Decomposition of wood, petiole and leaf litter by Xylaria species from northern Thailand

Abstract

Ten Xylaria isolates (five obtained from wood and five from leaf litter) collected in northern Thailand were tested for their ability to decompose 13 types of wood, petiole, and lamina from seven tropical tree species under pure culture conditions. The mass loss of the 13 substratum types caused by the 10 Xylaria isolates ranged from 1.2 % to 37.4 % of the original mass. The substratum, the origin of isolates, and the contents of lignin, total carbohydrates, and nitrogen in substrata affected the mass loss. Mass loss was generally in the order: petiole > lamina > wood. Overall, the strains isolated from wood caused greater mass loss than the strains isolated from litter. The mass loss caused by the 10 Xylaria isolates was negatively affected by lignin and total carbohydrate contents, and positively correlated with nitrogen content of the substrata. The values of mass loss in wood in the present study were in the same range as those reported for other Xylaria isolates in previous studies, whereas the mass losses in leaf litter were generally higher than those of previous results, which is partly due to the relatively low lignin contents in leaf litter used in the present study.

Introduction

Fungi in the genus Xylaria (Xylariaceae, Xylariales, Sordariomycetes, Ascomycota) are major components of mycobiota in tropical forests (Whalley, 1993, Whalley, 1996, Whalley, 1997, Rogers, 2000), and function as decomposers (e.g., Rogers et al., 1987, Rogers et al., 1988, Gonzalez and Rogers, 1989, Van der Gucht, 1996, Osono, 2007, Osono et al., 2008, Osono et al., 2009), endophytes (Rodrigues et al., 1993, Læssøe and Lodge, 1994, Rodrigues, 1994, Bayman et al., 1998, Okane et al., 2008), pathogens (Ko & Kunimoto 1991) and symbionts with termite nests (Rogers et al., 2005, Ju and Hsieh, 2007, Okane and Nakagiri, 2007, Visser et al., 2009). Saprobic Xylaria species inhabit the wood, petiole and lamina of tropical trees, and take part in decomposition and mineralization of these plant litters. Previous pure culture studies have demonstrated that tropical wood-inhabiting Xylaria isolates are able to cause significant mass loss in wood blocks of temperate beech and pine (Pointing et al. 2003). Tropical endophytic Xylaria species have also been shown to produce extracellular enzymes to decompose plant substrates (Rodrigues et al., 1993, Pointing et al., 2003, Pointing et al., 2005). However, few data are available regarding the ability of tropical Xylaria species to cause mass loss in wood and leaf litter of tropical trees. Such studies are crucial for understanding the functional roles of Xylaria species in decomposition processes in tropical forests.

The purposes of the present study were to examine the ability of 10 Xylaria isolates (five obtained from wood and five from leaf litter) to decompose wood, petiole and lamina of seven tropical tree species in pure culture tests and to compare these results with the decomposing ability of other Xylaria isolates reported in previous studies. The Xylaria isolates were collected in northern Thailand and tested for their ability to cause loss of mass of 13 substratum types (four woods, three petioles and six laminas) during laboratory incubation. We hypothesized that wood and litter isolates would be able to decompose both wood, petioles and lamina regardless of the isolate origin, and that petiole and lamina would decompose faster than wood, attributable to chemical quality of the substrata.