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Species Richness-Productivity Patterns Differ between N-, P-, and K-Limited Wetlands
H. Olde Venterink, M. J. Wassen, A. W. M. Verkroost and P. C. de Ruiter
Vol. 84, No. 8 (Aug., 2003), pp. 2191-2199
Stable URL: http://www.jstor.org/stable/3450042
Page Count: 9
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We evaluated whether the kind of nutrient limitation (N, P, or K) may affect species richness-productivity patterns and subsequently may explain variation in species richness and in richness of threatened species. We present a data set from previous studies in wetlands in Poland, Belgium, and The Netherlands and examine species richness-productivity patterns for vascular plants in all 150 sites together as well as for N-, P-, and K-limited sites separately. The kind of nutrient limitation was assessed by N:P, N:K, and K: P ratios in the vegetation. Critical values for these ratios were derived from a literature review of fertilization experiments. The kind of nutrient limitation influenced species richness-productivity patterns in our 150 sites through large differences in productivity. P (co)-limitation occurred only at low productivity, K (co)-limitation up to intermediate productivity, and N limitation along the entire productivity gradient. There was a decreasing trend in species richness with increasing productivity for K (co)-limited sites, whereas for both the N-limited sites and P (co)-limited sites a sort of "filled hump-shaped curve" was observed. The species richness-productivity relationship for threatened species was restricted to a much narrower productivity range than that for all species. Richness of threatened species was higher in P (co)-limited sites than in N-limited sites, suggesting that increased P availabilities in wetlands may be particularly important in causing disappearance of threatened species in western Europe. The role of nutrient limitation in species richness-productivity relationships not only reveals mechanisms that may explain variation in species richness and occurrence of threatened species, but it also may be important for nature management practice.
Ecology © 2003 Wiley