Growth and photosynthesis of seedling of five bottom land tree species following nutrient enrichment

Land management practices are increasingly focusing on the use of native plant communities to filter wastewater. Nutrient uptake from these effluents may affect overall growth and physiology. We examined the effects of increased nutrient levels on the seedlings of five species of bottomland trees. Seedlings of Carpinus caroliniana Walter. (hornbeam), Pinus serotina Michaux (pond pine), Acer rubrum L. (red maple), Quercus michauxii Nuttall (swamp chestnut oak), and Q, nigra L. (water oak) were grown outside in full sun under six levels of nutrient enrichment. During the 3rd growing season, height, component biomass, total biomass, net photosynthesis per unit leaf area and foliar nitrogen concentrations were determined. Height and total biomass of all species increased from low to high nutrient levels, with A. rubrum and P. serotina exhibiting the highest rates of increase. Biomass and foliar nitrogen relationships suggested differing patterns of nutrient uptake and use among the species. Acer rubrum, C. caroliniana and Q. michauxii used all nitrogen taken up for growth. Pinus serotina showed an accumulation of foliar nitrogen with a rapid rate of growth. Wuercus nigra grew more slowly. The effect of nutrient level on net photosynthesis was variable and species-specific. Only W. nigra and A. rubrum showed a positive relationship. Net photosynthesis and foliar nitrogen showed no clear relationship among individual species, although a regression of all species together showed net photosynthesis to be positively correlated to foliar nitrogen. In a natural setting, the biomass response of A. rubrum and P. serotina, along with a corresponding increase height, could give seedlings of these species a competitive advantage in capturing light or tolerating floods. Differential responses may thus alter the competitive relationships of these five species in nutrient-enriched bottomland forest communities. 37 refs., 4 figs., 3 tabs.