Response of clonal versus non-clonal herbs to disturbance: Different strategies revealed

摘要

Disturbance is an omnipresent selective factor that shapes plant strategies. While annual species that rely on rapid generative reproduction dominate in habitats frequently affected by severe disturbance, long-lived woody species occupy habitats where the effects of disturbance are weak. These are, however, the extremes in the disturbance gradient. Habitats under intermediate disturbance are occupied by the whole spectrum of plant strategies. In this study, we hypothesized that clonal herbs are better adapted to intermediate disturbance than non-clonal herbs because the characteristics of their bud bank and related belowground carbohydrate storage promote vegetative regeneration. In a greenhouse experiment, we tested the effects of disturbance on the survival and performance of 17 congeneric pairs of clonal and non-clonal herbs cultivated from seed. In addition to a non-disturbed control, we applied five disturbance treatments: biomass removal 2 cm above the soil surface, removal of 70 % of the aboveground biomass, late spring frost, flooding, and belowground injury. Mortality was negligible except the flooding treatment, where it was higher for non-clonal than for clonal plants. Total biomass was reduced more by the disturbance treatments for clonal than for non-clonal plants, suggesting that clonal species suffer more than non-clonal species. On the other hand, clonal plants had significantly greater total belowground biomass and R:S ratios than non-clonal plants, suggesting a strong investment in belowground organs by clonal plants. In response to disturbance, the SLA and SRL values increased in clonal plants but decreased in non-clonal plants, indicating that clonal and non-clonal plants differ in how they cope with disturbance. Although clonality is considered to be an adaptation to disturbance, our results indicate that, during the first year of life, clonal herbs are more sensitive to disturbance than non-clonal herbs, likely due to preferential investment in belowground biomass.