Lignotuber reserves support regrowth following clipping of two Mediterranean shrubs

1. We investigated whether reserves stored in the lignotubers of two Mediterranean shrubs, Arbutus unedo and Erica arborea, were significantly mobilized to support the demands of regrowth and respiration after clipping the tops at different frequencies. 2. After a single clipping, Arbutus showed a 29% decrease of phosphorus concentration by the end of the first growing season. Two years after recovery from clipping, the starch levels remained lower than those of unclipped plants. Similarly, Erica showed depletion of starch, but no nutrient reserves were depleted significantly. 3. Regrowth after multiple clippings mobilized a large fraction of the starch and nutri ents stored in the lignotuber. Mean starch concentrations were depleted by 87-93% after multiple clippings and concentrations of nitrogen, phosphorus, potassium and magnesium were depleted by 10-45%, 27-41%, 19-39% and 23-31%, respectively. 4. An average-sized lignotuber produced 288 resprouts for Arbutus and 1990 resprouts for Erica during a 27 month period of multiple clippings, at the end of which the first plants died. 5. Plant mortality after multiple clipping was 10% for Arbutus and 30% for Erica, and was primarily attributed to exhaustion of carbon reserves because starch concentrations decreased by 96% in dead plants.