The light environment, morphology and growth of the early successional tree species Litsea citriodora Yoshiyuki Miyazawa a, * , Shirasa Tatsuya a , Kihachiro Kikuzawa b , Kyoichi Otsuki a a Experimental Forest of Fukuoka, Graduate School of Kyushu University, Fukuoka 811-2415, Japan b Department of Environmental Science, Ishikawa Prefectural University, Nonoichi, Ishikawa 921-8836, Japan Received 3 March 2006; received in revised form 11 July 2006; accepted 11 September 2006 Abstract The light environment and growth traits of the pioneer tree species Litsea citriodora in a recently clear-cut plantation were investigated in order to reveal the establishment process and growth of this species under annual weeding after clear-cutting. We investigated the light environments and the morphology, physiology and aboveground architecture of L. citriodora saplings in a plot that included both clear-cut open areas and forest floor under a conifer canopy. Dense populations of L. citriodora saplings were found in the open sites but few were observed on the forest floor. Saplings that originated from old stumps (sprout-saplings) were tall in height and dense, but seedlings were sparse and lower in height than the competitive tall herbaceous species Solidago altissima. Saplings of L. citriodora showed a higher leaf area per aboveground mass and greater area-based photosynthetic capacity than saplings of the co-occurring pioneer tree species Mallotus japonicus and Clerodendron trichotomum. Moreover, the L. citriodora saplings had a main stem with a larger length per mass ratio and more efficiently elongated per unit aboveground mass than M. japonicus and C. trichotomum. Sprout-saplings of L. citriodora attained rapid vertical elongation with rapid biomass acquisition as a result of their aboveground shoot architecture, allowing competition with S. altissima. Clear-cutting and subsequent weeding not only created open sites favorable for this pioneer tree, but also promoted the formation of sprouts, allowing sprout-saplings with rapid vertical growth to successfully establish in the clear-cut zone by inhibiting complete coverage by other pioneer trees. # 2006 Elsevier B.V. All rights reserved. Keywords: Litsea citriodora; Clear-cut; Vertical growth; Sprout; Growth analysis; Pioneer species 1. Introduction In many parts of Kyushu Island, western Japan, areas are cleared for planting of monoculture conifer plantations consisting of young conifer or hardwood trees. Before these clear-cut areas are planted with trees, they become dominated by species specific to open sites (Halpern and Spies, 1995). Under high light availability, early successional trees species and tall herbaceous species with the ability to grow rapidly dominate such areas and, in the absence of weeding, inhibit the growth and establishment of the planted trees. In order to determine the transitional process of such areas and establish an appropriate management strategy for achieving the projected conversion, an understanding of the growth traits of these successional species is important, especially with regard to the dominant species. The early successional tree species Litsea citriodora is a deciduous subcanopy tree found in open sites such as forest- edge and clear-cut areas in western Kyushu Island. Its distribution is limited to western Kyushu, despite the lack of a clear geographical barrier between the west and east. However, several studies have reported the expanding habitat of L. citriodora in central Kyushu (Kuranari, 2002). Previous studies have focused on seed dispersal by birds as the mechanism promoting this habitat expansion (Nakamura, 2003); however, although they revealed the short-distance seed dispersal ability of L. citriodora and they failed to explain the mechanism of rapid habitat expansion. Ants are another disperser of L. citriodora but disperse seeds shorter distances than wind or vertebrates (McLachlan and Bazely, 2001). The limited range of growth habitats of L. citriodora also indicates its inability to disperse seeds a long distance. Therefore, the rapid habitat expansion of L. citriodora must be attributed to other mechanisms. www.elsevier.com/locate/foreco Forest Ecology and Management 236 (2006) 251–258 * Corresponding author. Present address: Institute of Tropical Agriculture, Kyushu University, Hakozaki, Fukuoka 812-8581, Japan. Tel.: +81 92 948 3122; fax: +81 92 948 3119. E-mail address: sclero@forest.kyushu-u.ac.jp (Y. Miyazawa). 0378-1127/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2006.09.010