Interspecific differences in above-ground growth patterns result in spatial and temporal partitioning of light among species in a tall-grass meadow

1 We compared allometric growth patterns, canopy structure and light interception for individual shoots of different species in a tall-grass meadow. 2 The vertical distributions of above-ground biomass, leaf area, height and leaf angles were measured, both early and late in the season, for individual shoots of Miscanthus sinensis (the dominant species), Lespedeza bicolor, Lysimachia clethroides, Astilbe thunbergii and Potentilla freyniana. A canopy model was developed to calculate light absorption by individual shoots. Light absorption per unit mass (Φ(mass)) was used to quantify the efficiency with which plants utilized biomass to capture light. 3 The leaf mass ratio (LMR), average specific leaf area (SLA) and therefore the leaf area ratio (LAR) decreased with shoot height and light availability. Light absorption per unit leaf area (Φ(arca)) increased with shoot height, and this increase was observed to be much stronger at greater than at smaller shoot heights. 4 In the taller species (Miscanthus and Lespedeza) (Φ(mass) (the product of LAR and Φ(area)) increased, while in the shortest species (Potentilia) it decreased with shoot height. Clones of Miscanthus and Lespedeza may thus increase total light capture by allocating shoot biomass among fewer taller shoots, and a clone of Potentilla by producing a larger number of shorter shoots. 5 Shoots of the shorter species were equally efficient in capturing light (i.e. they had similar Φ(mass)) early in the season, but less efficient later in the season than shoots of the taller species. Shorter species appear to be able to use the earlier part of the season for efficient light capture, while shoots of taller species gain an advantage from their height later in the season. 6 This study shows how different above-ground growth patterns of the species in a tall-grass meadow allow them to use different positions in vertical space and different periods of the season to absorb light efficiently. This is a clear example of niche separation and helps to explain the coexistence of these species.