Divergent demographic strategies drive population dynamics of temperate plants across varying deposition

A central question in biodiversity conservation is whether species can sustain viable population under current and future atmospheric N deposition. Assessing species viability under N deposition requires demographic studies integrating species vital rates responses to long-term N deposition across different levels. However, studies of this nature are rare. Our integral projection models (IPMs), parameterized with demographic data, revealed differing responses of two functionally similar coexisting species, Stipa bungeana and Leymus secalinus, to 12 years of N deposition at low N addition levels (1.15 and 2.30 g N m-2 yr-1) and high N addition levels (4.60, 9.20, and 13.80 g N m-2 yr-1) on the Loess Plateau grasslands. We found that the reduced survival across N addition levels was partially compensated by increased contributions from growth, shrinkage, and fecundity, alleviating the population decline of S. bungeana (with a longer lifespan and generation time) under different N additions. Contrasting, more positive correlations among vital rate enabled the population of L. secalinus (with a shorter lifespan and generation time) to track N additions, with population growth under low N additions and population decline under high N additions. Our results illustrate that the demographic response to N deposition may vary considerably between functionally similar coexisting species, and species with demographic compensation can buffer populations against N deposition while with demographic lability enable populations to track N deposition. Furthermore, our study demonstrates the potential of using life-history traits to predict species viability under N deposition, thereby informing biodiversity conservation under global change.