Trade-offs in the adaptation strategy of two dominant rhizomatous grasses to sand burial in arid sand dunes

Trade-offs have long been recognized as a crucial ecological strategy for plant species in response to environmental stresses and disturbances. However, it remains unclear whether trade-offs exist among different structures (or functions) of clonal plants in response to aeolian activities in sandy environments. We examined the growth (reproductive vs. vegetative), reproduction (sexual vs. asexual), and bud bank (tiller buds and rhizome buds, representing vertical and horizontal growth potential) characteristics of two dominant rhizomatous grasses (Psammochloa villosa and Phragmites australis) in the arid sand dunes of northwestern China. Our results showed that these two rhizomatous clonal species exhibited significant trade-offs in their adaptation strategies in response to changes in sand burial depth. Specifically, as sand burial depth increased, the clonal species tended to reduce their reproductive growth, sexual reproductive capacity, and horizontal growth potential, as evidenced by reductions in reproductive ramet number and proportion, panicles number, biomass, and their proportions, as well as rhizome bud number, biomass, and their proportions. Conversely, they increased vegetative growth, reproduction, and vertical growth potential, as evidenced by enhancements in vegetative ramet number and proportion, belowground bud number, biomass, and their proportions, and in tiller bud number, biomass, and their proportions. Our study underscores the importance of trade-offs in the adaptation strategies of rhizomatous clonal species in sandy environments where drought stress and aeolian disturbance coexist. Those trade-offs could ensure the population persistence and stability of pioneering psammophytes in sand dunes, which should be considered during sand-fixing and vegetation restoration efforts in arid sand dunes.