Soil aggregate stability,as an important indicator of soil functions,may be affected by seasonal freezing and thawing(SFT)and land use in high cold and wet regions.Therefore,comprehensive understanding the effects of ...Soil aggregate stability,as an important indicator of soil functions,may be affected by seasonal freezing and thawing(SFT)and land use in high cold and wet regions.Therefore,comprehensive understanding the effects of SFT on aggregate stability in orchards during winter and spring is crucial to develop appropriate management strategies that can effectively alleviate the degradation of soil quality to ensure sustainable development of orchard ecosystems.To determine the mechanism of degradation in orchard soil quality,the effects of SFT on the stability of water-stable aggregates were examined in apple-pear orchards(Pyrus ussuriensis var.ovoidea)of four different ages(11,25,40,and 63 yr)on 0 to 5%slopes before freezing and after thawing from October 2015 to June 2016 in Longjing City,Yanbian Prefecture,Northeast China,involving a comparison of planted versus adjacent uncultivated lands(control).Soil samples were collected to investigate water-stable aggregate stability in three incremental soil layers(0–20,20–40 and 40–60 cm).In the same samples,iron oxide,organic matter,and clay contents of the soil were also determined.Results showed that the destructive influences of SFT on water-stable aggregates were more pronounced with the increased orchards ages,and SFT exerted severe effects on water-stable aggregates of older orchards(40 and 63 yr)than juvenile orchards.Undergoing SFT,the soil instability index and the percentage of aggregate destruction increased by mean 0.15 mm and 1.86%,the degree of aggregation decreased by mean 1.32%,and the erosion resistance weakened,which consequently led to aggregate stability decreased.In addition,soil free,amorphous,and crystalline iron oxide as well as soil organic matter and clay contents are all important factors affecting the stability of water-stable aggregates,and their changes in their contents were consistent with those in the stability of water-stable aggregates.The results of this study suggest that long-term planting fruit trees can exacerbate the damaging effects of SFT on aggregate stability and further soil erosion increases and nutrient losses in an orchard,which hider sustainable use of soil and the productivity orchards.展开更多
Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied.To investigate the microstructure and mechanical properties,optical microscopy,scanning electro...Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied.To investigate the microstructure and mechanical properties,optical microscopy,scanning electron microscopy,X-ray diffraction,tensile test,and hardness test were used.The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of sub-microcrystalline Fe2（Mo,Ti） Laves phase particles,which are stable at high temperatures.These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment.展开更多
Aims The tropical conservatism hypothesis(TCH)links environmental tolerance,diversification,dispersal and evolutionary history in explaining why warm,wet tropical regions harbor more species than colder,drier regions....Aims The tropical conservatism hypothesis(TCH)links environmental tolerance,diversification,dispersal and evolutionary history in explaining why warm,wet tropical regions harbor more species than colder,drier regions.The TCH is considered as a dominant explanation for broad-scale patterns of species richness across the globe,such as the latitudinal diversity gradient.At its core,the TCH predicts a positive relationship between clade age and tempera-ture.Here,I test this prediction using a data set of angiosperm tree assemblages from Malesia.Methods I assembled an altitudinal gradient of 15 communities of angio-sperm trees.I calculated the mean family age(MFA)of tree species for each community.I used ordinary regression analysis and spatial autoregression analysis to determine the relationships of species richness and MFA with elevation,temperature and precipitation.I used correlation analysis to assess relationships between paired variables.Important Findings MFA is negatively correlated with tree species richness,and increases with elevation and decreases with temperature for the alti-tudinal gradient.MFA remains significantly increasing with decreas-ing temperature along the altitudinal gradient after accounting for spatial autocorrelation in a species-ordination space.The negative relationship between clade age and temperature along the altitudi-nal gradient in Malesia is contrary to the TCH.展开更多
