Abstract:

In Three Gorges reservoir region, a great many of trees are needed for vegetation restoration and land greening following the massive constructions (e.g. construction of roads, highways, buildings) associated with the great dam project at Three Gorges of Yangtze River. Ficus microcarpa L. and F. virens Ait. var. sublanceolata (Miq.) Cornor (Moraceae) are chosen and widely planted in this region as ornamental trees and/or shade trees due to their shapely crowns and ability of growing on soils with low fertility. Vegetative multiplication, which uses branch cuttings to cultivate saplings, is the main way for tree propagation of the two species in Three Gorges reservoir region. Obtaining branch cuttings causes the damage of tree crown and probably affects the growth of trees. In this study, the shoot production pattern of two Ficus tree species following crown damage, which is crucial to the regrowth of trees, was investigated. Data from a crown damage experiment with two damage seasons and a series of damage intensities were analyzed. It was shown that crown damage, regardless of damage intensity and damage season, had no effect on the shoot production of lateral branches of both species. However, the shoot production on the main stem was position-dependent in both F. microcarpa and F. virens trees. Crown damage, conducted either in spring or in autumn, did not affect the number and density of new shoots on the newly grown upper stem parts and the branched stem parts within the residual crown, but facilitated the shoot production on the bare stem parts beneath the residual crown in terms of both shoot number and density. Shoot production on the bare stem parts increased with damage intensity. In addition, it was found that damage in autumn led to a stronger emergence of shoots from the bare stem parts than spring damage. Some mechanisms which could be involved in these results are discussed. Based on the experimental results, it is suggested that among all investigated variables, only the enhanced shoot production on the bare stem parts may increase the biomass partitioning to leaves and benefit the regrowth of damaged trees.

Key words: crown damage, Ficus microcarpa , Ficus virens , shoot production, Three Gorges reservoir region