| 1. |
- Erhagen, Björn, et al.
(författare)
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Temperature sensitivity of heterotrophic soil CO2 production increases with increasing carbon substrate uptake rate
- 2015
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 80, s. 45-52
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Tidskriftsartikel (refereegranskat)abstract
- Temperature profoundly affects saprotrophic respiration rates, and carbon quality theory predicts that the rates' temperature Sensitivity should increase as the quality of the carbon source declines. However, reported relationships between saprotrophic respiration responses to temperature and carbon quality vary widely. Some of this variability may arise from confounding effects related to both substrate quality and substrate availability. The importance of these variables, as well as substrate diffusion and uptake rates, for the temperature sensitivity of saprotrophic respiration has been validated theoretically, but not empirically demonstrated. Thus, we tested effects of varying substrate uptake rates on the temperature sensitivity of organic carbon degradation. For this purpose we created a model system using the organic layer (O-horizon), of a boreal forest soil, specifically to test effects of varying monomer uptake and release rates. The addition of both monomers and polymers generally increased the temperature sensitivity of saprotrophic respiration. In response to added monomers, there was a linear increase in the temperature sensitivity of both substrate-induced respiration and the specific growth rate with increasing rate of substrate uptake as indicated by the CO2 production at 14 degrees C. Both of these responses diverge from those predicted by the carbon quality theory, but they provide the first empirical evidence consistent with model predictions demonstrating increased temperature sensitivity with increased uptake rate of carbon monomers over the cell membrane. These results may explain why organic material of higher carbon quality induces higher temperature responses than lower carbon quality compounds, without contradicting carbon quality theory.
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| 2. |
- Sundqvist, Maja K., et al.
(författare)
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Contrasting nitrogen and phosphorus dynamics across an elevational gradient for subarctic tundra heath and meadow vegetation
- 2014
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Ingår i: Plant and Soil. - : Springer Netherlands. - 0032-079X .- 1573-5036. ; 383:1-2, s. 387-399
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Tidskriftsartikel (refereegranskat)abstract
- This study explores soil nutrient cycling processes and microbial properties for two contrasting vegetation types along an elevational gradient in subarctic tundra to improve our understanding of how temperature influences nutrient availability in an ecosystem predicted to be sensitive to global warming. We measured total amino acid (Amino-N), mineral nitrogen (N) and phosphorus (P) concentrations, in situ net N and P mineralization, net Amino-N consumption, and microbial biomass C, N and P in both heath and meadow soils across an elevational gradient near Abisko, Sweden. For the meadow, NH4 (+) concentrations and net N mineralization were highest at high elevations and microbial properties showed variable responses; these variables were largely unresponsive to elevation for the heath. Amino-N concentrations sometimes showed a tendency to increase with elevation and net Amino-N consumption was often unresponsive to elevation. Overall, PO4-P concentrations decreased with elevation and net P immobilization mostly occurred at lower elevations; these effects were strongest for the heath. Our results reveal that elevation-associated changes in temperature can have contrasting effects on the cycling of N and P in subarctic soils, and that the strength and direction of these effects depend strongly on dominant vegetation type.
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| 3. |
- Downing, Andrea S., et al.
(författare)
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Unlocking the unsustainable rice-wheat system of Indian Punjab : Assessing alternatives to crop-residue burning from a systems perspective
- 2022
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Ingår i: Ecological Economics. - : Elsevier BV. - 0921-8009 .- 1873-6106. ; 195
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Tidskriftsartikel (refereegranskat)abstract
- Crop residue burning in Indian Punjab emits particulate matter with detrimental impacts on health, climate and that threaten agricultural production. Though legal and technological barriers to residue burning exist – and alternatives considered more profitable to farmers – residue burning continues. We review black carbon (BC) emissions from residue burning in Punjab, analyse social-ecological processes driving residue burning, and rice and wheat value-chains. Our aims are to a) understand system feedbacks driving agricultural practices in Punjab; b) identify systemic effects of alternatives to residue burning and c) identify companies and financial actors investing in agricultural production in Punjab. We find feedbacks locking the system into crop residue burning. The Government of India has greatest financial leverage and risk in the current system. Corporate stakeholders have little financial incentive to enact change, but sufficient stakes in the value chains to influence change. Agricultural policy changes are necessary to reduce harmful impacts of current practices, but insufficient to bringing about sustainability. Transformative changes will require crop diversification, circular business models and green financing. Intermediating financial institutions setting sustainability conditions on loans could leverage these changes. Sustainability requires the systems perspective we provide, to reconnect production with demand and with supporting environmental conditions.
