Species Matter!

Amazon forest species vary in drought tolerance, influencing their resilience to changing water conditions and ultimately the Amazon carbon sink. A collaboration involving 80 scientists has identified the regions of the Amazon rainforest where trees are most likely to face the greatest risk from drier conditions brought about by climate change.

Published in Nature “Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests” this painstaking pan-Amazon work across the RAINFOR network was led by Julia Tavares.  Julia’s team effort reveals the huge diversity of Amazon tree drought responses. The analysis combined decades of plot dynamics with careful measurements of xylem water potential and hydraulic safety margins.  Together, it was possible for the first time to assess regional variation in forest drought sensitivity and explore how hydraulic traits influence species distributions and forest biomass accumulation.  The differences among species are shown to be potentially crucial in determining how well Amazonia have – and will –  resist climate change droughts.

Laboratory equipment transported into the rainforest CREDIT Martin Gilpin
Laboratory equipment transported into the rainforest. CREDIT: Martin Gilpin

Dr Julia Tavares, who led the study while undertaking a PhD at Leeds and is now based at Uppsala University in Sweden, said:

“A lot of people think of the Amazon as one large forest. But it is not. It is made up of numerous forest regions that span different climate zones, from locations that are already very dry to those that are extremely wet, and we wanted to see how these different forest ecosystems are coping so we could begin to identify regions that are at particular risk of drought and drier conditions.”  

Some parts of the Amazon have already seen changes in rainfall patterns. In the southern Amazon, there is evidence that the dry season has become longer, and temperatures in this region have increased more than in other parts of the Amazon. The changes in the southern Amazon are partially due to extensive deforestation.

Based on the analysis, the scientists predict trees in the western and southern Amazon face the greatest risk of dying. They also warn that previous scientific investigations may have underestimated the impact of drought on the rainforest because those studies focused on the central-eastern part of the forest, which is the least vulnerable to drought.

The paper – “Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests” – is published in the journal Nature. 

Understand more about how the scientists conducted the study – and the challenges of working deep in the rainforest. 

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