Native species identity drives plant community growth and biotic resistance

Prepared by Elana V. Feldman, Timothy E. Walsworth, Karin M. Kettenring

To successfully restore wetlands, it is important to understand the factors that allow native species to block invasive species growth. Two potential factors—that can also be manipulated by restoration practitioners—are native plant diversity and seeding density. In two greenhouse experiments, we examined the effects of different native plant species, native plant diversity, native seeding density, and the presence of the invasive species Phragmites australis on both the growth of native species and the ability of those species to block the growth of P. australis. We quantified growth as the biomass, cover, and growth rate of individual species. In these experiments, native species were grown by themselves and in mixtures at both a low and high density and both with and without P. australis to view how these factors interact.

The results of these experiments show that both final native and P. australis growth were driven by a few individual high-performing native species. We also found that P. australis did not have a consistent effect on the growth of native species. Rather, the effect differed depending on the native species and whether biomass, cover, or growth rate were being considered. Finally, seeding native species at a higher density resulted in more native plant growth and less P. australis growth, with high-performing native species achieving these results faster.

Our results have three important implications for wetland restoration. First, it may be better to focus on individual native species that are successful at blocking P. australis rather than focusing on a diversity of species that perform different roles in the ecosystem. Second, it is important to consider that native species will act differently under different contexts. For example, a species that grows quickly when seeded at a high native seeding density may not grow as quickly when seeded at a low native seeding density or when grown with an invasive species. Finally, wetland restoration practitioners should seed at a much higher density than is currently in practice to more successfully increase native growth and decrease P. australis growth.

This is a plain language summary of the paper of Feldman et al. published in Applied Vegetation Science (https://doi.org/10.1111/avsc.12808). This blog post was written by Elana V. Feldman