High nitrogen : phosphorus ratios reduce nutrient retention and second-year growth of wetland sedges.
Shifts from nitrogen (N)- to phosphorus (P)-limited growth due to high N deposition may alter the functioning of wetland vegetation. This experiment tested how N vs P deficiency affects the growth and nutrient use of wetland sedges. Five wetland Carex species were grown at nine N : P supply ratios (0.6-405) with two absolute levels of N and P. Biomass and nutrient concentrations were determined after one and two growing seasons. Shoot biomass was maximal at N : P supply ratios of 15-26 after one season but 5-15 after two seasons. Photosynthesis after the first season, second-year growth, leaf longevity, and the fraction of nutrient supply retained by plants over two seasons were all negatively related to N : P supply ratios, with small effects of absolute supply. The five Carex species responded similarly to N : P ratios but differed in nutrient resorption efficiency and biomass allocation. Plants treated with high N : P ratios appeared to lose nutrients below ground. Such losses may reduce plant performance in P-limited wetlands affected by high N deposition.
Güsewell
Sabine
S
Geobotanical Institute ETH, Zürichbergstrasse 38, CH-8044 Zürich and Utrecht University, Department of Geobiology, PO Box 80084, NL-3508 TB Utrecht, the Netherlands. sabine.guesewell@env.ethz.ch
D018533:Biomass; D031255:Carex Plant / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D017753:Ecosystem; D035264:Flowers / Q000254:growth & development; D009584:Nitrogen / Q000502:physiology*; D010758:Phosphorus / Q000502:physiology*; D018515:Plant Leaves / Q000254:growth & development; D018517:Plant Roots / Q000254:growth & development; D018520:Plant Shoots / Q000254:growth & development; D027343:Rhizome / Q000254:growth & development; D013045:Species Specificity; D013997:Time Factors
D010758:Phosphorus; D009584:Nitrogen