In this paper, an updated vegetation map of the permafrost zone in the Qinghai-Tibet Plateau (QTP) was delineated. The vegetation map model was extracted from vegetation sampling with remote sensing (RS) datasets ...In this paper, an updated vegetation map of the permafrost zone in the Qinghai-Tibet Plateau (QTP) was delineated. The vegetation map model was extracted from vegetation sampling with remote sensing (RS) datasets by decision tree method. The spatial resolution of the map is 1 km×1 kin, and in it the alpine swamp meadow is firstly distinguished in the high-altitude areas. The results showed that the total vegetated area in the permafrost zone of the QTP is 1,201,751 km2. In the vegetated region, 50,260 km2 is the areas of alpine swamp meadow, 583,909 km2 for alpine meadow, 332,754 km2 for alpine steppe, and 234,828 km2 for alpine desert. This updated vegetation map in permafrost zone of QTP could provide more details about the distribution of alpine vegetation types for studying the vegetation mechanisms in the land surface processes of highaltitude areas.展开更多
Soil microbial communities are primarily regulated by environmental temperature. Our study investigated the effects of global warming on soil microbial community composition as measured via phospholipid fatty acid (P...Soil microbial communities are primarily regulated by environmental temperature. Our study investigated the effects of global warming on soil microbial community composition as measured via phospholipid fatty acid (PLFA) analysis and soil chemical characteristics in relation to soil depth in a dragon spruce plantation and a spruce-fir-dominated natural forestin the Eastern Tibetan Plateau. Opentop chambers were utilized to increase the soil and air temperature. Soil samples were collected from the o-10 cm, 10-20cm, and 20-30 cm layers after a 4-year warming. Our results showed that the soil microbial community and the contents of TC (Total carbon), TN (Total nitrogen). NO3-. and NH4+ responded differently to warming in the two contrasting forests, especially at the 0-10 cm soil depth. Warming increased soil microbial biomass at the 0-20 cm depth of soil in natural forest but reduced it at the o-lo cm depth ofsoil in the plantation. In contrast, the TC and TN contents were reduced in most soil layers of a natural forest but increased in all of the soil layers of the plantation under warming conditions. This result suggested that the effects of warming on soil microbial community and soil C and N pools would differ according to soil depth and forest types; thus, the two contrasting forests would under go differing changes following the future climate warming in this region.展开更多
Though aboveground biomass(AGB) has an important contribution to the global carbon cycle,the information about storage and climatic effects of AGB is scare in Three-River Source Region(TRSR)shrub ecosystems. This stud...Though aboveground biomass(AGB) has an important contribution to the global carbon cycle,the information about storage and climatic effects of AGB is scare in Three-River Source Region(TRSR)shrub ecosystems. This study investigated AGB storage and its climatic controls in the TRSR alpine shrub ecosystems using data collected from 23 sites on the Tibetan Plateau from 2011 to 2013. We estimated the AGB storage(both shrub layer biomass and grass layer biomass) in the alpine shrubs as 37.49 Tg, with an average density of 1447.31 g m^(-2). Biomass was primarily accumulated in the shrub layer, which accounted for 92% of AGB, while the grass layer accounted for only 8%. AGB significantly increased with the mean annual temperature(P < 0.05). The effects of the mean annual precipitation on AGB were not significant. These results suggest that temperature,rather than precipitation, has significantly effects on of aboveground vegetation growth in the TRSR alpine shrub ecosystems. The actual and potential increase in AGB density was different due to global warming varies among different regions of the TRSR. We conclude that long-term monitoring of dynamic changes is necessary to improve the accuracy estimations of potential AGB carbon sequestration across the TRSR alpine shrub ecosystems.展开更多
Tibet is located at the southwest boundary of China. It is the main body of the Qinghai-Tibet Plateau, the highest and the youngest plateau in the world. Owing to complicated geology, Neo-tectonic movements, geomorpho...Tibet is located at the southwest boundary of China. It is the main body of the Qinghai-Tibet Plateau, the highest and the youngest plateau in the world. Owing to complicated geology, Neo-tectonic movements, geomorphology, climate and plateau environment, various mountain hazards, such as debris flow, flash flood, landslide, collapse, snow avalanche and snow drifts, are widely distributed along the Jinsha River (the upper reaches of the Yangtze River), the Nu River and the Lancang River in the east, and the Yarlungzangbo River, the Pumqu River and the Poiqu River in the south and southeast of Tibet. The distribution area of mountain hazards in Tibet is about 589,000 km2, 49.3% of its total territory. In comparison to other mountain regions in China, mountain hazards in Tibet break out unexpectedly with tremendously large scale and endanger the traffic lines, cities and towns, farmland, grassland, mountain environment, and make more dangers to the neighboring countries, such as Nepal, India, Myanmar and Bhutan. To mitigate mountain hazards, some suggestions are proposed in this paper, such as strengthening scientific research, enhancing joint studies, hazards mitigation planning, hazards warning and forecasting, controlling the most disastrous hazards and forbidding unreasonable human exploring activities in mountain areas.展开更多