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| 4. |
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| 5. |
- Ferro-Vazquez, C., et al.
(författare)
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Metal and organic matter immobilization in temperate podzols : a high resolution study
- 2014
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Ingår i: Geoderma. - : Elsevier. - 0016-7061 .- 1872-6259. ; 217, s. 225-234
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Tidskriftsartikel (refereegranskat)abstract
- Aluminium and Fe fractions were obtained in samples from two temperate podzols by selective extraction with NaOH (Al-n, Fe-n), Na-dithionite-citrate (Al-d, Fe-d), acid NH4-oxalate (Al-o, Fe-o) and Na-pyrophosphate (Al-p, Fe-p) following the traditional fractionation procedures, and also by the use of the chlorides of K (Al-K), La (Al-La) and Cu (Al-cu) as non-buffered extractants for Al. Carbon content was also determined in the Na-pyrophosphate extract (C-p). Soil sampling was done at high-resolution to allow a more detailed characterization of the vertical processes than the traditional sampling by whole soil horizons. Results showed that Al-p and Fe-p make a large proportion of the Alo and Fe-o meaning that organoaluminic complexes dominated in the "active" metal pool instead of inorganic compounds. The degree of metal saturation of soil organic matter (estimated by the (Al-p Fe-p)/C-p molar ratios) increases with depth, especially in the uppermost samples of spodic horizons (Bhs1) where it increases up to 0.1. Aluminium dominates in the adsorption positions of the organic matter in the spodic horizon (Fe-p/Al-p ratios <0.5), except in the Bhs1 horizon (ratios > 1), indicating that the immobilization of Fe containing complexes occurs 10-15 cm above that of Al The highly stable Al-OM complexes accounted on average for 60% of the organoaluminic associations (>70% in the Bhs horizons). The moderately stable complexes predominate in A horizons (57-77% in ACB1 and 37-48% in ACB2) and the largest proportions of low stability complexes were found in the uppermost samples of the spodic horizons (Bhs1) of both soils (9-21%), together with the highest Fep contents and a decrease in pH values. From a stepwise multiple regression model it is suggested that pH is the main variable accounting for the stability of Al-OM compounds together with C and organically bound Fe contents. It is suggested that the illuviation of unsaturated organic acids lower the pH in upper spodic horizons, leading to the complexation of metals from formerly precipitated organometallic complexes and/or leading to their redissolution, enabling their migration to deeper soil layers. Iron complexes would be less soluble at soil pH, resulting in a differentiation of an upper Fe-rich Bhs1 horizon and a lower Bhs2 Al-rich horizon. The depth variation in C accumulation was found to be related to the proportion of highly stable Al-OM fraction.
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| 6. |
- Josefsson, Torbjörn, et al.
(författare)
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The history of early cereal cultivation in northernmost Fennoscandia as indicated by palynological research
- 2014
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Ingår i: Vegetation History and Archaeobotany. - : Springer-Verlag New York. - 0939-6314 .- 1617-6278. ; 23:6, s. 821-840
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Forskningsöversikt (refereegranskat)abstract
- The age of the introduction of cereal cultivation in northern Europe has long been debated by researchers from many disciplines, in particular archaeology and palaeoecology. Over the past 40 years extensive palynological data have been collected concerning pre-industrial land use in northern Fennoscandia. This paper reviews palynological studies that include records of fossil cereal pollen from northernmost Sweden, Finland and Norway at latitudes north of 63A degrees N. The geographical extent of known early cultivation sites is constantly expanding, with more than 100 records of cereal pollen pre-dating ad 1700. The oldest records of scattered cereal pollen derive from Neolithic times. Periods of continuous cultivation, indicated by cereal pollen recorded recurrently in the sediment profiles, derive from the Late Neolithic and Early Bronze Age. Collectively, the reviewed pollen records indicate that cereal cultivation was first introduced into areas close to the coast and later to the interior, and that it may have been practiced locally long before sedentary settlements based on intensive cultivation were established during medieval times. The data do not indicate a latitudinal spread of cultivation from south to north. However, methodological problems relating to pollen morphology of cereals, site characteristics and lack of connections to archaeologically excavated sites imply that the value of many early cereal pollen finds remains unclear. To increase our understanding of the context in which cereal cultivation was introduced in northernmost Fennoscandia, multidisciplinary studies integrating palaeoecology, archaeology and history are needed.
