| Objective: As a significant symbol of modern agriculture,facility agriculture has outstanding contribution to promoting agricultural modernization.It can resist a certain degree of adverse environment outside facilities and create suitable conditions for agricultural production.In recent years,the occurrence of extreme climatic events shows a certain periodicity,which has a negative impact on facility agriculture.Therefore,it is of great significance to study the suitable layout of facility agriculture under extreme climatic conditions for the increase and reduction of output and consumption of facility agriculture.Especially,with the passing of time,the accumulation of various types of data makes its realization possible.In this study,Turpan-Hami Basin was selected as the research area.Based on the daily meteorological data from December to February(winter)from 1965 to 2020,combined with previous studies,the index of facility agriculture extreme climate events was constructed to analyze the spatial and temporal distribution characteristics of extreme climate events in Turpan-Hami Basin in the past 55 years and to carry out extreme climate disaster risk assessment.The spatial distribution and land use changes of solar greenhouses in Tuha Basin in the past 20 years were analyzed by satellite remote sensing image extraction.Based on the spatial and temporal distribution characteristics of extreme climate events,combined with socio-economic statistical data and spatial distribution characteristics of solar greenhouses and other factors,the suitability of facility agriculture under extreme climate conditions was studied and the rational layout was discussed.Method:(1)Based on the daily values of surface meteorological stations in Turpan and Hami in the Turpan Basin from December to February(winter)from 1965 to 2020,four extreme climate events were selected,including extreme low temperature,extreme precipitation,extreme low light and extreme wind.Bonsal non-parametric scheme was used to select 90% as the threshold of extreme climate.The total number of days,frequency and intensity of extreme climate events were counted.Sen-MK test and MK mutation test were used to analyze the temporal and spatial variation characteristics of extreme climate disasters.According to the occurrence frequency and intensity of each extreme climate event,the disaster risk assessment factors of each extreme climate event were calculated,and the disaster risk assessment of the past 55 comprehensive extreme climate events in Turpan-Hami Basin was carried out by entropy weight-fuzzy comprehensive evaluation method.(2)Based on remote sensing image data of landsat-7 ETM and landsat-8 OLI,object-oriented classification method was adopted to determine the optimal segmentation scale of multi-scale segmentation method,and extract the land use types of Turpan-Hami Basin in 2002,2013 and 2020.The precision of land use types extracted in 2020 was evaluated.Combined with the land use type of the third stage,the land use change of the Turpan-Hami Basin in the past 20 years was analyzed by land use transfer matrix.Based on the spatial distribution characteristics of extreme climate,combined with traffic accessibility,location factors,socio-economic data and other indicators,this thesis regionalizes the suitable layout of facility agriculture in Turpan-Hami Basin,and discusses the rational layout of facility agriculture combined with the spatial distribution of solar greenhouse.Results:(1)Temporal and spatial distribution characteristics and disaster risk assessment of extreme climatic events in facility agriculture in Turpan-Hami BasinIn the Turpan Basin,the total number of days of extreme precipitation events is shorter than that of other extreme events,specifically 330 days in Turpan station and 490 days in Hami station,while the total number of days of extreme low temperature events is more,specifically 697 days in Turpan station and 612 days in Hami station.Other extreme events are different between Turpan Station and Hami station.In the past 55 years,the maximum frequency of extreme precipitation events at Turpan station and Hami station appeared in 1977,which were 10% and 5.24%,and the other extreme climate events were different between the two stations.The slope of Sen shows that in the past 55 years,the extreme wind index WS90 P has decreased,the extreme precipitation index PCRT has increased,the extreme low temperature index TN10 P,FD and CSDI in Turpan site has decreased,and the extreme missing radiation index LOR I has increased.The other indexes did not increase or decrease;In the past 55 years,the risk degree of comprehensive extreme climate events at Turpan site is unacceptable risk,while the risk degree of comprehensive extreme climate events at Hami site is the risk of catastrophe.(2)Analysis of temporal and spatial distribution characteristics of facility agriculture in Turpan-Hami Basin and its suitable layout under extreme climatic conditionsThe optimal segmentation scale of multiscale segmentation in Tuha Basin is scale factor 150,smoothness factor 0.1 and compactness factor 0.5 in the first layer,scale factor 30,smoothness factor 0.1and compactness factor 0.5 in the second layer,and scale factor 18,smoothness factor 0.1 and compactness factor 0.5 in the final layer.The overall classification accuracy of land use in 2020 was 86%,Kappa coefficient was 0.825,and the mapping accuracy of solar greenhouse was 87.50%.In the Turpan-Hami Basin,solar greenhouses are distributed in the west and north of Tokesun and around the county seat,the south and east of Gaochang District,the west and east of Shanshan County,the east and west of Hami Yizhou District and around Yizhou District.In the past 20 years,the solar greenhouse in Turpan-Hami Basin has developed in a rapid and orderly way,which is reflected in the period when the total area of solar greenhouse industry layout increases sharply to the period when the area increases or decreases slightly.The spatial distribution of solar greenhouses in 2020 is mainly located in high-quality layout areas suitable for the development of facility agriculture and supplementary development areas,among which there are a large number of high-quality layout areas suitable for the development of solar greenhouses around Toxon and Yizhou district.Conclusions:(1)Extreme precipitation events occur more frequently than other extreme climatic events,and extreme climatic events in Turpan are more unstable than those in Hami.Extreme precipitation index PCRT shows an insignificant increase trend,extreme wind index WS90 P shows a significant decrease trend,and the trend of extreme low temperature index shows spatial inconsistency.LOR I shows a significant increase trend in Turpan,but no trend in Hami,and no trend in other extreme climate indexes.In the past 55 years,the disaster risk assessment grade of Turpan was unacceptable risk,and the disaster risk assessment grade of Hami was risk of catastrophe.(2)The facility agriculture in the Turpan-Hami Basin is distributed in the oases centered on towns,specifically in the north and west of Tokesun County and the surrounding area of the county seat,the south and east of Gaochang District,the west and east of Shanshan County,the east and west of Hami Yizhou District and the surrounding area of Yizhou District;In the past 20 years,the solar greenhouse is a development mode of rapid and orderly development,which is reflected in the period of rapid growth and balanced growth or small reduction of the total area of solar greenhouse industry layout;In 2020,facility agriculture in Tuha Basin is mainly distributed in high-quality distribution areas and supplementary development areas,among which there are a large number of high-quality distribution areas suitable for facility agriculture around Toxon and Hami Prefecture.Through satellite image data,meteorological data and socio-economic statistics,this study realized the extraction of spatial distribution of solar greenhouse and the study of occurrence trend of extreme climate events in Tuha Basin,and carried out risk and disaster assessment of comprehensive extreme climate events in Tuha Basin.Finally,based on extreme climate factors,land use benefits,location advantages and transportation accessibility factors,The realization of space suitable layout of facility agriculture provides a new idea and reference for the layout of facility agriculture. |
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