Abstract: Using datasets of daily average temperature of 559 meteorological stations over China during 1961 and 2013, the spatiotemporal distribution of variations and trends for beginning day, ending day, accumulated temperature, and average duration days between neighboring temperatures of the agriculture critical temperature were studied with statistically diagnostic methods such as 5day running mean, climatic tendency analysis as well as GIS tool. Also, the changes of different meteorological variables under different guarantee rates were studied. The characteristics of the climatic tendency rates and variation coefficients of the beginning day, ending day, accumulative temperature of the agriculture critical temperature were investigated to provide a scientific basis for making full use of climate resources, optimizing agricultural layout and crop introduction. The  results showed that the beginning day and ending day shifted earlier and later, respectively; the duration became longer and accumulative temperature gradually increased from 1961 to 2013. The magnitude of variation was closely related to latitude and geographical features of research region. The variations of the beginning day under different agriculture critical temperatures (i.e. 0, 5, 10, 15, and 20 ℃) were within the range of 97 to 123 days in northern and southern China, and the ending day, duration, and accumulative temperature were within the range of 37 to 50 days, 75 to 106 days, and 2081 to 2506 ℃·d, respectively. Additionally, the amplitude of the beginning day, ending day, duration, and accumulative temperature ranged from 25.7 to 42.9 days, 11.1 to 31.7 days, 36.7 to 60.7 days, and 157 to 1221 ℃·d, respectively in the adjacent regions with neighboring agriculture critical temperature. With the increase of guarantee rate, the beginning day, ending day, and accumulative temperature exhibited various changes in different areas. Over the Yangtze River valley, the change of beginning day above 0 ℃ was the most distinct and the magnitude could reach 2.4 to 16.3 days, while appeared slightest in South China with the magnitude was less than 1 day with the guarantee rate equal to or less than 95%. Climatic tendency rates of the beginning day, ending day, and accumulative temperature during 1961 and 2013 ranged from -7.6 to 37.3, -47.1 to 40.9, and -250 to 456 d·10 a^-1, respectively; the values of their average relative variability ranged from 0 to 146.0, 4.8 to 24.5, and 1.2 to 196.2, respectively.

Key words: plant community structure, alpine meadow, nitrogen addition, species composition, warming