Aims Species assembly is shaped by the interactions among ecological and evolutionary processes.By integrating the niche conservatism and evolutionary history,the tropical niche conservatism hypoth-esis(TCH)has clarif...Aims Species assembly is shaped by the interactions among ecological and evolutionary processes.By integrating the niche conservatism and evolutionary history,the tropical niche conservatism hypoth-esis(TCH)has clarified species latitudinal diversity gradient at large scales.One of the TCH’s central predictions,though lack-ing empirical evidence,implies that positive relationship between clade age and temperature along the altitudinal gradient should also be observed.Thus,we aim to test this prediction using a data set derived from forest communities of Mt.Taibai,central China.Methods We systematically established 49 plots(20 m×30 m)along the north slope on Mt.Taibai,China.We calculated the mean family age(MFA)and its corresponding standardized values through rarefi-cation and standardization,for woody and herbaceous angiosperm assemblages in each community respectively.Generalized linear models with Akaike weight and correlation analysis was used to evaluate the relationships between MFA with seven environmental predictors.Important Findings For both woody and herbaceous assemblages,the standardized MFA showed significant decreasing tendencies along the eleva-tional gradient and positive associations with minimum temperature(measured as mean temperature of the coldest month).Additionally,minimum temperature is the dominant predictor compared with the others in the regression models.These findings are generally con-sistent with the age-related predictions of the TCH,but are contrary to the results of related studies conducted in tropical regions.展开更多
Quantitative assessment of natural internal variability and externally forced responses of Northern Hemisphere(NH)temperatures is necessary for understanding and attributing climate change signals during past warm and...Quantitative assessment of natural internal variability and externally forced responses of Northern Hemisphere(NH)temperatures is necessary for understanding and attributing climate change signals during past warm and cold periods.However,it remains a challenge to distinguish the robust internally generated variability from the observed variability.Here,largeensemble(70 member)simulations,Energy Balance Model simulation,temperature ensemble reconstruction,and three dominant external forcings(volcanic,solar,and greenhouse gas)were combined to estimate the internal variability of NH summer(June–August)temperatures over the past 2000 years(1–2000 CE).Results indicate that the Medieval Climate Anomaly was predominantly attributed to centennial-scale internal oscillation,accounting for an estimated 104%of the warming anomaly.In contrast,the Current Warm Period is influenced mainly by external forcing,contributing up to 90%of the warming anomaly.Internal temperature variability offsets cooling by volcanic eruptions during the Late Antique Little Ice Age.These findings have important implications for the attribution of past climate variability and improvement of future climate projections.展开更多
The C-repeat binding factors/dehydrationresponsive element binding protein 1 s(CBFs/DREB1 s)have been identified as major regulators of cold acclimation in many angiosperm plants.However,their origin and evolutionary ...The C-repeat binding factors/dehydrationresponsive element binding protein 1 s(CBFs/DREB1 s)have been identified as major regulators of cold acclimation in many angiosperm plants.However,their origin and evolutionary process associated to cold responsiveness are still lacking.By integrating multi-omics data of genomes,transcriptomes,and CBFs/DREB1 s genome-wide binding profiles,we unveil the origin and evolution of CBFs/DREB1 s and their regulatory network.Gene collinearity and phylogeny analyses show that CBF/DREB1 is an innovation evolved from tandem duplication-derived DREBⅢgene.A subsequent event of e-whole genome duplication led to two CBF/DREB1 archetypes(CladesⅠandⅡ)in ancient angiosperms.In contrast to cold-insensitivity of Clade I and their parent DREBⅢgenes,CladeⅡevolved a further innovation in cold-sensitive response and was stepwise expanded in eudicots and monocots by independent duplications.In geological time,the duplication events were mainly enriched around the Cretaceous-Paleogene(K-Pg)boundary and/or in the Late Cenozoic Ice Age,when the global average temperature significantly decreased.Consequently,the duplicated CBF/DREB1 genes contributed to the rewiring of CBFs/DREB1 s-regulatory network for cold tolerance.Altogether,our results highlight an origin and convergent evolution of CBFs/DREB1 s and their regulatory network probably for angiosperms adaptation to global cooling.展开更多
