高寒草地狼毒枝-叶性状对坡向的响应

Responses of Stellera chamaejasme twig and leaf traits to slope aspect in alpine grassland of Northwest China.

叶大小与小枝大小关系反映了植物对木质部同其所支持的光合作用面积的配置比例关系,不同生境中其生长关系的变异体现植物对异质环境的适应方式。在祁连山北坡高寒草地,利用ArcGIS建立研究区域的数字高程模型(DEM),并提取样地坡向数据,采用标准化主轴估计(standardized major axis estimation,SMA)方法,研究了不同坡向狼毒(Stellera chamaejasme)种群叶与枝的生长。结果表明:随着坡向由南坡向东坡、西坡和北坡转变,狼毒叶面积、叶片数和枝长度均呈逐渐增加趋势;狼毒叶片数、叶面积与枝长度均呈异速生长关系,枝长度增加的速度大于叶片数和叶面积增加的速度;随着坡向由北坡向东坡、西坡和南坡转变,狼毒叶片数与枝长度的异速斜率逐渐增大,叶面积与枝长度的异速斜率逐渐减小。生境对狼毒枝条与叶片的生长具有显著影响,北坡具有更适宜狼毒生长的生境条件,南坡土壤水分匮乏等不利影响使狼毒枝条与叶片变小,并且单位长度枝条支持更多的叶片。

The relationship between leaf size and twig size reflects the relationship between plant xylem and its supported photosynthesis area allocation ratio, and the variation of the relationship between leaf and twig growth reflects the plant adaptation mode to heterogeneous environment. By using the ArcGIS-established regional digital elevation model （DEM） for a alpine grassland on the northern slope of Qilian Mountains, Northwest China, and by abstracting the slope aspect data of the study area, this paper studied the relationship between the leaf and twig growth of SteUera chamaejasme population at different slope aspects with the method of standardized major axis estimation （SMA）. With the slope aspect changed from south to east, west, and north, the leaf area, leaf number, and twig length of the S. chamaejasme all presented an increasing trend. On all slope aspects, the leaf number, leaf area, and twig length existed allometric relationship, and the growth speed of twig length was greater than that of leaf number and leaf area. With the slope aspect changed from north to east, west, and south, the allometric slope of leaf number and twig length increased, but that of leaf area and twig length decreased. Habitat had significant effects on the leaf and twig growth of S. chamaejasme. Northern slope had more suitable habitat condition for S. chamaejasme growth, while southern slope made the twig and leaf of S. chamae- jasme become smaller, and made the twigs per unit length support more leaves due to the soil moisture shortage.