The source area of the Yellow River is located in the northeastern Tibetan Plateau, and is a high-elevation region with the annual mean temperature of -3.9℃. The ice-wedge pseudomorphs discovered in this region are r...The source area of the Yellow River is located in the northeastern Tibetan Plateau, and is a high-elevation region with the annual mean temperature of -3.9℃. The ice-wedge pseudomorphs discovered in this region are recognized as two types. One was found in sandy gravel beds of the second terrace of the Yellow River. This ice-wedge pseudomorph is characterized by higher ratio of breadth/depth, and are 1-1.4 m wide and about 1 m deep. The bottom border of the ice-wedge pseudomorph is round arc in section. Another discovered in the pedestal of the second terrace has lower ratio of width/depth, and is o.3-1.0 m wide and 1-2 m deep. Its bottom border is sharp. Based on the TL dating, the former was formed at the middleHolocene (5.69±0.43 ka BP and 5.43±0.41 ka BP), that is, the Megathermal, and the latter was formed at the late Last Glacial Maximum (13.49±1.43 ka BP). Additionally, the thawing-freezing folders discovered in the late Late Pleistocene proluvium are 39.83±3.84 ka BP in age. The study on the ice-wedge pseudomorphs showed that the air temperature was lowered by up to 6-7℃ in the source area of the Yellow River when the ice-wedge pseudomorphs and thawing-freezing folds developed.展开更多
The carbon pool stored in soil carbonate is comparable to the soil organic carbon.Therefore,secondary calcite precipitation in supersaturated catchment could be an important,yet poorly constrained,carbon sink within t...The carbon pool stored in soil carbonate is comparable to the soil organic carbon.Therefore,secondary calcite precipitation in supersaturated catchment could be an important,yet poorly constrained,carbon sink within the modern global carbon cycle.The chemical analysis of some dissolved species transported by rivers,such as elevated Sr/Ca and Mg/Ca ratios but also heavy stable Ca isotopic compositions,witness the formation of secondary calcite in rivers draining arid regions.However,in areas affected by active tectonics and rapid physical erosion,co-variations in the fluvial Sr/Ca and Mg/Ca ratios could also be related to incongruent carbonate weathering processes.Here,we present a model to assess the roles played by incongruent carbonate dissolution and secondary calcite precipitation in modern weathering processes.We tested and applied the model to rivers draining the Himalayan–Tibetan region.The results suggest that regional aridity in the drainage basin promotes carbon sequestration as secondary carbonate but that for a given runoff,incongruent dissolution of carbonate possibly related to rapid physical erosion amplifies such sequestration.The isotopic compositions(^(13)C/^(12)C and^(18)O/^(16)O)of detrital carbonate transported by the main rivers in South and South-East Tibet imply that around 1%of the suspended material transported by those rivers corresponds to secondary carbonate and can represent between 5%and 15%of the alkalinity flux.Most of these alkalinity transported as particulate material is,nevertheless related to the weathering of carbonate lithologies and is also subjected to dissolution prior its final storage in sedimentary basins.However,on glacial-interglacial timescale this will amplify the significant role of mountain weathering on climatic variations.展开更多
Aboveground biomass in grasslands of the Qinghai-Tibet Plateau has displayed an overall increasing trend during 2003–2016, which is profoundly influenced by climate change. However, the responses of different biomes ...Aboveground biomass in grasslands of the Qinghai-Tibet Plateau has displayed an overall increasing trend during 2003–2016, which is profoundly influenced by climate change. However, the responses of different biomes show large discrepancies, in both size and magnitude. By applying partial least squares regression, we calculated the correlation between peak aboveground biomass and mean monthly temperature and monthly total precipitation in the preceding 12 months for three different grassland types(alpine steppe, alpine meadow, and temperate steppe) on the central and eastern Qinghai-Tibet Plateau. The results showed that mean temperature in most preceding months was positively correlated with peak aboveground biomass of alpine meadow and alpine steppe, while mean temperature in the preceding October and February to June was significantly negatively correlated with peak aboveground biomass of temperate steppe. Precipitation in all months had a promoting effect on biomass of alpine meadow, but its correlations with biomass of alpine steppe and temperate steppe were inconsistent. It is worth noting that, in a warmer, wetter climate, peak aboveground biomass of alpine meadow would increase more than that of alpine steppe, while that of temperate steppe would decrease significantly, providing support for the hypothesis of conservative growth strategies by vegetation in stressed ecosystems.展开更多
