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Environmental predictors of forest structure, tree growth and wood production for Xylocarpus granatum in mixed-species mangrove forests

Alistar Robertson , Irena Zagorskis, Murray Logan, Paul Dixon, Paul Daniel

Abstract

Context. Restored mangrove forests are threatened by the restricted range of species used. Xylocarpus granatum has excellent timber and could add value in mangrove plantings. Methods. Forest structure and environmental variables were measured at 40 sites in northern Australia and Papua New Guinea. Tree growth was measured at 18 sites. For X. granatum boosted regression tree modeling identified environmental predictor variables for above-ground biomass (AGBX), mean annual DBH increment (MAIX) and wood production (PW). Aims. To determine the environmental conditions under which X. grantum has the greatest biomass and growth. Key results. Increasing stem density, basal area and AGB of other tree species were most important in limiting AGBX. MAIX (range 0.03 - 0.55 cm year-1) was greatest when sediment redox potential was >100 mV and mean annual catchment rainfall was >4000 mm. MAIX increased with increasing mean minimum air temperature and sediment % silt and % phosphorus. PW declined with the stem density of all species and increased with increasing % silt and when sediment redox potential was >180 mV. Conclusions and implications. Under optimal conditions X. granatum grows as fast as most mangrove species and could make an excellent, harvestable addition to the species-mix used in restoration projects.

MF23246  Accepted 17 April 2024

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