Theoretical Insights into the Metal–Nonmetal Interaction Inside M₂O@<i>C</i>_2<i>v</i>(31922)‑C₈₀ (M = Sc or Gd)

The metal–nonmetal interaction is complicated but significant in organometallic chemistry and metallic catalysis and is susceptible to the coordination surroundings. Endohedral metallofullerene is considered to be an excellent model for studying metal–nonmetal interactions with the shielding effect of fullerenes. Herein, with the detection of ScGdO@C80 in a previous mass spectrum, we studied the effects of metal atoms (Sc and Gd) on the metal–nonmetal interactions of the thermodynamically stable molecules M2O@C2v(31922)-C80 (M = Sc and Gd), where metal atoms M can be the same or different, using density functional theory calculations. The inner metal atom and the fullerene cage show mainly ionic interactions with some covalent character. The Sc atom with higher electronegativity plays a greater important role in the metal–nonmetal interactions than the Gd atom. This study would be useful for the further study of the metal–nonmetal interaction

Altitudinal Patterns of Species Diversity and Phylogenetic Diversity across Temperate Mountain Forests of Northern China

<div><p>The spatial patterns of biodiversity and their underlying mechanisms have been an active area of research for a long time. In this study, a total of 63 samples (20m × 30m) were systematically established along elevation gradients on Mount Tai and Mount Lao, China. We explored altitudinal patterns of plant diversity in the two mountain systems. In order to understand the mechanisms driving current diversity patterns, we used phylogenetic approaches to detect the spatial patterns of phylogenetic diversity and phylogenetic structure along two elevation gradients. We found that total species richness had a monotonically decreasing pattern and tree richness had a unimodal pattern along the elevation gradients in the two study areas. However, altitudinal patterns in shrub richness and herbs richness were not consistent on the two mountains. At low elevation, anthropogenic disturbances contributed to the increase of plant diversity, especially for shrubs and herbs in understory layers, which are more sensitive to changes in microenvironment. The phylogenetic structure of plant communities exhibited an inverted hump-shaped pattern along the elevation gradient on Mount Tai, which demonstrates that environmental filtering is the main driver of plant community assembly at high and low elevations and inter-specific competition may be the main driver of plant community assembly in the middle elevations. However, the phylogenetic structure of plant communities did not display a clear pattern on Mount Lao where the climate is milder. Phylogenetic beta diversity and species beta diversity consistently increased with increasing altitudinal divergence in the two study areas. However, the altitudinal patterns of species richness did not completely mirror phylogenetic diversity patterns. Conservation areas should be selected taking into consideration the preservation of high species richness, while maximizing phylogenetic diversity to improve the potential for diversification in the future.</p></div

Relationship between phylogenetic distance and altitudinal divergence for trees, shrubs, and herbs on Mount Tai and Mount Lao, China.

<p>Relationship between phylogenetic distance and altitudinal divergence for trees, shrubs, and herbs on Mount Tai and Mount Lao, China.</p

Pearson correlation coefficients between alpha diversity and environmental factors.

<p>Pearson correlation coefficients between alpha diversity and environmental factors.</p

The changes in phylogenetic community structure (NRI) along elevation gradientson Mount Tai and Mount Lao, China.

<p>The changes in phylogenetic community structure (NRI) along elevation gradientson Mount Tai and Mount Lao, China.</p

Relationship between Jaccard similarity index and altitudinal divergence for trees, shrubs, and herbs on Mount Tai and Mount Lao, China.

<p>Relationship between Jaccard similarity index and altitudinal divergence for trees, shrubs, and herbs on Mount Tai and Mount Lao, China.</p

Variation in phylogenetic diversity along elevation gradients for trees, shrubs, herbs, and total species on Mount Tai and Mount Lao, China.

<p>Variation in phylogenetic diversity along elevation gradients for trees, shrubs, herbs, and total species on Mount Tai and Mount Lao, China.</p

The simulated CH₄ flux

<p><strong>Figure 4.</strong> The simulated CH₄ flux. (a) The monthly CH₄ fluxes from 1961 to 2080. (b) The change of the CH₄ flux between the recent and the future periods. Values are for the wetland fraction of the study area only.</p> <p><strong>Abstract</strong></p> <p>One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model–downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961–1990) agreed well with a composite map of actual arctic vegetation. In the future (2051–2080), a poleward advance of the forest–tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH₄ emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH₄, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.</p

Tree-line

<p><strong>Figure 2.</strong> Tree-line. (a) The simulated tree-line comparisons between the CRU-forced run and the RCAO-forced run. (b) The recent and the future tree-line comparisons in the RCAO-forced run. (Green: the CAVM tree-line boundary; blue: tree-line advance for the latter; red: tree-line retreat for the latter; gray: no difference.)</p> <p><strong>Abstract</strong></p> <p>One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model–downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961–1990) agreed well with a composite map of actual arctic vegetation. In the future (2051–2080), a poleward advance of the forest–tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH₄ emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH₄, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.</p

The change of the simulated albedo between the recent and the future periods

<p><strong>Figure 5.</strong> The change of the simulated albedo between the recent and the future periods. (a) Summer albedo change. (b) Winter albedo change.</p> <p><strong>Abstract</strong></p> <p>One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model–downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961–1990) agreed well with a composite map of actual arctic vegetation. In the future (2051–2080), a poleward advance of the forest–tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH₄ emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH₄, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.</p