Woods Hole Research Center

Since 2004, the Woods Hole Research Center and the Amazon Environmental Research Institute (IPAM) have been conducting experimental burns to study the characteristics of fire in the transitional forest on the edge of the Amazon rainforest and the ecological damage they cause.

Left - WHRC scientists work at Fazenda Tanguro (red), in the Xingu watershed, in the Brazilian state of Mato Grosso, along the line where southern dry savannah meets wetter evergreen forests in the north. Right - Agriculture and forest borders present clearly defined markers in Mato Grosso.

Fazenda Tanguro: A satellite view of the Fazenda Tanguro, an 80,000 hectare property. Pink indicates agriculture; green indicates forest. The red numbered areas are dedicated for field experiments. Area 1 is the experimental fire plot. Click to view larger version.

The goal of this research is to better understand what role fire may play in reshaping the landscape of this region, which lies at the transition zone between the tall dense rainforests at the core of the Amazon and the savannas of central Brazil. Center researchers are learning how these accidental fires may affect the vigor, health, biodiversity, and animal habitats in these forests, and in the end, whether recurring fire may threaten the very existence of the forest. The concern is that repeated burning of transition forests in the Amazon could cause their eventual replacement by fire-prone scrub vegetation.

To replicate these types of fires in the Amazon, Center scientists have established a large-scale field experiment at the Fazenda Tanguro, a private soy ranch in eastern Mato Grosso state in Brazil.

Fires are set on the forest floor using kerosene drip torches along parallel 1000m-long transects every 50 meters through the square-kilometer parcels, and allowed to spread through the forest naturally. Firebreaks are cleared along perimeter trails and roads in preparation for the event, and swept clear of debris immediately prior to igniting the fires, to contain the fire within the experimental parcel.

The planned burn provides information that cannot be obtained by studying an accidental or escaped fire. The experiment is being conducted in an area in which researchers have taken many measurements prior to the burn – inventories of thousands of trees to catalogue their species, size, and number, surveys of seedlings, measurements of fuel on the forest floor, censuses of mammals, amphibians, and birds, and monthly measurements of canopy closure at more than 400 points in the forest.

Left - A aerial view of the 3 experimental fire subplots being used by Center scientists. Right - A field researcher lighting part of the 2009 experimental burn.

After the burn, a census is taken of the trees to see how many were unaffected, scorched, or how they may be reacting or recovering from the burn. Canopy density is measured at monthly intervals throughout the year, to monitor the impact of the fire and rate of tree mortality and recovery. Temperature and humidity are monitored at multiple spots in each forest throughout the year, to detect changes in the microclimate of the forest; and soil moisture is measured at set points in the parcels and in two 10-m deep pits at regular intervals, to see how the changes in forest density may affect the water available in the soil.

Field researchers taking measurements just prior to the 2009 experimental burn.

These experimental fires are a crucial part of understanding what is happening in the Amazon today, as fires set by landholders to improve their pastures or to burn recently felled forest in preparation for planting often escape beyond their intended boundaries. Undisturbed forests are resistant to burning because their dense leaf canopy prevents much of the incoming solar radiation from reaching the forest interior, keeping the litter layer too moist to sustain a fire. Now large areas of forest are selectively logged prior to being settled, leaving holes in the canopy; longer, more intense dry seasons provoke leaf thinning; and both of these changes allow the litter to become dry enough to sustain a fire. Once a forest has burned a first time, the combination of a more damaged forest canopy and a stock of larger fuel from trees killed by prior fires make it even more vulnerable to subsequent fires. When humans move into an area and begin clearing forest, they seldom abandon it and move away, so until education can alter their behavior, repeated sources of ignition in the future are all but guaranteed.

One of the soil pits – each nearly 10 meters deep – at the Fazenda Tanguro.

This “savannization experiment” is a learning laboratory for Brazilian students who live in the Amazon transition forest. School groups frequently visit the research station, and several undergraduate and graduate students are conducting their theses research within the project. The Grupo Maggi, the world’s largest private producer of soybeans, owns the study site. By conducting this work on this property, it is hoped that the fire experiment, along with concurrent studies of riparian zone recuperation, soil management, and water quality, will help this and other companies improve the ecological management of their properties. Grupo Maggi provides no funding for this research.

Through this work, researchers are learning not only how to predict the ways in which current trends in land use and climate change might alter forests throughout the southern Amazon in the near future but also what mitigation strategies can be effectively applied to reduce human impacts regionally and globally. Additionally, information gathered in this project assists in many other projects including; understanding of how the forest degradation affects the global carbon cycle and climate change; creating models to predict forest vulnerability to fire; and developing methods for satellite monitoring of forest fires to help enhance enforcement capabilities, develop zoning strategies and improve techniques for identifying and measuring the area affected by these fires.

The Amazon Environmental Research Institute (IPAM) is a key collaborator in this work.

Much of the Center’s work at Fazenda Tanguro is supported by NSF and by the Gordon and Betty Moore Foundation.

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