Abstract Sisorid catfishes are primarily limited in distribution to rivers of the Himalayan region and Tibetan Plateau. These species have external morphologies that are adapted for extremely fast-flowing riverine sys...Abstract Sisorid catfishes are primarily limited in distribution to rivers of the Himalayan region and Tibetan Plateau. These species have external morphologies that are adapted for extremely fast-flowing riverine systems. Given the diversity of the group and the above qualities of these catfishes, this lineage serves as an ideal group for inferring the geological history of this region based on their phylogenetic relationships reflecting evolu- tionary history. We sequenced the complete mitochondrial genome and four nuclear genes of representative sisorids distributed across river systems in China. Phylogenetic analyses strongly support the monophyly of the Sisoridae and the glyptosternoids. An analysis of the reconstructed ancestral states derived from inferred genealogical relationships suggests that the evolution of this lineage was accompanied by convergent evolution in morphological traits that were presumably in response to environmental pressure involving the rapid flowing river system that were generated during the uplift of the Tibetan Plateau (UTP). Molecular dating indicates that the Chinese sisorids and the glyptosternoids originated at the later Miocene (~ 10.9-9.8 Mya), and with further biogeographic analyses indicates that the species of Sisoridae likely originated from a widely distributed ancestor. Moreover, the divergence of the Sisoridae in China can be divided into two phases consis- tent with the UTP. All of these results indicate that the diversification and dispersal events in this lineage occurred as a result of drainage systems formed during and after the UTP in the late Miocene and Quaternary periods.展开更多
Placing precise constraints on the timing of the India-Asia continental collision is essential to understand the successive geological and geomorphological evolution of the orogenic belt as well as the uplift mechanis...Placing precise constraints on the timing of the India-Asia continental collision is essential to understand the successive geological and geomorphological evolution of the orogenic belt as well as the uplift mechanism of the Tibetan Plateau and their effects on climate,environment and life.Based on the extensive study of the sedimentary record on both sides of the Yarlung-Zangbo suture zone in Tibet,we review here the present state of knowledge on the timing of collision onset,discuss its possible diachroneity along strike,and reconstruct the early structural and topographic evolution of the Himalayan collided range.We define continent-continent collision as the moment when the oceanic crust is completely consumed at one point where the two continental margins come into contact.We use two methods to constrain the timing of collision onset:(1) dating the provenance change from Indian to Asian recorded by deep-water turbidites near the suture zone,and(2) dating the age of unconformities on both sides of the suture zone.The first method allowed us to constrain precisely collision onset as middle Palaeocene(59±l Ma).Marine sedimentation persisted in the collisional zone for another 20-25 Ma locally in southern Tibet,and molassic-type deposition in the Indian foreland basin did not begin until another 10-15 Ma later.Available sedimentary evidence failed to firmly document any significant diachroneity of collision onset from the central Himalaya to the western Himalaya and Pakistan so far.Based on the Cenozoic stratigraphic record of the Tibetan Himalaya,four distinct stages can be identified in the early evolution of the Himalayan orogen:(1) middle Palaeocene-early Eocene earliest Eohimalayan stage(from 59 to 52 Ma):collision onset and filling of the deep-water trough along the suture zone while carbonate platform sedimentation persisted on the inner Indian margin;(2) early-middle Eocene early Eohimalayan stage(from 52 to 41 or 35 Ma):filling of intervening seaways and cessation of marine sedimentation;(3) late Eocene-Oligocene late Eohimalayan stage(from 41 to 25 Ma):huge gap in the sedimentary record both in the collision zone and in the Indian foreland;and(4) late Oligocene-early Miocene early Neohimalayan stage(from 26 to 17 Ma):rapid Himalayan growth and onset of molasse-type sedimentation in the Indian foreland basin.展开更多
