荒漠植被红砂（Reaumurta soongorica）水热响应的年轮学研究

 红砂是黄土高原荒漠植被带主要建群植物种之一，在植被恢复重建和生态建设中具有重要意义。本文以皋兰县40 a天然植被封育区为例，运用树木年轮学方法，对不同坡向红砂与当地水热条件变化的时空响应及分布格局进行了研究。研究结果表明，红砂具有明显的年轮特征，可以进行树木年轮方面的研究。虽然不同坡向水分条件和植被状况有很大差异，但红砂径向生长对区域水热变化具有非常一致的响应模式：同生长季降水呈正相关关系，尤以7月降水量最为显著；同生长季气温呈负相关关系，以6月最为显著。根据不同坡向红砂年龄分布格局分析结果，并考虑到水土流失的防治效果，黄土高原西部荒漠植被带的封育期限不宜少于10 a。

Dendrochronology Study on Response of Reaumurta soongorica to Water-Heat Variation

Reaumurta soongorica is one of the constructive species in desert vegetation,which has important significance in vegetation rehabilitation and eco-construction in Loess Plateau.Taking the forty-year enclosed natural vegetation area in Gaolan County of Gansu province as study sample and by the method of dendrochronology,we studied the growth response of Reaumurta soongorica and the age structure in different slop orientations to local air temperature change and rainfall conditions.The result showed that Reaumurta soongorica has distinctive rings in its cross section,which are capable of being applied in dendrochronology research.The radial growth of Reaumurta soongorica has very consistent response model to the local environment condition,although the soil moisture and vegetation conditions varied in different slop orientations in the study site.In generally,the radial growth of Reaumurta soongorica was positively correlated with the precipitation in the growth season,significantly with that in July;and negatively correlated with the air temperature from May to August,significantly with that in June.Based on the result of analyzing the age structure of Reaumurta soongorica standing in different slop orientations and taking the effect of soil and water conservation into consideration,we suggested that the enclosure period of the desert vegetation in western Loess Plateau would be not less than 10 years.