祁连山高寒草地甘肃臭草叶性状与坡向间的关系

Relationship between leaf traits of Melica przewalskyi and slope aspects in alpine grassland of Qilian Mountains,China

植物功能性状可反映植物对环境的适应。在祁连山高寒退化草地,利用Arc GIS建立研究区域的数字高程模型,提取坡向数据,采用标准化主轴估计方法(standardized major axis estimation,SMA),研究了不同坡向甘肃臭草(Melica przewalskyi)叶性状间的关系。结果表明:1)甘肃臭草叶面积和叶体积在北坡最大,东坡、西坡、南坡逐渐减小,叶干质量无显著变化;2)叶面积与叶干质量在北坡、东坡和西坡呈等速生长关系,在南坡呈异速生长关系,且叶干质量的增长速度大于叶面积的增长速度;3)叶体积与叶干质量在4个坡向上呈异速生长关系,且叶干质量的增长速度均小于叶体积的增长速度。甘肃臭草叶性状关系随坡向的变化反映了该物种在异质生境中具有较强的叶片形态可塑性,从而有利于其适应和占据高寒退化生境。

Aims Variations in leaf characteristics can reflect plant acclimation to environments. We aimed to examine the relationship between leaf traits of Melica przewalskyi and slope aspect.Methods In alpine grassland of Qilian Mountains,Gansu Province,China,80 plots were sampled at intervals of 20 m along eight aspects. Latitude,longitude and altitude of each plot were recorded by GPS. At each plot,10 individuals of M. przewalskyi were random selected and harvested for measurements of leaf mass,leaf area,and leaf volume. A digital elevation model（DEM） was constructed to extract elevation,aspect,and slope for each plot by Arc GIS. The 80 plots were divided into groups of north,east,west and south aspect. Values for leaf traits were log-transformed. the standardized major axis（SMA） estimation method,was used to examine the covariation among leaf traits. Important findings Leaf area and leaf volume decreased significantly as aspect turns from north to east,from east to west,and from west to south,but not so for leaf mass,suggesting that leaf thickness increased as slope aspect changes,and thus led to the smaller and thicker leaves on the south-facing slope than that on north-facing slope. A clear allometric relationship between leaf mass and leaf area was found only on the south-facing slope where increase in leaf mass was greater than that in leaf area. While on other slope aspects,an isometric relationships between them was observed. The allometric relationship between leaf mass and leaf volume was found on all four aspects,with the growing speed of leaf volume greater than that of leaf mass,and a rising SMA slope. We can conclude that variations in leaf traits of M. przewalskyi with slope aspect could reflect plant acclimation.