基于异速生长理论的准噶尔盆地荒漠灌丛形态研究

Morphological investigation of desert shrubs of China's Junggar Basin based on allometric theory

为了揭示荒漠灌丛形态的发生发展机制并认识其在荒漠生态系统中的功能,从形态和结构决定功能的原理出发,对生长在准噶尔荒漠东南部的岛状灌丛进行了形态学调查。依据Malthusian方程微分形式,根据异速生长理论,建立了冠幅与株高生长、灌丛表面积与体积生长的数学关系式,利用植被调查数据进行了验证,并最终得出不同灌丛在不同株高时的情景示意图。结果表明:1)将荒漠灌丛形态假设成半三轴椭球体是合理的;2)虽然灌丛形态发展趋势可以是扁平、近半球和竖直3种类型,但是形态建成后,一般维持在扁平和近半球两种类型;3)18类荒漠灌丛的体积和表面积的数量关系具有一定的一致性,可能与同处于相同环境条件下的水分利用效率相近有关。

Aims Our objectives were to investigate how shape and structure affect shrub architecture and to understand its function in the desert ecosystem through simulating differences in crown architecture of desert shrubs in China＇s Junggar Basin. Methods We analyzed shrub height and crown form. The difference between observed crown area and height and the estimated crown model was found to be a good measure of degree of crown development. A Malthusian conceptual model is proposed where crown area and height modify the crown architecture, shrub surface area and volume. We assumed that the three-dimensional structure of desert shrubs is the triaxial ellipsoid and chose shrub desert island in Junggar Basin as our object of study. According to plant allometric theory, we started from the differential form of the Malthusian equation and set up models describing （a） crown area and height growth and （b） surface area and volume growth. In addition, simulations were used for calculating the potential crown architecture of the desert shrub. Important findings The assumption that the vertical distribution of desert shrub crown shape is semi-triaxial ellipsoid is valid. Three crown types were identified： flat, nearly hemispherical, and upright. These crown types corresponded well with the vertical distribution patterns of maximum height. The consistency of quantitative relationship between volume and surface area of desert shrubs is suggested as a useful tool for characterizing similar water-use strategy in the same environmental condition.