’Plumbing’ failure kills tallest rainforest trees »

Vulnerability to internal plumbing failure puts the tallest trees in rainforests at increased risk of death during drought, a study in the Amazon forests in Brazil has found. The research found that as water in the soil dried up during drought, the tallest trees were affected by air bubbles entering their internal plumbing, making it difficult for the trees to transport water and other nutrients to their leaves. "We found increased death rates in the larger trees, and the trigger that led to their demise was vulnerability to failure in the water-transporting tissues in the wood," said Professor Patrick Meir, from The Australian National University (ANU). "With droughts in some regions predicted to intensify and lengthen with global warming, the increased death of large trees in rainforests could signficantly increase carbon dioxide emissions from Amazonia, and influence the global carbon cycle," said Professor Meir, from ANU Research School of Biology. The new understanding will help improve predictions of the impacts of climate change. The Amazon is the largest rainforest in the world and droughts have the potential to switch Amazonia from being a net absorber of carbon to a source, adding carbon dioxide the atmosphere Widespread tree death would add further large amounts of carbon dioxide to the atmosphere as the dead trees decompose, said first author of the study Dr Lucy Rowland, of the University of Edinburgh's School of GeoSciences. "It could also mean rainforests in the future are populated by smaller trees, which store less carbon," Dr Rowland said.