There are a series of special mountain soils on the Tibetan Plateau of China in an alpine environment for the high altitude. However, very few studies have focused on major soil elements in relation to soil formation ...There are a series of special mountain soils on the Tibetan Plateau of China in an alpine environment for the high altitude. However, very few studies have focused on major soil elements in relation to soil formation in this area. Aluminum (Al), iron (Fe), calcium (Ca), sodium (Na), potassium (K) and magnesium (Mg) contents of 237 topsoil samples covering a 2.8-km altitudinal gradient in uncultivated areas along the Qinghai-Tibet Railway of China were measured using inductively coupled plasma atomic emission spectroscopy. The spatial distribution of the elements and its relationship to the parent rocks and climatic parameters were analyzed. Soils along the gradient are derived from a range of parent materials, but most are less than 30 cm deep with little development (Cambisols). Soil Al, Fe and Mg contents showed a decreasing trend from the start station (Xining Station) to end station (Lhasa Station) of the Qinghai-Tibet Railway, whereas soil K and Na contents were relative stable from Xining Station to the Kunlun Mountains and then increased gradually. Soil Ca content was lower in the southern part of the Tanggula Mountains. The major soil element contents clearly reflected the parent rock and climatic influences. Soils with higher Ca content appeared in areas with Ca-Mg carbonate rocks, soils with higher Al were found in areas with silicate-rich and high-Al silicate clastic rocks and silicate-rich aluminosilicate loose sediments. Soils with higher K and Na contents appeared in areas with high-K, high-Na and silicate-rich aluminosilicate rocks. Soil Na and K contents were affected by temperature, whereas the contents of Mg, Fe, Ca and Al were more affected by precipitation. Soil Na and K contents increased with increasing temperatures, whereas the contents of Mg, Fe, Ca and Al decreased with increasing precipitation. This analysis provides a relationship between soil properties and rapidly changing environmental conditions. The data can be used to investigate the effect of the climate or land use change on soil properties.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.41101055)the Hundred Talents Program of the Chinese Academy of Sciences granted to Tonghua Wu (Grant No.51Y251571)the “National Basic Research Program of China (973 Program)” (Grant No.2010CB951402)
文摘In this paper, an updated vegetation map of the permafrost zone in the Qinghai-Tibet Plateau (QTP) was delineated. The vegetation map model was extracted from vegetation sampling with remote sensing (RS) datasets by decision tree method. The spatial resolution of the map is 1 km×1 kin, and in it the alpine swamp meadow is firstly distinguished in the high-altitude areas. The results showed that the total vegetated area in the permafrost zone of the QTP is 1,201,751 km2. In the vegetated region, 50,260 km2 is the areas of alpine swamp meadow, 583,909 km2 for alpine meadow, 332,754 km2 for alpine steppe, and 234,828 km2 for alpine desert. This updated vegetation map in permafrost zone of QTP could provide more details about the distribution of alpine vegetation types for studying the vegetation mechanisms in the land surface processes of highaltitude areas.
基金supported by the National Natural Science Foundation of China(Grant Nos.31570477,31100446)the Research Fund of the Ecological Security and Protection Key Laboratory of Sichuan Province,Mianyang Normal University(Grant No.EPS201302)the Research Fund of State Key Laboratory of Soil and Sustainable Agriculture,Nanjing Institute of Soil Science,Chinese Academy of Science(Grant No.Y412201415)
文摘Soil microbial communities are primarily regulated by environmental temperature. Our study investigated the effects of global warming on soil microbial community composition as measured via phospholipid fatty acid (PLFA) analysis and soil chemical characteristics in relation to soil depth in a dragon spruce plantation and a spruce-fir-dominated natural forestin the Eastern Tibetan Plateau. Opentop chambers were utilized to increase the soil and air temperature. Soil samples were collected from the o-10 cm, 10-20cm, and 20-30 cm layers after a 4-year warming. Our results showed that the soil microbial community and the contents of TC (Total carbon), TN (Total nitrogen). NO3-. and NH4+ responded differently to warming in the two contrasting forests, especially at the 0-10 cm soil depth. Warming increased soil microbial biomass at the 0-20 cm depth of soil in natural forest but reduced it at the o-lo cm depth ofsoil in the plantation. In contrast, the TC and TN contents were reduced in most soil layers of a natural forest but increased in all of the soil layers of the plantation under warming conditions. This result suggested that the effects of warming on soil microbial community and soil C and N pools would differ according to soil depth and forest types; thus, the two contrasting forests would under go differing changes following the future climate warming in this region.
