PARENT SESSION
Poster Session 3: Aquatic Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 210 D, Level 2, Palais des congrès de Montréal

Effect of N, P and K supply on biomass and nutrient concentration of 12 plant species.

Lawniczak, Agnieszka Ewa^*,1, Verhoeven, Jos T.A.¹, ¹ Utrecht University, Utrecht, The Netherlands

ABSTRACT- The species composition, species diversity and biomass production of wetlands are strongly affected by the rates at which limiting nutrients such us nitrogen, phosphorus or potassium are supplied. Several studies have suggested that a decline in species richness is associated with shifts in growth limitation by these three elements. Shifts from N limitation to P or K limitation can occur as a result of high atmospheric N deposition, climate warming, elevated CO₂, vegetation management through mowing and grazing, haymaking or drainage. Increased nutrient availability, particularly N, often reduced species richness by increasing productivity, which is associated with a dominance of plant species with high relative growth rates and competitive ability. Changes in the balance of N, P and K availability may hamper attempts to restore species-rich wetland communities after human disturbance. In this project, the effects of nutrient availability changes on biomass production, nutrient concentration, and leaf turnover of wetland plant species have been tested. The aim of this study was to answer the following questions: 1. How do plants grown at high N supply respond to shortage of N, P or K in the next growing season? 2. How are short-term responses of different plant species to N, P, K enrichment related to their biomass N:P, N:K and P:K ratios? Three groups of plant species: grasses, forbs and sedges have been used with variations of supplies of N in the first year and of three nutrients (N, P, K) in a factorial design in the second year. This experiment has shown that increased supply of N, P and K affects the growth and nutrient use of plants differently. In the first year of growth all species responded significantly to N supply and fast growing species tended to benefit the most. In the second year high N supply had a smaller growth-stimulating effect because of strong limitation by P and K. Species with small biomass tended to benefit the most. ™á

Key words: fertilisation experiment, N,P,K limitation, nutrient concentration, biomass production