Long-term growth and xylem hydraulic responses of Albizia procera (Roxb.) Benth. to climate in a moist tropical forest of Bangladesh

Climate change is a serious concern around the world, particularly in tropical regions including Bangladesh. Yet, how tree growth and hydraulic behavior of Bangladeshi native tree species changed in response to past climate variability and changes have not been adequately understood. We developed the first ring-width and vessel chronologies of Albizia procera (Roxb.) Benth. from a moist tropical forest of Bangladesh (Rema-Kalenga Wildlife Sanctury, RKWS) to analyze the impact of inter-annual climate variability on tree growth and xylem hydraulic traits. The chronologies contained common environmental signals as shown by the values of expressed population signal (EPS) and other statistical parameters. Climate-growth analysis showed that maximum temperature (T_max) favored tree growth at the end of the wet season (November). Among the vessel and hydraulic trait chronologies, number of vessels (NV) had significant positive relation with May minimum temperature (T_min) and vessel density (VD) had a negative relationship with April T_min. Precipitation had a negative relation with vessel density (VD), and the potential specific hydraulic conductivity (K_S). Relative humidity (RH) and vapour pressure deficit (VPD) had contrasting effects on vessel and hydraulic traits. On a regional scale, the ring-width index and vessel chronologies were correlated with both gridded land surface temperature and precipitation, but during different periods of the year. Linear mixed effect modeling revealed significant positive relationships between VD and T_max implying a good acclimation potential of this tree to rising temperature. However, the absence of the generally expected trade-off between VD and D_H calls for further studies on the hydraulic functions of this species in moist tropical forests.