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Nitrogen and Phosphorus Tissue Concentrations in 41 Wetland Plants: A Comparison Across Habitats and Functional Groups
C. L. McJannet, P. A. Keddy and F. R. Pick
Vol. 9, No. 2 (Apr., 1995), pp. 231-238
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/2390569
Page Count: 8
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1. Increased nutrient loading to wetlands often results in an increase in emergent plant biomass and a decrease in species diversity. While these patterns are broadly predictable, the underlying mechanisms are unknown. We tested two related hypotheses by growing plants under standardized conditions: (1) emergent plants typical of infertile wetlands have higher tissue nutrient contents than plants from fertile wetlands and (2) plants belonging to different functional groups (ruderal, interstitial and matrix) have different tissue nutrient contents. 2. Concentrations of N and P in above-ground phytomass were measured for 41 plant species, from contrasting kinds of wetlands, after one season of growth in excess fertilizer (NPK in ratios 7:11:27 and 15:0:0). Tissue nutrient concentrations ranged from 0.25 to 2.14% dry weight for N and from 0.13 to 1.07% dry weight for P. 3. There was no significant difference in nutrient content between plants from infertile sites and plants from fertile sites. However, plants with `ruderal' life history traits (e.g. annual or functional annual/fast-growing) had significantly lower N and P tissue concentrations than plants having `interstitial' or `matrix' life-history traits. Interstitial perennials had significantly higher N concentrations than matrix perennials. Therefore, plant functional groups are likely to respond differently to eutrophication. 4. Plant size, estimated by maximum species biomass, explained 67% (r2 = 0.67, P < 0.001, n = 31) of the variation in N tissue concentrations but only 5% of the variation in P tissue concentrations.
Functional Ecology © 1995 British Ecological Society