黄土高原两种丛生禾草龄级结构及自疏特征

The Age Structure and Self-thinning Characteristics of Two Bunch Grasses in Loess Plateau

【目的】确定丛生禾草长芒草(Stipa bungeana)和无芒隐子草(Cleistogenes songorica)的年龄结构模式,探究其株丛分蘖数和个体分蘖质量之间是否存在自疏特征,阐释其对生境的适应性机制,进而预测草原演替趋势。【方法】以黄土高原地区丛生禾草长芒草和无芒隐子草为对象,通过对其株丛数量性状(株高、冠幅直径、基茎、分蘖数、株丛质量和个体分蘖质量)、年龄结构及自疏特征进行定量分析,研究2种丛生禾草的龄级结构及自疏特征。【结果】(1)2种植物株丛的高度、冠幅直径和基茎的稳定性较强,株丛质量和个体分蘖质量的稳定性较弱。(2)2种植物种群的年龄结构均为幼年个体少,成年个体储备丰富,老年个体相对较多,均属衰退型种群,且2种植物种群的稳定性较弱。(3)无芒隐子草株丛分蘖数和个体分蘖质量之间存在一定程度自疏特征,长芒草株丛分蘖数和个体分蘖质量之间不存在自疏特征。【结论】2种禾草的年龄锥呈衰退型且其自疏特征存在一定分异,是其对外界生境和长期封育适应的结果,表明研究区草原呈退化演替趋势。

[Purpose]To determine the age structure patterns of Stipa bungeana and Cleistogenes songorica,and to explore whether exhibits a self-thinning feature between the tillers and tiller weight for each species,the result will reveal their adaptive mechanism to the habitats,and predict the development trend of the typical steppe.[Method]We analyzed the quantitative traits(plant height,crown diameter,base plant stem,tiller number,plant weight,tiller weight),age structure and self-thinning law of bunch S.bungeana and C.songorica in the Loess Plateau,and studied the age structure and self-thinning characteristics of this species.[Result]1)The stabilities of plant height,crown diameter and base stem were relatively high,while the stabilities of plant weight and individual tiller weight were low.2)The age structure of the two plants was fewer young individuals,abundant adult individuals,relatively more elderly individuals,belonging to the declining population,and their respective stabilities were weak.3)A certain degree self-thinning law exhibited between the tiller number and tiller weight of C.songorica,but for S.bungeana it was not.[Conclusion]The age pyramid of each species exhibited a declining pattern and their self-thinning laws were different,due to their long-term adaptation to different habitats and long-term fencing management,which suggests that the typical steppe of this area is degradation succession.