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Boreal and temperate forests are undergoing structural, compositional and functional changes in response to increasing temperatures, changes in precipitation, and rising CO2, but the extent of the changes in forests will also depend on current and future forest management. This study utilized the dynamic vegetation model LPJ‐GUESS enabled with forest management (version 4.1.2, rev11016) to simulate changes in forest ecosystem functioning and supply of ecosystem services in Sweden. We compared three alternative forest policy scenarios: Business As Usual, with no change in the proportion of forest types within landscapes; Adaptation and Resistance, with an increased area of mixed stands; and EU‐Policy, with a focus on conservation and reduced management intensity. LPJ‐GUESS was forced with climate data derived from an ensemble of three earth system models to study long‐term implications of a low (SSP1‐2.6), a high (SSP3‐7.0), and a very high (SSP5‐8.5) emissions scenario. Increases in net primary production varied between 4% and 8% in SSP1‐2.6, 21%–25% in SSP3‐7.0 and 25%–29% in SSP5‐8.5 across all three forest policy scenarios, when comparing 2081–2100 to 2001–2020. Increased net primary production was mediated by a higher soil nitrogen availability and increased water use efficiency in the higher emission scenarios SSP3‐7.0 and SSP5‐8.5. Soil carbon storage showed small but significant decreases in SSP3‐7.0 and in SSP5‐8.5. Our results highlight differences in the predisposition to storm damage among forest policy scenarios, which were most pronounced in southern Sweden, with increases of 61%–76% in Business‐As‐Usual, 4%–11% in Adaptation and Resistance, and decreases of 7%–12% in EU‐Policy when comparing 2081–2100 to 2001–2020. Plain Language Summary Climate change will alter factors which determine forest productivity and composition. Here, we used a modeling approach to study the effects of climate change on productive forest land in Sweden. We simulated forest management and accounted for different pathways of regional forest development as outcomes of hypothetical changes in forest policy. Specifically, we compared the time periods 2081–2100 and 2001–2020. Our findings showed increased growth rates of 4%–8% in the low emissions scenario (SSP1‐2.6), of 21%–25% in the high (SSP3‐7.0) and of 25%–29% in the very high (SSP5‐8.5) emissions scenarios. The model results indicated that more carbon was gained by trees per unit of water loss due to higher CO2 concentrations in the atmosphere, which partly explained the increased growth rates. Higher soil nitrogen availability also contributed to increased growth. When the contemporary forest landscape composition was maintained, the forest vulnerability to storm damage increased by between 61% and 76% in southern Sweden, comparing the time periods 2081–2100 and 2001–2020. An end‐of‐century change in forest policy emphasizing an expansion of mixed stands lowered the increase of storm damage vulnerability to 4%–11%. In the conservation‐oriented forest policy, the storm damage vulnerability decreased by 7%–12% in southern Sweden. Key Points All emission scenarios led to higher end‐of‐century forest ecosystem net primary production (NPP) when compared to present Higher temperatures and CO2 concentrations mediated NPP increases in higher emission scenarios

If on one side the measurement units (W m–2 or μmolCO2 m−2 s−1) clearly define that nature of the variable reported (a flux density), it is also correct to point out that the right definition should be used, at least in the description of the variables. On the data availability, it is important to remark that ICOS is a fully open access Research Infrastructure, where all data (from raw data to final products) and all codes used to generate the products are available to all users, under a CC BY data policy, and that this is a pillar of the ICOS philosophy. [...]this is also the standard followed by the WMO that, in its Guide to Instruments and Methods of Observation (WMO 2021), suggests installing the pyranometers “levelled […] so that, when properly exposed, the receiving surface is horizontal, as indicated by the spirit-level.” Dario Papale Department for Innovation in Biological Agro-Food and Forest Systems, University of Tuscia, Viterbo, Italy, and IAFES, Euro-Mediterranean Center on Climate Change, Viterbo, Italy; Jouni Heiskanen Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland; Christian Brümmer Thünen Institute of Climate-Smart Agriculture, Braunschweig, Germany; Nina Buchmann Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland; Carlo Calfapietra Institute of Research on Terrestrial Ecosystems, National Research Council, Porano, Italy; Arnaud Carrara Fundación Centro de Estudios Ambientales del Mediterráneo, Paterna, Valencia, Spain; Huilin Chen Centre for Isotope Research, University of Groningen, Groningen, Netherlands; Bert Gielen Department of Biology, University of Antwerp, Wilrijk, Belgium; Thanos Gkritzalis Flanders Marine Institute, Ostend, Belgium; Samuel Hammer Institut für Umweltphysik, Heidelberg University, Heidelberg, Germany; Susan Hartman National Oceanography Centre, Southampton, United Kingdom; Mathias Herbst Centre for Agrometeorological Research, German Meteorological Service, Braunschweig, Germany; Ivan A. Janssens Department of Biology, University of Antwerp, Wilrijk, Belgium; Armin Jordan Max-Planck-Institute for Biogeochemistry, Jena, Germany; Eija Juurola Institute for Atmospheric and Earth System Research, University of Helsinki, Helsinki, Finland; Ute Karstens ICOS ERIC, Carbon Portal, Lund, Sweden; Ville Kasurinen Head Office, Integrated Carbon Observation System European Research Infrastructure Consortium, Helsinki, Finland; Bart Kruijt Department of Environmental Sciences, Wageningen University and Research, Wageningen, Netherlands; Harry Lankreijer ICOS ERIC, Carbon Portal, Lund, Sweden; Ingeborg Levin Institut für Umweltphysik, Heidelberg University, Heidelberg, Germany; Maj-Lena Linderson Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden; Denis Loustau INRAE, ISPA, Villenave d’Ornon, France; Lutz Merbold Agroscope, Research Division Agroecology and Environment, Zurich, Switzerland; Cathrine Lund Myhre Atmosphere and Climate Department, Norwegian Institute for Air Research, Kjeller, Norway; Marian Pavelka Department of Matter and Energy Fluxes, Global Change Research Institute, CAS, Brno, Czech Republic; Kim Pilegaard Department of Environmental Engineering, Technical University of Denmark, Lyngby, Denmark; Michel Ramonet Université Paris-Saclay, CEA, CNRS, UVSQ, Laboratoire des Sciences du Climat et de l’Environnement (LSCE/IPSL), Gif-sur-Yvette, France; Corinna Rebmann Institut of Meteorology and Climate Research, Karlsruhe Institut of Technology, Karlsruhe, Germany; Janne Rinne Bioeconomy and Environment, Natural Resources Institute Finland,

