Effects of Cutting or Planting after Prescribed Burning on the Flowering and Flowering Landscape of Native Rhododendrons

Abstract

Large colonies of native rhododendrons are usually well maintained on Naoshima Island in Western Japan. Human disturbances such as logging for fuel in salt manufacturing before the 1960s and frequent accidental fires after the 1960s have maintained these colonies. To determine how to preserve the colonies in the future, we compared effects of cutting and burning followed by planting on native rhododendrons. Plant biomass, except that of native rhododendrons, decreased in both treatments, and the light environment under the canopy of native rhododendrons became brighter. We also found that the flower bud ratio of Rhododendron kaempferi increased, and the flowering position of Rhododendron reticulatum and R. kaempferi expanded toward the ground in both treatments. However, treatment differences were observed in soil the nitrogen ratio, amount of sprouting, and cover of flowering colonies. Cutting caused these values to increase to a larger extent compared to burning followed by planting. Based on these results, we propose that cutting is more effective than burning followed by planting when attempting to extend the flowering landscape. In addition, cutting is the effective treatment for improving the landscape during the season when only R. reticulatum blooms.