| Landscape fragmentation has been recognized as the primary threats to the long-term survival of many wild animals.The Qinling Mountains of Shaanxi Province,isolated from the other five mountain systems,are the northernmost branches of giant pandas(Ailuropoda melanoleuca),and the only distribution area of the Qinling subspecies of giant pandas,which occupies a special position in the protection and research of giant pandas.Although great efforts have been made,giant panda in the Qinling Mountains still face big threats of habitat fragmentation caused by increasing anthropogenic developments.Therefore,how to prevent the partially disappear of giant pandas caused by habitat fragmentation has become the core issue of giant panda's protection.Existing studies on the impact of human disturbance mostly focused on predicting potential shifts in spatial distribution of giant pandas,habitat quality and habitat connectivity under the habitat fragmentation condition,and no attention has been paid to the relationship between population dynamics and habitat fragmentation.Understanding how landscape structure affects source-sink dynamics and population dynamics are crucial for endangered species conservation and management in fragmented landscapes.To explore how habitat fragmentation affects the source-sink strength and population persistence of giant pandas within this region,we constructed a spatially explicit individual-based population model in the HexSim environment and simulated source-sink dynamics and associated immigration flow of giant pandas.We then assessed the source-sink strength of protected areas for giant pandas under different habitat fragmentation scenarios.Our results suggest that:a)Habitat fragmentation has a certain impact on the spatial distribution pattern of giant pandas in the Qinling Mountains.Compared with the ideal scenario,under the habitat fragmentation scenario,the potential suitable habitat area of giant pandas will decrease by 71.30km2.Compared with the habitat fragmentation scenario,under the habitat restoration scenario,the potential suitable habitat area of giant panda will increase by 57.99km2.b)The analysis of population viability showed that the panda population in the Qinling Mountains would be stable with a slight increase over the next 100 years.The population density of Zhouzhi,Foping,Taibaishan,Huangbaiyuan,and Changqing nature reserves were relatively high,while the population density of Motianling,Yingzuishi and Huangguanshan were relatively small.Due to the influence of the habitat fragmentation,the population in Houzhenzi corridor decreased the most,whereas Jiuchihe and Erlangba Corridors increased slightly.Similarly,when the disturbance was reduced,the populations of Taibaishan,Niuweihe and Sangyuan increased most obviously;by contrast,the population of Banqiao and Foping decreased significantly.c)The dynamic analysis of source-sink of giant panda habitat showed that,under different scenarios,Zhouzhi,Taibaishan,Foping,Changqing and Huangbaiyuan functioned as sources,and the source strength were higher.On the contrary,Pingheliang,Huangguanshan,Yingzuishi,Motianling,Caiziping functioned as sinks,and the sink strength were higher.Under the influence of human interference,source strength of Tianhuashan and Houzhenzi decreased and sink strength of Niuweihe and Sangyuan increased.The mitigation of disturbance changed the source-sink attributes of Niuweihe and Sangyuan,increased the source strength of Tianhuashan and Houzhenzi,and decreased the sink strength of Panlong and Pingheliang.d)The analysis of landscape connectivity of giant panda habitat showed that the direction and intensity of the spread of giant pandas between adjacent reserves would be affected by human interference and corridors.Taking Foping,Changqing,Huangbaiyuan,and Laoxiancheng as the center,pandas mainly spread westward and northward under different scenarios.Individuals in Niuweihe had the same spread trend,while the pandas in other reserves such as Zhouzhi and Taibaishan tended to spread southward.The flux of giant pandas between most adjacent areas has decreased due to the habitat fragmentation,and increased owing to the construction of proposed reserves and corridors.To sum up,habitat fragmentation has significant impact on the population dynamics,source-sink dynamics and diffusion.Nevertheless,the construction of proposed reserves and corridors can effectively alleviate the pressure on the survival of giant panda populations caused by habitat fragmentation and maintain their long-term survival.The results of this research can provide scientific supports for the effective protection of giant pandas and their habitats in the Qinling Mountains. |
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