Since 1750, land-use change and fossil fuel combustion has led to a 46% increase in the atmospheric carbon dioxide (CO₂) concentrations, causing global warming with substantial societal consequences. The Paris Agreement aims to limit global temperature increases to well below 2°C above preindustrial levels. Increasing levels of CO₂ and other greenhouse gases (GHGs), such as methane (CH₄) and nitrous oxide (N₂O), in the atmosphere are the primary cause of climate change. Approximately half of the carbon emissions to the atmosphere are sequestered by ocean and land sinks, leading to ocean acidification but also slowing the rate of global warming. However, there are significant uncertainties in the future global warming scenarios due to uncertainties in the size, nature, and stability of these sinks. Quantifying and monitoring the size and timing of natural sinks and the impact of climate change on ecosystems are important information to guide policy-makers’ decisions and strategies on reductions in emissions. Continuous, long-term observations are required to quantify GHG emissions, sinks, and their impacts on Earth systems. The Integrated Carbon Observation System (ICOS) was designed as the European in situ observation and information system to support science and society in their efforts to mitigate climate change. It provides standardized and open data currently from over 140 measurement stations across 12 European countries. The stations observe GHG concentrations in the atmosphere and carbon and GHG fluxes between the atmosphere, land surface, and the oceans. This article describes how ICOS fulfills its mission to harmonize these observations, ensure the related long-term financial commitments, provide easy access to well-documented and reproducible high-quality data and related protocols and tools for scientific studies, and deliver information and GHG-related products to stakeholders in society and policy.

The Nordic region was subjected to severe drought in 2018 with a particularly long-lasting and large soil water deficit in Denmark, Southern Sweden and Estonia. Here, we analyse the impact of the drought on carbon and water fluxes in 11 forest ecosystems of different composition: spruce, pine, mixed and deciduous. We assess the impact of drought on fluxes by estimating the difference (anomaly) between year 2018 and a reference year without drought. Unexpectedly, the evaporation was only slightly reduced during 2018 compared to the reference year at two sites while it increased or was nearly unchanged at all other sites. This occurred under a 40 to 60% reduction in mean surface conductance and the concurrent increase in evaporative demand due to the warm and dry weather. The anomaly in the net ecosystem productivity (NEP) was 93% explained by a multilinear regression with the anomaly in heterotrophic respiration and the relative precipitation deficit as independent variables. Most of the variation (77%) was explained by the heterotrophic component. Six out of 11 forests reduced their annual NEP with more than 50 g C m −2 yr −1 during 2018 as compared to the reference year. The NEP anomaly ranged between −389 and +74 g C m −2 yr −1 with a median value of −59 g C m −2 yr −1 . This article is part of the theme issue ‘Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale’.

The Colorado potato beetle Leptinotarsa decemlineata is an insect pest that can cause a substantial reduction of the potato harvest if left uncontrolled. The aim of this study was to assess the impact of a warmer climate on the Colorado potato beetle in Europe, since temperature influences the beetles' activity and development from egg to adult, and thereby the potential distribution. The study focuses in particular on the potential northward spread in the Scandinavian countries. In this region, the current climate is not warm enough to sustain the completed development of one generation in all years, and the region does not host a permanent population. Temperature data for 1961−2050 from 4 regional climate models and gridded observed data for 1961−1990 (reference period) were used for model calculations. We simulated the earliest timing of completed development of the first and second generations of the Colorado potato beetle, and assessed the geographical and inter-annual variation in the number of generations per year. The model simulations indicated a shift in the northern limit for establishment of a permanent Colorado potato beetle population by 2020−2050 in comparison with 1961−1990. In particular, the model showed a substantial increase in the frequency of years in which the temperature requirement for development of one generation was fulfilled in the transient zone, i.e. the southern part of Scandinavia. In addition, 2 generations per year may occur more frequently at the current distribution border at 55°N, increasing the risk of northward migration to the Scandinavian countries.

