An official website of the United States government
Summary To what degree plant ecosystems thermoregulate their canopy temperature (Tc) is critical to assess ecosystems' metabolisms and resilience with climate change, but remains controversial, with opinions from no to moderate thermoregulation capability.With global datasets ofTc, air temperature (Ta), and other environmental and biotic variables from FLUXNET and satellites, we tested the ‘limited homeothermy’ hypothesis (indicated byTc&Taregression slope < 1 orTc < Taaround midday) across global extratropics, including temporal and spatial dimensions.Across daily to weekly and monthly timescales, over 80% of sites/ecosystems have slopes ≥1 orTc > Taaround midday, rejecting the above hypothesis. For those sites unsupporting the hypothesis, theirTc–Tadifference (ΔT) exhibits considerable seasonality that shows negative, partial correlations with leaf area index, implying a certain degree of thermoregulation capability. Spatially, site‐mean ΔTexhibits larger variations than the slope indicator, suggesting ΔTis a more sensitive indicator for detecting thermoregulatory differences across biomes. Furthermore, this large spatial‐wide ΔTvariation (0–6°C) is primarily explained by environmental variables (38%) and secondarily by biotic factors (15%).These results demonstrate diverse thermoregulation patterns across global extratropics, with most ecosystems negating the ‘limited homeothermy’ hypothesis, but their thermoregulation still occurs, implying that slope < 1 orTc < Taare not necessary conditions for plant thermoregulation.
more »
« less
Investigation of the effects on proton relaxation times upon encapsulation in a water-soluble synthetic receptor
TheT1andT2relaxation rates of different protons in small cyclic and polycyclic guests can be controlled by encapsulation in a water-soluble synthetic receptor.
more »
« less
- Award ID(s):
- 2306195
- PAR ID:
- 10521348
- Publisher / Repository:
- RSC
- Date Published:
- Journal Name:
- Physical Chemistry Chemical Physics
- Volume:
- 26
- Issue:
- 13
- ISSN:
- 1463-9076
- Page Range / eLocation ID:
- 10183 to 10190
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract PremisePrevious studies have suggested a trade‐off between trichome density (Dt) and stomatal density (Ds) due to shared cell precursors. We clarified how, when, and why this developmental trade‐off may be overcome across species. MethodsWe derived equations to determine the developmental basis forDtandDsin trichome and stomatal indices (itandis) and the sizes of epidermal pavement cells (e), trichome bases (t), and stomata (s) and quantified the importance of these determinants ofDtandDsfor 78 California species. We compiled 17 previous studies ofDt–Dsrelationships to determine the commonness ofDt–Dsassociations. We modeled the consequences of differentDt–Dsassociations for plant carbon balance. ResultsOur analyses showed that higherDtwas determined by higheritand lowere, and higherDsby higherisand lowere. Across California species, positiveDt–Dscoordination arose due toit–iscoordination and impacts of the variation ine. ADt–Dstrade‐off was found in only 30% of studies. Heuristic modeling showed that species sets would have the highest carbon balance with a positive or negative relationship or decoupling ofDtandDs, depending on environmental conditions. ConclusionsShared precursor cells of trichomes and stomata do not limit higher numbers of both cell types or drive a generalDt–Dstrade‐off across species. This developmental flexibility across diverse species enables differentDt–Dsassociations according to environmental pressures. Developmental trait analysis can clarify how contrasting trait associations would arise within and across species.more » « less
-
Abstract This study investigates the evolution of temperature and lifetime of evaporating, supercooled cloud droplets considering initial droplet radius (r0) and temperature (), and environmental relative humidity (RH), temperature (T∞), and pressure (P). The time (tss) required by droplets to reach a lower steady-state temperature (Tss) after sudden introduction into a new subsaturated environment, the magnitude of ΔT=T∞−Tss, and droplet survival time (tst) atTssare calculated. The temperature difference (ΔT) is found to increase withT∞, and decrease with RH andP. ΔTwas typically 1–5 K lower thanT∞, with highest values (∼10.3 K) for very low RH, lowP, andT∞closer to 0°C. Results show thattssis <0.5 s over the range of initial droplet and environmental conditions considered. Larger droplets (r0= 30–50μm) can survive atTssfor