Growth performance and lignin content of Acacia mangium Willd. and Acacia auriculiformis A. Cunn. ex Benth. under normal and stressed conditions

Acacia mangium Willdenow and Acacia auriculiformis A. Cunningham ex Bentham are fast-growing species with wide environmental adaptability. Fast-growing species which thrive in otherwise non-arable problematic soil and which hold the added advantage of improving the condition of the soil, can be used to increase production area, and, thus, are highly desired. We investigated the growth performance and lignin content under normal and stressed conditions for these Acacia mangium Willd. and Acacia auriculiformis A. Cunn. ex Benth. Normal growing conditions was represented by fertile soil, high water-holding capacity due to low soil drainage, high organic matter, low soil temperature, overall consistent rainfall and relatively milder temperatures, whilst stressed conditions were achieved with a sandy soil with low fertility, low water-holding capacity due to high drainage and low organic matter, and high soil temperature accompanied by inconsistent monthly temperature and rainfall. Growth performance under normal conditions was significantly better compared to the stressed conditions. A. mangium performed better than A. auriculiformis under the normal conditions. However A. auriculiformis performed better under stressed conditions due to better adaptability. The lignin content under normal conditions fluctuated from one DBH class to another. As for the stress conditions, A. mangium exhibited incremental increases in lignin content with increasing biomass. In contrast, lignin content in A. auriculiformis decreased with increasing biomass. The differences in performance may be attributable to both the micro- and macro-environments and adaptive differences between the two species. For growth under normal conditions, A. mangium appears to be the superior choice, whereas for problematic soils, A. auriculiformis can be recommended. However, for the selection of superior plants with a combination of desired growth rates and lower lignin content the breeding of interspecific hybrids would be a desirable approach.