Abstract
The Zoige alpine wetland of eastern Qinghai–Tibetan Plateau is one of the most important wetlands in the world, which suffered stronger human regulations of decades’ drainage and recent restoration. It is so fragile that great efforts should be made to strengthen wetland protection. Based on wetland type classification for seven periods by the object-oriented classification method, we quantitatively discussed dynamically changes of wetland cover types and their driving forces. Conclusions show that alpine meadows accounts for 44.59% of the whole area of the county, and the transition between alpine meadows and swamp meadows mostly occurs in the process of wetland landscape changes. Changes of wetland cover types have taken place in Zoige County from 1990 to 2018 in which wetland loss was mainly caused by the decrease of marsh areas during 1995–2005. Particularly, shift from alpine meadows to swamp meadows led to wetland slightly expansion in two periods, i.e., 1990–1995 and 2005–2018. There is a significant negative correlation between marsh area and average temperature in growing season, average wind speed and rural population, and a significant negative correlation between water area and maximum wind speed. The increase of air temperature and wind speed lead to an enhancement of surface evapotranspiration and a decrease of water retention capacity. Whereas, positive feedback of ecosystem lead to an increase in air temperature and a decrease of marsh area. Both climatic changes and human activities have caused changes in wetland cover type, especially temperature in growing season, wind speed, agricultural development, and animal husbandry.
Highlights
AS a highly productive and sensitive ecosystem, plateau wetland is vulnerable to wetland degradation and wetland loss for slow growth rate and short growth period of vegetation under alpine and harsh ecological conditions
Shift from alpine meadows to swamp meadows led to wetland slightly expansion in two periods, that is, 1990-1995 and 2005-2018
With the development of computer image processing technology, many one-class classification algorithms are used for extracting wetland cover types, such as object-oriented classification, spectral angle mapping classification, classification based on decision tree expert knowledge, artificial neural network classification, support vector machine classification [4]-[7]
Summary
AS a highly productive and sensitive ecosystem, plateau wetland is vulnerable to wetland degradation and wetland loss for slow growth rate and short growth period of vegetation under alpine and harsh ecological conditions. Wetland structure is reflected in the characteristics of hydrology, soil, and vegetation, whose interpretation signs behave same object with different spectrums and mixed spectral phenomena. It is not suitable for remote sensing images to do simple automatic classification with digital number (DN) of the pixel elements. The existing literatures mostly adopt field investigation and visual interpretation of remote sensing images for the identification and extraction of wetlands on the Zoige Plateau. The object-oriented multiscale segmentation algorithm can select an appropriate segmentation accuracy of a specific object at any specific spatial scale, which solves the problem of same object with different spectrums caused by pixel-based classification, and is widely used [8], [9]
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