Short‐forbs can be suppressed by dominant plants through vegetative and reproductive interactions in an alpine community

Abstract In a complex community, plant fecundity is determined by a combination of vegetative and reproductive plant interactions. Despite the importance of understanding how these dynamics contribute to the persistence of plant populations and the coexistence of various species, there has been a scarcity of research that examines the synergistic effects of these interactions on plants or functional groups. In this study, we conducted a long‐term two‐factor removal experiment in an alpine meadow on the Tibetan Plateau to investigate the impact of grasses and tall‐forbs (over 30 cm in height) on the reproductive success of six short‐forbs (below 30 cm in height). We assessed various plant traits, including height, flower diameter and the number of flowers as well as the pollinator visitation frequency and seed set of short flowering plants within the removal treatments, aiming to differentiate between direct and indirect effects resulting from vegetative and reproductive interactions. Removing grasses or tall‐forbs consistently reduced the height of short‐forbs while enhancing their mean seed set by more than 10%. This increase can be attributed to the changed vegetative interactions resulting from the removal of either tall‐forbs or grasses, independent of the pollinator visitation. Moreover, the simultaneous removal of tall‐forbs and grasses markedly increased the pollinator visits and the mean seed set of short‐forbs by 139.9% and 31.6%, respectively. This enhancement was linked to the production of more flowers, demonstrating the effects of vegetative and reproductive interactions. Synthesis. This study demonstrates a substantial impact of dominant grasses and tall‐forbs on the fecundity of short‐forbs within alpine grassland ecosystems. It reveals both vegetative interactions, such as competing for abiotic resources, and reproductive interactions, such as competing for pollinators, between plant functional groups. The findings shed light on the crucial role of diverse biotic interactions in maintaining species populations and biodiversity. This is especially relevant in the context of human‐induced disturbances, which can intensify interspecific interactions.