关键词: 水生植物, 群落特征, 河流生态系统, 栖息地异质性假说, 物种多样性, 水分-能量动态假说

Abstract: By using the observation data from 620 meteorological stations in China, the annual accumulated temperature above 10 ℃, its starting date, ending date, and duration days from 1951 to 1978 and from 1979 to 2005 were calculated and compared. The results showed that in most areas of China, especially in Northeastern, North, and South China, the accumulated temperature above 10 ℃ from 1979 to 2005 was higher than that from 1951 to1978. The starting date of accumulated temperature above 10 ℃ in northern areas of Yangtze River was 0-5 days earlier from 1979 to 2005 than from 1951 to 1979, while that in southern areas of Yangtze River was 0-5 days later from 1979 to 2005 than from 1951 to 1979. The ending date of accumulated temperature above 10 ℃ in most areas of China was delayed 0-5 days, except that in near coastal areas of South China and some regions of Southwest China, which was delayed more than 5 days. The duration days of accumulated temperature above 10 ℃ were generally increased by 0-5 days or 5-10 days in most areas of China, but the increase amplitude was different and could not be linked together in different areas. To accurately know the changing trend of accumulated temperature above 10 ℃ could provide an important basis for the adjustment of agricultural production structure and the assessment of agricultural potential productivity.

Key words: aquatic plant, species diversity, river ecosystem, community characteristics, habitat heterogeneity hypothesis, water-energy dynamic hypothesis