A comparison of the nutrient status of Molinia caerulea and neighbouring vegetation in a rich fen.

M. El-kahloun et al., A comparison of the nutrient status of Molinia caerulea and neighbouring vegetation in a rich fen., BELG J BOT, 133(1-2), 2000, pp. 91-102
Citations number
Categorie Soggetti
Plant Sciences
Journal title
ISSN journal
0778-4031 → ACNP
Year of publication
91 - 102
SICI code
In the absence of management and with sustained non-point source pollution, the diversity of European low productive herbaceous vegetation is under th reat. In many cases dominant grasses exclude other species. Molinia caerule a is such a potential dominant species. In a Campine rich fen near Mol, aer ial photos show progressive invasion by M. caerulea tussocks. Marginal zone s are completely closed by M. caerulea, while in ground water discharge zon es open low growing vegetation persists mixed with small M. caerulea tussoc ks or non-tussock individuals. During the tussock development process, M. c aerulea shows a preference for the slightly drier marginal sites, contrary to the wettest ground-water discharge flushes where it is present as non-tu ssock individual shoots. This contrast was used to make a comparative study between zones and growth form of M. caerulea and its relation with neighbo uring species. We investigate the hypothesis that differential M caerulea p erformance is caused by differences in nutrient availability. Biomass and n utrient concentrations of M . caerulea shoots were investigated in relation to their location (marginal I ground-water discharge) and in relation to t heir growth form (spread non-tussock individual shoots / tussock shoots). M . caerulea shoots from marginal sites grew larger than shoots from central sites and tussock shoots proved superior to individual shoots. From the nut rient concentrations and the known P-limitation of the site, it is conclude d that the P-availability is responsible. It appears that M. caerulea tusso cks set up an efficient retranslocation of P. The mechanism is also present in non-tussock individuals, where it proved more efficient in the marginal sites. The biomass and N- and P concentration in M. caerulea leaves from n on-tussock individuals and tussocks of increasing height in the ground-wate r discharge sites were investigated. June leaf P-concentrations, were unexp ectedly low in shoots from small (10-30 cm) tussocks as compared to non-tus sock shoots. This invalidates a straightforward relation between P-availabi lity and M. caerulea development in the wettest sites. Possible explanation s are discussed. Overall the set-up of an efficient retranslocation of P se ems crucial in the development of M. caerulea dominance in this type of fen s.