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1. Photosynthetic responses of switchgrass to light and CO ₂ under different precipitation treatments

   https://doi.org/10.1111/gcbb.13138  

   Kieffer, Christina; Kaur, Navneet; Li, Jianwei; Matamala, Roser; Fay, Philip A; Hui, Dafeng (August 2024, GCB Bioenergy)

   Abstract Switchgrass (Panicum virgatumL.) is a prominent bioenergy crop with robust resilience to environmental stresses. However, our knowledge regarding how precipitation changes affect switchgrass photosynthesis and its responses to light and CO₂remains limited. To address this knowledge gap, we conducted a field precipitation experiment with five different treatments, including −50%, −33%, 0%, +33%, and +50% of ambient precipitation. To determine the responses of leaf photosynthesis to CO₂concentration and light, we measured leaf net photosynthesis of switchgrass under different CO₂concentrations and light levels in 2020 and 2021 for each of the five precipitation treatments. We first evaluated four light and CO₂response models (i.e., rectangular hyperbola model, nonrectangular hyperbola model, exponential model, and the modified rectangular hyperbola model) using the measurements in the ambient precipitation treatment. Based on the fitting criteria, we selected the nonrectangular hyperbola model as the optimal model and applied it to all precipitation treatments, and estimated model parameters. Overall, the model fit field measurements well for the light and CO₂response curves. Precipitation change did not influence the maximum net photosynthetic rate (P_max) but influenced other model parameters including quantum yield (α), convexity (θ), dark respiration (R_d), light compensation point (LCP), and saturated light point (LSP). Specifically, the meanP_maxof five precipitation treatments was 17.6 μmol CO₂m⁻² s⁻¹, and the ambient treatment tended to have a higherP_max. The +33% treatment had the highestα, and the ambient treatment had lowerθandLCP, higherRd, and relatively lowerLSP. Furthermore, precipitation significantly influenced all model parameters of CO₂response. The ambient treatment had the highestP_max, largestα, and lowestθ,R_d, and CO₂compensation pointLCP. Overall, this study improved our understanding of how switchgrass leaf photosynthesis responds to diverse environmental factors, providing valuable insights for accurately modeling switchgrass ecophysiology and productivity. 

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2. Elevated CO₂ and N Gradually Weaken the Influence of Diversity on Ecosystem Stability

   https://doi.org/10.1111/ele.70170  

   Mohanbabu, Neha; Isbell, Forest; Hobbie, Sarah E; Reich, Peter B (August 2025, Ecology Letters)

   ABSTRACT Biodiversity promotes ecosystem productivity and stability, positive impacts that often strengthen over time. But ongoing global changes such as rising atmospheric carbon dioxide (CO₂) levels and anthropogenic nitrogen (N) deposition may modulate the impact of biodiversity on ecosystem productivity and stability over time. Using a quarter‐century grassland biodiversity‐global change experiment we show that diversity increasingly enhanced productivity over time irrespective of global change treatments. In contrast, the positive influence of diversity on ecosystem stability strengthened over time under ambient conditions but weakened to varying degrees under global change treatments, largely driven by a greater reduction in species asynchrony under global changes. Thus, over 25 years, CO₂and N enrichment gradually eroded some of the positive effects of biodiversity on ecosystem stability. As elevated CO₂, N eutrophication, and biodiversity loss increasingly co‐occur in grasslands globally, our results raise concerns about their potential joint detrimental effects on long‐term grassland stability. 

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3. Hydroxymethylbutenyl diphosphate accumulation reveals MEP pathway regulation for high CO ₂ -induced suppression of isoprene emission

   https://doi.org/10.1073/pnas.2309536120  

   Sahu, Abira; Mostofa, Mohammad Golam; Weraduwage, Sarathi M.; Sharkey, Thomas D. (October 2023, Proceedings of the National Academy of Sciences)

