Two novel monophosphoramidites were synthesized through a five-step transformation from commercially available L-proline. In the Rh-catalyzed asymmetric hydrogenation of α-dehydroamino acid derivatives, ligand (Sc,...Two novel monophosphoramidites were synthesized through a five-step transformation from commercially available L-proline. In the Rh-catalyzed asymmetric hydrogenation of α-dehydroamino acid derivatives, ligand (Sc,Rα)-1b showed good enantioselectivity and up to 91% e.e. was obtained.展开更多
Dicyclohexylmethyl diazoacetate was synthesized in excellent yield from the corresponding glycinate. which was derived in high yield from dicyclohexylmethyl chloroacetate via azide substitutuion, and reduction.
Recently a new grout material called water inflow sealing(WIS) was invented for sealing water inflow in tunneling and underground constructions. In this study, a special experimental method called intubated counter gr...Recently a new grout material called water inflow sealing(WIS) was invented for sealing water inflow in tunneling and underground constructions. In this study, a special experimental method called intubated counter grouting(ICG) was proposed to investigate the influence of water dispersion on the rheological properties of the grout during the grouting process, and to testify the sealing performance of the grout,such as instant gelling ability(IGA) and anti-dispersion ability(ADA). In the experiment, dispersion was restricted in the downstream of the channel with a high turbulence intensity. The influences of ADA and IGA were therefore decoupled and evaluated separately. Experimental results revealed two distinctive sealing mechanisms of WIS. For a low initial velocity of water, WIS turned the shear flow of water into an overall movement of a plug by absorbing water into the particles. For a high initial velocity and the situation that the particles reached the outlet before sufficiently expanding, WIS modified the rheology of the water in the channel and reduced its velocity till the static state. The distinctive feature of WIS brings a reformation on the sealing mechanism and provides an effective way to control water inflow with high pressure and velocity.展开更多
3-Acetamidotropolone 1 reacted with p-substitutedbenzenediazonium chloride in pyridine to afford 3-acetamido-5-(4-substitutedphenylazo)tropolones 2a~f. Hydrolysis of compounds 2a~f gave 3-amino-5-(4-substitutedphenyla...3-Acetamidotropolone 1 reacted with p-substitutedbenzenediazonium chloride in pyridine to afford 3-acetamido-5-(4-substitutedphenylazo)tropolones 2a~f. Hydrolysis of compounds 2a~f gave 3-amino-5-(4-substitutedphenylazo)tropolones 3a~f which could not be obtained directly from reactions of 3-aminotropolone with p-substitutedbenzenediazonium chloride. The structures of these new compounds 2a, 2c~f, 3a, 3c~f were confirmed from the elemental analysis and spectral data.展开更多
Several cyclopropanation catalysts for the synthesis of 3(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylates have been studied in this paper. Owing to electron deficiency of 1,1-dichloro-4-methyl-1,3-pentadiene, ...Several cyclopropanation catalysts for the synthesis of 3(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylates have been studied in this paper. Owing to electron deficiency of 1,1-dichloro-4-methyl-1,3-pentadiene, yield of this reaction is rather law compared with that of 2,5-dimethyl-2,4-pentadiene, Of all catalysts concerned. yield ranged from 25.1% to 47.2%.展开更多
A novel chiral bis(ferrocenyl) P2N ligand 1 with C2-symmetry was synthesized through a four-step procedure from (R)-N,N-dimethyl-1-ferrocenylethylamine. In a model reaction of Pd-catalyzed allylic alkylation of 1,3-d...A novel chiral bis(ferrocenyl) P2N ligand 1 with C2-symmetry was synthesized through a four-step procedure from (R)-N,N-dimethyl-1-ferrocenylethylamine. In a model reaction of Pd-catalyzed allylic alkylation of 1,3-diphenylprop-2-enyl acetate 6 with dimethyl malonate, good enantioselectivity (86% e.e.) was obtained.展开更多
A novel chiral phosphine-triazine ligand was synthesized from chiral α-phenylethylamine through a three-step procedure. In a model reaction of Pd-catalyzed allylic alkylation of rac-1,3-diphenylprop-2-en-1-y1 pivalat...A novel chiral phosphine-triazine ligand was synthesized from chiral α-phenylethylamine through a three-step procedure. In a model reaction of Pd-catalyzed allylic alkylation of rac-1,3-diphenylprop-2-en-1-y1 pivalate with dimethyl malonate, good enantioselectivity (90% e.e.) was obtained by using this ligand.展开更多
Two new C2-symmetrical bidentate phosphoramidite ligands were synthesized and employed in the Rh-catalyzed asymmetric hydrogenation of β-(acylamino)acrylates, up to 89% ee with full conversions was obtained.
