S. Greipsson et Aj. Davy, RESPONSES OF LEYMUS-ARENARIUS TO NUTRIENTS - IMPROVEMENT OF SEED PRODUCTION AND SEEDLING ESTABLISHMENT FOR LAND RECLAMATION, Journal of Applied Ecology, 34(5), 1997, pp. 1165-1176
1. Iceland has vast areas of mobile sand resulting from volcanic glaci
er bursts and erosion. Seed of the coastal, dune-building grass Leymus
arenarius is harvested from natural stands for use in extensive land
reclamation programmes. We investigated the economic use of fertilizer
treatments in managing the production of seeds, and to facilitate the
establishment and survival of seedlings. 2. Seed yield could be incre
ased dramatically-in coastal dunes by the application of nitrogen fert
ilizers, mainly as a result of increased flowering-spike density. Litt
le short-term advantage accrued from additions of phosphorus or potass
ium. Additions of N (rapid-release formulations) at 50-100 kg ha(-1) c
ould be highly cost-effective in providing the current production from
a much smaller area of dunes or in increasing seed production. Other
consequences would be to minimize the environmental impact of harvesti
ng and to allow more focused management of the seed resource. If perio
dic applications of P and K should prove necessary to maintain yield,
they would be economically justifiable. 3. Establishment of seedlings
on volcanic, sandy barrens over the first two seasons from sowing was
improved by the application of slow-release fertilizers; however, rapi
d-release formulations applied annually, produced a similar tiller den
sity and biomass after 4 years more economically. Untreated control po
pulations became extinct over the same period, underlining the necessi
ty for nutrient addition. A sand-culture experiment indicated that pla
nts severely deprived of P allocated more dry mass to roots and rhizom
es, and those deprived of K allocated more to above-ground parts. Thes
e responses might be manipulated to improve establishment in slowly an
d rapidly accreting environments, respectively. 4. The seed production
of moribund, late-successional stands could not be rejuvenated by fer
tilizer application. On the contrary, where there was a vegetational r
esponse, competing species were stimulated at the expense of L. arenar
ius.