Organ-specific plasticity in response to hydrothermal changes reveals adaptation strategies of sandy plants
Sandy ecosystems are inherently fragile, and plant morphological traits are exquisitely sensitive to climatic shifts. We investigated adaptive strategies of three dominant psammophytes (Artemisia scoparia, Cleistogenes squarrosa, and Lespedeza davurica) to simulated warming and precipitation reduction in a 3-year experiment (established September 2019) in the Horqin Sandy Land. Warming and reduced precipitation profoundly reshaped vegetative and reproductive traits. Under reduced precipitation, all species converged by decreasing specific leaf area and specific root length, increasing leaf thickness and roots diameter, while warming elicited species-specific vegetative responses. Reproductive traits exhibited life-form dependence. Warming diminished seed dimensions in L. davurica, yet combined warming and precipitation reduction 60% markedly increased seed dimensions (especially volume) in the herbaceous species A. scoparia and C. squarrosa. All species modestly enlarged pollen axes to mitigate water loss, with herbs showing stronger responses. Precipitation predominantly drove variation in vegetative and pollen traits, while temperature mainly influenced seed and reproductive traits in L. davurica. Plasticity was organ-specific: leaf area, specific root length and seed volume were highly variable (e.g., specific root length in L. davurica, CV = 56.58%), whereas pollen traits remained remarkably stable (CV < 6%). A. scoparia displayed outstanding plasticity among the three psammophytes. Structural equation modeling unveiled that climatic factors exerted the strongest influence on phenotypic plasticity in the annual/biennial A. scoparia. Notably, temperature and moisture indirectly modulated plasticity via direct effects on organ traits, yet driving mechanisms differed for perennials. These findings underscore multi-organ synergy and the critical role of plasticity in psammophytes adaptation.