关键词: 核桃幼苗, 核桃幼苗, Logistic 方程, 低温半致死温度, 隶属函数

Abstract: Based on the daily observational data of meteorological stations in central regions of Hunan from 1961 to 2010, the climatic extremes and agricultural climatic indexes closely related to crops were selected, statistical analysis, trend analysis and Mann-Kendall mutation test were used to analyze the agricultural hydrothermal climatic conditions and climate extremes in central regions of Hunan, and the authors then studied the tendency of the main agricultural climate indexes. The results showed that: in the past 50 years, the agricultural hydrothermal climatic conditions in central regions of Hunan had an increasing trend; annual heavy precipitation was increasing, especially in summer, indicating that the threat of flood in summer was increasing; the change of the highest (lowest) temperature threshold indicated that the extreme high (low) temperature was mitigating trend, and the number of days was decreasing, which indicated that the possibility of occurrence of meteorological disasters such as high temperature and low temperature damage caused by extreme weather was reduced; ≥0℃ and ≥10℃ accumulated temperature began to change in 1997 and 2000, and the rising trend was obvious, indicating that the effective thermal resource in central regions of Hunan was increasing; frost days showed decreasing trend indicating that the risk of frost damage was decreasing. All this has important guiding significance for determining the appropriate agricultural climate index and promoting agricultural production.