The swelling particle grouting material has demonstrated remarkable plugging effectiveness in high-pressure and large-flow burst water within karst pipelines.Currently,current research on the rheolog-ical model,flow c...The swelling particle grouting material has demonstrated remarkable plugging effectiveness in high-pressure and large-flow burst water within karst pipelines.Currently,current research on the rheolog-ical model,flow computation theory,and plugging mechanism of this material is lacking.The conven-tional grouting slurry diffusion process,using the liquid-liquid two-phase flow method,fails to accurately simulate high solubility slurry and particle swelling.To address these limitations,this study established a precise constitutive model to describe the swelling particle slurry diffusion process in dynamic water.Additionally,a coupling calculation method was proposed to analyze the spatiotemporal heterogeneity of viscosity during slurry diffusion by considering the migration of slurry and the changes in viscosity.To investigate the interaction between particle swelling and flow field changes,a Compu-tational Fluid Dynamics-Discrete Element Method(CFD-DEM)coupling model was developed for the diffusion of swelling particle slurry.It is demonstrated that slurry viscosity increases exponentially within the diffusion front as the particle swelling rate rises,and the drag force exhibits an intriguing behavior of initially increasing and then decreasing as the slurry flows through the pipeline.Further-more,the CFD-DEM coupling model proved to be more accurate in describing viscosity distribution and diffusion distance compared to the finite element solution.The primary objective of this paper is to reveal the plugging mechanism and provide theoretical support for the engineering application of the swelling particle grouting material.展开更多
Reconstructing the Holocene megaflood history is a key component of understanding the mechanism of past climate change and assessing the potential impact of future catastrophic events.The Pearl River is the longest wa...Reconstructing the Holocene megaflood history is a key component of understanding the mechanism of past climate change and assessing the potential impact of future catastrophic events.The Pearl River is the longest watercourse in southern China,and its lower reach has been identified as one of the world's most vulnerable regions for flood exposure.However,there is a complete lack of millennial-scale geological records of paleomegafloods for the future prediction of once-in-a-hundred(even once-in-a-thousand)year floods in southern China.Here,we identified a series of paleomegaflood deposits interbedded with wood-rich peat layers in the lower West Pearl River area.All paleoflood layers have been well dated using AMS~(14)C dating method.According to the regional correlation of the flood sequence,sediment characteristics and provenance analysis,there have been at least 7 megafloods corresponding to once-in-a-thousand-year events in the lower reaches of the West Pearl River during the past 6000 years,with an average return period of approximately 855 years.The identified paleomegafloods were coeval with periods of strong El Ni?o-Southern Oscillation(ENSO),indicating that weakening of the Asian summer monsoon,associated with enhanced ENSO variability,may have triggered abnormally high precipitation leading to flooding of exceptional magnitude in southern China.In addition,the most prominent paleomegafloods identified in the lower Pearl River coincided with intervals of lower precipitation and fewer storms in central-eastern China,indicating the intensification of the meridional“tripole”pattern of precipitation across eastern China during the latter half of the Holocene.Increased land use and deforestation over the last 2000 years have resulted in soil loss and rapid degradation of local primeval forest ecosystems,leading to more catastrophic flooding.Large amounts of rice pollen in the uppermost flood layer during the Song Dynasty indicate that this megaflood may have inundated a large area of cultivated land.The periodic occurrence of Holocene megafloods not only caused damage to human existence,but also affected the evolution of local civilization.This study reveals for the first time a series of Holocene millennial-scale megafloods and sheds new light on the importance of atmosphere-ocean interactions in the tropical Pacific and monsoon subtropical climate dynamics for precipitation anomalies in East Asia.Our data yield valuable information for future research into climate extremes and hazard prevention.展开更多
Quantitative climate reconstruction on long timescales can provide important insights for understanding the climate variability and providing valuable data for simulations. Unfortunately, the credibility of some attem...Quantitative climate reconstruction on long timescales can provide important insights for understanding the climate variability and providing valuable data for simulations. Unfortunately, the credibility of some attempts was hampered by incomplete reconstruction procedures. We here establish a comprehensive framework resting on high-quality Chinese modern pollen database, including modern pollen data screening, calibration set selection, major climate factor analysis, appropriate model selection, strict statistical assessment of results and ecological interpretation. The application of this framework to three high-resolution pollen records from the eastern Tibetan Plateau allows accurate quantitative inferences of Holocene temperature changes, which is the major control of regional vegetation. The results show that the mean warmest month temperature(MTwa)during the early Holocene was ca. 10.4℃ and reached the highest value at 8.5–6 ka BP(ca. 11℃). The early and mid-Holocene(11–5 ka BP) warmth was followed by 1.2℃ temperature decrease, culminating in the coolest temperatures of the Holocene during the Neoglacial cooling. Superimposing on the general cooling trend, MTwareveals a significant 500-yr periodicity with varying intensities through time, showing that warm(cold) intervals are in phase with solar maxima(minima) periods. This spectral similarity indicates a possible connection of multi-century scale climate fluctuations with solar forcing.展开更多
