Chin J Plan Ecolo ›› 2016, Vol. 40 ›› Issue (3): 212-220.DOI: 10.17521/cjpe.2015.0255

• Research Articles • Previous Articles     Next Articles

Plant size differences with twig and leaf traits of Zygophyllum xanthoxylum in the northern slope of Qilian Mountains, China

Jing DU, Cheng-Zhang ZHAO(), Qing-Hua SONG, Yuan-Chun SHI, Ji-Wei WANG, Jing CHEN   

  1. Research Center of Wetland Resources Protection and Industrial Development Engineering of Gansu Province, College of Geography and Environmental Science, Northwest Normal University, Lanzhou 730070, China
  • Received:2015-07-06 Revised:2016-01-07 Online:2016-04-11 Published:2016-03-25

Abstract: Aims

Understanding the effects of plant size on the trade-off between twigs and leaves is important for revealing strategies of plants forming different canopy structure, making full use of space resources, and enhancing their photosynthetic efficiency and competitiveness with adjusting plant configuration. Our objective was to study how twig and leaf traits of Zygophyllum xanthoxylum depended on size in the northern slope of Qilian Mountains, China.

Methods

The study was conducted in a desert grassland on the northern slope of the Qilian Mountains, Gansu Province, China. A transect was laid out horizontally along latitudinal direction, and three sample plots were set up along the transect at the interval of 50 m. Community traits were investigated by using double diagonal method, and all individuals of Z. xanthoxylum were used for measurement of the height, canopy, single leaf area, leaf numbers, twig length, cross-sectional area of twig, and bifurcation angle. Total of 90 plants were divided into different size classes based on the volume: d (the cube root of plant volume) ≤ 60 cm, 60 cm < d ≤ 120 cm, and d > 120 cm. Twig and leaf traits were log-transformed, and the standardized major axis (SMA) estimation method was used to examine the allometric relationships of twig length with leaf area or leaf number.

Important findings

With the increase of plant size, the height, individual leaf area, twig length, and twig cross-sectional area of Z. xanthoxylum increased gradually (p < 0.01), while the bifurcation angle and leaf number decreased gradually (p < 0.01). An isometric or allometric relationship was found between twig length and leaf area in all plant size, whereas an allometric relationship was found between twig length and leaf number. The allometric slope between twig and leaf area was significantly decreased with the increase of plant size, the y-intercepts between twig and leaf number was significantly decreased too. To improve the efficiency of resource utilization, small individuals of Z. xanthoxylum tend to have a large number of leaves on short twigs, and large individuals have relatively few leaves on thick and long twigs. The increase of leaf area and the decrease of leaf number influenced the resource allocation pattern of twigs.

Key words: plant size, Zygophyllum xanthoxylum, twig length, leaf area, leaf number, northern slope of Qilian Mountains