Adaptive traits of three dominant desert-steppe species under grazing-related degradation: Morphology, structure, and function

Understanding the adaptative behaviors of dominant desert-steppe species under varying levels of grazing-related environmental degradation is an important step in elucidating the survival strategies and environmental response mechanisms of desert plants. In this study, the Xilamuren desert steppe in Northwest China was used as a case study location to systematically investigate the adaptative traits of three dominant plant species (Stipa breviflora, Cleistogenes squarrosa, and Convolvulus ammannii) from the perspectives of plant morphology, leaf structure, and photosynthesis. As degradation intensified, the adaptive changes in the three dominant plant species manifested in the following ways: 1) adjustment of substance allocation strategy, such that biomass was preferentially concentrated in the leaves and roots for photosynthesis and resource acquisition; 2) miniaturization, including reduced plant height, reduced leaf size, and leaf narrowing; 3) thickening of the leaves, epidermis, and cuticle to increase water storage and resist illumination and temperature elevation and thickening of the midrib veins to increase water and nutrient transportation; and 4) increased water-use efficiency in Stipa breviflora, which showed a stronger capacity to adjust to water stress than Cleistogenes squarrosa and Convolvulus ammannii. The results suggested that the morphological, structural, and functional adjustments of desert plants were related to the development of drought-resistance mechanisms through water-use strategies, including increased water absorption and water-use efficiency and decreased water consumption. These results enrich the existing knowledge of the environmental adaptation mechanisms of dominant plants in desert steppes, providing a scientific basis for the restoration of desert steppe ecologies and the formulation of suitable grazing policies.