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Shade or sun? Forest structure affects tree responses to Amazon drought

17 / 04 / 2019, Mongabaycom News

An intact forest canopy in a sustainably managed forest in Pará state, Brazil. Degraded forests, with clearings where trees have been logged out, may be less resilient in Amazon droughts, a recent study suggests. Photo credit: USAID Biodiversity & Forestry on VisualHunt.com / CC BY-NC Small trees in the Amazon rainforest understory are more vulnerable to drought than their larger counterparts, but their fate depends on their local environment, according to a study published in New Phytologist. Marielle Smith from Michigan State University and an international team of researchers used hand-held lidar to complete monthly surveys of the surface area of leaves at different heights in Tapajós National Forest in Pará state in the Brazil Amazon between 2010 and 2017 to obtain their results. The portable lidar instrument uses a laser to map the leaves in the forest canopy in two-dimensional slices up through the forest structure. Across the whole forest, they found that trees in the upper canopy tended to gain leaves during the dry season and lose them again in the wet season, whereas trees in the lower canopy showed the opposite behavior. This opposing trend between the upper and lower canopies matches the results of a previous satellite-based study of seasonal changes in leaf area, and is thought to be due to limited light availability in the lower canopy. However, a closer look at the patterns of leaf growth and loss in different micro-environments within the forest ecosystem revealed a more complex pattern. “What was exciting for…

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