Variations and factors characterizing ecological niches of species in a stable grassland plant community

Abstract

To explore the primary factors affecting the ecological niches in a plant community, four dominant shrub species (Sophora viciifolia, Periploca sepium, Buddleja alternifolia, Clematis fruticosa) and six dominant grass species (Bothriochloa ischaemum, Artemisia sacrorum, Stipa bungeana, Cleistogenes squarrosa, Stipa grandis, Lespedeza bicolor) were selected from a stable grassland community in the Loess Plateau (China). The relative importance value and niche breadth were used as comprehensive quantitative indices to characterize the status, role, and degree of dominance of plant species in the community. We found that relative importance value and niche breadth were higher overall in shrub species than in most grass species, except B. ischaemum. Meanwhile, the relative importance value was significantly correlated with plant phosphorus concentration, plant carbon:nitrogen ratio, rhizosphere soil organic carbon, rhizosphere soil total nitrogen, rhizosphere soil total phosphorus, rhizosphere bacterial α-diversity. A stepwise regression analysis indicated that, among the plant and rhizosphere characteristics of these species, only their rhizosphere bacterial α-diversity and plant root carbon concentration primarily influence ecological niche patterns of these plant species in the community. In summary, our study reveals that shrub species occupy more advantageous ecological niches than grass species in a stable community due to the active rhizosphere interactions, providing a new opportunity to disentangle the mechanisms underlying the plant community assembly in grassland.