Imaging spectroscopy reveals the effects of topography and logging on the leaf chemistry of tropical forest canopy trees.
Ewers, Robert M
Teh, Yit Arn
Global change biology
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Swinfield, T., Both, S., Riutta, T., Bongalov, B., Elias, D., Majalap-Lee, N., Ostle, N., et al. (2020). Imaging spectroscopy reveals the effects of topography and logging on the leaf chemistry of tropical forest canopy trees.. Global change biology, 26 (2), 989-1002. https://doi.org/10.1111/gcb.14903
Logging, pervasive across the lowland tropics, affects millions of hectares of forest, yet its influence on nutrient cycling remains poorly understood. One hypothesis is that logging influences P cycling, because this scarce nutrient is removed in extracted timber and eroded soil, leading to shifts in ecosystem functioning and community composition. However, testing this is challenging because P varies within landscapes as a function of geology, topography and climate. Superimposed upon these trends are compositional changes in logged forests, with species with more acquisitive traits, characterised by higher foliar P concentrations, more dominant. It is difficult to resolve these patterns using traditional field approaches alone. Here we use airborne LiDAR-guided hyperspectral imagery to map foliar nutrient (i.e. P, N) concentrations, calibrated using field measured traits, over 400 km2 of northeastern Borneo, including a landscape-level disturbance gradient spanning old-growth to repeatedly logged forests. The maps reveal that canopy foliar P and N concentrations decrease with elevation. These relationships were not identified using traditional field measurements of leaf and soil nutrient concentrations. After controlling for topography, canopy foliar nutrient concentrations were lower in logged forest than in old-growth areas, reflecting decreased nutrient availability. However, foliar nutrient concentrations and specific leaf area were greatest in relatively short patches in logged areas, reflecting a shift in composition to pioneer species with acquisitive traits. N:P ratio increased in logged forest, suggesting reduced soil P availability through disturbance. Through the first landscape scale assessment of how functional leaf traits change in response to logging, we find that differences from old-growth forest become more pronounced as logged forests increase in stature over time, suggesting exacerbated phosphorus limitation as forests recover.
Sime Darby Foundation Frank Jackson Foundation Leverhulme Trust
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External DOI: https://doi.org/10.1111/gcb.14903
This record's URL: https://www.repository.cam.ac.uk/handle/1810/298996
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