Statistical downscaling models for precipitation in Scania, southern Sweden, have been developed and applied to calculate the changes in the future Scanian precipitation climate due to projected changes in the atmospheric composition. The models are based on multiple linear regression, linking large-scale predictors at monthly time resolution to regional statistics of daily precipitation on a monthly basis. To account for spatial precipitation variability within the area, the precipitation statistics were derived for different regions in Scania. The final downscaling models, developed for different regions and seasons, use atmospheric circulation, large-scale humidity and precipitation as predictors. Among the precipitation statistics examined, only the models for estimating the mean precipitation and the frequency of wet days were skilful. Based on the Canadian Global Circulation Model 1 (CGCM1), a future scenario of these two statistics was created. The downscaled scenario shows a significant increase of the annual mean precipitation by about 10% and a slight decrease in the frequency of wet days, indicating an increase in the precipitation amounts as well as in the precipitation intensity. The main increase of precipitation amounts and intensity occur during winter, while the summer precipitation amounts decrease slightly. The seasonal changes found in precipitation are likely attributed to changes in the westerly flow of the atmospheric circulation.

The aim of this study is to analyse the spatial variability of meso-scale precipitation in Scania and to assess the influence of synoptic scale atmospheric circulation. The modes of spatial variation are revealed by EOF analysis of monthly precipitation totals between 1963 and 1990, which were obtained from a dense rain-gauge network in Scania, southern Sweden. The influence of local physiography on the spatial distribution of precipitation is assessed by GIS techniques using a digital elevation model of Scania. The relation to synoptic scale atmospheric circulation is analysed using regional circulation indices and weather types. It is shown that the daily precipitation distribution in the area is significantly influenced by synoptic scale pressure patterns. Nevertheless, the covariability of the monthly precipitation within Scania is high. About 80% of the precipitation variability is connected to the passage of low-pressure centres over or close to the region, which are likely to produce precipitation over the whole area. A wind-direction dependency found in the distribution indicates that there might be a limit between precipitation regimes within the landscape. Topography greatly influences the spatial distribution in Scania. The distribution of land and surrounding sea is also an important factor and makes the relationship between physiography and precipitation rather complex. The physiographical effects vary over a single year. The dampening effect of the sea on the atmospheric temperature influences the local stability in coastal areas and results in seasonally dependent precipitation patterns.

The Nordic region was subjected to severe drought in 2018 with a particularly long-lasting and large soil water deficit in Denmark, Southern Sweden and Estonia. Here, we analyse the impact of the drought on carbon and water fluxes in 11 forest ecosystems of different composition: spruce, pine, mixed and deciduous. We assess the impact of drought on fluxes by estimating the difference (anomaly) between year 2018 and a reference year without drought. Unexpectedly, the evaporation was only slightly reduced during 2018 compared to the reference year at two sites while it increased or was nearly unchanged at all other sites. This occurred under a 40 to 60% reduction in mean surface conductance and the concurrent increase in evaporative demand due to the warm and dry weather. The anomaly in the net ecosystem productivity (NEP) was 93% explained by a multilinear regression with the anomaly in heterotrophic respiration and the relative precipitation deficit as independent variables. Most of the variation (77%) was explained by the heterotrophic component. Six out of 11 forests reduced their annual NEP with more than 50 g C m yr during 2018 as compared to the reference year. The NEP anomaly ranged between -389 and +74 g C m yr with a median value of -59 g C m yr . This article is part of the theme issue 'Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale'.

The terrestrial carbon and water cycles are intimately linked: the carbon cycle is driven by photosynthesis, while the water balance is dominated by transpiration, and both fluxes are controlled by plant stomatal conductance. The ratio between these fluxes, the plant water-use efficiency (WUE), is a useful indicator of vegetation function. WUE can be estimated using several techniques, including leaf gas exchange, stable isotope discrimination, and eddy covariance. Here we compare global compilations of data for each of these three techniques. We show that patterns of variation in WUE across plant functional types (PFTs) are not consistent among the three datasets. Key discrepancies include the following: leaf-scale data indicate differences between needleleaf and broadleaf forests, but ecosystem-scale data do not; leaf-scale data indicate differences between C3 and C4 species, whereas at ecosystem scale there is a difference between C3 and C4 crops but not grasslands; and isotope-based estimates of WUE are higher than estimates based on gas exchange for most PFTs. Our study quantifies the uncertainty associated with different methods of measuring WUE, indicates potential for bias when using WUE measures to parameterize or validate models, and indicates key research directions needed to reconcile alternative measures of WUE.