Terrestrial ecosystem-climate interactions of our EMERALD planet

Plants regulate the cycles of carbon dioxide and water, affect the composition of the atmosphere and how the landscape absorbs and reflects sunlight. As such vegetation is not only shaped by climate, it also feeds back to the atmosphere and shapes the environment. An example of such feedbacks is a change in the forest line due to global warming, which in turn affects the climate through changes in the reflection of solar radiation, the amount of water that is evaporated, how much carbon is stored - processes that in turn influence the climate. Such feedbacks can be positive (enhances the climate change signal) or negative (counteracts climate change). EMERALD is an interdisciplinary, nationally coordinated project that integrated research groups in Norway studying the role of vegetation in the climate system. The project worked to improve the understanding of ecosystem processes and their representation in global climate models. Focus has been on boreal and Arctic ecosystems, such as evergreen trees, deciduous trees, shrubs, mosses and lichens - vegetation types not yet satisfactory represented in climate models. We worked interdisciplinary - across scientific fields and expertise. EMERALD has had three specific goals: (a) improving the land module (CLM) in the Norwegian Earth System model (NorESM), (b) integrating data and knowledge from field-based ecosystem research into model development, testing and evaluation, and (c) improve projections of climate change for our northern region. This included working with a more advanced version of CLM that accounts for dynamic vegetation (CLM-FATES). The development of a joint model platform (NorESM Land Sites Platform), including a user-friendly interface for running CLM for selected sites, has facilitated coordinated testing and model development - also for non-expert users. For example, how vegetation changes with increasing temperature in the model as compared to data from a field-based experiment. The model and a tutorial are open-source (on GitHub) and used with positive experience within teaching. The platform is a key asset of much of the work done within the group and facilitates interdisciplinary and collaborative studies internally as well as with external partners. The development was done in close collaboration with the IT-group at the Department of Geosciences (UiO) and is documented in a separate scientific publication. Vegetation is represented in CLM-FATES through Plant Functional Types (PFTs). A particular effort has gone into creating a separate PFT for mosses and lichen. Results show that our model is able to capture the low photosynthetic activity of moss compared to grassland – in line with observations. We further worked towards a new representation of soil organic matter decomposition and a new frost mortality scheme in FATES. Field work and field experiments are located at Finse, Hedmark, western Norway, in Finnmark and on Svalbard, and have to a large degree been linked to existing projects and research infrastructure. The level of field activities was high during the project period, summers in particular, but not limited to. Worth mentioning is the winter warming experiment at Finse simulating a warm winter and rain-on-snow events (measuring effects on the vegetation the following two summers), as well as experiments both in the field and lab studying the tolerant limits of plants to extreme conditions (such as extreme temperatures, light conditions, air humidity and drought). We also studied the effect of wetland restauration on the water-, energy- and carbon budget, and the role of evaporation on the water balance in particular (local and regional scale). EMERALD placed large emphasis on disseminating research and has an active website where news are published, such as high impact science publications and popular science contributions. In collaboration with the Centre for Biogeochemistry in the Anthropocene (CBA) at UiO, EMERALD contributed with four articles (2022) in a special issue of ‘Naturen’ - a popular science journal. Results are also disseminated through the Norwegian Centre of Climate Services, and as contributions to exhibitions and the media (blog, newspapers, etc.). The temporary exhibition “Natur i Endring” by EMERALD – first displayed at the Climate House at its opening in 2020 - was moved in 2021 to the Norwegian Mountain Museum in Lom, where it still stands. The exhibition emphasis feedbacks between climate and vegetation and targets a young audience. Results from EMERALD were communicated at stakeholder meetings with participants from the agriculture and forestry sector. Worth mentioning is also our contributions to a blog at forskning.no on afforestation (“Søkelys på skogplanting”). Interdisciplinary knowledge at the interface between vegetation and climate is key in the course Ecological Climatology at UiO and in a course at UiB that offers hands-on training in different applications of plant functional traits.

EMERALD has strongly impacted the scientific community. We have formed a unique and interdisciplinary research community across Norway, united around the role of high latitude vegetation in the climate system. Several PhDs have been educated in EMERALD and synergy projects, and postdocs and researchers have developed expertise that is now integrated in research and developments in all EMERALD participant institutions and beyond. Together, we have made significant improvements in NorESM, including terrestrial ecosystems impacts and feedbacks through an observational model-based approach - building on novel observational systems and field and lab experiments. Data that have been key for the development, testing and evaluation of models, representative for our northern climate, including snow-vegetation interactions and frost processes. Increased knowledge gained in EMERALD through novel data acquisition and model development focusing on high latitude processes, have the potential to improve trust in projections of high latitude climate change – projections that are widely used to inform policy makers. The improvements in NorESM will further contribute to the next round of climate projections used by the IPCC (CMIP7) and the Arctic Monitoring and Assessment Programme (AMAP), a working group of the Arctic Council. As such, EMERALD responds to the societal need for improved climate change projections in northern environments.

Plants shape and are being shaped by climate on our Emerald Planet. Vegetation operates in feedbacks in the climate system, involving also the atmosphere, soils and the hydrological cycle. Shifts and migration of vegetation as a result of climate change are already taking place in northern environments. Research groups in Norway are currently contributing key knowledge on the interactions and feedbacks between land surface processes, terrestrial ecosystems and the climate systems, yet progress is hampered by the field being scattered and fragmented. EMERALD leadership brought together these research communities in two national seminars on terrestrial vegetation and ecological climatology in 2016 and 2017. Building on this, EMERALD will consolidate, structure, and develop this interdisciplinary research field by engaging global and regional scale climate modellers, land surface process experts and ecologists in a joint effort to assess ecosystem states and dynamics in response to climate variability and change. The focus is on high latitudes with boreal, alpine and Arctic vegetation, including Svalbard in a larger pan-Arctic context. EMERALD integrates across existing data from a wealth of already existing field sites covering a wide range of high latitude ecosystems, experimental facilities and observational systems such as SIOS (Svalbard) and ICOS flux towers in northern environments Based on observations EMERALD aims to explain the processes and improve their representation in the Norwegian Earth System model (NorESM) with a long-term goal to improve climate projections. EMERALD takes research in Norway on terrestrial ecosystems-climate interactions a big leap ahead. Our results will be disseminated to the public, targeted policy and decision makers and scientists. At the Climate House of the Natural History Museum, EMERALD will contribute to exhibitions, tours and lectures. Stakeholder groups will be involved through the Norwegian Centre for Climate Services.