THE LINEAR RELATION BETWEEN STAND YIELD AND INTEGRATED LIGHT IN A SHADE-ADAPTED ANNUAL GRASS

Many ecology textbooks state that the photosynthetic response of plant s to varying light is represented by the response of single leaves, wh ich is a downward concave curve that often reaches saturation. Single leaves of the shade-adapted, annual grass, Microstegium vimineum (Trin ius) A. Camus, saturate at 25% full sunlight. However, two field exper iments showed that stand dry weight yield at the end of the growing se ason was a linear function of integrated light, rather than a downward concave saturation-type curve. The linear relation for M. vimineum st ands concurs with results of several agricultural studies and may have implications for forest growth models that assume saturation-type res ponse curves for whole trees or forest canopies.