2024 Abstracts

Forest Dynamics After a Windthrow in the Central Amazon


Daisy C. Souza1,2* (dsouza@lbl.gov), Daniel M. Marra3, Kolby Jardine2, Bruno Gimenez1,4, Adriano Lima1, Niro Higuchi1, Jeffrey Chambers2,4, Robinson Negron-Juarez2


1National Institute of Amazonian Research, Manaus, Amazonas, Brazil; 2Lawrence Berkeley National Laboratory, Berkeley, CA; 3Institut für Waldschutz, Julius Kühn-Institut, Braunschweig, Germany; 4Department of Geography, University of California–Berkeley, CA



Windthrows are the most common natural disturbances in the Amazon, causing changes in the dynamics and functioning of these ecosystems. Comprehensive data of the natural regeneration niches and species establishment represents a significant achievement in better understanding the susceptibility of disturbed areas to climate change. However, it is still unknown how these dynamics patches interact at the gap-phase regeneration. The team investigated variations in the rates of recruitment and mortality every 2 months for 3 years in a gradient of disturbance severity and analyzed the factors that most affected these variations. The study site is in an old-growth windthrown forest in Manaus, Brazil. The windthrow occurred in 2019. Inventory plots were installed in four classes of severity: high, medium, low, and undisturbed. Preliminary results showed a significant effect of disturbance severity and time post disturbance on recruitment rates (p<0.001) but no variations for mortality rates of saplings (p=0.3295). In the first year in the high and medium severity classes, the recruitment was maximum and decreased until it was constant after the second year. In contrast, the mortality rates started to increase after the first year, presenting a peak in the second year of the study but remaining highly variable. Results demonstrate that even in 3 years, the recruitment is highly dynamic across the severity gradient. Changes in light availability caused by the windthrow increased recruitment rates, but the characteristics allowing the species succession still need to be identified. The results of this research promoted a better understanding of how fast disturbances caused by the wind affect the functional composition and demographic rate of the forest.