Research On Mangrove Disturbance Of Beilun Estuary In Guangxi From 1990 To 2020

Monitoring the disturbance of mangroves in national nature reserves can provide data support and decision support for the management and protection of coastal wetland ecosystems.In this study,Google Earth Engine(GEE)was used to build Landsat long time series satellite data sets.Combined with Land Trendr algorithm and CCDC(Continuous Change Detection and Classification)algorithm,the disturbance of mangrove forest in Guangxi Beilun Estuary Mangrove Nature Reserve from 1990 to 2020 was studied and the monitoring results of the two algorithms were compared to find the differences between the two algorithms in mangrove disturbance detection.Finally,combined with the actual situation of the study area,the change of mangrove area in Beilun Estuary under the influence of natural factors and human factors was analyzed,and corresponding protection suggestions were given according to the historical situation.The results show that:1)From 1990 to 2020,a total of 45.94 hm2 of mangrove forest was disturbed by Land Trendr algorithm.The disturbed area of mangrove forest was the largest in2001,12.91 hm2,followed by 2015 and 2020.Is 10.54 hm2 and 10.45 hm2,and the geographical location of the disturbance is mainly distributed along the northwest coast of Pearl Bay.At the same time,711.85 hm2 mangrove restoration was detected,and the restoration area was the largest in 1991,1992 and 1993,with 600.46 hm2 mangrove restoration,accounting for 84.35% of the total restoration.Spatial concentration was concentrated in the estuary of Beilun Estuary and the coast of Zhenzhu Bay.2)Based on Land Trendr algorithm,the disturbance degree of mangrove forest in Beilun Estuary protected area is mainly low-level and middle-low-level disturbance,and the disturbance area is 26.60 hm2,accounting for 56.85% of the total disturbance.The restoration degree of the reserve was mainly low-level and middle-low-level,with the restoration area of 444.60 hm2,accounting for 62.46%,or nearly two-thirds of the total restoration area.3)The disturbance of 98.98 hm2 of mangrove forest was detected by CCDC algorithm from 1990 to 2020,and the maximum disturbance occurred in 2020,which was 22.63 hm2.A high consistency was found in the interannual broken line chart of disturbance detected by CCDC and Land Trendr.The results show that the two algorithms are effective in detecting mangrove disturbance.The maximum disturbance detected by the two algorithms is significantly different in grade,and CCDC is more sensitive to middle-low disturbance.In addition,CCDC can detect the frequency of disturbance,and it is found that the areas with the frequency of one and two disturbances account for the vast majority,with an area of 101.79 hm2,accounting for 98.55% of the total area.This study based on analytic Land Trendr and CCDC algorithm for nearly 30 years Beilun Estuary protection zone mangrove disturbance years,frequency and area,combined with the actual situation type disturbance is analyzed and the driving factors,and that natural factors,such as pests and typhoons are the major cause of lead to interference,Beilun Estuary mangrove interference of human activities is a secondary reason,Natural replacement is the main reason for mangrove restoration,while human conservation is the secondary reason.The corresponding protection and management strategies are given.The conclusions and methods of this study can provide important decision support for making scientific and reasonable mangrove conservation and restoration policies.