A. Pornon et B. Doche, AGE STRUCTURE AND DYNAMICS OF RHODODENDRON-FERRUGINEUM L POPULATIONS IN THE NORTHWESTERN FRENCH ALPS, Journal of vegetation science, 7(2), 1996, pp. 265-272
The ericaceous shrub Rhododendron ferrugineum occupies large areas at
the subalpine level (1600-2200 m) of the northwestern French Alps. It
frequently reaches 90-100% cover, accumulates 60-70t/ha (dry weight) a
bove-ground biomass and is able to dominate many subalpine landscapes
by outcompeting other species. We formulated the hypothesis that the s
pecies shows a rapid and invasive seedling establishment and a fast po
pulation development. We investigated the age structure and developmen
t of two populations. Although classic colonization stages can be iden
tified, and variation did occur depending on the site, R. ferrugineum
populations showed a surprisingly slow development compared with other
ericaceous species. Curves obtained from polynomial regression equati
ons of cover on age allowed us to predict the future development of po
pulations. Thus, depending on the site, it would take 150 to 250 yr to
achieve total cover. We discuss the factors involved that could expla
in this slow development and discuss which biotic and abiotic factors
may be responsible for the large extension of this species in the suba
lpine belt.