Investigating the timing and features of climate transitions in East Asia during the Holocene, via the sensitive response of ecosystems on the East Asian Summer Monsoon(EASM) boundary, is crucial for understanding the...Investigating the timing and features of climate transitions in East Asia during the Holocene, via the sensitive response of ecosystems on the East Asian Summer Monsoon(EASM) boundary, is crucial for understanding the underlying mechanisms that drive these transitions. This study presents highresolution palynological sequences for the period 6800–900 cal a B.P. from peat cores retrieved from the Arxan region in the Greater Khingan Range, northeast China. The lithological changes in the cores show that peat deposition began at 6430 cal a B.P. Regional vegetation was dominated by forest steppes, with Artemisia prevailing the vegetation landscape. Variations in Artemisia/Chenopodiaceae(A/C) pollen ratios, Principal Component Analysis(PCA) results, and charcoal concentration derived from the pollen data suggest that regional moisture availability increased from 6800 to 4200 cal a B.P., thereafter experiencing a marked decline. These changes in moisture availability causes fluctuations in the water table of the Arxan marshes, resulting in the expansion and reduction of the marshland, as demonstrated by swamp and aquatic palynomorphs, however did not disrupt subsequent peat deposition. In addition to the forcing of low-latitude summer insolation, the climate transition in northeast China around 4200 cal a B.P. aligns with a notable increase in sea ice in the western Okhotsk Sea during the late Holocene, which probably resulted in a reduction of EASM precipitation over the region. Our study offers new insights into the vegetation response observed in montane marshlands on the EASM boundary to climate transitions during the mid-late Holocene period.展开更多
[Objective] This study aims to analyze the natural regeneration characteristics and growth factors of two cut-over lands of Larix gmelini forests in Greater Khingan Mountains. [Method] A database was established based...[Objective] This study aims to analyze the natural regeneration characteristics and growth factors of two cut-over lands of Larix gmelini forests in Greater Khingan Mountains. [Method] A database was established based on the information of natural regeneration cut-over sample plots of Larix gmelini forests in Greater Khingan Mountains. Natural regeneration characteristics of clear-cutting sample plot and shelterwood-cutting sample plot of Larix gmelini in the northern regions of Greater Khingan Mountains were investigated by programming analysis. [Result] The natural regeneration of two principal felling systems was both good, and that of shelterwood-cutting sample plot was better. There were significant linear regression relationships among various growth factors of naturally regenerated plants. [Conclusion] This study provided scientific theoretical guidance for subsequent deforestation and regeneration in Greater Khingan Mountains.展开更多
The Greater Khingan Mountains （Daxinganling） are China＇s important ecological protective screen and also the region most sensitive to climate changes. To gain an in-depth understanding and reveal the climate change...The Greater Khingan Mountains （Daxinganling） are China＇s important ecological protective screen and also the region most sensitive to climate changes. To gain an in-depth understanding and reveal the climate change characteristic in this high-latitude, cold and data-insufficient region is of great importance to maintaining ecological safety and corre- sponding to global climate changes. In this article, the annual average temperature, precipi- tation and sunshine duration series were firstly constructed using tree-ring data and the me- teorological observation data. Then, using the climate tendency rate method, moving-t-testing method, Yamamoto method and wavelet analysis method, we have investigated the climate changes in the region during the past 307 years. Results indicate that, since 1707, the annual average temperature increased significantly, the precipitation increased slightly and the sun- shine duration decreased, with the tendency rates of 0.06~C/10a, 0.79 mm/10a and -5.15 h/10a, respectively （P〈~0.01）. Since the 21 st century, the period with the greatest increase of the annual average temperature （also with the greatest increase of precipitation） corresponds to the period with greatest decrease of sunshine duration. Three sudden changes of the an- nual average temperature and sunshine duration occurred in this period while two sudden changes of precipitation occurred. The strong sudden-change years of precipitation and sunshine duration are basically consistent with the sudden-change