Effect of Light and Simulated Herbivory on Growth of Endangered Northeastern Bulrush, Scirpus ancistrochaetus Schuyler

The independent and interactive effects of light and simulated herbivory on growth and biomass allocation in the endangered emergent sedge, Scirpus ancistrochaetus Schuyler, were examined in a 15-week common garden experiment. Light level was manipulated through the use of shade cloth to attain shading levels of 0%, 30%, 63% and 90%, while herbivory was simulated by reducing plant height by 50% six weeks into the experiment. Multivariate Analysis of Variance (MANOVA) of final total (shoot + root) plant mass, leaf width and root to shoot ratio (R:S) indicated overall significant effects of both light and the interaction of light and clipping. Means of these variables decreased with decreasing light level. Furthermore, means of these variables were generally higher for clipped plants than unclipped plants in 0% shade, while they tended to be lower in clipped plants in all other levels of shade. Maximum leaf height was also significantly affected by light. Leaf height was similar in all treatments for the first 11 weeks. For the last four weeks of the experiment, however, leaf height was lowest in plants grown in 0% shade, highest in plants grown in 63 and 90% shade, and intermediate in plants grown in 30% shade. Clipped plants tended to be taller than unclipped plants at lower levels of shade, while the opposite was true at higher levels of shade, although effects were marginally significant. Both light and the interactive effect of light and clipping were important determinants of growth of S. ancistrochaetus in this experiment and therefore may be important influences on its distribution within and among pond habitats