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

PurposeTo 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.

MethodWe 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.

Result1) 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.

ConclusionThe 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.