基金Under the auspices of National Natural Science Foundation of China(No.31460117,41877024)。
文摘Soil aggregate stability,as an important indicator of soil functions,may be affected by seasonal freezing and thawing(SFT)and land use in high cold and wet regions.Therefore,comprehensive understanding the effects of SFT on aggregate stability in orchards during winter and spring is crucial to develop appropriate management strategies that can effectively alleviate the degradation of soil quality to ensure sustainable development of orchard ecosystems.To determine the mechanism of degradation in orchard soil quality,the effects of SFT on the stability of water-stable aggregates were examined in apple-pear orchards(Pyrus ussuriensis var.ovoidea)of four different ages(11,25,40,and 63 yr)on 0 to 5%slopes before freezing and after thawing from October 2015 to June 2016 in Longjing City,Yanbian Prefecture,Northeast China,involving a comparison of planted versus adjacent uncultivated lands(control).Soil samples were collected to investigate water-stable aggregate stability in three incremental soil layers(0–20,20–40 and 40–60 cm).In the same samples,iron oxide,organic matter,and clay contents of the soil were also determined.Results showed that the destructive influences of SFT on water-stable aggregates were more pronounced with the increased orchards ages,and SFT exerted severe effects on water-stable aggregates of older orchards(40 and 63 yr)than juvenile orchards.Undergoing SFT,the soil instability index and the percentage of aggregate destruction increased by mean 0.15 mm and 1.86%,the degree of aggregation decreased by mean 1.32%,and the erosion resistance weakened,which consequently led to aggregate stability decreased.In addition,soil free,amorphous,and crystalline iron oxide as well as soil organic matter and clay contents are all important factors affecting the stability of water-stable aggregates,and their changes in their contents were consistent with those in the stability of water-stable aggregates.The results of this study suggest that long-term planting fruit trees can exacerbate the damaging effects of SFT on aggregate stability and further soil erosion increases and nutrient losses in an orchard,which hider sustainable use of soil and the productivity orchards.
文摘Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied.To investigate the microstructure and mechanical properties,optical microscopy,scanning electron microscopy,X-ray diffraction,tensile test,and hardness test were used.The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of sub-microcrystalline Fe2（Mo,Ti） Laves phase particles,which are stable at high temperatures.These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment.
文摘Aims The tropical conservatism hypothesis(TCH)links environmental tolerance,diversification,dispersal and evolutionary history in explaining why warm,wet tropical regions harbor more species than colder,drier regions.The TCH is considered as a dominant explanation for broad-scale patterns of species richness across the globe,such as the latitudinal diversity gradient.At its core,the TCH predicts a positive relationship between clade age and tempera-ture.Here,I test this prediction using a data set of angiosperm tree assemblages from Malesia.Methods I assembled an altitudinal gradient of 15 communities of angio-sperm trees.I calculated the mean family age(MFA)of tree species for each community.I used ordinary regression analysis and spatial autoregression analysis to determine the relationships of species richness and MFA with elevation,temperature and precipitation.I used correlation analysis to assess relationships between paired variables.Important Findings MFA is negatively correlated with tree species richness,and increases with elevation and decreases with temperature for the alti-tudinal gradient.MFA remains significantly increasing with decreas-ing temperature along the altitudinal gradient after accounting for spatial autocorrelation in a species-ordination space.The negative relationship between clade age and temperature along the altitudi-nal gradient in Malesia is contrary to the TCH.
基金This research was supported by the National Natural Science Foundation of China(No.41630750 and No.41271059)the National Key Basic Research Special Foundation of China(No.2011FY110300).
