Adaptation of the main functional trait of Alhagi sparsifolia leaves and roots to soil water stress

Plants respond to changes in soil moisture by changing their functional traits and nutrients distribution across above-ground and underground organs. This research monitored the changes of the main functional traits of leaves and roots of Alhagi sparsifolia under four moisture levels (W₁: 30% field capacity (FC); W₂: 40% FC; W₃: 55% FC; CK: 75% FC). The results showed that a decrease in water significantly reduced the plant leaf, stem, thorn, aboveground and underground biomass of A. sparsifolia, but had no significant effect on the root: shoot ratio. A. sparsifolia seedlings adapted to water stress by reducing leaf area, increasing the specific leaf area, reducing root volume, and increasing specific root length. These preliminarily results suggest that different adaptive strategies can be formed using the synergistic or balance effect among the traits of A. sparsifolia. Under water stress, more nutrients absorbed by the A. sparsifolia seedlings were distributed in the root. The regular pattern of nutrients content among the organs ranked as follows: root > leaf > stem > thorn. We found a positive correlation between aboveground and underground nutrient contents under the water stress. This study provides an effective reference for vegetation ecological restoration in the south of Taklimakan.