Comparative analysis of physiological responses to topping in tropical tree species

• Topping cuts influence physiology differently across species, even within the same family and habitat. • Humidity and VPD variation in season affect Gs, E, and WUE of dipterocarp trees. • Drought and dust stress reduce Pn and Gs in D. alatus, while H. odorata maintains water uptake. • D. alatus tolerates heavy pruning but may be vulnerable to long-term stress, while H. odorata recovers quickly but experiences water stress. Urban tree management practices, including pruning, are crucial in maintaining safety, aesthetics, and urban ecological benefits. This study examines the physiological responses of two tropical tree species, Dipterocarpus alatus , and Hopea odorata , to topping cuts, a heavy pruning technique commonly used in urban areas of Thailand. The study assessed key physiological parameters—net photosynthesis ( Pn ), stomatal conductance ( Gs ), transpiration rate ( E ), water use efficiency ( WUE ), and leaf water potential ( LWP )—over 12 months, conducted in a forest plantation. Results revealed species-specific responses, with D. alatus showing resilience to topping cuts and minimal physiological changes, while H. odorata exhibited heightened sensitivity, including increased Gs, Pn , and E following crown removal. Seasonal variations, combined with urban stressors such as dust and drought, exacerbate tree stress and influence recovery dynamics. These findings underscore the detrimental effects of topping cuts on tropical trees, emphasizing the necessity to avoid this practice and adhere to tree pruning standards in urban tree management. The study contributes to a deeper understanding of tropical tree responses to pruning, providing essential guidance for sustainable urban forestry.