Tropical Grasslands (2007) Volume 41, 113–128

Tuft, shoot and leaf dynamics in Miscanthus sinensis in a young tree plantation under cattle grazing

M. HIRATA, N. HASEGAWA, K. NOGAMI AND T. SONODA

Faculty of Agriculture, University of Miyazaki, Japan

Abstract

This study investigated vegetation structure and dynamics of Miscanthus sinensis growing in a young Chamaecyparis obtusa (an evergreen conifer) plantation under cattle grazing in southwestern Japan, at 3 hierarchical levels of tuft, shoot and leaf, in an effort to develop a fundamental understanding of the productivity and persistence of this grass in forest grazing. After the initiation of grazing, M. sinensis plants were extensively defoliated by animals, leaving 12–26% of tufts and 10–21% of shoots undefoliated at the end of the grazing season. The density, mean height and mean basal area of M. sinensis tufts were in the range 9.2–16.0 x 103 tufts/ha, 26–89 cm and 75–315 cm2, respectively. Mean shoot number per tuft and shoot density were in the ranges 10–44 shoots/tuft and 111–514 x 103 shoots/ha, respectively. There were always considerable tuft-to-tuft variations in height, basal area and shoot number, and distribution was skewed with the majority of tufts being shorter and thinner and having fewer shoots than the mean. All or almost all shoots formed in summer died before the end of the second winter, showing a half-life of 9–10 months. The number of live leaves and rates of leaf appearance (LAR) and leaf death (LDR) were 0.6–8.6 leaves/shoot, 0–0.09 leaves/shoot/day and 0–0.18 leaves/shoot/ day, respectively. LAR increased as the mean daily air temperature increased, and LDR as the number of live leaves increased. M. sinensis growing in a young tree plantation under cattle grazing has low shoot densities and low LAR, which may limit production and persistence. In addition, M. sinensis is intolerant of grazing, with the size and shoot number of tufts, number of live leaves per shoot and LAR declining with time under grazing. Further studies to deepen our knowledge for better use of this grass in forest grazing appear warranted.

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