【摘要】 根据史料中丰歉记载和现代产量资料,分析了1736—1978年冬小麦收成与降水量的关系,表明在无灌溉条件下两者关系密切。能谱分析说明冬小麦收成有121,80年等周期,并同降水量变化周期一致。更多还原

【Abstract】 Based on the regional harvest reports of Ching Dynasty kept in the Palace Museum in Beijing and recent records, a series of harvest records of winter wheat during 1736-1978 over Beijing area was constructed. The harvest were presented as a percent of full harvest.Harvest records were spectrally analysed to obtain significant periods of oscillation. It may be seen that there exist 121, 80-years and other periods. 1744 (27% of full harvest) was the worst harvest since 1736. As concerns decade means, 1921-1930 (56%), 1741-1750(60%) were the two worst and 1801-1810 (80%) was the best.The correlations between harvest of winter wheat and the precipitation within the growing season (September-May) for different periods have been obtained and are shown in table 1. The correlations are positive and significant.During recent 20 years the correlation between the harvest and the precipitation tends to be not significant, because of the corresponding increase in irre-gation facilities subsequent to 1950’s.As a result of the shortage of rainfall during 1981-1982, the reservior and the underground water content were exhauseted, the irregation was deeply affected and which did an injury to the crop of winter wheat. The 2-years drought occures once every 18.4 years during 1724-1981.更多还原