基金funded by the National Science and Technology Support Project (Grant No.2014BAC05B01)National Program on Basic Work Project of China (Grant No.2015FY11030001)+1 种基金Strategic Priority Research Program of CAS (Grant No.XDA0505030304)National Natural Science Foundation of China (Grant No.40801076)
文摘Though aboveground biomass(AGB) has an important contribution to the global carbon cycle,the information about storage and climatic effects of AGB is scare in Three-River Source Region(TRSR)shrub ecosystems. This study investigated AGB storage and its climatic controls in the TRSR alpine shrub ecosystems using data collected from 23 sites on the Tibetan Plateau from 2011 to 2013. We estimated the AGB storage(both shrub layer biomass and grass layer biomass) in the alpine shrubs as 37.49 Tg, with an average density of 1447.31 g m^(-2). Biomass was primarily accumulated in the shrub layer, which accounted for 92% of AGB, while the grass layer accounted for only 8%. AGB significantly increased with the mean annual temperature(P < 0.05). The effects of the mean annual precipitation on AGB were not significant. These results suggest that temperature,rather than precipitation, has significantly effects on of aboveground vegetation growth in the TRSR alpine shrub ecosystems. The actual and potential increase in AGB density was different due to global warming varies among different regions of the TRSR. We conclude that long-term monitoring of dynamic changes is necessary to improve the accuracy estimations of potential AGB carbon sequestration across the TRSR alpine shrub ecosystems.
基金This research is supported by the West Key Research Project of the National Natural Science Foundation of China(No.90202007)the Researcher Introduced Project of Chengdu Institute of Mountain Hazards and Environment,the Chinese Academy of Sciences&Ministry of Water Conservancy(Y1006).
文摘Tibet is located at the southwest boundary of China. It is the main body of the Qinghai-Tibet Plateau, the highest and the youngest plateau in the world. Owing to complicated geology, Neo-tectonic movements, geomorphology, climate and plateau environment, various mountain hazards, such as debris flow, flash flood, landslide, collapse, snow avalanche and snow drifts, are widely distributed along the Jinsha River (the upper reaches of the Yangtze River), the Nu River and the Lancang River in the east, and the Yarlungzangbo River, the Pumqu River and the Poiqu River in the south and southeast of Tibet. The distribution area of mountain hazards in Tibet is about 589,000 km2, 49.3% of its total territory. In comparison to other mountain regions in China, mountain hazards in Tibet break out unexpectedly with tremendously large scale and endanger the traffic lines, cities and towns, farmland, grassland, mountain environment, and make more dangers to the neighboring countries, such as Nepal, India, Myanmar and Bhutan. To mitigate mountain hazards, some suggestions are proposed in this paper, such as strengthening scientific research, enhancing joint studies, hazards mitigation planning, hazards warning and forecasting, controlling the most disastrous hazards and forbidding unreasonable human exploring activities in mountain areas.
基金the Ministry of Land and Resource of P.R.China the National Natural Science Foundation of China(No.40172062).
文摘The source area of the Yellow River is located in the northeastern Tibetan Plateau, and is a high-elevation region with the annual mean temperature of -3.9℃. The ice-wedge pseudomorphs discovered in this region are recognized as two types. One was found in sandy gravel beds of the second terrace of the Yellow River. This ice-wedge pseudomorph is characterized by higher ratio of breadth/depth, and are 1-1.4 m wide and about 1 m deep. The bottom border of the ice-wedge pseudomorph is round arc in section. Another discovered in the pedestal of the second terrace has lower ratio of width/depth, and is o.3-1.0 m wide and 1-2 m deep. Its bottom border is sharp. Based on the TL dating, the former was formed at the middleHolocene (5.69±0.43 ka BP and 5.43±0.41 ka BP), that is, the Megathermal, and the latter was formed at the late Last Glacial Maximum (13.49±1.43 ka BP). Additionally, the thawing-freezing folders discovered in the late Late Pleistocene proluvium are 39.83±3.84 ka BP in age. The study on the ice-wedge pseudomorphs showed that the air temperature was lowered by up to 6-7℃ in the source area of the Yellow River when the ice-wedge pseudomorphs and thawing-freezing folds developed.
