spatial analyst to analyze the relationship between natural vegetation biomass and environmental factors in catchment. A prediction model is developed for the natural vegetation potential biomass. The model shows, the effects of potential biomass mainly affected by the proportion of temperature and season,Slope positions,average temperatures of vegetation grows season and the soil moisture content, and the proportion of temperature and season is the best influence factors. The simulation result of spatial distribution of potiential vegetation biomass in Yan river basin shows that actural biomass varies obviously with the change of environmental gradient, averger potential biomass goes down little by little from 8.03 t / hm2 to 4.09 t / hm2 and 1.97 t / hm2 respectively.(2) Based on the field survey biomass data of different vegetation types, combining with the vegetation index MSAVI,NDVI,PVI extraction based on the TM images. Establish the GAM model on measured biomass data and remote sensing vegetation index. The model shows, The actual biomass mainly by MSAVI and NDVI in Yanhe River catchment, the influence to model MSAVI is greater than NDVI. The simulation result of actural biomass distribution in Yan river basin shows that actural biomass varies obviously with the change of environmental gradient, averge actural biomass reduce gradually from 6.14 t / hm2 to 4.92t/ hm2 and 4.35t/ hm2; Respect- ively from southeast to northwest, the gap between actural and potential biomas becomes larger and larger by comparing with potential biomass.(3) Using ARCGIS spatial analysis method, the potential biomass is taken as a reference and compared with the reality biomass to evaluate environmental biomass carrying condition of catchment. The results showed that the area of over biomass capacity takes up 57% of entire area in Yanhe basin. From the space distribution, potential vegetation biomass is higher than the reality of vegetation in the southeast of Yanhe River catchment, vegetation have better growth potential; But in the north-central region, actural biomass is more than potential biomass and the difference between them is increasing gradually, the overload of environmental biomass is severe and the degree of artificial vegetation degradation is high.(4) In this paper, the overload regions of biomass and its spatial distribution were identified through evaluating the regional potential biomass and actural overload situation of biomass accroding to the biomass of potential natural vegetation. And the conclusion, which had the significant meanings for transformation, utilization, restoration and layout of vegetation in the watershed, equates with the fact.