| As an important part of terrestrial ecosystem,grassland not only provides an important material basis for animal husbandry,but also plays an important role in regulating climate,conserving water resources,preventing wind and fixing sand and protecting biodiversity.Xinjiang is one of the main pastoral areas in China.In recent years,the outbreak of rodent damage has been serious,and the Eolagurus luteus disaster in northern Xinjiang is the most typical.In the year of outbreak,the Eolagurus luteus often cause a large area of grass to be eaten,the surface is seriously bare,the grassland is degraded,and the land is desertified.It is of great significance for the sustainable development of animal husbandry and grassland ecological protection to grasp the disaster situation quickly and accurately.The traditional methods of rodent pest monitoring are mainly manual investigation.The population quantity of rodent pests is investigated by fixed-point observation,burglary detection and day(night)clamping method,so as to take preventive measures.These methods are often time-consuming and laborious,and have the shortcomings of high cost,small area and poor representativeness.With the development of UAV remote sensing,more and more light and small UAVs are used in the fields of geography,ecology and agricultural monitoring.The application of UAV remote sensing in rat damage monitoring has been preliminarily developed.At present,the low-altitude remote sensing rodent damage monitoring is mainly static single-phase monitoring,lacking of continuous observation data.In order to grasp the dynamic occurrence of rodent damage,this paper carried out multi-temporal monitoring of the occurrence area of Eolagurus luteus in Bayingou,and analyzed the influencing factors of rodent damage change.The main work and achievements are as follows:(1)To determine the best spatial resolution of aerial photography of rat hole and the preprocessing flow of aerial photography data of small UAV:Taking the biological control demonstration area of Eolagurus luteus in Xinjiang Bayingou ranch as the experimental area,the aerial photography image of rat hole in the research area was obtained by using a small UAV mounted on a visible light sensor,and the optimum spatial resolution of the aerial photography of Eolagurus luteus should be controlled within 1.5 cm.During the growing season of the rat,several flight missions were carried out,and the spatial resolution of 1 cm was obtained by splicing Pix4D with PhotoScan software.Multi-temporal Digital Orthophoto map(DOM)and digital surface model(DSM)are used in the study area.(2)The formation of object-oriented multi-temporal holes recognition and dynamic monitoring technology system:The object-oriented feature threshold method combined with fuzzy classification is used to classify multi-temporal aerial photographic images and extract rat holes.The overall classification accuracy is 0.90,and the recognition accuracy of rat holes is over 0.93.A dynamic monitoring technology system for rat holes from multi-temporal data acquisition and processing is formed.(3)Analysis the dynamic change and change of spatial distribution of Eolagurus luteus based on GIS:Based on the GIS grid,the hazard classification of multi-temporal rat holes data was carried out,and the hazard area statistics showed that the moderate hazard and serious hazard were the main hazards in the aerial photography area from April to August.Among them,the most serious hazard was in June,the area above moderate hazard accounted for 88.7%,the least in August,and the area above moderate hazard accounted for 52.3%.Based on Kernal nuclear density and SDE standard deviation ellipse,the spatial distribution changes of rat caves were analyzed.The results showed that the distribution of rat caves showed a trend of multi-nucleus aggregation,combining area distribution with scatter distribution.The characteristics of relatively stable northeast-southwest distribution are given.(4)Analysis of the influencing factors on the Change of holes by Eolagurus luteus and the the dynamic change analysis of typical cave groups:The influencing factors of rat holes change were analyzed.The results showed that the density of rat cave increased with the increase of altitude.There was a good linear correlation between the number of rat cave and vegetation coverage in aerial photography area,and the determination coefficient R~2 was 0.733.The correlation analysis between vegetation coverage and rat cave density based on grid showed that although the correlation between vegetation coverage and rat cave density was not obvious(R<0.5),while the monthly change of the two shows a good correlation(correlation coefficient R>0.5).The change of soil temperature and humidity reflects the change of vegetation coverage,and the change of vegetation will affect the change of rat caves.The statistics of typical caves in the study area shows that the change law of rat caves in the study area is consistent with that of the whole rat caves in the study area. |
PDF Full Text Request