years of annual average temperature, suggesting that in the mid-1860s, the climatic sudden change or transition really existed in this region. In the time domain, the climatic series of this region exhibit obvious local variation characteristics. The annual average temperature and sunshine duration exhibit the periodic variations of 25 years while the precipitation exhibits a periodic variation of 20 years. Based on these periodic characteristics, one can infer that in the period from 2013 to 2030, the temperature will be at a high-temperature stage, the precipitation will be at an abundant-precipitation stage and the sunshine duration will be at an less-sunshine stage. In terms of spatial distribution, the leading distribution type of the annual average temperature in this region shows integrity, i.e：, it is easily higher or lower in the whole region; and the second distribution type is more （or less） in the southwest parts and less （or more） in the northeast parts. Precipitation and sunshine duration exhibit complex spatial distribution and include four spatial distribution types. The present study can provide scientific basis for the security in- vestigation of homeland, ecological and water resources as well as economic development programming in China＇s northern borders.展开更多
Coal-bearing strata are widespread in the western Great Khingan Mountains. Abundant coal resources have been found in the Jurassic Alatanheli Groups, the Cretaceous Bayanhua Groups, the Damoguaihe Formation and the Yi...Coal-bearing strata are widespread in the western Great Khingan Mountains. Abundant coal resources have been found in the Jurassic Alatanheli Groups, the Cretaceous Bayanhua Groups, the Damoguaihe Formation and the Yimin Formation. The organic geochemical characteristics were analyzed in combination with hydrocarbon source rock evaluation and molecular organic geochemistry experiments, and the coal gas potential of coal seams was evaluated. The source rock evaluation results indicated that the Mesozoic coal samples have the characteristics of high organic matter abundance(TOC>30%), low maturity(Ro values of approximately 0.6%), and type Ⅲ composition. The hydrocarbon generation potentials of the Alatanheli Groups and Bayanhua Groups are high, while the generation potentials of the Damoguaihe Formation and the Yimin Formation are low. The results of geochemistry show that the depositional environment of the coal seam was a lacustrine, oxidizing environment with a low salinity, and the source of the organic matter was mainly higher plants. Affected by weak degradation, the coal seams mainly formed low-maturity gas of thermal catalytic origin. The Cretaceous coal seams contain a large amount of phytoplankton groups deposited in a low-stability environment affected by a transgression event, and the potential range varied widely. For the Jurassic coal seams, the depositional environment was more stable, and the coal seams feature a higher coal-forming gas potential.展开更多
Accurate assessment of postfire vegetation recovery is important for forest management and the conservation of species diversity.Topography is an important factor aff ecting vegetation recovery but whether species com...Accurate assessment of postfire vegetation recovery is important for forest management and the conservation of species diversity.Topography is an important factor aff ecting vegetation recovery but whether species composition varies with diff erent recovery stages and between valleys and slopes is unclear.Using fi eld data and a space-for-time substitution method,we quantifi ed species richness and diversity to obtain the successional trajectories of valleys and slopes.We surveyed the species of 10 burned areas from 1986 to 2010 in the Greater Khingan Mountains in northeastern China,and found that with increasing postfi re recovery time,species richness in both valleys and slopes gradually decreased.However,species richness in valleys was relatively higher.Shrubs recovered rapidly in the valleys,and species diversity maximized approximately 11 years after fi re.However,it maximized 17–18 years after fi re on the slopes.Numerous shade-tolerant species were present in the valleys 11 years after fi re but not until after 18 years on slopes.Larch appeared earlier than 11 years after fi re and its recovery was slow in the valleys but appeared quickly on slopes and established dominance early.Our study provides some new insights into vegetation succession after fi re at local scales.After fi re,the vegetation recovery processes diff er with topography and it aff ects the initial rate of recovery and species composition at diff erent successional stages.展开更多
