Spatial And Temporal Change Of Land Cover In Wuyishan National Park Based On Landsat Time Series Data

The national park system has become an important mechanism for protecting ecological environment and biodiversity and other objectives in China.Exploring the process of vegetation change and its influence on the current vegetation growth state can provide a good scientific basis for the conservation and management of national parks.Land cover types and their dynamics significantly affect the surface energy cycle.With the increase of human activities and the frequent occurrence of extreme climate events,the land cover type has changed significantly in recent decades,and it is important to carry out continuous dynamic change monitoring of land cover and reveal the characteristics of spatial and temporal change process of land cover type for the in-depth development of integrated management of forest,field,lake and grass under the influence of human and nature,evaluation of ecosystem service function,carbon and nitrogen water cycle,etc.It is of great significance.Based on the dense time-series Landsat enhanced vegetation index(EVI)data between 1986 and 2020,we utilized the Wild Binary Segmentation(WBS)approach to detect spatial and temporal characteristics of abrupt,gradual,and total changes in Wuyishan National Park.The differences of vegetation change in three protection-level areas(strictly protected,generally protected,and non-protected areas)were examined,and the contributions to their spatial patterns were evaluated through geodetector.At the same time,the change characteristic variables obtained from the change detection results were combined with the random forest classification method to classify the land cover types of Wuyishan National Park,revealing the spatial and temporal distribution patterns of Wuyishan National Park in terms of horizontal gradient and vertical gradient,respectively.The results showed the following:(1)The highest percentage of area without abrupt change was in strictly protected area(39.89%),and the lowest percentage was in non-protected area(17.44%).The percentage of abrupt change frequency(larger than 3 times)increased from 4.40% to9.10% and 12.49% with the decreases in protection.The significance test showed that the difference of changed frequencies was not significant among these regions,but the interannual variation of abrupt change in strictly protected area was significantly different from other areas.The vegetation coverage of the Wuyishan National Park generally improved.The total EVI change showed that the positive percentage of strictly protected area and generally protected area was 90.43% and 91.71%,respectively,slightly higher than that of non-protected area(88.44%).However,the mean greenness change of non-protected was higher than that of strictly protected area and generally protected area.(2)The park’s EVI spatial pattern in 1986 was the strongest factor determining the EVI spatial pattern in 2020;the explanatory power reduced as the protection level decreased.The explanation power of abrupt vegetation change was lower,and increased as the protection level decreased.The interaction detection showed that the park’s EVI spatial pattern in 1986 and vegetation accumulated total change area had the strongest explanatory powers,but the explanatory ability gradually weakened from 0.713 to 0.672 to 0.581 in strictly protected area,generally protected area,and non-protected area,respectively.(3)On the horizontal gradient,the degree of each land cover type change becomes more and more obvious as the degree of protection decreases.Overall,from 1986 to 2020,the proportion of bamboo forest and tea plantation increased and other types decreased.2002 tea plantation started to increase significantly,and the source of tea plantation was mainly fir,and the main source of bamboo forest was broad-leaved forest.Different land types have obvious spatial characteristics of vertical distribution.At low altitude,the proportion of Chinese fir and cropland decreases,and the proportion of Chinese fir decreases even more,and the proportion of tea plantations increases obviously,the proportion of bamboo forest increases slightly at middle altitude,and the proportion of other needle-leaved forests increase significantly at high altitude,and the proportion of broad-leaved forests decrease slightly.In 2020,as the degree of protection decreases,in the low elevation area,the proportion of fir and cropland will first decrease and then increase,and the proportion of tea plantations will gradually increase;in the middle elevation area,the proportion of bamboo forest will first increase and then decrease;in the high elevation area,the proportion of other needle-leaved and broad-leaved forests will remain basically unchanged.There are obvious spatial distribution differences of slope and aspect on different land types.Slope has certain constraints on all land types in this study area,and all land types have a tendency to rise and then fall at different slopes.Compared with other types,cropland is the most adaptable at lower slopes,except for broad-leaved forest,the selection of other types for aspect gradually weakens.The percentage of slope and aspect of each type under the same grade does not differ much in areas with different degrees of protection.