Wetland Boundary Delineation And Quality Assessment In Zhalong National Nature Reserve

The evaluation of wetland quality is an effective basis for the formulation of wetland conservation measures.In the process of establishing the evaluation system,indicators that reflect the ecological characteristics of wetlands and the quality of the natural environment should be selected to establish a set of wetland quality evaluation systems with wide application and high operability.Wetland information extraction using multi-source remote sensing data is a hot issue in the field of wetland remote sensing,and this paper takes the wetlands of Zhalong National Nature Reserve as the research object.The hydrological boundary of the study area fluctuates greatly,so we extracted the lower boundary of the marsh wetlands using infrared remote sensing sources based on the "three elements of wetland".After pre-processing the SAR data with speckle filtering,radiation correction,and geocoding,we inferred the soil moisture and determined the upper boundary of the marsh wetlands.Afterward,using a combination of sample site survey and remote sensing survey,a survey of wetlands resources in Zhalong National Nature Reserve was carried out in six aspects: distribution of wetlands in Zhalong National Nature Reserve,physical geographic environment,wetland water environment,wetland soil,wetland wildlife resources,and wetland conservation and utilization methods,and a set of index system suitable for quality evaluation of wetlands in Zhalong National Nature Reserve was constructed and quality evaluation analysis of wetlands in Zhalong National Nature Reserve was carried out This study provides a reference for the study of typical swampy wetlands in semi-arid areas.The main findings of this paper are as follows.(1)Using Landsat8 images and high resolution images,the proposed decision tree method for boundary extraction can extract marshes boundaries with high efficiency and accuracy.The advancement of the boundary extraction method from remote sensing images improves the accuracy of wetland boundary delineation and makes it more compatible with the requirements of territorial spatial control.The overall mapping accuracy of the wetland dataset is 97%,with 100% correct for lake wetlands,94.7% accurate for other sites,97.9% accurate for marshes,and 94.4% accurate for swamps.(2)There are six soil types in Zhalong National Nature Reserve,of which the dominant ones are meadow soils and swamp soils.The organic matter content of the soils varies considerably from region to region,with an average p H of 9.0.raccoon algae,a national Class I protected plant,was also found during the field survey.This paper compares the water quality assessment results of wetlands in Zhalong National Nature Reserve in 2008 and 2020,and finds that the water quality of wetlands in Zhalong National Nature Reserve has increased in pollution over the past 12 years,showing a high degree of heterogeneity,especially the core area is also affected to a certain extent.ammonia nitrogen and mineralization in the wetlands of Zhalong National Nature Reserve from2008 to 2020 increased significantly,while total nitrogen,total phosphorus,and dissolved oxygen showed a significant decline.In 2008,the water quality of Kerrtai and the core area was lightly polluted,while that of Dongsheng Reservoir,Lindian,and Kachin was moderately polluted;in 2020,the water quality of Dongsheng Reservoir was lightly polluted,the core area was moderately polluted,while Lindian and Kachin were heavily polluted.From an overall analysis,the water quality of the wetlands in Zhalong National Nature Reserve is lightly polluted according to the analysis of 23 subzones collected in 2008,while the results of 13 subzones surveyed in 2020 indicate that the water quality in Zhalong National Nature Reserve is moderately polluted.(3)This paper uses the expert scoring method to build a hierarchical structure model and establish an evaluation index system for the quality of wetlands in Zhalong National Nature Reserve,divided into five assessment objects: water resources,soil,biology,landscape and wetland protection,including hydrology,water quality,soil nutrients,soil organic matter content,higher plants,birds,fish,landscape index,wetland area change rate,surrounding land use/cover rate,and conversion rate between wetlands and other land use types,for a total of 13 evaluation indexes.According to the results of the 2020 survey indicators,the Zhalong National Nature Reserve is currently suffering from a shortage of water resources,increased water pollution,severe plant degradation,and a decline in animal resources.Overall,water resources in the wetlands of Zhalong National Nature Reserve are relatively scarce,and natural rainfall cannot sustain the wetlands,with a score of 65 for water resources;water quality is average,with most sample sites having a moderate pollution index,with a score of 60 for water quality.Soil condition is good,with a score of 80 for soil quality and 100 for soil organic matter content.The wetlands are more heavily fragmented and the surrounding land is more intensely developed,with the lowest Landscape Pattern Index score of49.The scores of each indicator were multiplied by their respective weights and then multiplied by the weight of the target to which they belonged and summed to obtain a comprehensive score for the quality of wetlands in Zhalong National Nature Reserve.The overall score for the quality of wetlands in Zhalong National Nature Reserve was 74.57,which is a good level.