6 research outputs found
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Transformation of natural habitat disrupts biogeographical patterns of orchid diversity
Physical gradients are major natural drivers of global biodiversity. A key question is understanding how biogeographic patterns are impacted by transformation of natural habitats. We aim to elucidate the complex relationships between two core biogeographic drivers of biodiversity—elevation and precipitation—, local deforestation, and their additive and interactive effects on Andean orchid diversity in the Colombian Andes. We sampled understory orchids across 341 plots pairing natural and transformed habitats along a wide elevational (1163–3415 m) and precipitation range (879–3817 mm per year). We found 35,891 adult individuals in 341 species peaking at mid-elevations (∼2500 m) and mid-to-high precipitations (>1600 mm/yr). Conversion of natural to transformed habitats caused substantial orchid diversity loss, with ten-fold fewer species at the plot level equating to a 6-fold loss in overall species richness, and 23-times fewer individuals. The additive and interactive effects better explained the main patterns: conversion reconfigured the natural mid-elevation trends in orchid diversity and positive trend in diversity with precipitation to a quasi-linear trend in transformed habitats. This reflects the inherent dependency of orchid species to a host tree as well as lower resilience to transformed habitats. Our findings highlight the importance of halting deforestation across environmental gradients, but in particular at elevations and precipitations where reshaping of biogeographic patterns maximises the losses of biodiversity
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Monitoring lianas from space: Using Sentinel-2 imagery to observe liana removal in logged tropical forests
Liana removal – the cutting of over-abundant woody climbing plants (lianas) – has the potential to substantially increase tree growth and biomass accumulation across millions of hectares of degraded tropical forest. Satellite imagery could provide data capable of observing the effect of liana removal on the forest canopy, enabling the large-scale monitoring and validation of liana removal, which remains a key hurdle to its widespread implementation. Using a 320-ha liana removal experiment in Sabah, Malaysian Borneo, we tested whether a time series of Sentinel-2 images could observe the canopy signature of liana removal. Calculating a range of metrics derived from the Normalized Burn Ratio – a vegetation index based on spectral reflectance that differentiates leaf from non-leaf – we quantified satellite-derived canopy disturbance and fragmentation across a range of liana removal intensities and examined how canopy disturbance changed in the 12-months following removal treatments. We find that liana removal significantly increases canopy disturbance and fragmentation metrics one month after removal, with partial removal having a smaller effect than complete removal. The impact of liana removal on the canopy metrics declined over time, with measures of canopy disturbance and fragmentation largely indistinguishable from control forest within 12-months of treatment. Our findings evidence that freely available satellite imagery can be used to efficiently monitor large-scale liana removal applied at a range of intensities and suggest that partial liana removal could significantly reduce canopy disturbance of this restoration method