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Differential recovery of above‐ and below‐ground rich fen vegetation following fertilization
Authors:Mohssine El‐Kahloun  Dirk Boeye  Vronique Van Haesebroeck  Bart Verhagen
Institution:Mohssine El‐Kahloun,Dirk Boeye,Véronique Van Haesebroeck,Bart Verhagen
Abstract:Abstract. For seven years we studied the recovery of vegetation in a Belgian P limited rich fen (Caricion davallianae), which had been fertilized with nitrogen (200 g.m?2) and phosphorus (50 g.m?2) in 1992. The vegetation in this fen has low above‐ground biomass production (< 100 g m?2) due to the strong P limitation. Above‐ground biomass was harvested from 1992 to 1998 and P and N concentrations measured. In 1998, below‐ground biomass was also harvested. The response to fertilization differed markedly between below‐ and above‐ground compartments. Above‐ground, P was the single most important factor that continued to stimulate growth 7 yr after fertilization. Below‐ground, N tended to decrease live root biomass and increase dead root biomass and seemed to have a toxic effect on the roots. In the combined NP treatment the stimulating effect of P (an increase of live root biomass) was countered by N. The 1998 soil analysis showed no difference in soil P in the plots. Thus, Fe hydroxides are not capable of retaining P in competition with fen vegetation uptake. However, higher capture of P in root Fe coatings from N plots may partially explain this negative N effect. The results suggest that N root toxicity will be amplified in strongly P limited habitats but that its persistence will be less influenced by P availability. This mechanism may be a competitive advantage for N2 fixing species that grow in strongly P limited wetlands.
Keywords:Belgium  Biomass  Caricion davallianae  Fertilization  Wetland  Phanerogams: Van der Meijden et al  (1983)  Cryptogams: Margadant & During (1982)
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