The effect of experimental defoliation on the growth and reproduction of a woodland orchid, Tipularia discolor

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Abstract
Leaves of individuals of Tipularia discolor were subjected to 3 years of manual defoliation to simulate natural patterns of herbivory. Compared with controls, plants that were 100% defoliated did not reproduce sexually after two defoliations, the biomass of new belowground corms decreased significantly in the 1st year and each year thereafter, and leaf biomass declined significantly after three defoliations. Senescence of belowground corms and mortality of entire plants were highest in the 100% defoliation treatment. The responses of plants with 50% defoliation were intermediate. The study demonstrates that belowground corms are the first biomass component to be negatively impacted by complete and partial defoliation. Reductions in corm biomass resulting from leaf herbivory would eventually reduce leaf biomass and sexual reproduction. Key words: woodland herb, herbivory, biomass allocation, reproduction, Tipularia discolor, Orchidaceae, defoliation.