During the action we covered both experimental and computational work. Custom growth chamber were build to measure drought responses in seedlings of both tropical and temperate species during the spring of 2020. The chambers consist of two stand alone growth chambers outfitted with precision scales to measure drought responses using a mass balance methodology (see attached image). Data were collected by a bespoke data logger and open hardware and software. Due to COVID disturbance further experimental results are lacking, but retrospective XRF scans were made at the SOLEIL/INRAE synchrotron platform using co-funding. Preliminary data and results of the measured wood cores were communicated during a vPICO session at the 2021 European Geoscience Union (EGU) meeting.
We characterized the historical context of forest growth and regrowth in the central Congo Basin using historical aerial photographs from the late 1950s. Given the impact of tropical forest disturbances on atmospheric carbon emissions, biodiversity, and ecosystem productivity, accurate long-term reporting of Land-Use and Land-Cover (LULC) change in the pre-satellite era (<1972) is an imperative. Our analysis therefore provides crucial spatial information to inform on all these processes. A comparison with contemporary LULC data showed a shift from previously highly regular industrial deforestation of large areas to discrete smallholder farming clearing, increasing landscape fragmentation and providing opportunties for substantial forest regrowth.
Furthermore, data recovery and synthesis of historical phenology records was successful. A first study, covering leaf phenology across tropical species and their relation to climate has been submitted to the Journal of Ecology. We analyze the leaf phenological patterns of 129 species (4706 individual observation years, 91.2 percent basal area, 94 evergreen, 35 deciduous). We illustrated the divergent behaviour within and across species, the variability of climate-phenology relationships and underscore the importance of accounting for constituent signals in canopy-wide scaling, and the interpretation of remotely-sensed phenology signals, with strong contributions of annually deciduous species but also the relative importance of large and/or abundant trees. Our results provide a baseline reference for future remote sensing and modelling studies aiming to establish and predict tropical forest ecosystem dynamics.
