Phenology and Reproductive Success in Arctic Plants: Susceptibility to Climate Change

Abstract

Reproductive success in tundra plants is highly influenced by phenology and microclimatic variations in time and space (Molau, 1993a; Walker et al., 1995). Climate change and associated alteration of the growing season could therefore have a strong impact on the performance of arctic and alpine plants (Bazzaz, 1990; Galen and Stanton, 1995). Recent autecological studies (e.g., Eriksen et al., 1993; Molau, 1993b; Stenström and Molau, 1992) have shown that there are strong correlations between reproductive strategies and flowering phenology in tundra plant species (see Molau, 1993a, for review). In this context, Bliss’s (1956) categorization of the species in phenoclasses (vernal, early aestival, and late aestival) reflecting their flowering time is most useful. Early flowering (“vernal”) species tend to be predominantly outcrossing, and they spend considerable time on selective seed abortion prior to final maturation of the fruits. At the other end of the phenological gradient, “late aestival”species, such as many snowbed species, show the opposite strategy, being predominantly inbreeding and with low levels of seed and fruit abortion (Eriksen et al., 1993; Molau, 1993a, 1993b). Sexual reproduction in vernal species is mainly pollen-limited, since pollination is hazardous in early summer in the Arctic, but there is usually some seed output every year. Late-flowering species have a reliable, although mainly autogamous, pollination, but successful seed maturation and, thereby, reproductive success does not take place all years due to variable onset of winter (Molau, 1993a).