Clonal growth and demography of a hemicryptophyte alpine plant: Leontopodium alpinum Cassini

Abstract

Clonally reproducing hemicryptophytic rosette plants are common in the alpine belt. However, their demography and, indirectly, their growth and reproductive strategy in these harsh conditions were rarely studied. We analysed the morphology, clonal reproduction and demography of one such species, Leontopodium alpinum, in two populations of the Swiss Alps. The species forms small colonies of 1–5 (maximum 30) sterile rosettes with a few flowering stalks. After flowering, the apical meristem dies and one or two new axillary buds grow below the previous rosette in the following year, developing into short rhizomes (<2 cm), which decay after 4 years. The new stalk produces sterile rosettes before flowering after 2–4 years, depending on climatic conditions. The apical meristem often dies during the sterile stage, and is replaced by a new axillary bud. Levkovitch matrices on two stages (sterile and flowering rosettes) showed that rosette survival and clonal reproduction maintain long-lived populations (λ = 0.96). Elasticities indicated that a change in the survival of sterile rosettes had the strongest effect on population dynamics, and this stage lasts, on average, 6.8 years at 2,480 m. Altogether, L. alpinum is following Tomlinson’s architectural model. This growth form appears perfectly adapted to harsh alpine conditions: the clonal ramification ensures longevity to genets and the semelparous behaviour of the rosettes allows an efficient flowering, whatever the climatic conditions. L. alpinum appears to follow a common growth model among rosette possessing hemicryptophytes in the alpine belt.