• Energy Research

Coastal sand dunes near the Baltic Sea are a dynamic environment marking the boundary between land and sea and oftentimes covered by Scots pine (Pinus sylvestris L.) forests. Complex climate-environmental interactions characterize these ecosystems and largely determine the productivity and state of these coastal forests. In the face of future climate change, understanding interactions between coastal tree growth and climate variability is important to promote sustainable coastal forests. In this study, we assessed the effect of microsite conditions on tree growth and the temporal and spatial variability of the relationship between climate and Scots pine growth at nine coastal sand dune sites located around the south Baltic Sea. At each site, we studied the growth of Scots pine growing at microsites located at the ridge and bottom of a dune and built a network of 18 ring-width and 18 latewood blue intensity chronologies. Across this network, we found that microsite has a minor influence on ring-width variability, basal area increment, latewood blue intensity, and climate sensitivity. However, at the local scale, microsite effects turned out to be important for growth and climate sensitivity at some sites. Correlation analysis indicated that the strength and direction of climate-growth responses for the ring-width and blue intensity chronologies were similar for climate variables over the 1903–2016 period. A strong and positive relationship between ring-width and latewood blue intensity chronologies with winter-spring temperature was detected at local and regional scales. We identified a relatively strong, positive influence of winter-spring/summer moisture availability on both tree-ring proxies. When climate-growth responses between two intervals (1903–1959, 1960–2016) were compared, the strength of growth responses to temperature and moisture availability for both proxies varied. More specifically, for the ring-width network, we identified decreasing temperature-growth responses, which is in contrast to the latewood blue intensity network, where we documented decreasing and increasing temperature-growth relationships in the north and south respectively. We conclude that coastal Scots pine forests are primarily limited by winter-spring temperature and winter-spring/summer drought despite differing microsite conditions. We detected some spatial and temporal variability in climate-growth relationships that warrant further investigation.

SummaryBoreal peatland energy balances using the eddy covariance technique have previously been made in Alaska, Canada, Scandinavia, and Western Siberia, but not in the European portion of the Russian Federation. European Russia contains approximately 200,000km2 of peatlands and has a boreal (subarctic), continental climate influencing the region’s energy balance. To help fill this research gap, the surface energy balance was determined for a boreal peatland fen in the Komi Republic of Russia for an 11-month period in 2008–2009 using the eddy covariance method. The total measurement period’s cumulative energy balance closure rate was 86%, with higher closure during the critical summer growing season. Similar to other boreal peatland sites, the mid-summer shortwave radiation demonstrated albedo between 0.13 and 0.19 as calculated on a cumulative monthly basis, whereas monthly albedo was >0.9 during the months with greatest snow (January, February 2009). Mid-summer Bowen ratios averaged 0.20–0.25 on a cumulative basis, with monthly averaged mid-day values in the range 0.35–0.53 during the growing season. Latent energy (LE) fluxes exceeded 70% of net radiation and 60% of potential evapotranspiration. During the study period, total evapotranspiration (406mm) was slightly greater than rainfall (389mm), with later snowfalls creating excess moisture in the atmospheric water budget. These characteristics together point to a peatland whose energy balance behavior is generally consistent with data from other boreal fens. The LE fluxes were dominantly controlled by net radiation, with less canopy resistance than at other northern fens and a lighter role for vapor pressure deficit to play in the energy balance. The aerodynamic and canopy conductance terms were of similar magnitude, both through the season and through any given diurnal cycle. The consequently high decoupling coefficient (0.65±0.16 in the growing season) allows further modeling of fens in this region with reduced effects from the uncertainties of parameterizing surface conductance terms and their responses to water table and vapor pressure deficit changes. The Priestley–Taylor method provides a reasonable approach to modeling evapotranspiration, given some assumptions about the site’s energy balance closure. This understanding of the local drivers on the energy and water budgets has important implications for peatland ecology and growth, regional carbon dynamics, and downstream hydrology.

AbstractThe mechanistic pathways connecting ocean-atmosphere variability and terrestrial productivity are well-established theoretically, but remain challenging to quantify empirically. Such quantification will greatly improve the assessment and prediction of changes in terrestrial carbon sequestration in response to dynamically induced climatic extremes. The jet stream latitude (JSL) over the North Atlantic-European domain provides a synthetic and robust physical framework that integrates climate variability not accounted for by atmospheric circulation patterns alone. Surface climate impacts of north-south summer JSL displacements are not uniform across Europe, but rather create a northwestern-southeastern dipole in forest productivity and radial-growth anomalies. Summer JSL variability over the eastern North Atlantic-European domain (5-40E) exerts the strongest impact on European beech, inducing anomalies of up to 30% in modelled gross primary productivity and 50% in radial tree growth. The net effects of JSL movements on terrestrial carbon fluxes depend on forest density, carbon stocks, and productivity imbalances across biogeographic regions.

AbstractCurrent analyses and predictions of spatially explicit patterns and processes in ecology most often rely on climate data interpolated from standardized weather stations. This interpolated climate data represents long‐term average thermal conditions at coarse spatial resolutions only. Hence, many climate‐forcing factors that operate at fine spatiotemporal resolutions are overlooked. This is particularly important in relation to effects of observation height (e.g. vegetation, snow and soil characteristics) and in habitats varying in their exposure to radiation, moisture and wind (e.g. topography, radiative forcing or cold‐air pooling). Since organisms living close to the ground relate more strongly to these microclimatic conditions than to free‐air temperatures, microclimatic ground and near‐surface data are needed to provide realistic forecasts of the fate of such organisms under anthropogenic climate change, as well as of the functioning of the ecosystems they live in. To fill this critical gap, we highlight a call for temperature time series submissions to SoilTemp, a geospatial database initiative compiling soil and near‐surface temperature data from all over the world. Currently, this database contains time series from 7,538 temperature sensors from 51 countries across all key biomes. The database will pave the way toward an improved global understanding of microclimate and bridge the gap between the available climate data and the climate at fine spatiotemporal resolutions relevant to most organisms and ecosystem processes.

AbstractThe growth of past, present, and future forests was, is and will be affected by climate variability. This multifaceted relationship has been assessed in several regional studies, but spatially resolved, large-scale analyses are largely missing so far. Here we estimate recent changes in growth of 5800 beech trees (Fagus sylvatica L.) from 324 sites, representing the full geographic and climatic range of species. Future growth trends were predicted considering state-of-the-art climate scenarios. The validated models indicate growth declines across large region of the distribution in recent decades, and project severe future growth declines ranging from −20% to more than −50% by 2090, depending on the region and climate change scenario (i.e. CMIP6 SSP1-2.6 and SSP5-8.5). Forecasted forest productivity losses are most striking towards the southern distribution limit of Fagus sylvatica, in regions where persisting atmospheric high-pressure systems are expected to increase drought severity. The projected 21st century growth changes across Europe indicate serious ecological and economic consequences that require immediate forest adaptation.