文摘Aims Species assembly is shaped by the interactions among ecological and evolutionary processes.By integrating the niche conservatism and evolutionary history,the tropical niche conservatism hypoth-esis(TCH)has clarified species latitudinal diversity gradient at large scales.One of the TCH’s central predictions,though lack-ing empirical evidence,implies that positive relationship between clade age and temperature along the altitudinal gradient should also be observed.Thus,we aim to test this prediction using a data set derived from forest communities of Mt.Taibai,central China.Methods We systematically established 49 plots(20 m×30 m)along the north slope on Mt.Taibai,China.We calculated the mean family age(MFA)and its corresponding standardized values through rarefi-cation and standardization,for woody and herbaceous angiosperm assemblages in each community respectively.Generalized linear models with Akaike weight and correlation analysis was used to evaluate the relationships between MFA with seven environmental predictors.Important Findings For both woody and herbaceous assemblages,the standardized MFA showed significant decreasing tendencies along the eleva-tional gradient and positive associations with minimum temperature(measured as mean temperature of the coldest month).Additionally,minimum temperature is the dominant predictor compared with the others in the regression models.These findings are generally con-sistent with the age-related predictions of the TCH,but are contrary to the results of related studies conducted in tropical regions.
基金This work was jointly funded by the National Natural Science Foundation of China(Grant Nos.41888101 and 42077406)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB26020000)+1 种基金the Key Research Program of the Institute of Geology&Geophysics,CAS(No.IGGCAS-201905)Feng Shi is funded by the Youth Innovation Promotion Association CAS.
文摘Quantitative assessment of natural internal variability and externally forced responses of Northern Hemisphere(NH)temperatures is necessary for understanding and attributing climate change signals during past warm and cold periods.However,it remains a challenge to distinguish the robust internally generated variability from the observed variability.Here,largeensemble(70 member)simulations,Energy Balance Model simulation,temperature ensemble reconstruction,and three dominant external forcings(volcanic,solar,and greenhouse gas)were combined to estimate the internal variability of NH summer(June–August)temperatures over the past 2000 years(1–2000 CE).Results indicate that the Medieval Climate Anomaly was predominantly attributed to centennial-scale internal oscillation,accounting for an estimated 104%of the warming anomaly.In contrast,the Current Warm Period is influenced mainly by external forcing,contributing up to 90%of the warming anomaly.Internal temperature variability offsets cooling by volcanic eruptions during the Late Antique Little Ice Age.These findings have important implications for the attribution of past climate variability and improvement of future climate projections.
基金supported by National Key R&D Program of China(2018YFD1000604)National Natural Science Foundation of China(31871233)Natural Science Foundation of Zhejiang Province(LY22C160005)。
文摘The C-repeat binding factors/dehydrationresponsive element binding protein 1 s(CBFs/DREB1 s)have been identified as major regulators of cold acclimation in many angiosperm plants.However,their origin and evolutionary process associated to cold responsiveness are still lacking.By integrating multi-omics data of genomes,transcriptomes,and CBFs/DREB1 s genome-wide binding profiles,we unveil the origin and evolution of CBFs/DREB1 s and their regulatory network.Gene collinearity and phylogeny analyses show that CBF/DREB1 is an innovation evolved from tandem duplication-derived DREBⅢgene.A subsequent event of e-whole genome duplication led to two CBF/DREB1 archetypes(CladesⅠandⅡ)in ancient angiosperms.In contrast to cold-insensitivity of Clade I and their parent DREBⅢgenes,CladeⅡevolved a further innovation in cold-sensitive response and was stepwise expanded in eudicots and monocots by independent duplications.In geological time,the duplication events were mainly enriched around the Cretaceous-Paleogene(K-Pg)boundary and/or in the Late Cenozoic Ice Age,when the global average temperature significantly decreased.Consequently,the duplicated CBF/DREB1 genes contributed to the rewiring of CBFs/DREB1 s-regulatory network for cold tolerance.Altogether,our results highlight an origin and convergent evolution of CBFs/DREB1 s and their regulatory network probably for angiosperms adaptation to global cooling.
