Effects of Simulated Environmental Changes on Growth and Growth Form in a Late Snowbed Population of Pohlia wahlenbergii (Web. et Mohr) Andr
Sylvi M. Sandvik, Einar Heegaard
In a factorial field experiment we increased the temperature (Open Top Chambers) and nutrients (nitrogen, phosphorus, and potassium [NPK]) to simulate predicted future climate changes and studied the growth response of the acrocarpous bryophyte Pohlia wahlenbergii (Bryaceae) in a wet snowbed environment. The species shows a positive growth-length response to added nutrients and increased temperature. The stronger response to nutrients indicates a strong limitation of nutrients in the snowbed environment. There was an immediate response to nutrient treatment, whereas the temperature response was delayed. The growth response shows a clear interaction between temperature and nutrients. The immediate positive growth response is interpreted as a function of the wet habitat, since water makes the added nutrients immediately available to the plants. The growth form changed toward a more lax (loose) and desiccation-intolerant form with added nutrients. In a climate change scenario based on these results we hypothesize that bryophyte response will depend on the water availability from precipitation and from meltwater. In a drier environment we predict that bryophytes will become more constrained toward areas with a high continuity of meltwater, whereas increased precipitation may compensate for any changes in growth form, which would be positive for bryophytes.