El Niño drought increased canopy turnover in Amazon forests.

Area of Science:

• Ecology
• Forestry
• Climate Science

Background:

• Amazon droughts, like the 2015-2016 El Niño, can decrease forest productivity and increase tree mortality, affecting carbon balance.
• Traditional monitoring methods like inventory plots and flux towers may not fully represent regional drought impacts on forests.

Purpose of the Study:

• To assess how drought affects canopy turnover and carbon loss in intact and fragmented central Brazilian Amazon forests.
• To quantify changes in canopy turnover rates and coarse woody debris production during drought conditions.

Main Methods:

• Utilized multi-temporal airborne Light Detection and Ranging (Lidar) data.
• Integrated field measurements of coarse woody debris.
• Analyzed data from 2013-2014 and 2014-2016, encompassing a major drought period.

Main Results:

• Annualized canopy turnover rates increased by 65% during the drought period in both forest types.
• Coarse woody debris production rose by 62% to 1.22 Mg C ha⁻¹ yr⁻¹ in drought years.
• The size and height of turnover events were similar across drought and non-drought periods, contrary to expectations of disproportionate large tree impacts.

Conclusions:

• El Niño conditions significantly accelerated canopy turnover in central Amazonian forests.
• Droughts increase coarse woody debris production, impacting forest carbon dynamics.
• Airborne Lidar provides valuable data for monitoring drought-induced changes in forest structure and carbon cycling.