Effects of light availability on the germination, growth and survival of alien grasses and native trees and shrubs.

摘要

Strategic canopy development may reduce the presence of alien grasses and foster native, self-sustaining communities in abandoned pastures. In a three-part study I examined the effect of light availability on common native woody and alien grass species found in secondary forests in Hawaii. In the first part, I examined the relationship between light availability and canopy type on understory grass and litter biomass under different canopy types. In the second and third parts, I manipulated light availability in two separate experiments to determine the effect of light availability on germination, growth, and survival of six native woody species and three alien grasses. I found a reduction in understory grass biomass with canopy development and a significant positive relationship between understory light availability and grass biomass. Although germination and survival were not suppressed by low light conditions, relative growth rate was reduced for seven of the nine species tested.