The role of root nutrient reserves in regrowth of two savanna shrubs

Abstract

The critical nutrient(s) limiting vegetative regrowth following shoot destruction by burning or cutting were identified in two neotropical savanna shrubs, Miconia albicans and Clidemia sericea, growing in the Mountain Pine Ridge Forest Reserve, Belize. Only starch, and not Ca, Mg, K, or P, was significantly depleted in the roots of these shrubs after both a single burn and repeated annual burns. Phosphorus was depleted only after repeated burns, while the other mineral nutrients showed no significant decline. In roots that failed to sprout following repeated shoot cuttings at 2-month intervals, phosphorus was reduced by 35–45% and starch was reduced by 97–98% compared with unburned roots. Therefore, root starch was indicated as a critical nutrient that limited resprouting ability. Root starch reserves were replenished to preburn levels within 2 years following a burn, suggesting that a cumulative net decline would occur only with annual burning. The decline in root starch was paralleled by a decline in growth of 1-year-old shoots under annual burning.