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Tree growth, forest carbon storage and climate change in a Canadian boreal region using a model-data fusion approach

Periodic Reporting for period 1 - MAIDEN-SPRUCE (Tree growth, forest carbon storage and climate change in a Canadian boreal region using a model-data fusion approach)

Reporting period: 2015-10-01 to 2017-09-30

The boreal forest is one of the most important global carbon sinks but its carbon fluxes and total amount of sequestered carbon depend on the regional climate variability. Because of this sensitivity to climate, boreal trees are also important natural archives of current and past climate change. During MAIDEN-SPRUCE, we used a data-model approach to improve our understanding of the links between forests and climate in a Canadian boreal region over the last millennium. Multidisciplinary techniques mixing climatology, geochemistry, dendrochronology, tree physiology and numerical modelling were applied in a project that linked together European and Canadian scientists.

The specific objectives of MAIDEN-SPRUCE were the following:
1. We wanted to improve the understanding of boreal ecosystem functioning. Hence, we studied the climate imprint on photosynthesis, carbon allocation and δ18O in tree-rings through mechanistic modeling using the MAIDEN model.
2. We wanted to reduce the uncertainties on the estimates of the climate variability of the last millennium in a region that was historically under-represented in the Northern Hemisphere network of climate reconstructions. Hence, we produced the first multiproxy (ring widths and δ18O and δ13C in tree-ring cellulose) regional temperature reconstruction in Eastern North America.
3. We wanted to enlighten about the potential long-term legacy effects of specific past climatic events in the boreal forest. Hence, we analyzed the Tambora impact on taiga ecosystems.
4. We wanted to establish long-term collaborations between European research institutes and between European and Canadian scientists.
5. We wanted to enhance the societal awareness in Southeastern France of the diversity of the research activities funded by public money. Hence, we participated to scientific outreach events.
"Work Package 1 (understanding of boreal ecosystem functioning)

Photosynthesis and carbon allocation.

During MAIDEN-SPRUCE, we adapted the MAIDEN ecophysiological forest model to consider important processes for boreal tree species, such as non-linear acclimation of photosynthesis to temperature changes, canopy development as a function of previous-year climate variables influencing bud formation and the temperature dependence of carbon partition in summer.

Oxygen isotopes in tree-rings.

During MAIDEN-SPRUCE, we used the MAIDEN model to decipher the variability of δ18O in tree rings of two temperature-sensitive species of relevant paleoclimatological interest (Picea mariana and Nothofagus pumilio) and growing at cold high-latitudes in North and South America.

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Work package 2 (uncertainties of the climate variability of the last millennium)

During MAIDEN-SPRUCE, we used a new tree-ring dataset (ring widths, δ13C and δ18O) to develop a significantly improved millennium-long multiproxy temperature reconstruction (997-2006 CE) in Northeastern North America accounting for uncertainties with a Bayesian approach that evaluates the likelihood of each proxy model.

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Work package 3 (legacy of specific past climatic events)

During MAIDEN-SPRUCE, we collected an extensive network of early meteorological time series, climate simulation data and numerous, well-replicated proxy records from Eastern Canada to analyze the strength and the persistence of the Tambora impact on the regional climate and forest processes.

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Work package 4 (establish long-term collaborations)

MAIDEN-SPRUCE allowed the establishment of a large network of research collaborations within Europe and between American and European scientists. The Experienced Researcher (ER, Fabio Gennaretti) was invited one month at the University of Helsinki (Finland), one week at the CIFOR-INIA Institute (Madrid, Spain), two weeks at the UQAR University (Rimouski, Canada) to strengthen these international collaborations. Furthermore the list of co-authors of the publications resulting from MAIDEN-SPRUCE highlights the importance of this scientific network.

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Work package 5 (enhance the societal awareness of research diversity)

Following the principles of the European Charter for Researchers and the Code of Conduct for the Recruitment of Researchers, we ensured that our research activities were made known to the society at large by participating to several initiatives and popular science events (National science festival, European Researchers’ Night: Marseille). In these occasions, we did an effort to present our results in such a way that they could be understood by non-specialists. Furthermore, the ER was involved in the co-supervision of two Master students.

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Publications in international scientific reviews:

1. Biogeosciences, 2017, 1-26, doi:10.5194/bg-2017-51 2017.
2. Climate of the Past, 2017, 1-29, doi:10.5194/cp-2017-93 2017.
3. Climate Dynamics, doi:10.1007/s00382-017-3565-5 2017.
4. Environmental Research Letters, under review.

Conference organization:

1. Fabio Gennaretti was the main organizer of the session “Model-data fusion approaches in biogeosciences” during the “EGU General Assembly”, Vienna, Austria, 23–28 April 2017.

Release of source code in public repositories:

1. Gennaretti, Fabio (2017): MAIDEN ecophysiological forest model. figshare. https://doi.org/10.6084/m9.figshare.5446435.v1

Oral presentations in international conferences:

1. Sfecologie. Marseille, France, 24-28 October 2016. [English].
2. EMS Annual Meeting. Trieste, Italy, 11-16 September 2016. [English].
3. Bayesian Statistics Applied to Archaeology. Nantes, France, 24-26 May 2016. [English – Fabio Gennaretti was an invited speaker].
4. EGU General Assembly, Vienna, Austria, 17–22 April 2016. [English].

Poster presentations in international conferences:

1. PAGES Open Science Meeting, Zaragoza, Spain, 9-13 May 2017. [English].
2. EGU General Assembly"
Community involvement / exhibitions:

1. Fabio Gennaretti (FG) organized a workshop for children about dendrochronology at the “Fête de la science – National science festival” (http://www.pytheas.univ-amu.fr/spip.php?article1501). 13/10/2016
2. FG co-organized an event at the “Nuit des chercheurs: Marseille – European Researchers’ Night: Marseille” (http://nuitdeschercheurs-france.eu/) on the impact of volcanic eruptions. 30/09/2016

Student training:

1. FG supervised the Master student Mélanie Guardiola (CEREGE, France) over 1.5 months (year 2017; rate of supervision = 100%). She was trained to conduct climate analyses.
2. FG co-supervised the Master student Jeanne Rezsöhazy (UCL, Belgique) over 10 months (years 2016-2017; rate of supervision = 20%). She was trained in ecophysiological modeling and data assimilation

Participation to workshops:

1. FG participated to the workshop “Proxy system modelling and data assimilation in paleosciences” (organized by the DAPS working group of PAGES, Louvain-la-Neuve, Belgium, May 29-June 1 2017).
2. FG participated to the workshop “Volcanic Impacts on Climate and Society” (organized by the VICS working group of PAGES, Zaragoza, Spain, 9 May 2017)

FG organized 2 open seminars at the CEREGE institute (on Friday September 22th 2017 and on Friday November 13th 2015).
Processes considered by the MAIDEN ecophysiological model