| Habitat patches within an ecosystem are not isolated but are embedded in the surrounding landscape matrix.The resources and environmental conditions required for populations to survive within the ecosystem depend not only on the habitat itself,but also on the composition and structure of the surrounding landscape matrix.The Blacknecked Crane is a flagship species of the Tibetan Plateau ecosystem,and the highaltitude wetlands in the middle reaches of the Yarlung Zangbo River Valley comprise the world’s largest wintering grounds for this species,providing them with high-quality foraging habitats.Therefore,understanding how the Black-necked Crane selects its foraging habitats in this region and how it is affected by the composition and structure of the surrounding landscape matrix is of great importance for the conservation of flagship species on the Tibetan Plateau,and for the integrated management of river basin ecosystems.However,a complete population survey of black-necked cranes has not been carried out in this area before 2020.In this study,we used remote sensing imagery,climate data,and on-site survey data of Black-necked Crane populations from 2020 to 2021 to analyze the spatiotemporal variability of landscape patterns in the highaltitude wetlands of the Yarlung Zangbo River Valley,as well as the distribution and habitat characteristics of wintering Black-necked Cranes.We also conducted Pearson correlation analysis to reveal the relationship between the distribution of Black-necked Crane populations and the composition and structure of the surrounding landscape matrix.Additionally,we used a combination of the moving window method and the Maxent model to simulate and predict the distribution and trend of Black-necked Crane habitat suitability under three scenarios based on landscape pattern factors,climate factors,and the combined effects of landscape pattern and climate factors.This allowed us to explore the key factors affecting habitat suitability.Based on our analysis,we drew the following conclusions:(1)From 2000 to 2020,there were significant changes in the landscape pattern of alpine wetlands in the middle reaches of the Yarlung Zangbo River.On a temporal scale,the landscape connectivity of the entire study area improved,while the degree of landscape fragmentation decreased.The area of cultivated land initially increased and then decreased,while the area of construction land continued to increase.In contrast,the area of beach land decreased,and there was more active patch circulation among different landscape types.This was especially evident in the frequent transfer of areas between cultivated land,beach,and grassland due to rotational ploughing,fallow,and other factors.On a spatial scale,cultivated land was mainly concentrated in the area where the Yarlung Zangbo River and Xiangqu rivers met.The allocation of landscape elements in different functional zones also varied,with a relatively large area of cultivated land,beach,and water types in the core area.(2)The population numbers and spatial distribution of black-necked cranes were consistent between 2020 and 2021.Population density decreased gradually from the core area to the periphery in different functional zones.The population of black-necked crane is concentrated at the confluence of Yajiang River and Xiangqu River.and its range was similar to that of cultivated land in the river valley.Regarding habitat characteristics,overwintering black-necked cranes were more likely to choose foraging habitats closer to cultivated land and grassland.Additionally,the landscape pattern surrounding their habitats demonstrated a spatial scale effect.(3)There is a significant correlation between the composition and structure of the landscape matrix and the selection of foraging sites by black-necked cranes.Blacknecked crane populations tend to choose landscape substrates with high connectivity and dominance in terms of landscape structure.In terms of landscape composition,cultivated land and water types are the most influential factors,and black-necked cranes are more likely to choose areas with high patch connectivity,dominance,and water density of cultivated land as foraging sites.Furthermore,the composition of the landscape matrix has a significant scale effect on the foraging site selection of blacknecked cranes.The most significant spatial scale of landscape structure is about 1500 m,while the effects of different landscape compositions on foraging site selection are diverse,which may be related to the feeding habits of black-necked cranes and their niche demands for environmental safety.(4)The distribution and trend of habitat suitability for black-necked cranes vary under different scenarios.Habitat suitability based on landscape pattern factors initially increases and then decreases.When only considering changes in climate factors,the suitable area for overwintering habitats of black-necked cranes is likely to increase in the future.However,the habitat suitability under the SSP126 scenario is higher than that under the SSP585 scenario.Under the combined influence of landscape pattern and climate factors,the quality of black-necked crane habitat suitability initially improves and then declines in the future.The habitat suitability during the period of 2060-2080 is lower than that during the historical period.Furthermore,scenarios with high forcing and high greenhouse gas emissions will result in a more significant decline in habitat suitability.(5)The distribution of habitat suitability of black-necked crane is affected not only by landscape pattern,but also by climatic factors.Among the landscape factors,cultivated land,construction land,water areas,and grassland are key factors affecting black-necked crane habitat suitability.Overwintering black-necked cranes prefer foraging in areas with large arable land,good connectivity,and low fragmentation.Additionally,areas with relatively small grassland areas and rich water areas are also common habitat choices.Regarding climatic factors,air temperature and precipitation have a significant influence on black-necked crane habitat suitability.There is a specific temperature range that is most suitable for their habitat suitability.If the temperature is too low or too high,the habitat suitability will decrease.The effects of landscape pattern and climate factors on habitat suitability vary in different scenarios.In the SSP126 scenario,the impact of landscape factors on habitat suitability is more significant,whereas in the SSP585 scenario,the impact of climate factors on habitat suitability increases.This study highlights the importance of considering habitat landscape patterns in the ecological protection of alpine wetlands.It is crucial to optimize crop production and residents’ lives in the black-necked crane habitat and its landscape matrix as a whole,in coordination with the niche needs of the black-necked crane population,such as food supply and habitat security.Furthermore,we should take into account the potential impact of global climate change,strengthen climate monitoring,and formulate measures and plans to deal with climate change.We should also establish an integrated management model of the alpine wetland ecosystem with black-necked crane protection as the core.This not only enhances the stability and sustainability of the alpine ecosystem of the Tibetan Plateau,but also provides ideas for further studying the habitat selection mechanism of species. |
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