Forest Fragmentation Changes Architecture of Amazonian Woodland, Causes Edge Effects on Tropical Trees With Worsened Biomass Loss

The environmental pressure on plant growth, reproduction, and survival leads to tree architecture, which determines trees' light capture, height extension, and mechanical stability. Tree architecture varies across species in Amazonian forests due to evolutionary processes over millions of years. However, it was found that this three-dimensional form could be affected by disturbances that arise from forest fragmentation.

What is Forest Fragmentation?

Forest fragmentation refers to breaking large, contiguous forested areas into smaller pieces. Agriculture, roads, subdivisions, utility corridors, or other human development typically separate these portions of land.

This process usually occurs incrementally, but the non-forest patches multiply and expand until the forest is reduced to disconnected scattered forest islands. The surrounding non-forest lands can seriously threaten the remaining forest's function, health, and value.

Forests can be affected by any large-scale canopy disturbance, so it is important to distinguish between forest fragmentation due to human infrastructure development and a forest of combined ages and different canopy closures due to good forest management. The former is typically much more damaging to forest health and habitat quality, while the latter may only cause temporary change in the forest.

A Look at Morphing Trees

At the University of Helsinki, an international project investigates tree shapes on the edges of the tropical rainforest. Headed by Matheus Nunes, the research team conducts an experiment where Amazonian trees are modeled using data collected from terrestrial laser scanning.

In the study "Edge effects on tree architecture exacerbate biomass loss of fragmented Amazonian forests," the scientists used remote sensing to collect data from Central Amazonia, Brazil. After creating a 3D tree representation, the team calculated tree properties like trunk size and their ability to use water and light.

The findings demonstrated that trees growing on forest edges are shaped differently from those that grow deep in the forest. The young trees that colonize the forest fragments have thicker branches and architectural traits that optimize light capture. This results in 50% more woody volume than their counterparts of similar stem size and height in the forest interior.

In ecology, these changes in population or community structures occurring at the boundary of two or more habitats are known as edge effects. These are observed in the thickness of tree trunks and canopy symmetry. By adjusting these characteristics, trees can adapt to obtain as much light as possible and increase their chances of survival.

Despite increasing wood production, the amount of biomass binding carbon dioxide in the Amazonian rainforest is reduced by as much as 20%, according to University of Helsinki Associate Professor Eduardo Maeda. It has been previously reported that there is less biomass in fragmented forests since tall trees are more likely to fall over the edges.

Maeda also suggests that the impact of human activity on climate change must be re-evaluated. This study offers new insights into the adaptation of the rainforest to environmental change and provides tools for researchers to mitigate climate change.

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