| Stellera Chamaejasme L.,a perennial herbaceous plant,lives through winter in the form of underground rhizome storage.So far,it is the main toxic species on the grassland,distributing on the alpine meadow,sandy and degraded grassland of northwestern,southwestern and northeastern China,and becomes the important indicator of alpine rImeadow degradation.Its propagation has brought great troubles to the local animal husbandry and ecological balance,which requires urgent and comprehensive study,and especially solution to the issues about Stellera Chamaejasme L.community's distribution,migration patterms,local environmental factors,adaptabilities and etc.This study is targeted on Stellera Chamaejasme L.'s distribution characteristics,spatial patterns,environmental factors,potential distribution area,prevention and utilization of Haibei Tibetan autonomous prefecture,directed,and aimed at completing the technological frame and theoretical system of Stellera Chamaejasme L.research.The main research contents are in five aspects:(1)Stellera Chamaejasme L.'s spectral and phenological characteristics were systematically analyzed;The technology and theory of remote sensing extraction were established and the sensitive bands for extracting Stellera Chamaejasme L.based on MODIS images were determined from the spectral differences between Stellera Chamaejasme L.and other green plants,correlation between Stellera Chamaejasme L.coverage and spectral band,and the unique spectrum of Stellera Chamaejasme L.in the blooming period.(2)According to the sensitive bands of MODIS,combined with the correlation and difference in(1),the optimal method was found for extracting Stellera Chamaejasme L.from MODIS image.The distribution of Stellera Chamaejasme L.in Haibei during the period of 2008 and 2016 was derived,from which simple statistical analysis were done,there was a gradual downward trend of the distribution of Stellera Chamaejasme L..(3)The change pattern in the period of 2008 and 2016 was obtained according to quantitative expression of Stellera Chamaejasme L.'s spatial distribution in Haibei by landscape pattern indicator and the analysis of patch-level and landscape-level.The migration track of Stellera Chamaejasme L.'s spatial pattern was obtained by the calculation of the center of gravity in the whole study area and every county area.The change pattern and migration track have practical guidance meaning for the prevention and control ofstellera Chamaejasme L..(4)The environmental factors influence the spatial distribution pattern of Stellera Chamaejasme L.directly or indirectly.This study analyzed natural environmental elements which include 5 aspects and 18 factors,and human factors which include 4 aspects and 10 factors.It is of critical impact on the prediction precision and great reference values for taking the measures of preventing and controlling Stellera Chamaejasme L.by using the method of quantitatively analysis and qualitatively discussion to determine the sensitive environmental factors and related ones of Stellera Chamaejasme L.'s distribution.(5)Human factors were introduced into the forecasting application of the Ecological Niche Modeling,and the potential distribution area of S Stellera Chamaejasme L.in Haibei was predicted by MaxEnt model.Besides,the precision was evaluated by ROC curve and extraction results from remote sensing data in 2012.These obserbations could provide the basis for the measures of preventing and controlling Stellera Chamaejasme L..In general,in the process of studying Stellera Chamaejasme L.'s occurrence,development,propagation,and prevention,this paper explored the technological frame and theoretical system for extracting spatial distribution characteristics,analyzing spatial pattern change and environmental factors,predicting the potential distribution areas,which provides reference for Steppe Poisonous Weeds' research and theoretical basis and technological support for grassland biodiversity and regional ecological equilibrium. |
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