Rehabilitation of deteriorated plantations

Rehabilitation is urgently needed for deteriorated plantations because deterioration of plantations and natural disasters have resulted in low productivity of these plantations. The objective of our study was to investigate the effects of row salvage cutting on stand composition and structure, planted seedlings and light environment in poor productivity plantations of ILan County, Taiwan, for improving forest form and replanting step by step in order to build multi-storied stand. The plot A in the experimental area included a cut belt and an uncut belt, 20 m wide each; the plot B included a 8 m wide cut belt, and a 10 m wide uncut belt. The targets of cutting were shrubs and weak trees. After cutting, the seedlings of Sapindus mukoross, Michelia formosana, and Calocedrus formosana were replanted in patches on November 2011, and growth adaptation in forest gaps was compared. The investigation of stands two years after salvage cutting showed that growth of retained trees was promoted, but prone to wind damage. There was a big variation of light intensity in daytime was affected by cutting width and land form. The amount of adopted light in plot A was higher than that in plot B, and canopy cover was restored gradually two years after cutting in plot B. The survival rate of seedlings in plot A was slightly higher than that in plot B, but without significant difference. The survival rate (87%) of S. mukorossi seedlings was higher than that (50%) of M. formosana and C. formosana. The mortality rate of S. mukorossi and M. formosana varied with season due to environmental and biological damages. The poor quality of C. formosana seedlings limited its survival rate. The plot A was the best if taking into account the height and basal area of seedlings, and the seedlings of S. mukorossi grew fastest. Regarding index of robust (ratio of height to diameter of the tree), seedlings in plot B with small gaps grew to be thin type. From the 2 year growth of seedlings of three species in the gap between two crowns, we concluded that plot B with small gap is not in favor of the growth of seedlings and we suggest that the width of cutting should be greater than the height of the trees. While planting multi-storied forest of belt type in the future, the width of cutting should be greater than the height of original stand, which leads to greater gaps and is in favor of growth of planted seedlings. Furthermore, seedlings in best quality should be utilized. Especially management in the initial stage of planting should be conducted because new seedlings can be damaged by surrounding environment and wild animals.