在“八五”期间对白桦所做全分布区种源试验的基础上 ,又做了一次局部分布区的种源试验。试验选取来自 7个省份的 16个种源 ,在 3个试验点定植。对 16个种源的 2年生幼树高进行方差分析 ,结果表明 ,各种源间的差异极显著 ;利用幼树高与种源的地理因子 (经、纬度 )、气候因子 (温度、积温、降水、湿度、日照、无霜期 )作相关分析 ,研究白桦种源的地理变异 ,发现幼树高与纬度呈负相关 ,与经度呈正相关 ,温度与无霜期是影响地理变异的主要气候因子。初步判断 ,白桦的地理变异符合经纬向双重渐变的模式 ,反映了冷—暖的气候生态模式 ,但并未反映干—湿的气候生态模式 Based on the provenance test of Betula platyphylla in the Eighth Five-Year Plan period, a provenance experiment was carried out in a localized area. Sixteen provenances from seven provinces were selected and planted at three sites. The results of variance analysis of two-year-old tree height of 16 provenances showed that there was significant difference among all provenances. Based on the geographical factors (latitude and longitude) of sapling height and provenance, climatic factors (temperature, accumulated temperature, Precipitation, humidity, sunshine and frost-free period). The results showed that the height of sapling was negatively correlated with latitude, and positively correlated with longitude. Temperature and frost-free period were the main climatic factors that affected the geographical variation. According to preliminary judgment, the geographical variation of Betula platyphylla accords with the latitude-longitude dual gradient model, which reflects the cold-warm climate ecological model but does not reflect the dry-wet climate ecological model