about 5 s to over 10 min, depending on the subsaturation of the environment. For higher RH and larger droplets, droplet lifetimes can increase by more than 100 s compared to those with droplet cooling ignored.Tssof the evaporating droplets can be approximated by the environmental thermodynamic wet-bulb temperature. Radiation was found to play a minor role in influencing droplet temperatures, except for larger droplets in environments close to saturation. The implications for ice nucleation in cloud-top generating cells and near cloud edges are discussed. UsingTssinstead ofT∞in widely used parameterization schemes could lead to enhanced number concentrations of activated ice-nucleating particles (INPs), by a typical factor of 2–30, with the greatest increases (≥100) coincident with low RH, lowP, andT∞closer to 0°C. Significance StatementCloud droplet temperature plays an important role in fundamental cloud processes like droplet growth and decay, activation of ice-nucleating particles, and determination of radiative parameters like refractive indices of water droplets. Near cloud boundaries such as cloud tops, dry air mixes with cloudy air exposing droplets to environments with low relative humidities. This study examines how the temperature of a cloud droplet that is supercooled (i.e., has an initial temperature < 0°C) evolves in these subsaturated environments. Results show that when supercooled cloud droplets evaporate near cloud boundaries, their temperatures can be several degrees Celsius lower than the surrounding drier environment. The implications of this additional cooling of droplets near cloud edges on ice particle formation are discussed.more » « less
-
Abstract Kagome materials are of topical interest for their diverse quantum properties linked with correlated magnetism and topology. Here, we report anomalous hydrostatic pressure (p) effect on ErMn6Sn6through isobaric and isothermal-isobaric magnetization measurements. Magnetic field (H) suppresses antiferromagneticTNwhile simultaneously enhancing the ferrimagneticTCby exhibiting dual metamagnetic transitions, arising from the triple-spiral-nature of Er and Mn spins. Counter-intuitively, pressure enhances bothTCandTNwith a growth rate of 74.4 K GPa−1and 14.4 K GPa−1respectively. Pressure unifies the dual metamagnetic transitions as illustrated throughp-Hphase diagrams at 140 and 200 K. Temperature-field-pressure (T-H,T-p) phase diagrams illustrate distinct field- and pressure-induced critical points at (Tcr= 246 K,Hcr= 23.3 kOe) and (Tcr= 435.8 K,pcr= 4.74 GPa) respectively. An unusual increase of magnetic entropy by pressure aroundTcrand a putative pressure-induced tricritical point pave a unique way of tuning the magnetic properties of kagome magnets through simultaneous application ofHandp.more » « less
-
Abstract Evidence is mounting that temperate‐zone reforestation cools surface temperature (Tsurf), mitigating deleterious effects of climate warming. WhileTsurfdrives many biophysical processes, air temperature (Ta) is an equally important target for climate mitigation and adaptation. Whether reductions inTsurftranslate to reductions inTaremains complex, fraught by several nonlinear and intertwined processes. In particular, forest canopy structure strongly affects near‐surface temperature gradients, complicating cross‐site comparison. Here the influence of reforestation onTais assessed by targeting temperature metrics that are less sensitive to local canopy effects. Specifically, we consider the aerodynamic temperature (Taero), estimated using a novel procedure that does not rely on the assumptions of Monin‐Obukhov similarity theory, as well as the extrapolated temperature into the surface layer (Textrap). The approach is tested with flux tower data from a grass field, pine plantation, and mature hardwood stand co‐located in the Duke Forest (North Carolina, USA). During growing season daytime periods,Tsurfis 4–6 °C cooler, andTaeroand near‐surfaceTextrapare 2–3 °C cooler, in the forests relative to the grassland. During the dormant season, daytime differences are smaller but still substantial. At night, differences inTaeroare small, and near‐surfaceTextrapis warmer over forests than grasslands during the growing season (by 0.5 to 1 °C). Finally, the influence of land cover onTextrapat the interface between the surface and mixed layer is small. Overall, reforestation appears to provide a meaningful opportunity for adaption to warmer daytimeTain the southeastern United States, especially during the growing season.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d3cp06099c
