Global patterns of species richness of the holarctic alpine herb Saxifraga: The role of temperature and habitat heterogeneity

Postponed access: the file will be available after 2022-08-03The effects of contemporary climate, habitat heterogeneity and long-term climate change on species richness are well studied for woody plants in forest ecosystems, but poorly understood for herbaceous plants, especially in alpine–arctic ecosystems. Here, we aim to test if the previously proposed hypothesis based on the richness–environment relationship could explain the variation in richness patterns of the typical alpine–arctic herbaceous genus Saxifraga. Using a newly compiled distribution database of 437 Saxifraga species, we estimated the species richness patterns for all species, narrow- and wide-ranged species. We used generalized linear models and simultaneous autoregressive models to evaluate the effects of contemporary climate, habitat heterogeneity and historical climate on species richness patterns. Partial regressions were used to determine the independent and shared effects of different variables. Four widely used models were tested to identify their predictive power in explaining patterns of species richness. We found that temperature was negatively correlated with the richness patterns of all and wide-ranged species, and that was the most important environmental factor, indicating a strong conservatism of its ancestral temperate niche. Habitat heterogeneity and long-term climate change were the best predictors of the spatial variation of narrow-ranged species richness. Overall, the combined model containing five predictors can explain ca. 40%–50% of the variation in species richness. We further argued that additional evolutionary and biogeographical processes might have also played an essential role in shaping the Saxifraga diversity patterns and should be considered in future studies.acceptedVersio

Equivalent Conditions of a Hilbert-Type Multiple Integral Inequality Holding

Let ∑i=1n1/pi=1pi>1, in this paper, by using the method of weight functions and technique of real analysis; it is proved that the equivalent parameter condition for the validity of multiple integral Hilbert-type inequality ∫R+nKx1,⋯,xn∏i=1nfixi dx1⋯dxn≤M∏i=1nfipi,αi with homogeneous kernel Kx1,⋯,xn of order λ is ∑i=1nαi/pi=λ+n−1, and the calculation formula of its optimal constant factor is obtained. The basic theory and method of constructing a Hilbert-type multiple integral inequality with the homogeneous kernel and optimal constant factor are solved

The necessary and sufficient conditions for the existence of a kind of Hilbert-type multiple integral inequality with the non-homogeneous kernel and its applications

Abstract For x = ( x 1 , … , x n ) ${x}= ( {x}_{1},\ldots, {x}_{{n}} )$ , u ( x ) = ( ∑ i = 1 n a i x i ρ ) 1 / ρ ${u} ( {x} ) = ( \sum_{{i}=1}^{{n}} {a}_{{i}} {x}_{{i}}^{\rho} )^{1/\rho}$ , v ( y ) = ( ∑ i = 1 n b i y i ρ ) 1 / ρ ${v} ( {y} ) = ( \sum_{{i}=1}^{{n}} {b}_{{i}} {y}_{{i}}^{\rho} )^{1/\rho}$ , by using the methods and techniques of real analysis, the sufficient and necessary conditions for the existence of the Hilbert-type multiple integral inequality with the kernel K ( u ( x ) , v ( y ) ) = G ( u λ 1 ( x ) v λ 2 ( y ) ) ${K} ( {u} ( {x} ),{v} ( {y} ) ) ={G} ( {u}^{\lambda_{1}} ( {x} ) {v}^{\lambda_{2}} (y) )$ and the best possible constant factor are discussed. Furthermore, its application in the operator theory is considered

Spatial analysis enables priority selection in conservation practices for landscapes that need ecological security.

