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1. Nitrogen Recovery from Enhanced Efficiency Fertilizers and Urea in Intensively Managed Black Walnut (Juglans nigra) Plantations

   https://doi.org/10.3390/f12030352  

   Sloan, Joshua L. ; Salifu, Francis K. ; Jacobs, Douglass F. ( March 2021 , Forests)

   Intensively managed forest plantations often require fertilization to maintain site fertility and to improve growth and yield over successive rotations. We applied urea-based “enhanced-efficiency fertilizers” (EEF) containing 0.5 atom% 15N at a rate of 224 kg N ha−1 to soils under mid-rotation black walnut (Juglans nigra L.) plantations to track the fate of applied 15N within aboveground ecosystem components during the 12-month period after application. Treatments included Agrotain Ultra (urea coated with a urease inhibitor), Arborite EC (urea coated with water-soluble boron and phosphate), Agrium ESN (polymer-coated urea), uncoated urea, and an unfertilized control. Agrotain Ultra and Arborite EC increased N concentrations of competing vegetation within one month after fertilization, while neither Agrium ESN nor uncoated urea had any effect on competing vegetation N concentrations during the experiment. Agrotain Ultra and Arborite EC increased δ15N values in leaves of crop trees above those of controls at one and two months after fertilization, respectively. By contrast, Agrium ESN and uncoated urea had no effect on δ15N values in leaves of crop trees until three months after fertilization. Fertilizer N recovery (FNR) varied among ecosystem components, with competing vegetation acting as a sink for applied nutrients. There were no significant differences in FNR for all the urea-based EEF products compared to uncoated urea. Agrium ESN was the only EEF that exhibited controlled-release activity in this study, with other fertilizers behaving similarly to uncoated urea. 

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2. Resistance and change in a High Arctic ecosystem, NW Greenland: Differential sensitivity of ecosystem metrics to 15 years of experimental warming and wetting

   https://doi.org/10.1111/gcb.16027  

   Jespersen, Robert Gus ; Leffler, Alan Joshua ; Väisänen, Maria ; Welker, Jeffrey M. ( December 2021 , Global Change Biology)

   Dramatic increases in air temperature and precipitation are occurring in the High Arctic (>70°N), yet few studies have characterized the long‐term responses of High Arctic ecosystems to the interactive effects of experimental warming and increased rain. Beginning in 2003, we applied a factorial summer warming and wetting experiment to a polar semidesert in northwest Greenland. In summer 2018, we assessed several metrics of ecosystem structure and function, including plant cover, greenness, ecosystem CO₂exchange, aboveground (leaf, stem) and belowground (litter, root, soil) carbon (C) and nitrogen (N) concentrations (%) and pools, as well as leaf and soil stable isotopes (δ¹³C and δ¹⁵N). Wetting induced the most pronounced changes in ecosystem structure, accelerating the expansion ofSalix arcticacover by 370% and increasing aboveground C, N, and biomass pools by 94%–101% and root C, N, and biomass pools by 60%–122%, increases which coincided with enhanced net ecosystem CO₂uptake. Further, wetting combined with warming enhanced plot‐level greenness, whereas in isolation neither wetting nor warming had an effect. At the plant level, the effects of warming and wetting differed among species and included warming‐linked decreases in leaf N and δ¹⁵N inS. arctica, whereas leaf N and δ¹⁵N inDryas integrifoliadid not respond to the climate treatments. Finally, neither plant‐ nor plot‐level C and N allocation patterns nor soil C, N, δ¹³C, or δ¹⁵N concentrations changed in response to our manipulations, indicating that these ecosystem metrics may resist climate change, even in the longer term. In sum, our results highlight the importance of summer precipitation in regulating ecosystem structure and function in arid parts of the High Arctic, but they do not completely refute previous findings of resistance in some High Arctic ecosystem properties to climate change.

    

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3. Shading decreases and delays NDVI and flowering of prostrate Arctic shrubs

   https://doi.org/10.1139/as-2020-0043  

   May, Jeremy L. ; Oberbauer, Steven F. ; Unger, Steven L. ; Simon, Matthew J. ; Betway, Katlyn R. ; Hollister, Robert D. ( September 2022 , Arctic Science)

   Increases in shrub growth and canopy cover are well documented community responses to climate warming in the Arctic. An important consequence of larger deciduous shrubs is shading of prostrate plant species, many of which are important sources of nectar and berries. Here, we present the impact of a shading experiment on two prostrate shrubs, Vaccinium vitis-idaea L. and Arctous alpina L., in northern Alaska over two growing seasons. We implemented three levels of shading (no shade, 40% shade, and 80% shade) in dry heath and moist acidic tundra. Plots were monitored for soil moisture content, surface temperature, normalized difference vegetation index (NDVI), and flowering. Shading was shown to, on average, lower surface temperature (0.7 °C to 5.3 °C) and increase soil moisture content (0.5% to 5.6%) in both communities. Both species- and plot-level NDVI values were delayed in timing of peak values (7 to 13 days) and decreased at the highest shading. Flower abundance of both species was lower in shaded plots and peak flowering was delayed (3 to 8 days) compared with controls. Changes in timing may result in phenological mismatches and can impact other trophic levels in the Arctic as both the flowers and resulting berries are important food sources for animals. 

