Objective 1 is still ongoing, Objective 2 & 3 are completed.
Objective 1:
EucFACE is a free-air CO2 enrichment experiment in a mature evergreen broadleaved forest. At the start of the project, TLS data for the six EucFACE rings was already available at three timestamps: 2012 (start of the experiment), 2015 and 2018. In March 2020, additional measurements were done, therefore adding a 4th timestamp, and extending the timeseries data to 8 years. Across the six rings, a total of 171 individual trees were segmented into individual point clouds. Tree height and vertical crown projected area were calculated per tree per timestamp. Due to some occlusion in the TLS data, we opted to use dendrometer band measurements (collected at the same day as the scanning) for the diameter measurements. This occlusion in the TLS data was due to the limited scanning setup (two locations per ring). Due to COVID-19 entry restrictions for Australia, the planned fieldwork in 2021 to collect very highly detailed scans using more scan locations could not be carried out. I therefore could not make full quantitative structure models to estimate the volume and derive biomass per tree level.
Even though limited to some extent due to the scan setup, several structural parameters could be extracted using the 3D data. Whereas the analysis of all 171 trees across all timestamps is finalized, interpretation of the results (i.e. to answer the question if enhanced levels of CO2 have an impact on the forest dynamics) is still in progress. This is due to the complexity of EUCFace, where not only enhanced CO2 is a parameter, but also other disturbances (e.g. insects, drought) occurred.
Objective 2:
We quantified the impacts of integrating structural observations of individual trees (namely tree height, leaf area, woody biomass, and crown area) derived from TLS into the state-of-the-art Ecosystem Demography model (ED2.2) at a temperate forest site Wytham Woods. We assessed the relative model sensitivity to initial conditions, allometric parameters, and canopy representation by changing them in turn from default configurations to site-specific, TLS-derived values. We show that forest demography and productivity as modelled by ED2.2 are sensitive to the imposed initial state, the model structural parameters, and the way canopy is represented. In particular, we show that:
- the imposed openness of the canopy dramatically influenced the potential vegetation, the optimal ecosystem leaf area, and the vertical distribution of light in the forest, as simulated by ED2.2;
- TLS-derived allometric parameters increased simulated leaf area index and aboveground biomass by 57 and 75%, respectively;
- the choice of model structure and allometric coefficient both significantly impacted the optimal set of parameters necessary to reproduce eddy covariance flux data.
Objective 3:
The fellow participated in an interdisciplinary workshop on ‘Degradation of Tropical Forests: observations, modelling and socio-environmental implications’ in Manaus, Brazil. Outcomes of this workshop are currently being prepared for publication.
In 2019, the fellow was the main organiser of the 4th Scientific Meeting on TLS in Forest Ecology (hosted by CAVElab at Ghent University). This interdisciplinary two-day interactive conference attracted ~80 participants globally and resulted in a review & perspective paper.
The fellow was the lead-author of the chapter "Terrestrial Laser Scanning & UAVs" in Aboveground Woody Biomass Product Validation Good Practices Protocol. Version 1.0. by Duncanson et al. (2021).
