Spatial-temporal analysis of wetland landscape pattern under the influence of artificial dykes in the Yellow River delta

The influence of anthropogenic activities, especially artificial dykes, on the coastal wetland landscape is now considered as a serious problem to the coastal ecosystem. It is important and necessary to analyze changes of coastal landscape pattern under the influence of artificial dykes for the protection and management of coastal wetland. Our study aimed to reveal the quantitative characteristics of the coastal wetland landscape and its spatial-temporal dynamics under the influence of artificial dykes in the Yellow River delta (YRD). It was analyzed by the methods of the statistical analysis of landscape structure, five selected landscape indices and the changes of spatial centroids of three typical wetland types, including reed marshes, tidal flats and aquaculture-salt fields. The results showed that: (1) Reduction of wetland area, especially the degradation of natural wetlands, had been the principal problem since the dykes were constructed in the YRD. The dykes created conditions for the development of artificial wetlands. However, the new born artificial wetlands were still less than the vanished natural wetlands. (2) Compared with the open area, the building of artificial dykes significantly speeded up the changes of landscape patterns and the aggravation of the landscape fragmentation in the closed area. (3) The changes of area-weighted centroids of three typical wetland landscapes were greatly affected by dykes, and the movement of the centroid of the aquaculture-salt field was very sensitive to the dykes constructed in the corresponding period.