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Semenchuk, Philipp R.
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Publications (3 of 3) Show all publications
Semenchuk, P. R., Krab, E. J., Hedenström, M., Phillips, C. A., Ancin-Murguzur, F. J. & Cooper, E. J. (2019). Soil organic carbon depletion and degradation in surface soil after long-term non-growing season warming in High Arctic Svalbard. Science of the Total Environment, 646, 158-167
Open this publication in new window or tab >>Soil organic carbon depletion and degradation in surface soil after long-term non-growing season warming in High Arctic Svalbard
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2019 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 646, p. 158-167Article in journal (Refereed) Published
Abstract [en]

Arctic tundra active-layer soils are at risk of soil organic carbon (SOC) depletion and degradation upon global climate warming because they are in a stage of relatively early decomposition. Non-growing season (NGS) warming is particularly pronounced, and observed increases of CO2 emissions during experimentally warmed NGSs give concern for great SOC losses to the atmosphere. Here, we used snow fences in Arctic Spitsbergen dwarf shrub tundra to simulate 1.86 degrees C NGS warming for 9 consecutive years, while growing season temperatures remained unchanged. In the snow fence treatment, the 4-11 cm thick A-horizon had a 2% lower SOC concentration and a 0.48 kg Cm-2 smaller pool size than the controls, indicating SOC pool depletion. The snow fence treatment's A-horizon's alkyl/O-alkyl ratio was also significantly increased, indicating an advance of SOC degradation. The underlying 5 cm of B/C-horizon did not show these effects. Our results support the hypothesis that SOC depletion and degradation are connected to the long-term transience of observed ecosystem respiration (ER) increases upon soil warming. We suggest that the bulk of warming induced ER increases may originate from surface and not deep active layer or permafrost horizons. The observed losses of SOC might be significant for the ecosystem in question, but are in magnitude comparatively small relative to anthropogenic greenhouse gas enrichment of the atmosphere. We conclude that a positive feedback of carbon losses from surface soils of Arctic dwarf shrub tundra to anthropogenic forcing will be minor, but not negligible.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Snow fence, NMR, Carbon loss, Decomposition, Anthropogenic C emission feedback, Tundra
National Category
Environmental Sciences Soil Science
Identifiers
urn:nbn:se:umu:diva-166522 (URN)10.1016/j.scitotenv.2018.07.150 (DOI)000445164800017 ()30056226 (PubMedID)
Available from: 2019-12-17 Created: 2019-12-17 Last updated: 2019-12-17Bibliographically approved
Bøhn, T., Rover, C. M. & Semenchuk, P. R. (2016). Daphnia magna negatively affected by chronic exposure to purified Cry-toxins. Food and Chemical Toxicology, 91, 130-140
Open this publication in new window or tab >>Daphnia magna negatively affected by chronic exposure to purified Cry-toxins
2016 (English)In: Food and Chemical Toxicology, ISSN 0278-6915, E-ISSN 1873-6351, Vol. 91, p. 130-140Article in journal (Refereed) Published
Abstract [en]

Cry-toxin genes originating from Bacillus thuringiensis are inserted into genetically modified (GM) plants, often called Bt-plants, to provide insect resistance to pests. Significant amounts of Bt-plant residues, and thus Cry-toxins, will be shed to soil and aquatic environments. We exposed Daphnia magna to purified Cry1Ab and Cry2Aa toxins for the full life-span of the animals. We used single toxins in different doses and combinations of toxins and Roundup, another potential stressor on the rise in agricultural ecosystems. Animals exposed to 4.5 mg/L (ppm) of Cry1Ab, Cry2Aa and the combination of both showed markedly higher mortality, smaller body size and very low juvenile production compared to controls. Animals exposed to 0.75 mg/L also showed a tendency towards increased mortality but with increased early fecundity compared to the controls. Roundup stimulated animals to strong early reproductive output at the cost of later rapid mortality. We conclude that i) purified Cry-toxins in high concentrations are toxic to D. magna, indicating alternative modes-of-action for these Cry-toxins; ii) Cry-toxins act in combination, indicating that 'stacked events' may have stronger effects on non-target organisms; iii) further studies need to be done on combinatorial effects of multiple Cry-toxins and herbicides that co-occur in the environment.

Keywords
Bt-transgenic plants, Cry-toxins, Daphnia magna, Non-target organisms, Roundup, Toxicity
National Category
Pharmacology and Toxicology Food Science
Identifiers
urn:nbn:se:umu:diva-121455 (URN)10.1016/j.fct.2016.03.009 (DOI)000375629200014 ()26993955 (PubMedID)
Available from: 2016-06-22 Created: 2016-06-02 Last updated: 2018-06-07Bibliographically approved
Semenchuk, P. R., Christiansen, C. T., Grogan, P., Elberling, B. & Cooper, E. J. (2016). Long-term experimentally deepened snow decreases growing-season respiration in a low- and high-arctic tundra ecosystem. Journal of Geophysical Research - Biogeosciences, 121(5), 1236-1248
Open this publication in new window or tab >>Long-term experimentally deepened snow decreases growing-season respiration in a low- and high-arctic tundra ecosystem
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2016 (English)In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, no 5, p. 1236-1248Article in journal (Refereed) Published
Abstract [en]

Tundra soils store large amounts of carbon (C) that could be released through enhanced ecosystem respiration (ER) as the arctic warms. Over time, this may change the quantity and quality of available soil C pools, which in-turn may feedback and regulate ER responses to climate warming. Therefore, short-term increases in ER rates due to experimental warming may not be sustained over longer periods, as observed in other studies. One important aspect, which is often overlooked, is how climatic changes affecting ER in one season may carry-over and determine ER in following seasons. Using snow fences, we increased snow depth and thereby winter soil temperatures in a high-arctic site in Svalbard (78 degrees N) and a low-arctic site in the Northwest Territories, Canada (64 degrees N), for 5 and 9years, respectively. Deepened snow enhanced winter ER while having negligible effect on growing-season soil temperatures and soil moisture. Growing-season ER at the high-arctic site was not affected by the snow treatment after 2years. However, surprisingly, the deepened snow treatments significantly reduced growing-season ER rates after 5years at the high-arctic site and after 8-9years at the low-arctic site. We speculate that the reduction in ER rates, that became apparent only after several years of experimental manipulation, may, at least in part, be due to prolonged depletion of labile C substrate as a result of warmer soils over multiple cold seasons. Long-term changes in winter climate may therefore significantly influence annual net C balance not just because of increased wintertime C loss but also because of legacy effects on ER rates during the following growing seasons.

Keywords
ecosystem respiration, cold season, climate change, snow fence, winter
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-124203 (URN)10.1002/2015JG003251 (DOI)000378703200002 ()
Available from: 2016-08-03 Created: 2016-07-28 Last updated: 2018-06-07Bibliographically approved
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