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4. Press–pulse interactions: effects of warming, N deposition, altered winter precipitation, and fire on desert grassland community structure and dynamics

   https://doi.org/10.1111/gcb.13493  

   Collins, Scott L. ; Ladwig, Laura M. ; Petrie, Matthew D. ; Jones, Sydney K. ; Mulhouse, John M. ; Thibault, James R. ; Pockman, William T. ( September 2016 , Global Change Biology)

   Global environmental change is altering temperature, precipitation patterns, resource availability, and disturbance regimes. Theory predicts that ecological presses will interact with pulse events to alter ecosystem structure and function. In 2006, we established a long‐term, multifactor global change experiment to determine the interactive effects of nighttime warming, increased atmospheric nitrogen (N) deposition, and increased winter precipitation on plant community structure and aboveground net primary production (ANPP) in a northern Chihuahuan Desert grassland. In 2009, a lightning‐caused wildfire burned through the experiment. Here, we report on the interactive effects of these global change drivers on pre‐ and postfire grassland community structure andANPP. Our nighttime warming treatment increased winter nighttime air temperatures by an average of 1.1 °C and summer nighttime air temperature by 1.5 °C. Soil N availability was 2.5 times higher in fertilized compared with control plots. Average soil volumetric water content (VWC) in winter was slightly but significantly higher (13.0% vs. 11.0%) in plots receiving added winter rain relative to controls, andVWCwas slightly higher in warmed (14.5%) compared with control (13.5%) plots during the growing season even though surface soil temperatures were significantly higher in warmed plots. Despite these significant treatment effects,ANPPand plant community structure were highly resistant to these global change drivers prior to the fire. Burning reduced the cover of the dominant grasses by more than 75%. Following the fire, forb species richness and biomass increased significantly, particularly in warmed, fertilized plots that received additional winter precipitation. Thus, although unburned grassland showed little initial response to multiple ecological presses, our results demonstrate how a single pulse disturbance can interact with chronic alterations in resource availability to increase ecosystem sensitivity to multiple drivers of global environmental change.

    

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5. Microencapsulation optimization of cinnamon essential oil in the matrices of gum Arabic, maltodextrin, and inulin by spray‐drying using mixture design

   https://doi.org/10.1111/jfpe.13341  

   Shahidi Noghabi, Mostafa ; Molaveisi, Mohammad ( December 2019 , Journal of Food Process Engineering)

   A simple centroid mixture design was used to optimize the ratio of the wall materials for the production of the cinnamon essential oil microcapsules by spray‐drying. Gum Arabic (GA), maltodextrin (MD), and inulin (IN) were used as wall materials. Four parameters were evaluated as responses, containing the surface cinnamaldehyde, the encapsulation efficiency of cinnamaldehyde, the release of cinnamaldehyde (RC), and powder recovery (PR). The cinnamon essential oil was purely formed of cinnamaldehyde (about 99.96%), based on results obtained from the gas chromatography device. The multiple response optimization analysis showed that the optimum compound concentration for walls will be 27.87% wt/wt GA, 27.59% MD, and 44.53% IN. It can be concluded that the optimal compound was suitable to the RC in the mouth medium due to its Tg. The microscopy images of the optimal compound showed a smooth surface, spherical, and slight crack in the microparticles. Furthermore, the optimum compound improved the stability of antioxidant activity compared to the pure oil during 30 days storage. It was observed that the Fickian diffusion was the main mechanism involved in the release process of the microencapsulated cinnamon essential oil in the mouth medium.

   In the food industry, the major aromatic components utilized are essential oils, synthetic flavoring agents, and natural oleoresin. The key constituent of cinnamon essential oil is cinnamaldehyde. Cinnamaldehyde is often used as a flavoring agent, but its importance as a natural antimicrobial, antioxidant, and antiseptic agent has recently been established. The knowledge of encapsulation techniques allows the control of the bioactive components, the release time, and the dosage of essential oil in the structure of the food. Moreover, the encapsulation of essential oils helps to reduce the oxidation of process by exposure to the environment, increasing the shelf life and the solubility. The results of this work lead to the use of flavored components for implementation in similar products, thereby improving their flavor.

    

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