Coomes group

Making sense of canopies

Béatrice Wedeux and David Coomes published a paper in Biogeosciences analysing how environmental factors and selective logging interact to shape the canopies of tropical forests. Using airborne laser scanning technology across a 750 km2peat swamp forest landscape in Borneo, the study reveals strong shifts in canopy height and gap patterns along environmental gradients linked to changing peat depth. In areas where logging roads were detected on historical satellite imagery, the canopy is lowered and has larger gaps, especially so on deep peat where tree growth is thought to be limited by low nutrient availability and waterlogging. The study identifies a close link between the height and the gap structure of tropical peat swamp forests at the landscape scale and reinforces the vulnerability of this ecosystem to human disturbance. The degradation of tropical peat swamps has been at the heart of climate negotiations in Paris, as emissions from fires in Indonesian peatlands over the last couple of months – exacerbated by a dry El Niño spell – approach the total annual emissions of Brazil (1.62 billion metric tons;www.wri.org).

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Airborne laser scanning allows the detection of openings at different height cross-sections of the canopies of old-growth and selectively logged forests.

Read online: Wedeux, BMM and Coomes DA (2015) Landscape-scale changes in forest canopy structure across a partially logged tropical peat swamp, BIOGEOSCIENCES 12(22):6707–6719, DOI: 10.5194/bg-12-6707-2015.

What have we been learning about the Cerrado?

Cerrado landscape invaded by sugarcane fields.

Cerrado landscape invaded by sugarcane fields

In the beginning of 2014, my adventure in the Brazilian Cerrado had just started! It’s now been a year I took the airplane to Brasília, in the heart of Brazil. We decided to study the effects of agriculture, specifically of sugarcane crops, on the gases emissions from soils of this region. Nothing would have been possible without the collaboration with the EMBRAPA Cerrados. But why there??

Cerrado woodland vegetation

Cerrado woodland vegetation

Cerrado, the richest savannah in the world and the most extensive savannah complex in the Neotropics, has been historically affected by a number of human activities. By now, it has lost half of its 2 mi km2 of native vegetation. The expansion of the sugarcane fields, often used for bio-ethanol production, is one of the current threats to this biome.

We are currently measuring the emissions of greenhouse gases, specifically the nitrous oxide (N2O), in response to the management of fertilisers. Our preliminary results show a large increase in the emissions from the combined treatment using nitrogen and vinasse*, that is, 450 times more than the native areas on average! Our longer monitoring activities will be important to understand the variation on the emissions throughout the sugarcane cycle and to assess the sustainability of this crop in the region.

*Vinasse=a waste from the ethanol production that is re-used as fertiliser.  

Experimental sugarcane field in May/2014

Experimental sugarcane field in May/2014

Experimental sugarcane field in November/2014

Experimental sugarcane field in November/2014

Applying vinasse to the field

Applying vinasse to the field

                                              

Collecting gases in the Cerrado

Collecting gases in the Cerrado

Collecting gases from the sugarcane field

Collecting gases from the sugarcane field

Part of the staff in a rare relaxing time!!!

Part of the staff in a rare relaxing time!!!