O impacto das variações climáticas e hidrológicas no crescimento arbóreo de Nectandra amazonum (família Lauraceae) em uma floresta de várzea na Amazônia Central

Abstract

During the last two decades, the Central Amazon region has been impacted by increasing atmospheric temperatures and an intensified hydrological cycle characterized by enhancing magnitudes and frequency of severe floods and droughts. Little is known about the effects of these climate trends on tree growth in floodplain forests. In this study, we analyzed Nectandra amazonum Nees (Lauraceae), an evergreen and flood-adapted tree species, dominant in the nutrient-rich Amazonian floodplains (várzea) but also occurring in other environments 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 dendrochonological (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 on tree growth mainly during the period of transition between the dry and the wet season, and during the aquatic phase affecting physiological processes such as photosynthesis and respiration, respectively. The results suggest that this species probably colonized the Amazonian floodplains originating from environments of higher altitudes or latitudes in the Southern Hemisphere conserving its growth responses to temperature seasonality and water deficit, which turns the species resilient against flood-pulse disturbances.