As the second common type of volcanic vent on Earth, maar-diatreme volcanoes and their post-eruptive lacustrine sediments are a main focus of volcanology, palaeolimnology, palaeoclimatology and palaeontology. A number...As the second common type of volcanic vent on Earth, maar-diatreme volcanoes and their post-eruptive lacustrine sediments are a main focus of volcanology, palaeolimnology, palaeoclimatology and palaeontology. A number of maar-type volcanoes have been found in Leizhou Peninsula, South China, but little is known about their eruption processes and detailed stratigraphy of the post-eruptive sediments. We present a combined geophysical and geological analysis to study the eruptive history and post-eruptive sediment stratigraphy of a large maar, the elliptical(1.8 × 3.0 km^(2)) Jiudouyang(JDY) maar. The lacustrine stratigraphy revealed by drilling cores shows that the JDY maar lake has three major stages of evolution:(i) deep-lake sedimentary environment characterized by high autochthonous diatom productivity;(ii) shallow lake to swamp with very low water levels, characterized by a high total organic carbon(TOC) and abundant wood fragments;and,(iii) intermittent shallow lake and alluvial deposits composed of clay minerals and sand. The electrical resistivity tomography(ERT) values and lithological features are highly consistent, which clearly reveal the presence of ca. 50 m thick lacustrine sediments, directly underlain by a ca. 70 m thick basaltic lava rather than diatreme breccia in the crater. This infill sequence implies an alternation of eruption style from phreatomagmatic to Strombolian and/or lava flow, due to high magma flux and ascent rate of the Hainan Plume during the middle Pleistocene. The ERT data also reveal the initial phreatomagmatic crater floor at ca. 120 m depth. The initial crater had a large diameter/depth ratio(ca. 17), with an elongated shape(major axis to minor axis = 0.6), implying possible lateral vent migration during the eruption. A significant erosion under tropical weathering condition during the last few hundred thousand years, accounted for the large size of the maar crater. The study provides insights into the eruptive history and post-eruptive evolution of a large maar, as well as the spatial distribution of the lacustrine sediments.展开更多
Aims Comparisons of climate envelopes among species have shown that niche conservatism tends to break down over time.Here,we use the Asian tree genus Platycarya(Juglandaceae)as a case study to test this tendency at re...Aims Comparisons of climate envelopes among species have shown that niche conservatism tends to break down over time.Here,we use the Asian tree genus Platycarya(Juglandaceae)as a case study to test this tendency at relatively short timescales in a single lineage.This,together with a reanalysis of the extant literature,should help evaluate prospects of using correlations between climate and spe-cies occurrence data to infer evolutionary processes.Methods We rely on species distribution models(SDMs)and multivari-ate analyses to compare current and past(Last Glacial Maximum~21ka)climatic envelopes between the two extant Platycarya spe-cies(Platycarya strobilacea and Platycarya longipes)and between mainland and Taiwan populations of P.strobilacea,paying particu-lar attention to autocorrelation issues.We also review interpreta-tions provided in similar studies comparing climate envelopes between and within species,including in studies involving native and introduced populations of the same species.Important Findings We find intraspecific but not interspecific differentiation in climate envelopes of Platycarya,despite the prediction that niche differen-tiation should be stronger between older groups.Our review also suggests that differentiation in climate envelopes need not imply rapid evolutionary divergence.Whereas SDMs can be used to raise evolutionary hypotheses to be validated with other data,we con-clude that it should not be used to directly infer short-term evolu-tionary processes.展开更多
Timing of the precipitation optimum in the Holocene for the semi-arid northern China affects our understanding of the temporal-patterns of the East Asian Summer Monsoon and its connection with precipitation in the mon...Timing of the precipitation optimum in the Holocene for the semi-arid northern China affects our understanding of the temporal-patterns of the East Asian Summer Monsoon and its connection with precipitation in the monsoon fringe area.Discrepancies about when this occurs(early Holocene or mid-Holocene)exist in paleoclimate records based on various proxies and models.展开更多
基金The authors would like to thank the National Natural Science Foundation of China(20472083)for financial support.