Fire is an important disturbance in terms of forest management.A comprehensive understanding of the relationships between the spatial distribution of fire occurrence and its driving factors are critical for effective ...Fire is an important disturbance in terms of forest management.A comprehensive understanding of the relationships between the spatial distribution of fire occurrence and its driving factors are critical for effective forest fire management.To reveal biogeoclimatic and anthropogenic influences,this study introduced a geographical detector model to quantitatively examine the effects of multiple individual factors and their combinations on spatial patterns of fire occurrence in the Greater Khingan Mountains between 1980 and 2009.The geographical detector computes the explanatory power(q value)to measure the connection between driving factors and spatial distributions of fire occurrence.Kernel density estimation revealed the spatial variability of fire occurrence which was impacted by bandwidth.30 km might be the optimal bandwidth in this study.The biogeoclimatic and anthropogenic effects were explored using topography,climate,vegetation,and human activity factors as proxies.Our results indicated that solar radiation had the most influence on the spatial pattern of fire occurrence in the study area.Meanwhile,Normalized Difference Vegetation Index,temperature,wind speed,and vegetation type were determined as the major driving factors.For various groups of driving factors,climate variables were the dominant factors for the density of fire occurrence,while vegetation exerted a strong influence.The interactions between the driving factors had a more significant impact than a single factor.Individually,the factors in the topography and human activity groups exhibited weaker influences.However,their effects were enhanced when combined with climate and vegetation factors.This study improves our understanding of various driving factors and their combined influences on fire occurrences of the study area in a spatial context.The findings of this study verify that the geographical detector is applicable in revealing the driving factors of fire occurrence.展开更多
Objective Typical Early Cretaceous non-marine bivalve fossils from Eastern Asia are represented by the Arguniella-Sphaerium assemblage,and they were important members of the Jehol Biota.Historically,the genus Arguniel...Objective Typical Early Cretaceous non-marine bivalve fossils from Eastern Asia are represented by the Arguniella-Sphaerium assemblage,and they were important members of the Jehol Biota.Historically,the genus Arguniella in western Liaoning had been mistakenly identified as the Jurassic Ferganoconcha,re-identified as Arguniella with。展开更多
基金supported by the National Key Research and Development Program of China (Grant NO.2022YFF0801501)the National Natural Science Foundation of China (Grant NOs.42171157,41907379,and 42101146)+2 种基金Postgraduate Research & Practice Innovation Program of Jiangsu Province (SJCX25_2041)Large Instruments Open Foundation of Nantong University (KFJN2474)Jiangsu Province College Students Innovation and Entrepreneurship Training Program (Grant NOs.S202510304190 and S202510304188)。
文摘Investigating the timing and features of climate transitions in East Asia during the Holocene, via the sensitive response of ecosystems on the East Asian Summer Monsoon(EASM) boundary, is crucial for understanding the underlying mechanisms that drive these transitions. This study presents highresolution palynological sequences for the period 6800–900 cal a B.P. from peat cores retrieved from the Arxan region in the Greater Khingan Range, northeast China. The lithological changes in the cores show that peat deposition began at 6430 cal a B.P. Regional vegetation was dominated by forest steppes, with Artemisia prevailing the vegetation landscape. Variations in Artemisia/Chenopodiaceae(A/C) pollen ratios, Principal Component Analysis(PCA) results, and charcoal concentration derived from the pollen data suggest that regional moisture availability increased from 6800 to 4200 cal a B.P., thereafter experiencing a marked decline. These changes in moisture availability causes fluctuations in the water table of the Arxan marshes, resulting in the expansion and reduction of the marshland, as demonstrated by swamp and aquatic palynomorphs, however did not disrupt subsequent peat deposition. In addition to the forcing of low-latitude summer insolation, the climate transition in northeast China around 4200 cal a B.P. aligns with a notable increase in sea ice in the western Okhotsk Sea during the late Holocene, which probably resulted in a reduction of EASM precipitation over the region. Our study offers new insights into the vegetation response observed in montane marshlands on the EASM boundary to climate transitions during the mid-late Holocene period.