文摘The carbon pool stored in soil carbonate is comparable to the soil organic carbon.Therefore,secondary calcite precipitation in supersaturated catchment could be an important,yet poorly constrained,carbon sink within the modern global carbon cycle.The chemical analysis of some dissolved species transported by rivers,such as elevated Sr/Ca and Mg/Ca ratios but also heavy stable Ca isotopic compositions,witness the formation of secondary calcite in rivers draining arid regions.However,in areas affected by active tectonics and rapid physical erosion,co-variations in the fluvial Sr/Ca and Mg/Ca ratios could also be related to incongruent carbonate weathering processes.Here,we present a model to assess the roles played by incongruent carbonate dissolution and secondary calcite precipitation in modern weathering processes.We tested and applied the model to rivers draining the Himalayan–Tibetan region.The results suggest that regional aridity in the drainage basin promotes carbon sequestration as secondary carbonate but that for a given runoff,incongruent dissolution of carbonate possibly related to rapid physical erosion amplifies such sequestration.The isotopic compositions(^(13)C/^(12)C and^(18)O/^(16)O)of detrital carbonate transported by the main rivers in South and South-East Tibet imply that around 1%of the suspended material transported by those rivers corresponds to secondary carbonate and can represent between 5%and 15%of the alkalinity flux.Most of these alkalinity transported as particulate material is,nevertheless related to the weathering of carbonate lithologies and is also subjected to dissolution prior its final storage in sedimentary basins.However,on glacial-interglacial timescale this will amplify the significant role of mountain weathering on climatic variations.
基金National Key R&D Program of China,No.2018YFA0606102National Natural Science Foundation of China,No.41771056National Key Technology Support Program,No.2012BAH31B02
文摘Aboveground biomass in grasslands of the Qinghai-Tibet Plateau has displayed an overall increasing trend during 2003–2016, which is profoundly influenced by climate change. However, the responses of different biomes show large discrepancies, in both size and magnitude. By applying partial least squares regression, we calculated the correlation between peak aboveground biomass and mean monthly temperature and monthly total precipitation in the preceding 12 months for three different grassland types(alpine steppe, alpine meadow, and temperate steppe) on the central and eastern Qinghai-Tibet Plateau. The results showed that mean temperature in most preceding months was positively correlated with peak aboveground biomass of alpine meadow and alpine steppe, while mean temperature in the preceding October and February to June was significantly negatively correlated with peak aboveground biomass of temperate steppe. Precipitation in all months had a promoting effect on biomass of alpine meadow, but its correlations with biomass of alpine steppe and temperate steppe were inconsistent. It is worth noting that, in a warmer, wetter climate, peak aboveground biomass of alpine meadow would increase more than that of alpine steppe, while that of temperate steppe would decrease significantly, providing support for the hypothesis of conservative growth strategies by vegetation in stressed ecosystems.
基金supported by the National Natural Science Foundation of China (31090254, 30770300 and U1036603)the Chinese Academy of Sciences (KSCX2-EW-Q-12)the endowment of William S. Barnickle, Saint Louis University, St. Louis, Missouri, USA
文摘Abstract Sisorid catfishes are primarily limited in distribution to rivers of the Himalayan region and Tibetan Plateau. These species have external morphologies that are adapted for extremely fast-flowing riverine systems. Given the diversity of the group and the above qualities of these catfishes, this lineage serves as an ideal group for inferring the geological history of this region based on their phylogenetic relationships reflecting evolu- tionary history. We sequenced the complete mitochondrial genome and four nuclear genes of representative sisorids distributed across river systems in China. Phylogenetic analyses strongly support the monophyly of the Sisoridae and the glyptosternoids. An analysis of the reconstructed ancestral states derived from inferred genealogical relationships suggests that the evolution of this lineage was accompanied by convergent evolution in morphological traits that were presumably in response to environmental pressure involving the rapid flowing river system that were generated during the uplift of the Tibetan Plateau (UTP). Molecular dating indicates that the Chinese sisorids and the glyptosternoids originated at the later Miocene (~ 10.9-9.8 Mya), and with further biogeographic analyses indicates that the species of Sisoridae likely originated from a widely distributed ancestor. Moreover, the divergence of the Sisoridae in China can be divided into two phases consis- tent with the UTP. All of these results indicate that the diversification and dispersal events in this lineage occurred as a result of drainage systems formed during and after the UTP in the late Miocene and Quaternary periods.
