Seed density is more effective than multi‐trait limiting similarity in controlling grassland resistance against plant invasions in mesocosms

Abstract

Question: Disturbed areas offer great opportunities for restoring native biodiversity, but they are also prone to invasion by alien plants. Following the limiting similarity hypothesis, we address the question of whether or not similarity of plant functional traits helps developing seed mixtures of native communities with high resistance to invasive species at an early stage of restoration.Methods: Using a system of linear equations, we designed native communities maximizing the similarity between the native and two invasive species according to ten functional traits. We used native grassland plants, two invasive alien species that are often problematic in disturbed areas (i.e., Ambrosia artemisiifolia and Solidago gigantea) and trait information obtained from databases. The two communities were then tested for resistance against establishment of the two invaders separately in a greenhouse experiment. We measured height of the invasive species and above-ground biomass, along with leaf area index, 4 and 8 months after sowing respectively.Results: Both invasive species were successfully reduced by the native community designed to suppress S. gigantea dominated by small-seeded species. These results could be considered as partial support for the limiting similarity hypothesis. However, given the success of this mixture against both invasive species, suppression was better explained by a seed density effect resulting from the smaller seed mass of the native species included in this mixture. Further, the dominance of a fast-developing competitive species could also contribute to its success. Conclusions:There was no unequivocal support for the limiting similarity hypothesis in terms of the traits selected. Instead we found that increasing seeding density of native species and selecting species with a fast vegetative development is an effective way to suppress invasive plants during early stages of restoration. If limiting similarity is used to design communities for restoration, early life-history traits should be taken into account.

Are two strategies better than one? Manipulation of seed density and soil community in an experimental prairie restoration

“…Our finding that increased seeding density resulted in both lower cover of nonseeded species relative to seeded species, and lower diversity of nonseeded species, is consistent with previous studies such as Carter and Blair () and Yannelli et al (). This result can likely be attributed to a general effect of increased establishment of sown species with higher seeding density.…”

Using limiting similarity to enhance invasion resistance: Theoretical and practical concerns

“…Different groups based on similarities in growth form or other morphological or phenological trait similarities have been defined, assuming that species from the same group should have greater niche overlap and compete more intensively than species from different groups (Johansson & Keddy, 1991;MacArthur & Levins, 1967). However, most studies found no or very limited support for limiting similarity in invasion resistance (Abella, Craig, Smith, & Newton, 2012;Byun & Lee, 2017;Cleland, Larios, & Suding, 2013;Daneshgar & Jose, 2009;Emery, 2007;Eriksson, Wikström, Eriksson, & Lindborg, 2006;Fargione, Brown, & Tilman, 2003;Funk & Wolf, 2016;Larson et al, 2013;Longo, Seidler, Garibaldi, Tognetti, & Chaneton, 2013;Öster & Eriksson, 2012;Prieur-Richard, Lavorel, Grigulis, & Dos Santos, 2000;Turnbull et al, 2005;von Holle, 2005;Yannelli, Karrer, Hall, Kollmann, & Heger, 2018). While such failures do not necessarily invalidate the limiting similarity theory, they are probably due to an inability to reach the domain of validity of this theory.…”

Generating species assemblages for restoration and experimentation: A new method that can simultaneously converge on average trait values and maximize functional diversity

“…While historical reference conditions have traditionally provided empirical data about how to define compositional targets for restoration projects, historical assemblages may not be well-adapted to future climate or novel environmental conditions (Harris, Hobbs, Higgs, & Aronson, 2006). This realization prompted the development of quantitative algorithms that derive species assemblages that exhibit traits to achieve specific functions (Laughlin, 2014a), such as optimizing pollinator habitat (M'Gonigle, Williams, Lonsdorf, & Kremen, 2016), invasion resistance (Yannelli, Karrer, Hall, Kollmann, & Heger, 2018), or drought resistance and fire tolerance (Laughlin, Strahan, Huffman, & Sánchez Meador, 2017).…”