Short-term effects of simulated environmental changes on phenology, reproduction, and growth in the late-flowering snowbed herb Saxifraga stellaris L

Manipulations of temperature, soil nutrient, and light conditions were conducted over two years in alpine southwest Norway to simulate impacts of climate change in the late-flowering, perennial snowbed herb Saxifraga stellaris L. The temperatures were increased with Open Top Chambers by 1.6∞C (air) and 2.6∞C (soil) during daytime and light availability reduced for about seven hours per day by shading sheets. Reproduction and seasonal changes in plant size showed differential sensitivity to temperature and soil nutrient. In general, reproduction was more restricted by temperature than by soil nutrients, whereas plant size responded to nutrient addition and not to increased temperature. The experimentally warmed plants had shorter prefloration time and were capable of accelerating their seed maturation as compared to the control plants. This suggests that seed set may be more regular in a warmer climate. By contrast, shading exerted strong negative effects on both seed number and growth in the second year, but there was no significant impact of shading on pre- and postfloration time, fruit number per plant, or seed weight in the second year. Except for an interactive effect of soil nutrient addition and shading on seed weight, no other interactions between treatments were significant. Accelerated phenology and increased reproductive output of Saxifraga stellaris under warming may be particularly important for the species' ability to accommodate to new available terrain at higher altitudes, where it may be displaced to in a future warmer climate.