New research led by Griffith University has measured individual tree heights across 3.1 million hectares in the New South Wales Northern Rivers region, revealing old growth forests and a tree as tall as a 27-storey building at 81m.
In the study published in Australian Journal of Botany, advanced mapping techniques using LiDAR (Light Detection and Ranging) and computational power revealed a detailed assessment of forest structure at the single-tree level over large geographic extents of the Northern Rivers region.
LiDAR uses laser light to measure distances to create detailed three-dimensional (3D) models of the landscape, including trees.
Lead author on the National Environmental Science Program Resilient Landscapes Hub project, Dr Patrick Norman from Griffith University, said the advanced mapping techniques allowed them to use publicly available Airborne Laser Scanning data to model forest canopy height and individual trees across 3.1 million hectares, at a level of detail that had not been achievable until now.
“This has allowed us to map the forest canopy in incredible detail capturing more than 180 million individual trees across this huge area,” Dr Norman said.
“We have been able to identify the tallest trees, including an 81m flooded gum (Eucalyptus grandis) and a 77m hoop pine (Araucaria cunninghamii). This has also allowed us to understand a better picture of where the remaining areas of old growth forest are, which will be important for conservation efforts.”
Dr Patrick Norman
The analysis of tree heights across different vegetation types and land uses showed the tallest trees were found in wet sclerophyll forests, in areas of native forest designated for nature conservation or timber production.
“This information provides valuable insights into the influence of environmental and human impacts on tree heights, which could be used to inform management strategies and conservation efforts within the region and can also be applied to other forested landscapes,” Dr Norman said.
This research was part of a project to develop climate change adaptation plans for the Northern Rivers region of New South Wales and the Wet Tropics of Queensland.
Both regions were home to many threatened species and ecological communities and contained a diverse range of land uses and protected areas, including significant wetlands, national parks, World Heritage Areas, Indigenous Protected Areas and Indigenous Land Use Agreements.
They were also places of rapid change: in a three-year period in the Northern Rivers region, unprecedented drought had been followed by bushfires and floods in rapid succession.
The study ‘Landscape-wide modelling of canopy tree crowns and heights using LiDAR: a case study in the Northern Rivers of New South Wales, Australia’ has been published in Australian Journal of Botany.
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