基金Supported by Forestry Industry Public Welfare Project of State Forestry Bureau of China(201204205)~~
文摘[Objective] This study aims to analyze the natural regeneration characteristics and growth factors of two cut-over lands of Larix gmelini forests in Greater Khingan Mountains. [Method] A database was established based on the information of natural regeneration cut-over sample plots of Larix gmelini forests in Greater Khingan Mountains. Natural regeneration characteristics of clear-cutting sample plot and shelterwood-cutting sample plot of Larix gmelini in the northern regions of Greater Khingan Mountains were investigated by programming analysis. [Result] The natural regeneration of two principal felling systems was both good, and that of shelterwood-cutting sample plot was better. There were significant linear regression relationships among various growth factors of naturally regenerated plants. [Conclusion] This study provided scientific theoretical guidance for subsequent deforestation and regeneration in Greater Khingan Mountains.
基金National Natural Science Foundation of China,No.41165005,No.40865005
文摘The Greater Khingan Mountains （Daxinganling） are China＇s important ecological protective screen and also the region most sensitive to climate changes. To gain an in-depth understanding and reveal the climate change characteristic in this high-latitude, cold and data-insufficient region is of great importance to maintaining ecological safety and corre- sponding to global climate changes. In this article, the annual average temperature, precipi- tation and sunshine duration series were firstly constructed using tree-ring data and the me- teorological observation data. Then, using the climate tendency rate method, moving-t-testing method, Yamamoto method and wavelet analysis method, we have investigated the climate changes in the region during the past 307 years. Results indicate that, since 1707, the annual average temperature increased significantly, the precipitation increased slightly and the sun- shine duration decreased, with the tendency rates of 0.06~C/10a, 0.79 mm/10a and -5.15 h/10a, respectively （P〈~0.01）. Since the 21 st century, the period with the greatest increase of the annual average temperature （also with the greatest increase of precipitation） corresponds to the period with greatest decrease of sunshine duration. Three sudden changes of the an- nual average temperature and sunshine duration occurred in this period while two sudden changes of precipitation occurred. The strong sudden-change years of precipitation and sunshine duration are basically consistent with the sudden-change years of annual average temperature, suggesting that in the mid-1860s, the climatic sudden change or transition really existed in this region. In the time domain, the climatic series of this region exhibit obvious local variation characteristics. The annual average temperature and sunshine duration exhibit the periodic variations of 25 years while the precipitation exhibits a periodic variation of 20 years. Based on these periodic characteristics, one can infer that in the period from 2013 to 2030, the temperature will be at a high-temperature stage, the precipitation will be at an abundant-precipitation stage and the sunshine duration will be at an less-sunshine stage. In terms of spatial distribution, the leading distribution type of the annual average temperature in this region shows integrity, i.e：, it is easily higher or lower in the whole region; and the second distribution type is more （or less） in the southwest parts and less （or more） in the northeast parts. Precipitation and sunshine duration exhibit complex spatial distribution and include four spatial distribution types. The present study can provide scientific basis for the security in- vestigation of homeland, ecological and water resources as well as economic development programming in China＇s northern borders.
基金the National Natural Science Foundation of China(Grant No.41430322)The anonymous journal reviewers and editors are acknowledged for their valuable comments.
文摘Coal-bearing strata are widespread in the western Great Khingan Mountains. Abundant coal resources have been found in the Jurassic Alatanheli Groups, the Cretaceous Bayanhua Groups, the Damoguaihe Formation and the Yimin Formation. The organic geochemical characteristics were analyzed in combination with hydrocarbon source rock evaluation and molecular organic geochemistry experiments, and the coal gas potential of coal seams was evaluated. The source rock evaluation results indicated that the Mesozoic coal samples have the characteristics of high organic matter abundance(TOC>30%), low maturity(Ro values of approximately 0.6%), and type Ⅲ composition. The hydrocarbon generation potentials of the Alatanheli Groups and Bayanhua Groups are high, while the generation potentials of the Damoguaihe Formation and the Yimin Formation are low. The results of geochemistry show that the depositional environment of the coal seam was a lacustrine, oxidizing environment with a low salinity, and the source of the organic matter was mainly higher plants. Affected by weak degradation, the coal seams mainly formed low-maturity gas of thermal catalytic origin. The Cretaceous coal seams contain a large amount of phytoplankton groups deposited in a low-stability environment affected by a transgression event, and the potential range varied widely. For the Jurassic coal seams, the depositional environment was more stable, and the coal seams feature a higher coal-forming gas potential.
