Photo Shutterstock Forest fires are becoming increasingly common in the Amazon due to climate change. That has consequences for the forest: it partially dies off and grows back, but some trees can resist fire better than others. Forest ecologist Masha van der Sande has secured a European grant that will let her investigate which are the winners and which are the losers.
There have been forest fires in the Amazon ever since humans first settled there, about 10,000 years ago. Today’s forest is the result of those fires. But it is not clear how the current mix of trees arose. ‘We don’t know exactly what effect a fire has,’ says Van der Sande. ‘How does the forest recover? Which trees are gone for good, which aren’t and why?’
Lake sediment cores
To find out more, Van der Sande will be delving into the past. A postdoc will analyse core samples taken from the beds of lakes. These are samples of sediment that was deposited over the course of thousands of years, creating a kind of history book of the surrounding area. Charcoal deposits are signs of fire, while the pollen that is found can tell you which tree species were involved.
‘Deciphering core samples lets us reconstruct the mix of trees that the forest used to contain,’ explains Van der Sande. ‘Trees can be identified down to the level of the genus (group of species). You can then look at how that correlates with the frequency and intensity of fires. It lets you work out what effect fires have on the forest.’
The researchers will be using a new technique developed at the University of Amsterdam that lets you determine from the charcoal how intense the fire was. In particular, Van der Sande wants to know what properties of a tree make it tolerate fire. Is it all about the thickness of the bark, for example, or the leaves?
Field experiments will be carried out in addition to these analyses of the forest’s history. A PhD candidate will study what happens at sites that recently suffered a fire. ‘We look at what is still standing, what has died and what regenerates. We then compare that against control sites nearby that didn’t suffer a wildfire.’
More frequent and intense
Wildfires are becoming more frequent and more intense due to climate change. ‘We will also be studying plots that have had a fire for a second or even third time. Coincidentally, we already have field measurements from a site that had a fire in 2021 and again last year. That gives us a unique dataset for our research.’
Furthermore, trees on the site will be deliberately burned or subjected to heat. Van der Sande: ‘A PhD candidate will investigate what happens in physiological terms. What actually kills off a tree that is burned? We will use that information in a plant model developed by my colleague Jorad de Vries.’
Understanding
At the end of the day, all the information should give a better understanding of the effect a fire has on trees and therefore what effect an increase in forest fires due to global warming will have on tropical forests. ‘Forest fires in the Amazon at the current scale and frequency are a new phenomenon. They will have a huge impact on the forest over the next while.’
The ERC Starting Grant is 1.5 million euros. The Netherlands received 44 of the 478 grants awarded this year; WUR got just one of those grants. In addition to Van der Sande herself, one postdoc and two PhD candidates will be working on the project.
