A Modelling Stndy of Potential Evapotranspiration and the Estimation of Chinese Soil Moistnre Regimes

Based on the conception of fluid mechanics, the paper propounds a model for monthly potential evapo-transpiration ETi （mm）: where i is the number of a month, Pi the mean monthly atmospheric pressure （hpa）, ti the mean monthlyair temperature （° C）, di the number of days in the month, Ui the mean monthly wind velocity measured atheight 10-12 m （m/s）, woi the saturated water vapour pressure at ti（mmHg, 1 mmHg=133.322 Pa）, and hithe mean monthly relative humidity. The annual aridity K is:where ra is the mean annual precipitation （mm）. Based upon the data of 669 sites in China during 1951-1980, the relations among the soil moisture regime, the vegetation and the value of K may be illustrated asfollows:K Soil moisture regime VegetationK 【 1 Udic Forest Semi-udic Forest, forest-steppe and steppeSemi-aridic Arid steppe Aridic Desert-steppe Very aridic Desert

节丛孢属rDNA ITS区RFLPs分析

利用PCR朢FLP方法对捕食线虫真菌节丛孢属进行了系统发育研究。以ITS1和ITS4为引物对该属10种12个菌株的核糖体DNA转录间区（ITS）进行了PCR扩增，4种内切酶（AluI、HaeIII、HpaII、TaqI）酶切。结果表明该属的ITS区长度没有明显差异，其长度范围在658～705之间，酶切图谱能体现不同种间的多态性，根据4种内切酶酶切结果，利用UPGMA法构建的节丛孢属分子系统树，基本体现了属内不同种间的亲缘关系，从分子水平证明了节丛孢属形态分类上的合理性，同时对该属属征的扩大提出疑议。