文摘Two novel monophosphoramidites were synthesized through a five-step transformation from commercially available L-proline. In the Rh-catalyzed asymmetric hydrogenation of α-dehydroamino acid derivatives, ligand (Sc,Rα)-1b showed good enantioselectivity and up to 91% e.e. was obtained.
文摘Dicyclohexylmethyl diazoacetate was synthesized in excellent yield from the corresponding glycinate. which was derived in high yield from dicyclohexylmethyl chloroacetate via azide substitutuion, and reduction.
基金financially supported by National Postdoctoral Program for Innovative Talent (No. BX20200200)Youth Fund of National Natural Science Foundation of China (No. 52109126)Joint Funds of the National Natural Science Foundation of China (No. U1706223)。
文摘Recently a new grout material called water inflow sealing(WIS) was invented for sealing water inflow in tunneling and underground constructions. In this study, a special experimental method called intubated counter grouting(ICG) was proposed to investigate the influence of water dispersion on the rheological properties of the grout during the grouting process, and to testify the sealing performance of the grout,such as instant gelling ability(IGA) and anti-dispersion ability(ADA). In the experiment, dispersion was restricted in the downstream of the channel with a high turbulence intensity. The influences of ADA and IGA were therefore decoupled and evaluated separately. Experimental results revealed two distinctive sealing mechanisms of WIS. For a low initial velocity of water, WIS turned the shear flow of water into an overall movement of a plug by absorbing water into the particles. For a high initial velocity and the situation that the particles reached the outlet before sufficiently expanding, WIS modified the rheology of the water in the channel and reduced its velocity till the static state. The distinctive feature of WIS brings a reformation on the sealing mechanism and provides an effective way to control water inflow with high pressure and velocity.
基金The National Natural Science Foundation of China (29933050) and Natural Science Foundation of Liaoning Province (972004).
文摘3-Acetamidotropolone 1 reacted with p-substitutedbenzenediazonium chloride in pyridine to afford 3-acetamido-5-(4-substitutedphenylazo)tropolones 2a~f. Hydrolysis of compounds 2a~f gave 3-amino-5-(4-substitutedphenylazo)tropolones 3a~f which could not be obtained directly from reactions of 3-aminotropolone with p-substitutedbenzenediazonium chloride. The structures of these new compounds 2a, 2c~f, 3a, 3c~f were confirmed from the elemental analysis and spectral data.
文摘Several cyclopropanation catalysts for the synthesis of 3(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylates have been studied in this paper. Owing to electron deficiency of 1,1-dichloro-4-methyl-1,3-pentadiene, yield of this reaction is rather law compared with that of 2,5-dimethyl-2,4-pentadiene, Of all catalysts concerned. yield ranged from 25.1% to 47.2%.
基金supported by the National Natural Science Foundation of China(29933050)
文摘A novel chiral bis(ferrocenyl) P2N ligand 1 with C2-symmetry was synthesized through a four-step procedure from (R)-N,N-dimethyl-1-ferrocenylethylamine. In a model reaction of Pd-catalyzed allylic alkylation of 1,3-diphenylprop-2-enyl acetate 6 with dimethyl malonate, good enantioselectivity (86% e.e.) was obtained.
文摘A novel chiral phosphine-triazine ligand was synthesized from chiral α-phenylethylamine through a three-step procedure. In a model reaction of Pd-catalyzed allylic alkylation of rac-1,3-diphenylprop-2-en-1-y1 pivalate with dimethyl malonate, good enantioselectivity (90% e.e.) was obtained by using this ligand.
基金The authors would like to thank the National Natural Science Foundation of China (No. 20472083) for financial support of this work.
文摘Two new C2-symmetrical bidentate phosphoramidite ligands were synthesized and employed in the Rh-catalyzed asymmetric hydrogenation of β-(acylamino)acrylates, up to 89% ee with full conversions was obtained.
基金supported by the National Natural Science Foundation of China for the Young Scientists Fund,China (grant No.52109126)the National Key Research and Development Program of China,China (grant No.202103AA080016).
