关键词: 景观特征, 视觉特征, 美学评价, 景观管护, 农田格局

Abstract: The onset of greenness of vegetation is one of the important parameters to investigate the relationship between growth periodicity of vegetation and climate change. This study selected three areas including Tibetan Plateau, mideastern and northeast of China as typical research areas. Based on the cumulative frequency data of NDVI on NOAA/AVHRR in 1983—2012, Logistic fitting functional model was used to calculate the DOY (days of year) of onset of greenness with MODIS Collection 5 landcover data. The characteristics and differences of the onset of greenness with different vegetations in different areas were analyzed. The results showed that the onset of greenness by different vegetations of grasslands, shrub, deciduous tree and cropland generally presented a trend in advance. The different types of vegetation had different onsets of greenness in the same area. The interannual variability of the onset of greenness by the same vegetation types showed different trends in the different areas. The onset of greenness of grassland in the Tibetan Plateau changed at a rate of 6.11 d·10 a^-1 in advance, 5.37 d·10 a^-1 in the mideastern regions in China, and 2.13 d·10 a^-1 in the northeast of China. The amplitude of interannual change of deciduous trees was roughly similar to that of the grassland. The changing rate of onset of greenness in advance would gradually be smaller with the increase of latitude and the decrease of altitude. The onset of greenness of the vegetation types of shrubs and cropland in northeast China appeared a delaying trend, with respective delaying rates of 1.49 and 1.03 d·10 a^-1.

Key words: landscape character, visual character, aesthetic assessment, landscape stewardship, field pattern.