PARENT SESSION
Contributed Oral Session 164: Wetland Chemistry
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 520 C, Level 5, Palais des congrès de Montréal

The effects of the N:K supply ratio on plant species performances in wetlands.

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

ABSTRACT- In the last decade, species richness in mesotrophic wetlands has drastically decreased. In many types of wetlands (wet-meadows, fens and bogs) shifts have occurred from low-productive and species-rich communities to highly productive and species-poorer communities. The productivity increase is the result of increased availabilities of nutrients, in particular nitrogen (N), phosphorus (P) and potassium (K). Several studies have suggested that a decline in species richness is associated with shifts in nutrient limitation by these three elements. These shifts may not only affect species composition in the wetlands, but also influence plant growth, nutrient use, plant productivity, interspecific composition and plant species diversity. Although many studies have provided important clues for understanding the differences in species composition among ecosystems, only few of them have directly compared the effects of N and P supply to those of K supply. The latter would be needed to understand changes in N-limited to either P- or K-limited conditions. The use of nutrient concentrations in plant biomass as an indicator of nutrient availability and limitation in wetlands has been subject of debate. Some studies suggested that K limitation can be detected by determining N:K and P:K ratios in addition to N:P ratio. Moreover, many studies indicated that a N:P ratio of 15 is the optimum for plant growth. However, researchers disagree on the optimal value of the N:K ratio. In this study, we have identified a critical N:K ratio on the basis of experimental nutrient addition studies to pot plants in which we directly manipulated the N:K ratio to understand the effect of different N:K supply ratios on plant performance.

Key words: N:K ratio, N,K limitation, biomass production, nutrient concentration