基金supported by the National Natural Science Foundation of China(Grant No.41525007)the Stratigraphic Pilot Science and Technology Projects of the Chinese Academy of Sciences(Class B)(Grant No.XDB03010400)
文摘Placing precise constraints on the timing of the India-Asia continental collision is essential to understand the successive geological and geomorphological evolution of the orogenic belt as well as the uplift mechanism of the Tibetan Plateau and their effects on climate,environment and life.Based on the extensive study of the sedimentary record on both sides of the Yarlung-Zangbo suture zone in Tibet,we review here the present state of knowledge on the timing of collision onset,discuss its possible diachroneity along strike,and reconstruct the early structural and topographic evolution of the Himalayan collided range.We define continent-continent collision as the moment when the oceanic crust is completely consumed at one point where the two continental margins come into contact.We use two methods to constrain the timing of collision onset:(1) dating the provenance change from Indian to Asian recorded by deep-water turbidites near the suture zone,and(2) dating the age of unconformities on both sides of the suture zone.The first method allowed us to constrain precisely collision onset as middle Palaeocene(59±l Ma).Marine sedimentation persisted in the collisional zone for another 20-25 Ma locally in southern Tibet,and molassic-type deposition in the Indian foreland basin did not begin until another 10-15 Ma later.Available sedimentary evidence failed to firmly document any significant diachroneity of collision onset from the central Himalaya to the western Himalaya and Pakistan so far.Based on the Cenozoic stratigraphic record of the Tibetan Himalaya,four distinct stages can be identified in the early evolution of the Himalayan orogen:(1) middle Palaeocene-early Eocene earliest Eohimalayan stage(from 59 to 52 Ma):collision onset and filling of the deep-water trough along the suture zone while carbonate platform sedimentation persisted on the inner Indian margin;(2) early-middle Eocene early Eohimalayan stage(from 52 to 41 or 35 Ma):filling of intervening seaways and cessation of marine sedimentation;(3) late Eocene-Oligocene late Eohimalayan stage(from 41 to 25 Ma):huge gap in the sedimentary record both in the collision zone and in the Indian foreland;and(4) late Oligocene-early Miocene early Neohimalayan stage(from 26 to 17 Ma):rapid Himalayan growth and onset of molasse-type sedimentation in the Indian foreland basin.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences (No.XDB03030500)the National Key Technology Research and Development Program of China (No.2013BAC04B02)the National Natural Science Foundation of China (Nos.40801042 and 90202012)
文摘There are a series of special mountain soils on the Tibetan Plateau of China in an alpine environment for the high altitude. However, very few studies have focused on major soil elements in relation to soil formation in this area. Aluminum (Al), iron (Fe), calcium (Ca), sodium (Na), potassium (K) and magnesium (Mg) contents of 237 topsoil samples covering a 2.8-km altitudinal gradient in uncultivated areas along the Qinghai-Tibet Railway of China were measured using inductively coupled plasma atomic emission spectroscopy. The spatial distribution of the elements and its relationship to the parent rocks and climatic parameters were analyzed. Soils along the gradient are derived from a range of parent materials, but most are less than 30 cm deep with little development (Cambisols). Soil Al, Fe and Mg contents showed a decreasing trend from the start station (Xining Station) to end station (Lhasa Station) of the Qinghai-Tibet Railway, whereas soil K and Na contents were relative stable from Xining Station to the Kunlun Mountains and then increased gradually. Soil Ca content was lower in the southern part of the Tanggula Mountains. The major soil element contents clearly reflected the parent rock and climatic influences. Soils with higher Ca content appeared in areas with Ca-Mg carbonate rocks, soils with higher Al were found in areas with silicate-rich and high-Al silicate clastic rocks and silicate-rich aluminosilicate loose sediments. Soils with higher K and Na contents appeared in areas with high-K, high-Na and silicate-rich aluminosilicate rocks. Soil Na and K contents were affected by temperature, whereas the contents of Mg, Fe, Ca and Al were more affected by precipitation. Soil Na and K contents increased with increasing temperatures, whereas the contents of Mg, Fe, Ca and Al decreased with increasing precipitation. This analysis provides a relationship between soil properties and rapidly changing environmental conditions. The data can be used to investigate the effect of the climate or land use change on soil properties.