peer reviewedGlobal urbanization has not only promoted social and economic development, but also contributed to seriously ecological challenges. As a type of sustainable landscape patterns, ecological security pattern is considered as an effective spatial pathway to simultaneously conserve ecological security and maintain social-economic development. However, the fragmentation issue of ecological sources of ecological security pattern has not been effectively addressed, although many case studies have been conducted to identify ecological security pattern. In this study, we used spatial conservation prioritization to identify the ecological security pattern of the city belt along the Yellow River in Ningxia, China. Ecological sources were selected using Zonation model while ecological corridors and key ecological nodes were identified with circuit model. The results showed that the ecological security pattern was composed of 97 ecological sources, 226 ecological corridors, 267 pinch points and 22 barriers, covering a total area of 7713.1 km2 and accounting for 34% of the study area. Ecological sources were concentrated in the Helan Mountain, Xiang Mountain and along the Yellow River. Besides, ecological corridors were dense in the southern and eastern part of the study area. Both indicated that the Yellow River and Helan Mountain were the conservation hotspots. Landscape connectivity of ecological sources identified through Zonation-based spatial conservation prioritization was better than that with the scoring approach based on ecosystem service importance. Particularly, in the Zonation approach the landscape connectivity increased with 44% while the average patch area increased with 28% when comparing with the scoring approach. The spatial conservation prioritization approach proposed in this study provides a new effective tool to construct ecological security pattern, which is conducive to the synergic enhancement of landscape connectivity and ecosystem services conservation

Reversing Conventional Reactivity of Mixed Oxo/Alkyl Rare-Earth Complexes: Non-Redox Oxygen Atom Transfer

International audienceThe preferential substitution of oxo ligands over alkyl ones of rare-earth complexes is commonly considered as "impossible" due to the high oxophilicity of metal centers. Now, it has been shown that simply assembling mixed methyl/oxo rare-earth complexes to a rigid trinuclear cluster framework cannot only enhance the activity of the Ln-oxo bond, but also protect the highly reactive Ln-alkyl bond, thus providing a previously unrecognized opportunity to selectively manipulate the oxo ligand in the presence of numerous reactive functionalities. Such trimetallic cluster has proved to be a suitable platform for developing the unprecedented non-redox rare-earth-mediated oxygen atom transfer from ketones to CS2 and PhNCS. Controlled experiments and computational studies shed light on the driving force for these reactions, emphasizing the importance of the sterical accessibility and multimetallic effect of the cluster framework in promoting reversal of reactivity of rare-earth oxo complexes

Rare-Earth-Metal-Catalyzed Addition of Terminal Monoalkynes and Dialkynes with Aryl-Substituted Symmetrical or Unsymmetrical Carbodiimides

A high-efficiency and atom-economic route for the synthesis of N-aryl-substituted propiolamidines was established through the addition of terminal alkynes with aryl-substituted symmetrical or unsymmetrical carbodiimides catalyzed by mixed Tp^Me2/Cp rare-earth-metal alkyl complexes (Tp^Me2)­CpLnCH₂Ph­(THF) (<b>1</b>^<b>Ln</b>). Moreover, the gadolinium alkyl complex <b>1</b>^<b>Gd</b> can also serve as a catalyst for the double addition of dialkynes with carbodiimides. Mechanism studies indicated that the variable coordination modes (κ³ or κ²) of the Tp^Me2 ligand on the rare-earth-metal species may play an important role in the catalytic cycles

Versatile Reactivity of β‑Diketiminato-Supported Yttrium Dialkyl Complex toward Aromatic N‑Heterocycles

