Accounting intra-tree radial wood density variation provides more accurate above ground mangrove biomass estimation in the Sundarbans

Abstract

Abstract Wood density is an important functional trait used to estimate forest biomass and carbon stocks. Its wider range of variations, such as inter- and intra-specific level, and within tree disparity, repeatedly invoke wood density as a potential source of variation in biomass or carbon estimation. We aim to (i) measure pith-to-bark wood density profiles in major mangrove tree species in the Sundarbans and (ii) quantify the deviation in above ground biomass estimations by comparing the method that ignores wood density variation across the radius. One hundred and fifty wood cores were collected from five widely distributed ecologically distinct mangrove species in three distinct salinity zones (low, medium, and high) in the Bangladesh Sundarbans. Wood density was measured for each 1 cm long wood core segment from pith to bark. Among the three light-demanding species, Sonneratia apetala and Avicennia officinalis showed a decreasing wood density trend from pith to bark while Excoecaria agallocha exhibited an increasing trend. Shade tolerant Xylocarpus moluccensis displayed a decreasing wood density trend, whereas the most dominant Heritiera fomes unveiled almost less variable wood density values from pith to bark. Albeit wood density varied positively with slenderness ratio, a significant relationship was found only for the shade tolerant species. Shade tolerant species also had a significantly higher mean wood density than light demanders. Wood density was significantly higher at the high saline zone for the studied species, except S. apetala and A. officinalis. Depending on the species, ignoring radial wood density variation increased deviations in AGB estimations up to ~ 17%. This study suggests for considering radial wood density variations, and their possible site- and species-specific influences to increase the accuracy of mangrove biomass estimations. Furthermore, these preliminary results pave the avenue for a better understanding of wood functional traits in the Sundarbans.