Webinar: Pantropical tree growth responses to climatic variation and extremes

Increasing drought stress under anthropogenic climate change jeopardizes the potential of tropical forests to capture carbon in woody biomass and act as CO2 sink. A pantropical quantification of drought impacts on tree stem growth is needed to evaluate this risk. We established and used the tropical tree-ring network to assess climate sensitivity and drought impacts. Based on 477 tree-ring chronologies we found modest stem growth declines (median: 2-4%) during the 10% driest years. Growth declines were larger for dry-season than wet-season droughts, specifically for Gymnosperms, and at hotter and more arid sites. Using empirical relationships between growth anomalies and tropical tree mortality, we estimate the pantropical growth reduction to induce a rise of 0.1% in annual tree mortality (compared to 1% baseline). Lagged growth reductions during post-drought years were rare. Over half of the growth reduction during drought years was mitigated during wet extreme years. Drought impacts on tropical forest carbon sequestration through stem growth have been small and short-lived, but will aggravate under climate change, in particular through associated elevated mortality risks.

Speaker

Dr. Pieter Zuidema, Wageningen University