Minimum temperature and evapotranspiration in Central Amazonian floodplains limit tree growth of Nectandra amazonum (Lauraceae)

Abstract

Key message: Tree growth of Nectandra amazonum (Lauraceae) in the Central Amazonian floodplains does not respond to the annual long-term flooding but responds to variation of minimum temperature and potential evapotranspiration. Abstract: During the last two decades, the Central Amazon region has been impacted by increasingly frequent and more severe floods and droughts and increasing temperature. Little is known about the effects of these climate trends on tree growth in floodplain forests. In this study, we analysed Nectandra amazonum (Lauraceae), an evergreen and flood-adapted tree species, dominant not only in the nutrient-rich Amazonian floodplains (várzea), but also occurring in other environments within and outside the Amazon basin. For the period from 2001 to 2017, intra- and interannual climate–growth relationships of N. amazonum were analysed applying a combination of conventional dendrochronological (cross-dating) and densiometric techniques to construct a robust tree-ring chronology. Six wood parameters were derived from the chronology (ring width, width of earlywood and latewood and corresponding wood density values) and correlated with local climate and hydrologic data. The analysed 32 trees did not show correlation between wood parameters and variation of the hydrological regime. Climate–growth relationships indicated that potential evapotranspiration and minimum temperature play an important role in tree growth mainly during the period of transition between the dry and the wet seasons, and during the aquatic phase affecting physiological processes such as photosynthesis and respiration, respectively. We discuss these results in the background of changing hydroclimatic conditions induced by climate and land-use change in the Amazon basin. Based on our findings, we emphasize the need for more dendroclimatic studies in the tropics applying a multiproxy approach. This will deepen our understanding of tree growth responses, helping to elucidate the dynamic processes of tropical forests that grow under global change impacts. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.