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Climate change increases the frequency and severity of fire in the Arctic tundra regions. We assessed effects of fire in combination with summer warming on soil biogeochemical N- and P cycles with a focus on mineral N over two years following an experimental fire in a dry heath tundra, West Greenland. We applied stable isotopes ( 15 NH 4 + -N and 15 NO 3 - -N) to trace the post-fire mineral N pools. The partitioning of 15 N in the bulk soils, soil dissolved organic N (TDN), microbes and plants (roots and leaves) was established. The fire tended to increase microbial P pools by four-fold at both one and two years after the fire. Two years after the fire, the bulk soil 15 N recovery has decreased to 10.4% in unburned plots while relatively high recovery was maintained (30%) in burned plots, suggesting an increase in soil N retention after the fire. The contribution of microbial 15 N recovery to bulk soil 15 N recovery increased from 11.2% at 21 days to 31.5% two years after the fire, suggesting that higher post-fire N retention was due largely to the increased incorporation of N into microbial biomass. Fire also increased 15 N recovery in bulk roots after one and two years, but only under summer warming. This suggests that higher retention of post-fire N can strongly increase the potential for N uptake of recovering plants under a future warmer climate. There was significantly lower 15 N enrichment of Betula nana leaves while higher 15 N enrichment of Vaccinium uliginosum leaves (after three years) in burned than control plots. This shows that fire can alter the N uptake differently among dominant shrub species in this tundra ecosystem, and implies that wildfires may change plant species composition in the longer term., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

The frequency and severity of fire is increasing in Arctic tundra regions with climate change. Here we investigated effects of experimental low-intensity fire and shrub cutting, in combination with warming, on soil biogeochemical cycles and post-fire greenhouse gas (GHG) emissions in a dry heath tundra, West Greenland. We performed in vitro incubation experiments based on soil samples collected for up to two years after the fire. We observed tendency for increased soil nitrate (14-fold) and significant increases in soil ammonium and phosphate (four-fold and five-fold, respectively) two years after the fire, but no effects of shrub cutting on these compounds. Thus, changes appear to be largely due to fire effects rather than indirect effects by vegetation destruction. Two years after fire, nitrous oxide (N 2 O) and carbon dioxide (CO 2 ) production was significantly increased (three-fold and 32% higher, respectively), in burned than unburned soils, while methane (CH 4 ) uptake remained unchanged. This stimulated N 2 O and CO 2 production by the fire, however, was only apparent under conditions when soil was at maximum water holding capacity, suggesting that fire effects can be masked under dry conditions in this tundra ecosystem. There were positive effects by modest 2.5 °C warming on CO 2 production in control but not in burned soils, suggesting that fire may decrease the temperature response in soil respiration. Methane uptake was neither altered by the modest warming in shrub-cut nor in burned soils after two years, suggesting that the removal of vegetation may play a key role in controlling future temperature response of CH 4 oxidation. Altogether, our results show that post-fire tundra soils have the potential to enhance soil GHG emissions (e.g. N 2 O and CO 2 ) especially during episodes with wet soil conditions. On the other hand, the lack of warming responses in post-fire soil respiration may weaken this positive feedback to climate change., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

The effects of soil succession after glacial retreat and fertilisation by marine animals are known to have major impacts on soil greenhouse gas (GHG) fluxes in polar terrestrial ecosystems. While in many polar coastal areas retreating glaciers open up new ground for marine animals to colonise, little is known about the combination of both factors on the local GHG budget. We studied the magnitude of GHG fluxes (CO 2 , CH 4 and N 2 O) on the combined effect of glacial retreat and penguin-induced fertilisation along a transect protruding into the world's largest King Penguin (Aptenodytes patagonicus) colony at Saint Andrews Bay on sub-Antarctic South Georgia. GHG production and consumption rates were assessed based on laboratory incubations of intact soil cores and nutrients and water additional experimental incubations. The oldest soils along the transect show significant higher contents of soil carbon, nutrients and moisture and were strongly influenced by penguin activity. We found a net CH 4 consumption along the entire transect with a marked decrease within the penguin colony. CO 2 production strongly increased along the transect, while N 2 O production rates were low near the glacier front and increased markedly within the penguin colony. Controlled applications of guano resulted in a significant increase in CO 2 and N 2 O production, and decrease in CH 4 consumption, except for sites already strongly influenced by penguin activity. The results show that soil microbial activity promptly catalyses a turnover of soil C and atmospheric methane oxidation in de-glaciated forelands. The methane oxidizers, however, may increase relatively slowly in their capacity to oxidise atmospheric CH 4 . Results show also that the increase of nutrients by penguins reduces CH 4 oxidation whereas N 2 O production is greatly increased. A future expansion of penguins into newly available ice-free polar coastal areas may therefore markedly increase the local GHG budget., Competing