ACHIM GRELLE results 12
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Microclimate research gained renewed interest over the last decade and its importance for many ecological processes is increasingly being recognized. Consequently, the call for high‐resolution microclimatic temperature grids across broad spatial extents is becoming more pressing to improve ecological models. Here, we provide a new set of open‐access bioclimatic variables for microclimate temperatures of European forests at 25...
Global maps of soil temperatureNARA Subscribed
Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1‐km 2 r...
Ecological research heavily relies on coarse‐gridded climate data based on standardized temperature measurements recorded at 2 m height in open landscapes. However, many organisms experience environmental conditions that differ substantially from those captured by these macroclimatic (i.e. free air) temperature grids. In forests, the tree canopy functions as a thermal insulator and buffers sub‐canopy microclimatic conditions,...
Do the energy fluxes and surface conductance of boreal coniferous forests in Europe scale with leaf area?NARA Subscribed
Earth observing systems are now routinely used to infer leaf area index ( LAI ) given its significance in spatial aggregation of land surface fluxes. Whether LAI is an appropriate scaling parameter for daytime growing season energy budget, surface conductance ( G s ), water‐ and light‐use efficiency and surface–atmosphere coupling of European boreal coniferous forests was explored using eddy‐covariance ( EC ) energy and CO 2 f...
Latent heat exchange in the boreal and arctic biomesNARA Subscribed
In this study latent heat flux ( λE ) measurements made at 65 boreal and arctic eddy‐covariance ( EC ) sites were analyses by using the Penman–Monteith equation. Sites were stratified into nine different ecosystem types: harvested and burnt forest areas, pine forests, spruce or fir forests, Douglas‐fir forests, broadleaf deciduous forests, larch forests, wetlands, tundra and natural grasslands. The Penman–Monteith equation was...
Storms can cause Europe‐wide reduction in forest carbon sinkNARA Subscribed
Disturbance of ecosystems is a major factor in regional carbon budgets, and it is believed to be partly responsible for the large inter‐annual variability of the terrestrial part of the carbon balance. Forest fires have so far been considered as the most important disturbance but also other forms of disturbance such as insect outbreaks or wind‐throw might contribute significantly to the largely unexplained inter‐annual variabi...
Contemporary carbon accumulation in a boreal oligotrophic minerogenic mire – a significant sink after accounting for all C‐fluxesNARA Subscribed
Based on theories of mire development and responses to a changing climate, the current role of mires as a net carbon sink has been questioned. A rigorous evaluation of the current net C‐exchange in mires requires measurements of all relevant fluxes. Estimates of annual total carbon budgets in mires are still very limited. Here, we present a full carbon budget over 2 years for a boreal minerogenic oligotrophic mire in northern...
Addressing the influence of instrument surface heat exchange on the measurements of CO 2 flux from open‐path gas analyzersNARA Subscribed
There is a growing concern in the flux community that using the eddy covariance method with open‐path CO 2 analyzers often leads to measurements of an apparent ecosystem CO 2 uptake during off‐season periods, especially in cold climates. Such uptake has not been observed when measurements were made with closed‐path analyzers, chambers, or profile methods, suggesting it is an artifact due in some way to the use of open‐path ana...
Air temperature triggers the recovery of evergreen boreal forest photosynthesis in springNARA Subscribed
The timing of the commencement of photosynthesis ( P * ) in spring is an important determinant of growing‐season length and thus of the productivity of boreal forests. Although controlled experiments have shed light on environmental mechanisms triggering release from photoinhibition after winter, quantitative research for trees growing naturally in the field is scarce. In this study, we investigated the environmental cues init...
Long‐term measurements of boreal forest carbon balance reveal large temperature sensitivityNARA Subscribed
We present results from two years’ net ecosystem flux measurements above a boreal forest in central Sweden. Fluxes were measured with an eddy correlation system based on a sonic anemometer and a closed path CO 2 and H 2 O gas analyser. The measurements show that the forest acted as a source during this period, and that the annual balance is highly sensitive to changes in temperature. The accumulated flux of carbon dioxide duri...
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