The reactions of β-diketiminatoyttrium dialkyl complex LY­(CH₂Ph)₂(THF) (<b>1</b>, L = [{N­(2,6-^<i>i</i>Pr₂C₆H₃)­C­(Me)}₂CH]⁻) with a series of aromatic N-heterocycles such as 2-phenylpyridine, benzothiazole, and benzoxazole were studied and displayed discrete reactivity including C–H activation, C–C coupling, ring-opening/insertion, and dearomatization. The reaction of <b>1</b> with 2-phenylpyridine in 1:2 molar ratio in THF at 30 °C for 14 days afforded a structurally characterized metal complex, LY­(η²-<i>N,C</i>-C₅H₄NC₆H₄-2)­[C₅H₄N­(CH₂Ph-4)­Ph] (<b>2</b>), in 73% isolated yield, indicating the occurrence of phenyl ring C­(sp²)–H activation and pyridine ring 1,4-addition/dearomatization. However, when this reaction was done at 5 °C for 7 days, it gave the pyridine ring 1,2-addition product LY­(η²-<i>N,C</i>-C₅H₄NC₆H₄-2)­[C₅H₄N­(CH₂Ph-2)­Ph] (<b>3</b>) in 54% isolated yield. Further investigations revealed that complex <b>2</b> is the thermodynamic controlled product and complex <b>3</b> is the kinetically controlled product; <b>3</b> converted slowly into <b>2</b>, as confirmed by ¹H NMR spectroscopy. The equimolar reaction of <b>1</b> with benzothiazole or benzoxazole produced two C–C coupling/ring-opening/insertion products, LY­[η²-<i>S,N</i>-SC₆H₄NCH­(CH₂Ph)₂]­(THF) (<b>4</b>) and {LY­[μ-η²:η¹-<i>O,N</i>-OC₆H₄NCH­(CH₂Ph)₂]}₂ (<b>5</b>), in 84% and 78% isolated yields, respectively

Synthesis, Structural Characterization, and Reactivity of Mono(amidinate) Rare-Earth-Metal Bis(aminobenzyl) Complexes

Three kinds of solvated lithium amidinates with different coordination models were obtained via recrystallization of [PhC­(NC₆H₄^<i>i</i>Pr₂-2,6)₂]­Li­(THF) (<b>1a</b>) in different solvents. Treatment of <i>o</i>-Me₂NC₆H₄CH₂Li with LLnCl₂(THF)_<i>n</i> (<b>2</b>; L = [PhC­(NC₆H₄^<i>i</i>Pr₂-2,6)₂]⁻ (NCN^dipp), [<i>o</i>-Me₂NC₆H₄CH₂C­(NC₆H₄^<i>i</i>Pr₂-2,6)₂]⁻ (NCN^dipp′)) formed in situ from reaction of LnCl₃(THF)_<i>x</i> with LLi­(THF) gave the rare-earth-metal bis­(aminobenzyl) complexes LLn­(CH₂C₆H₄NMe₂-<i>o</i>)₂ (L = NCN^dipp, Ln = Sc (<b>3a</b>), Y (<b>3b</b>), Lu (<b>3c</b>); L = NCN^dipp′, Ln = Sc (<b>3d</b>), Lu (<b>3e</b>)) in high yields. Reactions of complexes <b>3</b> with CO₂, PhNCO, 2,6-diisopropylaniline, and S have been explored. CO₂ inserted into each Ln–C bond of complexes <b>3a</b>–<b>c</b> to form the dual-core complexes [(NCN^dipp)­Sc­(μ-η¹:η¹-O₂CCH₂C₆H₄NMe₂-<i>o</i>)₂]₂ (<b>4a</b>) and [(NCN^dipp)­Ln­(μ-η¹:η²-O₂CCH₂C₆H₄NMe₂-<i>o</i>)­(μ-η¹:η¹-O₂CCH₂C₆H₄NMe₂-<i>o</i>)]₂ (Ln = Y (<b>4b</b>), Lu (<b>4c</b>)). The reaction of <b>3b</b>,<b>c</b>,<b>e</b> with PhNCO produced LLu­[OC­(CH₂C₆H₄NMe₂-<i>o</i>)­NPh]₂(thf) (L = NCN^dipp, Ln = Y (<b>5b</b>), Lu (<b>5c</b>); L = NCN^dipp′, Ln = Lu (<b>5e</b>)). Protonolysis of <b>3a</b>,<b>b</b> by 2,6-diisopropylaniline formed straightforwardly the μ₂-imido complexes [(NCN^dipp)­Ln­(μ-NC₆H₄^<i>i</i>Pr₂-2,6)]₂ (Ln = Sc (<b>6a</b>), Lu (<b>6c</b>)). Reaction of <b>3e</b> with S₈ afforded the sulfur insertion products (NCN^dipp′)­Lu­(CH₂C₆H₄NMe₂-<i>o</i>)­(SCH₂C₆H₄NMe₂-<i>o</i>)­(thf) (<b>7e</b>) and (NCN^dipp′)­Lu­(SCH₂C₆H₄NMe₂-<i>o</i>)₂(thf)₂ (<b>7f</b>) in high yields, respectively, depending on the stoichiometric ratio. All of these complexes were fully characterized by elemental analysis, NMR spectroscopy, and X-ray structural determinations

