Effect of nutrient and light stress on the mortality and growth of young clonal and non-clonal herbs after biomass removal

Abstract

Clonal herbs form belowground organs where they store reserves and bear regenerative buds. Based on these characteristics, clonal herbs may deal with disturbances better than non-clonal herbs, and clonality is seen as an adaptive strategy in disturbed habitats. The advantage of being clonal is likely to be enhanced in stressful conditions where larger belowground storage is beneficial. We conducted a greenhouse experiment to examine the ability of young plants to deal with biomass removal when exposed to light or nutrient stress or its combination. Using congeneric pairs of species, we evaluated the ability of clonal versus non-clonal groups to cope with biomass removal in terms of mortality, biomass productivity, specific leaf area and root-to-shoot ratio. We found that clonal and non-clonal herbs produce the same amount of biomass when injured and that nutrient and light stress does not alter biomass production. Both groups responded similarly to the biomass removal by increasing the specific leaf area and root-to-shoot ratio. Very young clonal herbs had higher mortality than non-clonal herbs of the same age. This fact suggests a higher survival probability in the non-clonal group, presumably originating from a greater population dependence on generative reproduction. We conclude that belowground organs in young plants, and thus bud banks and belowground storage, are not yet formed enough to give clonal herbs an advantage over non-clonal ones, and the advantage of clonality might manifest later in life when belowground organs are fully developed.