文摘The swelling particle grouting material has demonstrated remarkable plugging effectiveness in high-pressure and large-flow burst water within karst pipelines.Currently,current research on the rheolog-ical model,flow computation theory,and plugging mechanism of this material is lacking.The conven-tional grouting slurry diffusion process,using the liquid-liquid two-phase flow method,fails to accurately simulate high solubility slurry and particle swelling.To address these limitations,this study established a precise constitutive model to describe the swelling particle slurry diffusion process in dynamic water.Additionally,a coupling calculation method was proposed to analyze the spatiotemporal heterogeneity of viscosity during slurry diffusion by considering the migration of slurry and the changes in viscosity.To investigate the interaction between particle swelling and flow field changes,a Compu-tational Fluid Dynamics-Discrete Element Method(CFD-DEM)coupling model was developed for the diffusion of swelling particle slurry.It is demonstrated that slurry viscosity increases exponentially within the diffusion front as the particle swelling rate rises,and the drag force exhibits an intriguing behavior of initially increasing and then decreasing as the slurry flows through the pipeline.Further-more,the CFD-DEM coupling model proved to be more accurate in describing viscosity distribution and diffusion distance compared to the finite element solution.The primary objective of this paper is to reveal the plugging mechanism and provide theoretical support for the engineering application of the swelling particle grouting material.
基金This work was supported by the National Key Research and Development Program of China(2022YFF0801501 and 2016YFA0600500)the National Natural Science Foundation of China(41902184,42072205,and 42077414)the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(311022010).
基金supported by the National Natural Science Foundation of China(Grant Nos.42072205&41301582)the National Key R&D Program of China(Grant No.2022YFF0801501)the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(Grant No.311022010)。
文摘Reconstructing the Holocene megaflood history is a key component of understanding the mechanism of past climate change and assessing the potential impact of future catastrophic events.The Pearl River is the longest watercourse in southern China,and its lower reach has been identified as one of the world's most vulnerable regions for flood exposure.However,there is a complete lack of millennial-scale geological records of paleomegafloods for the future prediction of once-in-a-hundred(even once-in-a-thousand)year floods in southern China.Here,we identified a series of paleomegaflood deposits interbedded with wood-rich peat layers in the lower West Pearl River area.All paleoflood layers have been well dated using AMS~(14)C dating method.According to the regional correlation of the flood sequence,sediment characteristics and provenance analysis,there have been at least 7 megafloods corresponding to once-in-a-thousand-year events in the lower reaches of the West Pearl River during the past 6000 years,with an average return period of approximately 855 years.The identified paleomegafloods were coeval with periods of strong El Ni?o-Southern Oscillation(ENSO),indicating that weakening of the Asian summer monsoon,associated with enhanced ENSO variability,may have triggered abnormally high precipitation leading to flooding of exceptional magnitude in southern China.In addition,the most prominent paleomegafloods identified in the lower Pearl River coincided with intervals of lower precipitation and fewer storms in central-eastern China,indicating the intensification of the meridional“tripole”pattern of precipitation across eastern China during the latter half of the Holocene.Increased land use and deforestation over the last 2000 years have resulted in soil loss and rapid degradation of local primeval forest ecosystems,leading to more catastrophic flooding.Large amounts of rice pollen in the uppermost flood layer during the Song Dynasty indicate that this megaflood may have inundated a large area of cultivated land.The periodic occurrence of Holocene megafloods not only caused damage to human existence,but also affected the evolution of local civilization.This study reveals for the first time a series of Holocene millennial-scale megafloods and sheds new light on the importance of atmosphere-ocean interactions in the tropical Pacific and monsoon subtropical climate dynamics for precipitation anomalies in East Asia.Our data yield valuable information for future research into climate extremes and hazard prevention.
基金supported by the National Key Research and Development Program of China (Grant No. 2016YFA0600501)the National Natural Science Foundation of China (Grant Nos. 41690113, 41888101 and 41471169)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA20070101)。
文摘Quantitative climate reconstruction on long timescales can provide important insights for understanding the climate variability and providing valuable data for simulations. Unfortunately, the credibility of some attempts was hampered by incomplete reconstruction procedures. We here establish a comprehensive framework resting on high-quality Chinese modern pollen database, including modern pollen data screening, calibration set selection, major climate factor analysis, appropriate model selection, strict statistical assessment of results and ecological interpretation. The application of this framework to three high-resolution pollen records from the eastern Tibetan Plateau allows accurate quantitative inferences of Holocene temperature changes, which is the major control of regional vegetation. The results show that the mean warmest month temperature(MTwa)during the early Holocene was ca. 10.4℃ and reached the highest value at 8.5–6 ka BP(ca. 11℃). The early and mid-Holocene(11–5 ka BP) warmth was followed by 1.2℃ temperature decrease, culminating in the coolest temperatures of the Holocene during the Neoglacial cooling. Superimposing on the general cooling trend, MTwareveals a significant 500-yr periodicity with varying intensities through time, showing that warm(cold) intervals are in phase with solar maxima(minima) periods. This spectral similarity indicates a possible connection of multi-century scale climate fluctuations with solar forcing.
