Vegetative traits predict grass species’ invasiveness and the invasibility of restored grassland

Abstract

Understanding how grass species’ traits relate to their invasiveness and the invasibility of their monocultures can inform restoration of diverse grassland. We measured vegetative traits for 18 bunch grass species local to Pietermaritzburg (KwaZulu-Natal, South Africa) and measured  their competitive effect on a phytometer. Using 3 m × 3 m plots  planted as monocultures 12 years earlier, we related principal components of these traits to how species had invaded other species’ plots (invasiveness), and how their monocultures had been invaded (invasibility). Species with high total leaf mass, many tillers and low specific leaf area (SLA) were most invasive and most resistant to  invasion by other grasses. Short, slow-growing grasses were most  invasible by forbs. This was partly explained by linking traits to invasion through competitive effect: grasses with high total leaf mass,  many tillers and low SLA showed the strongest competitive effect,  which appears to be necessary but not sufficient for invasiveness. Thus, traits can predict species’ ecological performance and provide  insight into the processes structuring plant communities. Restoring  grasses with short stature, slow growth, low leaf mass, few tillers, and  high SLA may facilitate invasion by other native species, thereby increasing species richness.

African Journal of Range & Forage Science 2009, 26(2): 59–68