关键词: 沙坡头地区, 一年生植物, 异速生长动态

Abstract: To annuals, soil moisture competition is the radical reason of individual variation, and the rivaling object is still the rare water supply among the individuals. As the change of the moisture gradient, the individual competition among Eragrostis poaaeoides population also changes, from no competition to root competition for limited water supply. Once there is relatively well moisture condition, the individuals would convert massive energy to supporting tissues such as stems, leaves, etc, which strengthens its competitive abilities for light. A dominant instinct of annuals is that it has many shallow root systems that could absorb rainfall quickly during a rainfall season.

Key words: Shapotou region, annual plant, allometry dynamics