Biomass and shoot/root allocation of five species from a grassland succession series at different combinations of light and nutrient supply

In recent literature the relative importance of interspecific differences in shoot/root allocation patterns and differences in growth rate have been discussed, especially with regard to the mechanisms of succession. We studied growth, leaf area and shoot/root ratio under controlled conditions at various combinations of light and nutrient supply of five species from a grassland successional series. This series was initiated by stopping the application of fertilizers to agricultural grassland but continuing hay-making. Species from the later successional stages (lower nutrient availability, higher level of light at the soil surface) had a higher shoot/root ratio at most treatments, contrary to the predictions of the resource ratio hypothesis. However, a three-way interaction was also found, and thus the combination of light and nutrient level determined whether or not a correspondence between successional position and the sequence of species in shoot/root ratio was found. Some possible explanations are discussed for these results with regard to the mechanisms of succession