Synthesis, Structural Characterization, and Reactivity of Mono(amidinate) Rare-Earth-Metal Bis(aminobenzyl) Complexes

Three kinds of solvated lithium amidinates with different coordination models were obtained via recrystallization of [PhC­(NC₆H₄^<i>i</i>Pr₂-2,6)₂]­Li­(THF) (<b>1a</b>) in different solvents. Treatment of <i>o</i>-Me₂NC₆H₄CH₂Li with LLnCl₂(THF)_<i>n</i> (<b>2</b>; L = [PhC­(NC₆H₄^<i>i</i>Pr₂-2,6)₂]⁻ (NCN^dipp), [<i>o</i>-Me₂NC₆H₄CH₂C­(NC₆H₄^<i>i</i>Pr₂-2,6)₂]⁻ (NCN^dipp′)) formed in situ from reaction of LnCl₃(THF)_<i>x</i> with LLi­(THF) gave the rare-earth-metal bis­(aminobenzyl) complexes LLn­(CH₂C₆H₄NMe₂-<i>o</i>)₂ (L = NCN^dipp, Ln = Sc (<b>3a</b>), Y (<b>3b</b>), Lu (<b>3c</b>); L = NCN^dipp′, Ln = Sc (<b>3d</b>), Lu (<b>3e</b>)) in high yields. Reactions of complexes <b>3</b> with CO₂, PhNCO, 2,6-diisopropylaniline, and S have been explored. CO₂ inserted into each Ln–C bond of complexes <b>3a</b>–<b>c</b> to form the dual-core complexes [(NCN^dipp)­Sc­(μ-η¹:η¹-O₂CCH₂C₆H₄NMe₂-<i>o</i>)₂]₂ (<b>4a</b>) and [(NCN^dipp)­Ln­(μ-η¹:η²-O₂CCH₂C₆H₄NMe₂-<i>o</i>)­(μ-η¹:η¹-O₂CCH₂C₆H₄NMe₂-<i>o</i>)]₂ (Ln = Y (<b>4b</b>), Lu (<b>4c</b>)). The reaction of <b>3b</b>,<b>c</b>,<b>e</b> with PhNCO produced LLu­[OC­(CH₂C₆H₄NMe₂-<i>o</i>)­NPh]₂(thf) (L = NCN^dipp, Ln = Y (<b>5b</b>), Lu (<b>5c</b>); L = NCN^dipp′, Ln = Lu (<b>5e</b>)). Protonolysis of <b>3a</b>,<b>b</b> by 2,6-diisopropylaniline formed straightforwardly the μ₂-imido complexes [(NCN^dipp)­Ln­(μ-NC₆H₄^<i>i</i>Pr₂-2,6)]₂ (Ln = Sc (<b>6a</b>), Lu (<b>6c</b>)). Reaction of <b>3e</b> with S₈ afforded the sulfur insertion products (NCN^dipp′)­Lu­(CH₂C₆H₄NMe₂-<i>o</i>)­(SCH₂C₆H₄NMe₂-<i>o</i>)­(thf) (<b>7e</b>) and (NCN^dipp′)­Lu­(SCH₂C₆H₄NMe₂-<i>o</i>)₂(thf)₂ (<b>7f</b>) in high yields, respectively, depending on the stoichiometric ratio. All of these complexes were fully characterized by elemental analysis, NMR spectroscopy, and X-ray structural determinations