基金funded by the National Natural Science Foundation of China(No.41871103).
文摘Accurate assessment of postfire vegetation recovery is important for forest management and the conservation of species diversity.Topography is an important factor aff ecting vegetation recovery but whether species composition varies with diff erent recovery stages and between valleys and slopes is unclear.Using fi eld data and a space-for-time substitution method,we quantifi ed species richness and diversity to obtain the successional trajectories of valleys and slopes.We surveyed the species of 10 burned areas from 1986 to 2010 in the Greater Khingan Mountains in northeastern China,and found that with increasing postfi re recovery time,species richness in both valleys and slopes gradually decreased.However,species richness in valleys was relatively higher.Shrubs recovered rapidly in the valleys,and species diversity maximized approximately 11 years after fi re.However,it maximized 17–18 years after fi re on the slopes.Numerous shade-tolerant species were present in the valleys 11 years after fi re but not until after 18 years on slopes.Larch appeared earlier than 11 years after fi re and its recovery was slow in the valleys but appeared quickly on slopes and established dominance early.Our study provides some new insights into vegetation succession after fi re at local scales.After fi re,the vegetation recovery processes diff er with topography and it aff ects the initial rate of recovery and species composition at diff erent successional stages.
基金funded by the National Natural Science Foundation of China(Grant No.41601438)Fundamental Research Funds for the Central Universities(Grant NO.2412019FZ002)。
文摘Fire is an important disturbance in terms of forest management.A comprehensive understanding of the relationships between the spatial distribution of fire occurrence and its driving factors are critical for effective forest fire management.To reveal biogeoclimatic and anthropogenic influences,this study introduced a geographical detector model to quantitatively examine the effects of multiple individual factors and their combinations on spatial patterns of fire occurrence in the Greater Khingan Mountains between 1980 and 2009.The geographical detector computes the explanatory power(q value)to measure the connection between driving factors and spatial distributions of fire occurrence.Kernel density estimation revealed the spatial variability of fire occurrence which was impacted by bandwidth.30 km might be the optimal bandwidth in this study.The biogeoclimatic and anthropogenic effects were explored using topography,climate,vegetation,and human activity factors as proxies.Our results indicated that solar radiation had the most influence on the spatial pattern of fire occurrence in the study area.Meanwhile,Normalized Difference Vegetation Index,temperature,wind speed,and vegetation type were determined as the major driving factors.For various groups of driving factors,climate variables were the dominant factors for the density of fire occurrence,while vegetation exerted a strong influence.The interactions between the driving factors had a more significant impact than a single factor.Individually,the factors in the topography and human activity groups exhibited weaker influences.However,their effects were enhanced when combined with climate and vegetation factors.This study improves our understanding of various driving factors and their combined influences on fire occurrences of the study area in a spatial context.The findings of this study verify that the geographical detector is applicable in revealing the driving factors of fire occurrence.
基金funded by the National Science Foundation of China(41688103)Chinese National Mineral Rock and Fossil Specimens Resource Center(2020)ProgramSelf-determined Foundation of Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources of China(Grant No:DBY-ZZ-19-18)。
文摘Objective Typical Early Cretaceous non-marine bivalve fossils from Eastern Asia are represented by the Arguniella-Sphaerium assemblage,and they were important members of the Jehol Biota.Historically,the genus Arguniella in western Liaoning had been mistakenly identified as the Jurassic Ferganoconcha,re-identified as Arguniella with。