Interests: Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Little is known about the accumulation of persistent organic pollutants (POPs) and its consequences for seabirds in the Mediterranean basin. We characterised the plasma contaminant profile (polychlorinated biphenyls ΣPCBs; organochlorine pesticides ΣOCPs; polybrominated diphenyl ethers ΣPBDEs) of a population of the seabird Scopoli's shearwater (Calonectris diomedea) that breeds in the southern Mediterranean (Linosa Island) and investigated (i) whether sex, stable isotope ratios (related to diet), reproductive phase (early incubation vs. late breeding season) and body mass explained variation in contaminant burden and (ii) whether they predict health-related variables. The predominant category of POPs was ΣPCBs contributing between 53.0 and 92.4% of the total POPs in each shearwater. The percentage contribution of ΣOCPs to total POPs ranged between 7.6 and 47.0%, while that of ΣPBDEs ranged between <1% and 22.1%. Near the end of the breeding season, concentrations of ΣPCBs, ΣOCPs and ΣPOPs were significantly higher than at the beginning of the incubation period. ΣPBDEs were higher in males than females near the end of the breeding season, while they were higher in females than males at the beginning of the egg incubation period. Carbon- and nitrogen isotope ratios and individual body mass were not significantly associated with any contaminant class. Mates differed in the concentration of POPs, but they had similar stable isotope values. There was little evidence for a connection between contaminants and blood-based markers of oxidative balance. None of the contaminants predicted the probability of a bird being resighted as a breeder the following year. Thus, although POPs were present at high concentrations in some individuals, our study suggests little concern regarding POP exposure for this shearwater population., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Little is known about the levels of organochlorines (OCs) in predatory bird species from Asia or the factors governing their concentrations. This study is the first report on concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in predatory birds of Pakistan. The concentrations of PCBs and OCPs were investigated using tail feathers of ten different species of predatory birds. In addition, concentration differences among body, tail, primary and secondary feathers were investigated for six individuals of black kite (Milvus migrans). Ranges of concentrations were highest for dichlorodiphenyldichloroethylene (p,p'-DDE: 0.11-2163ngg(-1) dry wt.) followed by dichlorodiphenyltrichloroethane (p,p'-DDT: 0.36-345ngg(-1) dry wt.), hexachlorobenzene (HCB: 0.02-34ngg(-1) dry wt.), ∑PCBs (0.03-16ngg(-1) dry wt.) and trans-nonachlor (TN; 0.01-0.13ngg(-1) dry wt.). CB 118, 153, 138, and 180 along with p,p'-DDE were found as the most prevalent compounds. ∑PCBs and ∑DDTs were significantly different among species (both p<0.01) and omnivorous, scavengers, carnivorous and piscivorous trophic guilds (all p<0.03). Only ∑PCBs were significantly differentamong different families of birds (p<0.01). Values of stable isotopes (δ(13)C and δ(15)N) differed significantly (all p<0.01) among species, families, trophic guilds as well as terrestrial and aquatic habitat but not between nocturnal and diurnal predators (p=0.22 for δ(13)C; p=0.50 for δ(15)N). Concentrations of ∑PCBs, ∑DDTs and trans-nonachlor, but not HCB (p=0.86), were significantly different among different feather types (all p<0.01). Trophic and taxonomic affiliation as well as dietary carbon sources (δ(13)C) for species were identified as the variables best explaining the observed variation in exposure to the studied compounds. The significance of contributing factors responsible for OC contamination differences in predatory birds should be further elucidated in future studies., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A three-season field experiment was established and repeated twice with spring barley used as cover crop for different perennial grass-legume intercrops followed by a full year pasture cropping and winter wheat after sward incorporation. Two fertilization regimes were applied with plots fertilized with either a high or a low rate of mineral nitrogen (N) fertilizer. Life cycle assessment (LCA) was used to evaluate the carbon footprint (global warming potential) of the grassland management including measured nitrous oxide (N2O) emissions after sward incorporation. Without applying any mineral N fertilizer, the forage legume pure stand, especially red clover, was able to produce about 15 t above ground dry matter ha(-1) year(-1) saving around 325 kg mineral Nfertilizer ha(-1) compared to the cocksfoot and tall fescue grass treatments. The pure stand ryegrass yielded around 3t DM more than red clover in the high fertilizer treatment. Nitrous oxide emissions were highest in the treatments containing legumes. The LCA showed that the low input N systems had markedly lower carbon footprint values than crops from the high N input system with the pure stand legumes without N fertilization having the lowest carbon footprint. Thus, a reduction in N fertilizer application rates in the low input systems offsets increased N2O emissions after forage legume treatments compared to grass plots due to the N fertilizer production-related emissions. When including the subsequent wheat yield in the total aboveground production across the three-season rotation, the pure stand red clover without N application and pure stand ryegrass treatments with the highest N input equalled. The present study illustrate how leguminous biological nitrogen fixation (BNF) represents an important low impact renewable N source without reducing crop yields and thereby farmers earnings., (Copyright © 2015. Published by Elsevier B.V.)