Above- and Below-ground Mass Allocation and Characteristics of Root Distribution in a 13-Year-old Melia azedarach Stand

Abstract

Sendan (Melia azedarach), a broad-leaved deciduous species native in Japan, grows fast and can assume straight trunk by bud removal management, and is in recent years regarded as promising silvicultural tree species. The objective of this study is to examine the mass allocated to above- and below-ground organs of M. azedarach and to clarify the characteristics of root distribution. In November 2016, the research was conducted in a 13-year-old plantation in Kumamoto Prefecture, Japan. Six sample trees were harvested and separated into each organ, and root systems were dug out using excavator. Trunk, branch and leaf constituted 81.5, 17.4, and 1.1％ in above-ground total mass, and the root/shoot ratio was 0.25 on average, while the root/shoot ratio was greater in large individuals than in smaller ones. Sinker roots dominated 54 (39-75)％ of all roots in this soil type (andosol), with maximum depth being 1.9 m on average. Length of sinker roots was larger than that of horizontal ones (weighted mean, 1.67, 1.48 m). Fine roots were most abundant at the surface 0-10 cm soil depth, and horizontal distribution of fine roots was considerably even in this stand.