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| 7. |
- Kumar, Umesh, et al.
(författare)
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Multi-omics approaches in plant-microbe interactions hold enormous promise for sustainable agriculture
- 2023
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Ingår i: Agronomy. - Switzerland : MDPI. - 2073-4395. ; 13:7
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Forskningsöversikt (refereegranskat)abstract
- Plants do not grow in isolation; they interact with diverse microorganisms in their habitat.The development of techniques to identify and quantify the microbial diversity associated with plantscontributes to our understanding of the complexity of environmental influences to which plants areexposed. Identifying interactions which are beneficial to plants can enable us to promote healthygrowth with the minimal application of agrochemicals. Beneficial plant–microbial interactionsassist plants in acquiring inaccessible nutrients to promote plant growth and help them to copewith various stresses and pathogens. An increased knowledge of plant–microbial diversity can beapplied to meet the growing demand for biofertilizers for use in organic agriculture. This reviewhighlights the beneficial effects of soil–microbiota and biofertilizers on improving plant health andcrop yields. We propose that a multi–omics approach is appropriate to evaluate viability in thecontext of sustainable agriculture.
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| 8. |
- Liem-Nguyen, Van, et al.
(författare)
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Effects of Nutrient Loading and Mercury Chemical Speciation on the Formation and Degradation of Methylmercury in Estuarine Sediment
- 2016
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 50:13, s. 6983-6990
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Tidskriftsartikel (refereegranskat)abstract
- Net formation of methylmercury (MeHg) in sediments is known to be affected by the availability of inorganic divalent mercury (HgII) and by the activities of HgII methylating and MeHg demethylating bacteria. Enhanced autochthonous organic matter deposition to the benthic zone, following increased loading of nutrients to the pelagic zone, has been suggested to increase the activity of HgII methylating bacteria and thus the rate of net methylation. However, the impact of increased nutrient loading on the biogeochemistry of mercury (Hg) is challenging to predict as different geochemical pools of Hg may respond differently to enhanced bacterial activities. Here, we investigate the combined effects of nutrient (N and P) supply to the pelagic zone and the chemical speciation of HgII and of MeHg on MeHg formation and degradation in a brackish sediment-water mesocosm model ecosystem. By use of Hg isotope tracers added in situ to the mesocosms or ex situ in incubation experiments, we show that the MeHg formation rate increased with nutrient loading only for HgII tracers with a high availability for methylation. Tracers with low availability did not respond significantly to nutrient loading. Thus, both microbial activity (stimulated indirectly through plankton biomass production by nutrient loading) and HgII chemical speciation were found to control the MeHg formation rate in marine sediments.
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| 9. |
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| 10. |
- Martín, Carlos, et al.
(författare)
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Dilute-sulfuric acid pretreatment of de-starched cassava stems for enhancing the enzymatic convertibility and total glucan recovery
- 2019
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Ingår i: Industrial crops and products (Print). - : Elsevier. - 0926-6690 .- 1872-633X. ; 132, s. 301-310
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Tidskriftsartikel (refereegranskat)abstract
- Cassava stems are an abundant feedstock that is becoming attractive for biochemical conversion to fuels and chemicals. Since cassava stems are rich in both cellulose and starch, carefully designed pretreatment and digestion procedures are required for achieving high glucan recovery. In this study, partially de-starched cassava stems resulting from a water extraction stage were hydrolyzed with amylases, and the resulting starch-depleted material was pretreated with dilute sulfuric acid, and submitted to enzymatic hydrolysis of cellulose. The effects of acid pretreatment on glucan recovery, enzymatic convertibility, and by-product formation were investigated using a Box-Behnken experimental design with temperature (165-195 degrees C), time (5-35 min), and acid concentration (0.2-1.0%) as independent variables. In further experimental series, the time period was extended up to 110 min while maintaining temperature at 195 degrees C and sulfuric acid concentration at 0.6%. Using those conditions, pretreatment for 50 min gave the best results (83.8% enzymatic convertibility of pretreated cellulose, and (similar to)72% overall glucan-to-glucose conversion).
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