Journal Article

test of the effects of functional group richness and composition on grassland invasibility

Symstad, Amy J.

2000

Overview

Although many theoretical and observational studies suggest that diverse systems are more resistant to invasion by novel species than are less diverse systems, experimental data are uncommon. In this experiment, I manipulated the functional group richness and composition of a grassland community to test two related hypotheses: (1) Diversity and invasion resistance are positively related through diversity's effects on the resources necessary for invading plants' growth. (2) Plant communities resist invasion by species in functional groups already present in the community. To test these hypotheses, I removed plant functional groups (forbs, C3graminoids, and C4graminoids) from existing grassland vegetation to create communities that contained all possible combinations of one, two, or three functional groups. After three years of growth, I added seeds of 16 different native prairie species (legumes, nonleguminous forbs, C3graminoids, and C4graminoids) to a 1× 1 m portion of each 4× 8 m plot. Overall invasion success was negatively related to resident functional group richness, but there was only weak evidence that resident species repelled functionally similar invaders. A weak effect of functional group richness on some resources did not explain the significant diversity-invasibility relationship. Other factors, particularly the different responses of resident functional groups to the initial disturbance of the experimental manipulation, seem to have been more important to community invasibility.

• Publisher: Ecological Society of America
• Subject: Animal and plant ecology / Animal, plant and microbial ecology / Biodiversity / Biological and medical sciences / Biological invasions / botanical composition / Cedar Creek Natural History Area, Minnesota, USA / Colonizing ability / Communities / community assembly / community composition / disturbance / diversity / Ecological invasion / ecosystem properties / Ecosystems / Environmental aspects / Forbs / Functional groups / Fundamental and applied biological sciences. Psychology / graminoids / Grasses / grassland / Grassland ecology / Grasslands / invasion / Invasive species / legumes / Observational studies / plant communities / plant ecological groups / plant functional groups / Plant growth / Plant introduction / plant invasiveness / Plants / seeds / Species / Species diversity / Synecology / Terrestrial ecosystems