Grazing exclusion erodes the forbs functional group without altering offspring recruitment composition in a typical steppe

Abstract

AbstractThe underlying mechanism of grazing exclusion on grassland community structure and dynamics may be determined by offspring recruitment. However, little is known about the role of plant functional groups in community recruitment. A chronosequence of grazing‐excluded grasslands was selected to analyze the aboveground community composition and offspring recruitment based on plant functional groups. Grazing exclusion significantly increased grasses biomass (111.7–480.7%), height (95.6–241.8%), and coverage (84.8–148.5%) and decreased grasses density (10.2–59.7%). Grazing exclusion eroded total species richness (13.2–25.0%) and forbs richness (16.6–39.4%). Grazing exclusion shifted the dominance from forbs to grasses. Grasses functional group (GFG) determined community structure, but forbs functional group (FFG) regulated species diversity in typical steppe. Clonal recruitment played a decisive role in the community regeneration, especially tiller recruit mode by GFG. Grazing exclusion had different effects on offspring recruitment of grasses and FFG. Total asexual, grasses asexual, and tiller offspring density both first significantly increased and then significantly decreased with grazing exclusion time. Forbs asexual offspring density did not significantly decrease in 10‐ and 20‐year grazing exclusion grasslands but significantly reduced after 30 years. Change in community dominance caused by grazing or grazing exclusion did not alter the tiller recruitment dominance in this area. Our results indicate that grazing exclusion presents a negative effect on community regeneration and biodiversity conservation in the studied typical steppe.