Analysis of Growth and Nutrition of Six Plant Species of Woodland Clearings

SUMMARY (1) The work reported here deals with a glasshouse experiment to evaluate the application of growth analysis of dry weight and of four other variables to ecological problems, such as niche differentiation of co-existing species. (2) Six ecologically related species (i.e. species that facultatively occur together in one type of habitat, woodland clearings) with different life cycles were grown under defined conditions, and harvested at regular intervals during the first cycle of growth to determine the rate of ontogenetic drift of the growth variables. In addition to dry weight and leaf area per plant, the total amount of nitrogen (N), phosphorus (P), and potassium (K) in the plant organs was measured. (3) In all the species the relative accumulation rates of N, P and K show a similar pattern. (4) The differences between the species in productivity (maximum dry weight produced) seem to depend on differences in the maximum leaf area. (5) Species that differ in productivity and in life cycle strategy can have a similar niche with regard to N, P and K nutrition during the first year of growth. The (re)allocation of these elements, however, shows that niches differ in the next and subsequent years. (6) Ontogenetic drift of the various growth variables seems to be species specific. (7) Experiments dealing with both population ecology and growth of individuals, are needed to evaluate the mechanisms of niche differentiation.