基金This work was supported by the National Key R&D Program of China(Grant No.2016 YFA0600500)the National Natural Science Foundation of China(Grant Nos.41472143 and 41661144003)the Guangdong Province Introduction of Innovative R&D Team of Geological Processes and Natural Disasters around the South China Sea(Grant No.2016ZT06N331)。
文摘As the second common type of volcanic vent on Earth, maar-diatreme volcanoes and their post-eruptive lacustrine sediments are a main focus of volcanology, palaeolimnology, palaeoclimatology and palaeontology. A number of maar-type volcanoes have been found in Leizhou Peninsula, South China, but little is known about their eruption processes and detailed stratigraphy of the post-eruptive sediments. We present a combined geophysical and geological analysis to study the eruptive history and post-eruptive sediment stratigraphy of a large maar, the elliptical(1.8 × 3.0 km^(2)) Jiudouyang(JDY) maar. The lacustrine stratigraphy revealed by drilling cores shows that the JDY maar lake has three major stages of evolution:(i) deep-lake sedimentary environment characterized by high autochthonous diatom productivity;(ii) shallow lake to swamp with very low water levels, characterized by a high total organic carbon(TOC) and abundant wood fragments;and,(iii) intermittent shallow lake and alluvial deposits composed of clay minerals and sand. The electrical resistivity tomography(ERT) values and lithological features are highly consistent, which clearly reveal the presence of ca. 50 m thick lacustrine sediments, directly underlain by a ca. 70 m thick basaltic lava rather than diatreme breccia in the crater. This infill sequence implies an alternation of eruption style from phreatomagmatic to Strombolian and/or lava flow, due to high magma flux and ascent rate of the Hainan Plume during the middle Pleistocene. The ERT data also reveal the initial phreatomagmatic crater floor at ca. 120 m depth. The initial crater had a large diameter/depth ratio(ca. 17), with an elongated shape(major axis to minor axis = 0.6), implying possible lateral vent migration during the eruption. A significant erosion under tropical weathering condition during the last few hundred thousand years, accounted for the large size of the maar crater. The study provides insights into the eruptive history and post-eruptive evolution of a large maar, as well as the spatial distribution of the lacustrine sediments.
基金This work was supported by the National Natural Science Foundation of China[grant numbers 41230101,41472142 and 41472143]and the China Scholarship Council.
文摘Aims Comparisons of climate envelopes among species have shown that niche conservatism tends to break down over time.Here,we use the Asian tree genus Platycarya(Juglandaceae)as a case study to test this tendency at relatively short timescales in a single lineage.This,together with a reanalysis of the extant literature,should help evaluate prospects of using correlations between climate and spe-cies occurrence data to infer evolutionary processes.Methods We rely on species distribution models(SDMs)and multivari-ate analyses to compare current and past(Last Glacial Maximum~21ka)climatic envelopes between the two extant Platycarya spe-cies(Platycarya strobilacea and Platycarya longipes)and between mainland and Taiwan populations of P.strobilacea,paying particu-lar attention to autocorrelation issues.We also review interpreta-tions provided in similar studies comparing climate envelopes between and within species,including in studies involving native and introduced populations of the same species.Important Findings We find intraspecific but not interspecific differentiation in climate envelopes of Platycarya,despite the prediction that niche differen-tiation should be stronger between older groups.Our review also suggests that differentiation in climate envelopes need not imply rapid evolutionary divergence.Whereas SDMs can be used to raise evolutionary hypotheses to be validated with other data,we con-clude that it should not be used to directly infer short-term evolu-tionary processes.
基金supported by the National Natural Science Foundation of China(41988101 and 41877459)the Pioneer Hundred Talents Program of Chinese Academy of Sciences。
文摘Timing of the precipitation optimum in the Holocene for the semi-arid northern China affects our understanding of the temporal-patterns of the East Asian Summer Monsoon and its connection with precipitation in the monsoon fringe area.Discrepancies about when this occurs(early Holocene or mid-Holocene)exist in paleoclimate records based on various proxies and models.