Determinants of plant establishment success in a multispecies introduction experiment with native and alien species

Abstract

Determinants of plant establishment and invasion are a key issue in ecology and evolution. Although establishment success varies substantially among species, the importance of species traits and extrinsic factors as determinants of establishment in existing communities has remained dif fi cult to prove in observational studies because they can be confounded and mask each other. Therefore, weconducted a large multispecies fi eld experiment to disentangle the relative importance of extrinsic factors vs. species characteristics for the establishment success of plants in grass- lands. We introduced 48 alien and 45 native plant species at different seed numbers into multiple grassland sites with or without experimental soil disturbance and related their establish- ment success to species traits assessed in five independent multispecies greenhouse experiments. High propagule pressure and high seed mass were the most important factors increasing establishment success in the very beginning of the experiment. However, after 3 y, propagule pressure became less important, andspeciestraits relatedtobiotic interactions(includingherbivore resistance andresponses to shading andcompetition) became the most important drivers of success or failure. The relative impor- tanceof different traits wasenvironment-dependent andchanged over time. Ourapproach of combining a multispecies introduction experiment in the field with trait data from independent multi-species experiments in the greenhouse allowed us to detect the relative importance of species traits for early establishment and provided evidence that species traits—fine-tuned by environmen- tal factors—determine success or failure of alien andnative plants in temperate grasslands.