Change and its prediction of landscape patterns in the watershed of typical karst lake wetland

As a research focus of landscape pattern change, the change and its prediction of landscape patterns in the watershed of karst lake is explored with the purpose of providing a scientific basis for the ecological safety in karst watershed in this study. The data of remote sensing image in the watershed of Puzhehei karst lake was collected in 1990, 1995, 2000, 2005, 2010, and 2015 respectively. With the remote sensing and geographic information system, those images were classified and interpreted based on the actual situation of this area. In addition, landscape patterns and the dynamic characteristics were analyzed and the pattern of future wetland landscape was simulated and predicted with CA-Markov model. Results show that landscape patterns of the watershed of Puzhehei karst wetland changed significantly from 1990 to 2015, during which construction land and agricultural land continued to increase, but woodland, wetland and unused land continued to decrease. The number of blocks (NP) rose from 861 to 889. Generally speaking, agricultural land is increasing year by year, but the growth rate is slow and the wetland landscape area is decreasing. Besides, from 1990 to 2015 the degree of landscape fragmentation in the Puzhehei watershed was generally augmented,and the number of landscape patches, patch density and number index of maximum patches also increased. The number of patches reached a maximum of 936, and the patch density index increased from 2.596 in 1990 to 2.822 in 2000, and then decreased to 2.689 in 2015. The number of maximum patches increased from 58.345 in 1990 to 62.036 in 2015, which means that the impact of human activities on the landscape pattern in the Puzhehei watershed made the landscape structure more complex and the fragmented. Finally, the dominant patch area of landscape types gradually increased from 1990 to 2015. The diversity index decreased from 1.064 to 0.966, and the edge density increased from 47.552 to 48.063. But the landscape shape index decreased from 30.175 to 29.625. Due to the continuous reduction of forest land and wetland in 2000, the landscape shape index increased and both the edge density and landscape shape index peaked at 49.987 and 31.012 respectively, which made the landscape structure complex. In the next 20 years, the landscape type change in Puzhehei watershed will generally show an increase in construction land, agricultural land and wetland, but a decrease in forest land, garden land and unused land. This trend can be reflected from the previous data: construction land increased from 2.79% to 2.97%, agricultural land from 60.12% to 60.74%, wetlands from 6.67% to 7.02%, but of forest land dropped from 26.70% to 26.40%. Accordingly, the land use pattern of Puzhehei watershed will change significantly. By 2030, the existing construction land will be expanded mainly around the scenic area of sinkholes as well as new in the villages and new towns around the National Wetland Park. Constrcution land will spread to the surrounding areas along with the main traffic roads. It is predicted that wetland, construction land and agricultural land will experience the largest change. The research findings can provide suggestions and reference for the ecological protection of the watershed Puzhehei karst lake.