Environmental control of the prostrate growth form in two high arctic grasses

In the High Arctic, leaf angles of graminoids are lower than would be expected to optimize absorption of incident solar radiation. Inflorescence, leaf, and culm angle of two prostrate grasses, Phippsia algida and Puccinellia vaginata , were measured in a variety of plant communities with differing microtopographic and microenvironmental conditions (surface relief, soil stability, soil moisture, and soil and air temperature). Growth form was found to be controlled primarily by environmental factors. Both species exhibited a plastic response to an amelioration of physical factors in situ. Leaf angles of both species were higher under conditions of increased soil moisture and temperature, and decreased vapor pressure deficit and windspeed. Adaptation to reduce the severity of the environment apparently holds a greater selective advantage than adaptation to maximize leaf orientation to a low sun angle.