Search results for "sub-Arctic"
showing 8 items of 8 documents
UV-screening and springtime recovery of photosynthetic capacity in leaves of Vaccinium vitis-idaea above and below the snow pack
2019
International audience; Evergreen plants in boreal biomes undergo seasonal hardening and dehardening adjusting their photosynthetic capacity and photoprotection; acclimating to seasonal changes in temperature and irradiance. Leaf epidermal ultraviolet (UV)-screening by flavonols responds to solar radiation, perceived in part through increased ultraviolet-B (UV-B) radiation, and is a candidate trait to provide cross-photoprotection. At Hyytiälä Forestry Station, central Finland, we examined whether the accumulation of flavonols was higher in leaves of Vaccinium vitis-idaea L. growing above the snowpack compared with those below the snowpack. We found that leaves exposed to colder temperature…
Comparison of quantitative Holocene temperature reconstructions using multiple proxies from a northern boreal lake
2017
Four biotic proxies (plant macrofossils, pollen, chironomids and diatoms) are employed to quantitatively reconstruct variations in mean July air temperatures ( Tjul) at Lake Loitsana (northern Finland) during the Holocene. The aim is to evaluate the robustness and biases in these temperature reconstructions and to compare the timing of highest Tjul in the individual reconstructions. The reconstructed Tjul values are evaluated in relation to local-scale/site-specific processes associated with the Holocene lake development at Loitsana as these factors have been shown to significantly influence the fossil assemblages found in the Lake Loitsana sediments. While pollen-based temperatures follow…
Sources of nitrous oxide and fate of mineral nitrogen in sub-Arctic permafrost peat soils
2021
Nitrous oxide (N2O) emissions from permafrost-affected terrestrial ecosystems have received little attention, largely because they have been thought to be negligible. Recent studies, however, have shown that there are habitats in subarctic tundra emitting N2O at high rates, such as bare peat surfaces on permafrost peatlands. The processes behind N2O production in these high-emitting habitats are, however, poorly understood. In this study, we established an in situ 15N-labelling experiment with the main objectives to partition the microbial sources of N2O emitted from bare peat surfaces (BP) on permafrost peatlands and to study the fate of ammonium and nitrate in these soils and in adjacent …
The trophic transfer of persistent pollutants (HCB, DDTs, PCBs) within polar marine food webs.
2017
Biomagnification (increase in contaminant concentrations at successively higher levels of trophic web), is a process that can transversally impair biodiversity and human health. Most research shows that biomagnification should be higher at poles with northern sites having a major tendency to biomagnify Persistent Organic Pollutants (POPs) through their marine food webs. We investigated the biomagnification degree into two marine trophic webs combining carbon and nitrogen stable isotopes and POP analyses. We showed that the Antarctic trophic web was more depleted than the sub-Arctic one and the differences highlighted for the basal part could explain the difference in length between them. Co…
Adaptive radiation along a thermal gradient: preliminary results of habitat use and respiration rate divergence among whitefish morphs.
2014
Adaptive radiation is considered an important mechanism for the development of new species, but very little is known about the role of thermal adaptation during this process. Such adaptation should be especially important in poikilothermic animals that are often subjected to pronounced seasonal temperature variation that directly affects metabolic function. We conducted a preliminary study of individual lifetime thermal habitat use and respiration rates of four whitefish (Coregonus lavaretus (L.)) morphs (two pelagic, one littoral and one profundal) using stable carbon and oxygen isotope values of otolith carbonate. These morphs, two of which utilized pelagic habitats, one littoral and one …
Bacterial Diversity in a Dynamic and Extreme Sub-Arctic Watercourse (Pasvik River, Norwegian Arctic)
2020
Microbial communities promptly respond to the environmental perturbations, especially in the Arctic and sub-Arctic systems that are highly impacted by climate change, and fluctuations in the diversity level of microbial assemblages could give insights on their expected response. 16S rRNA gene amplicon sequencing was applied to describe the bacterial community composition in water and sediment through the sub-Arctic Pasvik River. Our results showed that river water and sediment harbored distinct communities in terms of diversity and composition at genus level. The distribution of the bacterial communities was mainly affected by both salinity and temperature in sediment samples, and by oxygen…
Lake size and fish diversity determine resource use and trophic position of a top predator in high-latitude lakes
2015
Prey preference of top predators and energy flow across habitat boundaries are of fundamental importance for structure and function of aquatic and terrestrial ecosystems, as they may have strong effects on production, species diversity, and food-web stability. In lakes, littoral and pelagic food-web compartments are typically coupled and controlled by generalist fish top predators. However, the extent and determinants of such coupling remains a topical area of ecological research and is largely unknown in oligotrophic high-latitude lakes. We analyzed food-web structure and resource use by a generalist top predator, the Arctic charr Salvelinus alpinus (L.), in 17 oligotrophic subarctic lakes…
The impact of weather and the phase of the rodent cycle on breeding populations of waterbirds in Finnish Lapland
2016
Climate change may affect bird populations both directly by changing the weather conditions, and indirectly through changes in the food chain. While both theoretical and empirical studies have shown climate change having drastic impacts on polar areas, its consequences on Arctic bird species are still poorly known. Here we investigated how weather and changes in predator–prey interactions affected the annual growth rates of sub-Arctic birds by monitoring the breeding numbers of three duck and seven wader species in the alpine tundra of Finnish Lapland during 2005–2015 (except for 2006). We hypothesized that growth rates of waterbirds would be positively associated with warm and dry weather …