过去50年中国森林资源和降水变化的统计分析

论文对过去50年中国森林资源和降水变化进行了统计分析，以期在大尺度上寻找森林资源与降水变化之间的关系。主要结论为：①建国以来我国的森林覆盖率呈上升趋势；②过去50年全国、林区、非林区降水量均呈减少趋势，干旱化趋势明显；③对建国后历次森林资源调查（清查）时段内降水差值（以百分数为单位）、森林覆盖率（以相邻两次变化百分数为单位）变化关系的分析表明，二者的统计关系并不显著，即：过去50年我国森林资源的变化对降水没有显著的影响；④森林影响降水是一个复杂的系统问题，该研究还存在着许多不确定性因素，需进一步实验验证与理论探讨。

Statistical analysis about the changes of forest resource and precipitation in China over the past 50 years

There exists much dispute about the influence of forest on precipitation．Presently the research is very weak to analyze the influence of afforestation and deforestation on precipitation at large scale．Therefore，changes of forest resources and precipitation in China over the past 50 years are analyzed in order to find the relation between changes of forest resources and precipitation at large scale． The main conclusions are as follows． (a) The percentage of forest coverage has been tending to increase since the foundation of P．R．China(i．e．，1949)，which rose from 8．6％ in 1948 to 13．9％ within 1989 1993， and 16． 55％ in 2001．(b) The average precipitation for forestland is 53．4 mm higher than that for non forestland，while the average precipitation variation in forestland is 9％ less than that in non forestland，which indicates that the forest has the function of mitigating variation of precipitation．In addition，the precipitation of the whole country， forestland， and non forestland all tends to drop during the past 50 years．(c)For each period of the forest survey implemented since 1949，the statistical analysis discloses that the relationship between changes of percentage of forest coverage and precipitation is insignificant．The percentage of forest coverage in China is increasing obviously，while the annual precipitation is declining．That means the increasing percentage of forest coverage does not result in the increasing of precipitation at large scale，i．e．，there is no significant relationship between the change of forest resources and the precipitation in China．(d)The research about relationship between the change of forest coverage and precipitation is a complex system， and there also exists much uncertainties (e．g．，the inherent problem of statistical data about forest resources， declining of forest quality，etc．)，which will affect the result of this research directly and(or) indirectly．Hence，it is indispensable to probe the influence of forest on precipitation by experimental verification and theoretical discussion．