New 3D and 4D tree and forest models from laser scanning
Professor Mikko Kaasalainen, Tampere University of Technology, Finland
Laser scanning techniques have brought about the possibility to model trees and forests efficiently in 3D detail. These quantitative structure models (QSMs) contain any desired geometric, volumetric, and topological properties of the trees. (Raumonen et al. 2013, Rem. Sens. 5, 491. Sample models can be interactively viewed at http://math.tut.fi/inversegroup/treegallery).
With the advent of lightweight and mobile scanners, this approach will, for the first time, allow the fast and precise 3D mapping of entire forests from billions of data points. Such models can be used for a wide variety of ecological studies, especially since tree species can be automatically identified from QSMs (Akerblom et al., this meeting and and Rem. Sens. Env., in press). The scheme has been expanded to 4D growth models by modifying theoretical plant growth algorithms to have stochastic components that produce the characteristic structural properties for each species (Potapov et al. 2016, Silva Fenn. 50, 1413).
The measurements are made by a large international collaboration network that also develops new types of instruments, such as the hyperspectral lidar that allows the identification of the surface material (chlorophylll, moisture, the condition of the tree, etc.) in addition to the laser scanning point cloud (S. Kaasalainen et al., this meeting). The combination of new methods and instrumentation allows the modelling of forests with unprecedented detail and quality.
Linking TLS measurements to global forest initiatives
Professor Martin Herold, Wageningen University, The Netherlands
Accurate, timely and transparent forest monitoring is relevant to several international policy processes such the Paris Climate Agreement and the Sustainable Development Goals; in particular keeping progress on progress to reduce deforestation and degradation and enhance forest stocks and functioning. Of particular in there is tropical forest biomass as a crucial component of global carbon emission estimations while large uncertainties on the carbon stocks and carbon stock changes due to human activities remain. Robust estimates require accurate and effective methods to estimate in-situ above ground biomass (AGB) and present methods rely on allometric models that are highly uncertain for many tropical countries and for large tropical trees in particular.
In a recent meeting in November 2016 of the Global Observations Forest Initiatives (GFOI), a first synthesis of the potential TLS for supporting country carbon monitoring activities, including:
- Improve allometry for tropical trees, reduce underestimation of biomass for large trees given that many countries are using Chave’s equation
- Increase transparency and traceability, and ability to produce long-term records of change in canopies and wood damage
- Better data to calibrate remote sensing based estimation, plot scale relationships between height, structure and biomass – research topic
- Interest for TLS to be tested in/with countries
- TLS community effort to make use of already acquired data across tropics to provide more empirical evidence
Despite that potential, the uptake of such technologies into national and international reporting requires additional steps and actions, including:
- Demonstration on how TLS can contribute to national inventory efforts with countries
- Development of community-consensus good practice guidelines based on experiences
- Evolve TLS processing to open source solutions
- Training materials and capacity development efforts
A particular interest of international initiatives is in methods to assess the type and impacts of forest change and to enhance transparency and increase stakeholder participation. These are areas where TLS might contribute even more in the future.
Linking ground to space for environmental applications
Dr Michael Schaefer, CSIRO Land and Water, Australia
Australia is one of the largest users of earth observation data world-wide, in part because the overall terrestrial and marine Australian territory that has to be monitored covers about 1/10 of the earth’s surface, and also due to the low population density and limited number of on-ground monitoring systems that operate across this vast territory.
The ‘AusCover’ remote sensing facility of the Terrestrial Ecosystem Research Network (TERN), was explicitly designed to help bring many disparate earth observation research teams together, and provide a level of national coordination and standardisation to the data and derived products that they use for both R&D and for use by government natural resources management purposes. This facility has operated since early 2010, and to-date has close to 12 institutional partners. It supports over 30 staff across the country, with eight regional ‘nodes’, that in turn provide important linkages to the various regional users of EO-derived products served via the AusCover data Facility.
Among the important ongoing activities performed by the AusCover partnership are to provide ground-based product validation services and in-situ data collection in support of international satellite programs as well as domestic research activities. AusCover has collected 5 km x 5 km high-resolution airborne hyperspectral and lidar data coverages for over ten ‘TERN Supersites’ across the continent that are complimented by detailed ground-based terrestrial lidar and other ancillary measurements at each site. This paper will highlight some of the results from this intensive field, and airborne work, and how it is being used for scaling to larger-scale regional or continental-scale products.
Coordinating TLS research for ecological applications
Professor Alan Strahler, Boston University, USA
Enhancing the development of terrestrial laser scanning (TLS) for ecological applications is the objective of a Research Coordination Network (RCN) now funded by the US National Science Foundation. The activity has two primary goals: (1) development of a low-cost lidar scanner that will provide accurate estimates of above-ground forest biomass for carbon modeling and monitoring procedures; and (2) development of a range of new ecological applications for TLS, based on rapid forest structure measurements and 3-D reconstructions of forest plots and stands. The network, first constituted in 2015, presently includes 73 participants, including researchers, professors, postdocs, and students at 32 institutions from Australia, Belgium, Canada, China, Finland, Netherlands, Switzerland, United Kingdom, and the United States.
A primary activity of the TLSRCN is to facilitate communication of TLS developments and applications both within the group and to the broader scientific community at meetings and workshops. In 2015-2016, RCN participants presented 40 TLS papers and posters at international meetings and forums. Within the group, bimonthly telecons allow the exchange of recent research developments and planning for group meetings and international conference presentations. Encouraging collaborative publications is also a focus of the RCN; 12 of 15 journal papers published in 2015-2016 that reported TLS research by participants also combined authors from more than one research group participating in the network.
Through these efforts, the TLSRCN has demonstrated that research coordination can enhance efforts to advance science and increase collaboration among researchers and groups. The TLSRCN is supported by NSF Grant DBI-1455636.
Summary of discussions and rapporteur remarks
Professor Alan Strahler, Boston University, USA