Dynamic Change Of Black-necked Crane Habitat Suitability In The Middle Yarlung Zangbo River

In view of the constraints and main threats to black-necked crane habitat suitability in the Black-necked Crane National Nature Reserve of the middle Yarlung Zangbo River, this paper makes use of landscape pattern index, habitat suitability index,conservation ratio and conservation efficiency index and so on to evaluate black-necked crane habitat suitability in the third period of Black-necked Crane National Nature Reserve of the middle Yarlung Zangbo River, estimate the conservation status and analyze its dynamic changes, and meanwhile analyze the impact of human activities and natural factors on black-necked crane habitat.The main results are as follows:(1)The number of available habitat patches increases first and then decreases,and the number of unavailable habitat patches decreases first and then increases. In 1994, the disturbed degree of central bar was not high, while woodland and meadows and wetlands were greatly disturbed. In 2005 and 2015, meadows and wetlands and the central bar with vegetation were less disturbed, but dry rivers and sandy land were seriously disturbed. In 1994, the distance between farmland,meadows and wetland was far, and the distance between the central bar and grass patches was close. They were easy to be connected with each other due to the closer distance, which was beneficial to the migration of species,breeding ground and habitats as well as the conservation of species diversity. In 2005 and 2015,the distance between sand patches and the central bar with vegetation was farther, while the distance between grass patches was closer.(2) After analyzing the present habitat situation of black-necked cranes in the three zones of the Reserve and the changes since the establishment of the Reserve, it is found that today' s suitable habitat of Shigatse Yajiang River middle valley area and lhasa River valley area is lower than year 1994, and the second-suitable habitat of them is higher than year 1994, and Yamdrok Lake wetland is opposite to these two. In general, the black-necked crane habitat quality of Shigatse Yajiang River middle valley area and lhasa River valley area decreases and the total habitat area increases,while the habitat quality of Yamdrok Lake wetland increases and habitat area decreases.(3) The suitable habitat protection capacity of Shigatse Yajiang River middle valley area and the valley area, core area and buffer area of lhasa River is higher than that of the early days, but the protection capacity of experimental area decreases. The protection capacity of core area of Yamdrok Lake wetland decreases,its protection capacity of buffer area is basically stable, and its protection capacity of experimental area increases on the whole. Comparing with the beginning of this Reserve, the planning of Shigatse Yajiang River middle valley area and lhasa River valley area remains reasonable, but the rationality of Yamdrok Lake wetland decreases.(4) Since the establishment of the Black-necked Crane National Nature Reserve in middle Yarlung Zangbo River, it has experienced a climate change characterized by warming and drying. The precipitation of Black-necked Crane National Nature Reserve is mainly concentrated in the non-wintering period of black-necked cranes,and the precipitation of these three areas has reached more than 94% of the annual precipitation. Black-necked cranes' temperature in wintering period is on the rise,and in non-wintering periodits temperature is relatively stable.(5)Precipitation is a crucial factor that affects the habitat of black-necked cranes. It not only affects foraging habitat, but also has an impact on night habitat. In the three kinds of human activities analyzed in this paper, the population growth in Shigatse Yajiang River middle valley area has a negative effect on black-necked crane habitat, and the effect of other human activities on black-necked crane habitat gradually reduces.