   Isoprene is emitted by some plants and is the most abundant biogenic hydrocarbon entering the atmosphere. Multiple studies have elucidated protective roles of isoprene against several environmental stresses, including high temperature, excessive ozone, and herbivory attack. However, isoprene emission adversely affects atmospheric chemistry by contributing to ozone production and aerosol formation. Thus, understanding the regulation of isoprene emission in response to varying environmental conditions, for example, elevated CO₂, is critical to comprehend how plants will respond to climate change. Isoprene emission decreases with increasing CO₂concentration; however, the underlying mechanism of this response is currently unknown. We demonstrated that high-CO₂-mediated suppression of isoprene emission is independent of photosynthesis and light intensity, but it is reduced with increasing temperature. Furthermore, we measured methylerythritol 4-phosphate (MEP) pathway metabolites in poplar leaves harvested at ambient and high CO₂to identify why isoprene emission is reduced under high CO₂. We found that hydroxymethylbutenyl diphosphate (HMBDP) was increased and dimethylallyl diphosphate (DMADP) decreased at high CO_2.This implies that high CO₂impeded the conversion of HMBDP to DMADP, possibly through the inhibition of HMBDP reductase activity, resulting in reduced isoprene emission. We further demonstrated that although this phenomenon appears similar to abscisic acid (ABA)-dependent stomatal regulation, it is unrelated as ABA treatment did not alter the effect of elevated CO₂on the suppression of isoprene emission. Thus, this study provides a comprehensive understanding of the regulation of the MEP pathway and isoprene emission in the face of increasing CO₂. 

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4. Ambient‐Pressure Relithiation of Degraded Li _x Ni _0.5 Co _0.2 Mn _0.3 O ₂ (0 < x < 1) via Eutectic Solutions for Direct Regeneration of Lithium‐Ion Battery Cathodes

   https://doi.org/10.1002/aenm.201900454  

   Shi, Yang; Zhang, Minghao; Meng, Ying_Shirley; Chen, Zheng (April 2019, Advanced Energy Materials)

   Abstract With the rapid growth of the lithium‐ion battery (LIBs) market, recycling and re‐use of end‐of‐life LIBs to reclaim lithium (Li) and transition metal (TM) resources (e.g., Co, Ni), as well as eliminating pollution from disposal of waste batteries, has become an urgent task. Here, for the first time the ambient‐pressure relithiation of degraded LiNi_0.5Co_0.2Mn_0.3O₂(NCM523) cathodes via eutectic Li⁺molten‐salt solutions is successfully demonstrated. Combining such a low‐temperature relithiation process with a well‐designed thermal annealing step, NCM523 cathode particles with significant Li loss (≈40%) and capacity degradation (≈50%) can be successfully regenerated to achieve their original composition and crystal structures, leading to effective recovery of their capacity, cycling stability, and rate capability to the levels of the pristine materials. Advanced characterization tools including atomic resolution electron microscopy imaging and electron energy loss spectroscopy are combined to demonstrate that NCM523's original layered crystal structure is recovered. For the first time, it is shown that layer‐to‐rock salt phase change on the surfaces and subsurfaces of the cathode materials can be reversed if lithium can be incorporated back to the material. The result suggests the great promise of using eutectic Li⁺molten–salt solutions for ambient‐pressure relithiation to recycle and remanufacture degraded LIB cathode materials. 

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5. Testing and evaluation of a new airborne system for continuous N₂O, CO₂, CO, and H₂O measurements: the Frequent Calibration High-performance Airborne Observation System (FCHAOS)

   https://doi.org/10.5194/amt-11-6059-2018  

   Gvakharia, Alexander; Kort, Eric A.; Smith, Mackenzie L.; Conley, Stephen (January 2018, Atmospheric Measurement Techniques)

   Abstract. We present the development and assessment of a new flight system that uses acommercially available continuous-wave, tunable infrared laser directabsorption spectrometer to measure N₂O, CO₂, CO, andH₂O. When the commercial system is operated in an off-the-shelfmanner, we find a clear cabin pressure–altitude dependency forN₂O, CO₂, and CO. The characteristics of this artifactmake it difficult to reconcile with conventional calibration methods. Wepresent a novel procedure that extends upon traditional calibrationapproaches in a high-flow system with high-frequency, short-duration samplingof a known calibration gas of near-ambient concentration. This approachcorrects for cabin pressure dependency as well as other sources of drift inthe analyzer while maintaining a ∼90% duty cycle for 1Hz sampling.Assessment and validation of the flight system with both extensive in-flightcalibrations and comparisons with other flight-proven sensors demonstrate thevalidity of this method. In-flight 1σ precision is estimated at0.05ppb, 0.10ppm, 1.00ppb, and 10ppm for N₂O,CO₂, CO, and H₂O respectively, and traceability to WorldMeteorological Organization (WMO) standards (1σ) is 0.28ppb,0.33ppm, and 1.92ppb for N₂O, CO₂, and CO. We showthe system is capable of precise, accurate 1Hz airborne observations ofN₂O, CO₂, CO, and H₂O and highlight flightdata, illustrating the value of this analyzer for studying N₂Oemissions on ∼100km spatial scales. 

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