Contrasting survival and physiological responses of sub‑Arctic plant types to extreme winter warming and nitrogen

Abstract Main conclusion: Evergreen plants are more vulnerable than grasses and birch to snow and temperature variability in the sub-Arctic. Most Arctic climate impact studies focus on single factors, such as summer warming, while ecosystems are exposed to changes in all seasons. Through a combination of field and laboratory manipulations, we compared physiological and growth responses of dominant sub-Arctic plant types to midwinter warming events (6 °C for 7 days) in combination with freezing, simulated snow thaw and nitrogen additions. We aimed to identify if different plant types showed consistent physiological, cellular, growth and mortality responses to these abiotic stressors. Evergreen dwarf shrubs and tree seedlings showed higher mortality (40–100%) following extreme winter warming events than Betula pubescens tree seedlings and grasses (0–27%). All species had growth reductions following exposure to − 20 °C, but not all species suffered from − 10 °C irrespective of other treatments. Winter warming followed by − 20 °C resulted in the greatest mortality and was strongest among evergreen plants. Snow removal reduced the biomass for most species and this was exacerbated by subsequent freezing. Nitrogen increased the growth of B. pubescens and grasses, but not the evergreens, and interaction effects with the warming, freezing and snow treatments were minor and few. Physiological activity during the winter warming and freezing treatments was inconsistent with growth and mortality rates across the plants types. However, changes in the membrane fatty acids were associated with reduced mortality of grasses. Sub-Arctic plant communities may become dominated by grasses and deciduous plants if winter snowpack diminishes and plants are exposed to greater temperature variability in the near future

A Simplified Biorefinery Concept for the Valorization of Sugar Beet Pulp: Ecofriendly Isolation of Pectin as a Step Preceding Torrefaction

The valorization of sugar beet pulp (SBP) from sugar industry as a source of valuable substances has been taken in consideration in this work. In particular, the eco-friendly extraction of pectins with citric acid has been adopted as a preliminary step in a simplified biorefinery concept where the pectin-free solid is subsequently subjected to a torrefaction treatment for its upgrading into a commodity solid biofuel. An extensive physicochemical characterization of the raw feedstock and the isolated pectins has also been performed, which may be useful to identify suitable application routes. Results show that the extraction conditions [1.5 pH, 90 °C, 4 h contact time and SBP-to-solvent ratio of 1:30 (g/mL)] selected in this work allow obtaining a relatively high yield (25% wt, db) of high methoxyl pectins (with some impurities), which exhibit the same colorimetric characteristics of commercial citrus pectins and are not conducive to microbial growth. A further purification step of isolated pectins is required to improve the emulsifying properties. Graphical Abstract: [Figure not available: see fulltext.]

Effects of drying on the nutrient content and physico-chemical and sensory characteristics of the edible kelp Saccharina latissima

The effects of convective air-drying at 25, 40, and 70 °C and freeze-drying on the quality of the edible kelp Saccharina latissima to be used for food were investigated. Based on the analysis of the carbohydrate and amino acid profiles, as well as polyphenol, fucoxanthin, and ash contents, no significant differences were detected among sample groups, and air-drying up to 70 °C results in equally nutritious products at shorter processing times. Only the iodine content was found lower in freeze-dried compared to air-dried samples. The swelling capacity of the air-dried samples was significantly lower than in freeze-dried samples, particularly at high temperatures (40 and 70 °C), reflecting alteration of the physico-chemical properties of the seaweed during air-drying (attributed to product shrinkage) and reduced capacity of the final product to rehydrate. Structural differences between air-dried products at 25 and 70 °C may explain the differences in mouthfeel perception (dissolving rate) among the two sample groups observed during a sensory evaluation. Overall, the drying temperature within this range did not alter neither the aroma (i.e. odor) nor the flavor intensity of the product. In food applications where the product’s mechanical properties (e.g. porosity) are essential, freeze-drying, and to a lesser extent, air-drying at low temperatures, will result in higher quality products than air-drying at higher temperatures.acceptedVersio