Climate change and invasive species present significant barriers to restoration. Contrasting evidence from investigations into how diversity and species abundances influence invasion processes raise the question of whether land managers should restore for diversity or monocultures of high biomass species. In this study, we assessed the effect of restored perennial grassland species richness and composition on invasive species re-establishment in a calcareous, savannah ecosystem in central Texas, USA. The study also became a test of the effectiveness of restoration with climate change, as during the establishment phase (2010-2011), 88% of Texas experienced “exceptional drought” conditions. We hypothesized that invasive species re-establishment would be slowed at higher levels of restored species diversity and in plots with species with high initial biomass. We employed a two-way factorial experiment in a randomized complete block design where richness (1-4) and native species composition were manipulated in 1 x 1 m plots. All possible species combinations were included at richness levels 2 and 3 with four replicate blocks. We found that suppression of the invasive species was greatest in monocultures of the dominant native species but that suppression at the four-species treatment level was on par with this monoculture. We also found that complementarity (diversity-invasion hypothesis) operates to reduce invasive species re-establishment and that the abundance and suppressive effect of the dominant species may be reduced at intermediate levels of richness (i.e. 1 and 2 species). For each system, optimal monocultures and richness levels need be assessed.
Audio/Video, Conference Presentation, SER2019
Pre-approved for CECs under SER's CERP program
Society for Ecological Restoration