Fine-root production in response to nutrient application at three forest plantations in Sabah, Malaysia: higher nitrogen and phosphorus demand by Acacia mangium

AbstractWe measured fine-root production at Acacia mangium (AM), Swietenia macrophylla (SM), and Araucaria cunninghamii (AC) sites in response to nitrogen (N) and phosphorus (P) application using the root-ingrowth core method for a period of 5 months in Sabah, Malaysia. Root growth increased significantly using a combined N and P application at the AM site, whereas it did not increase at the SM and AC sites. The number of nodules at the AM site increased significantly following N application and the combined application of N and P. Root production was not significantly enhanced by nutrient application at the SM and AC sites. At the AM site, both P and N were in high demand despite a larger N pool compared with at the SM and AC sites. These results can be explained by the larger nutrient demand by legumes. We conclude that both N and P is limiting for AM plantations under natural conditions and that N fertilization may be more effective than expected, depending on the site conditions.Keywords: Acacia mangiumAraucaria cunninghamiiRoot-ingrowth coreSwietenia macrophyllaTropical plantations AcknowledgmentsThe authors thank Shinji Kaneko for his valuable comments on the draft report. This study was carried out as a part of an international cooperative research project between the Sabah Forestry Department and the Japan International Research Center for Agricultural Sciences and was funded by the Ministry of Agriculture, Forestry and Fisheries of Japan, "Development of Agroforestry Technology for the Rehabilitation of Tropical Forests."