[Objective] This study aimed to accomplish a biome classification of helophytes at Maqu,the first bend of the Yellow River.[Method] Helophgtes in the Maqu wetland were investigated using quadrat sampling method with r...[Objective] This study aimed to accomplish a biome classification of helophytes at Maqu,the first bend of the Yellow River.[Method] Helophgtes in the Maqu wetland were investigated using quadrat sampling method with references to plant specimens.[Result] The helophyte communities at Maqu wetland could be divided into two categories：sedge marshes and non-sedge marshes,which can be further subdivided into 4 biomes.The constructive species mainly included Blysmus sinocompressus,Blysmocarex nudicarpa,Eleocharis valleculosa and Polygonum amphibian.The sub-constructive species consisted mainly of Carex brunnescens,Catabrosa aquatica,Kobresia kansuensis,Polygonum amphibium and Leontopodium alpinum.The total coverage of communities ranged from 5% to 90%,which were commonly found in areas permanently ponded with water,such as watercourse depressions,floodplains,valley depressions,terrace scarp depressions and riverhead depressions,with the underground water depth of 20-30 cm.[Conclusion] The biome classification of helophyte communities provided scientific basis for the ecological restoration and control of Maqu wetland prairie.展开更多
The Late Quaternary slip rate along the Maqu segment of the eastern Kunlun Fault was estimated using a combination of high-resolution remote sensing imagery interpretation, field observations and differential Global P...The Late Quaternary slip rate along the Maqu segment of the eastern Kunlun Fault was estimated using a combination of high-resolution remote sensing imagery interpretation, field observations and differential Global Positioning System（GPS） measurements of offset river terraces, and 14 C dating of snail shells collected from offset risers. The results show that the left-slip rate along the segment is 3–5 mm/a, and that the vertical slip rate is 0.3–0.5 mm/a. Both the horizontal and vertical slips on the segment remain consistent over a distance of ~100 km. It means that no slip gradient as previously suggested occurred along the Maqu segment, and which thus might behave as an independent seismogenic fault. Judging from multiple relationships among young terrace offsets, we infer that co-seismic surface rupture produced by a characteristic earthquake with a magnitude of Ms7.0–7.5 on the Maqu fault could generate a horizontal slip of 4.5–5 m and a vertical slip of 0.45–0.5 m, with a corresponding ratio（Dh/Dv） of about 9. Two surface rupture events must have occurred over the past 3300 years, the latest one possibly between 1485 cal BP and 1730 cal BP.展开更多
Maqu County is located in the northeast Qinghai-Tibetan Plateau, and it is the main watershed for the Yellow River. The ecosystem there is extremely vulnerable and sensitive to climate change and human activities, whi...Maqu County is located in the northeast Qinghai-Tibetan Plateau, and it is the main watershed for the Yellow River. The ecosystem there is extremely vulnerable and sensitive to climate change and human activities, which have caused significant deterioration of the eco-environment in this region. In order to restore the ecological environment, a government project to restore the grazing areas to grassland was implemented in Maqu County in early 2004. This study evaluates the effects of that restoration project on land use and land cover change （LUCC）, and explores the driving forces of LUCC in Maqu County. In the study we used Landsat images obtained in 1989, 2004, 2009, and 2014 to establish databases of land use and land cover. Then we derived LUCC information by overlaying these layers using GIS software. Finally, we analyzed the main forces responsible for LUCC. The results showed that forests, high-coverage grasslands, and marshes experienced the most significant decreases during 1989–2004, by 882.8 ha, 35,250.4 ha, and 2,753.4 ha, respectively. However, moderate- and low-coverage grasslands and sand lands showed the opposite trend, increasing by 12,529.7 ha, 25,491.0 ha, and 577.5 ha, respectively. LUCC in 2004–2009 showed that ecological degradation slowed compared with 1989？2004. During 2009–2014, high- and moderate-coverage grasslands increased obviously, but low-coverage grasslands, marshes, unused lands, sand lands, and water areas showed the opposite trend. These results suggested that the degradation of the eco-environment was obvious before 2009, showing a decrease in the forests, grasslands, and water areas, and an increase in unused lands. The ecological degradation was reversed after 2009, as was mainly evidenced by increases in high- and mod-erate-coverage grasslands, and the shrinkage rate of marshes decreased obviously. These results showed that the project of restoring grazing lands to grassland had a positive effect on the LUCC. Other major factors that influence the LUCC include increasing temperature, variation in the seasonal frozen soil environment, seasonal overgrazing, and pest and rodent damage.展开更多
Carex brunnescens(Pers.)Poir.is considered to be the only clonal herb found to date that can develop and form fixed dunes in Maqu alpine degraded grasslands of northwestern China.However,due to strong dormant characte...Carex brunnescens(Pers.)Poir.is considered to be the only clonal herb found to date that can develop and form fixed dunes in Maqu alpine degraded grasslands of northwestern China.However,due to strong dormant characteristics of C.brunnescens seeds,the sand-fixing effect of the plant is severely limited.This study explores a technique that can rapidly promote the seed germination of C.brunnescens,and also investigates the adaptation and sand-fixing effect by cultivating C.brunnescens seedlings to establish living sand barriers in the sand ridges of moving sand dunes.Results show that the seed germination rate obtained a maximum of 63.7%or 65.1%when seeds were treated with 150 mg/L gibberellic acid(GA3)for 24 h followed by soaking in sulfuric acid(98%H2SO4)for 2.5 min or sodium hydroxide(10%NaOH)for 3.5 h,and then germinated(25°C in daytime and 5°C at nighttime)in darkness for 10 d.After breaking seed dormancy of C.brunnescens,the living sand barrier of C.brunnescens(plant spacing 15−20 cm;sand barrier spacing 10−20 m)was established in the perpendicular direction to the main wind in the middle and lower parts of the sand ridges on both sides of the moving sand dunes.When the sand ridges were leveled by wind erosion,the living sand barrier(plant spacing 15−20 cm;sand barrier spacing 0.5−1.0 m)of C.brunnescens was reestablished on the wind-eroded flat ground.Finally,a stable sand-fixing surface can be formed after connecting the living sand barriers on both sides,thus achieving a good sand-fixing effect.These findings suggest that rapid seed germination technology combined with the sand−fixing method of C.brunnescens can shorten the seed germination period and make the seedling establishment become much easier which may be an effective strategy to restore and reconstruct Maqu degraded grasslands.展开更多
The East Kunlun active fault is an important NWW-trending boundary fault on the northeastern margin of the Qinghai-Xizang (Tibet) Plateau. The Maqu fault is the easternmost segment of the East Kunlun active fault. Bas...The East Kunlun active fault is an important NWW-trending boundary fault on the northeastern margin of the Qinghai-Xizang (Tibet) Plateau. The Maqu fault is the easternmost segment of the East Kunlun active fault. Based on three trenches, four Holocene palaeo-earthquake events are identified along the Maqu fault. The latest palaeo-earthquake event is (1730±50) ～ (1802±52) a BP, the second is (3736±57) ～ (4641±60) a BP, the third is (8590±70) a BP, and the earliest is (12200±1700) ka BP. The time of the first and second palaeo-earthquake events is more reliable than that of the third and last ones. As a result, the recurrence interval of the palaeo-earthquakes on the easternmost segment of the East Kunlun active fault is approximately 2400 a, and the palaeo-earthquake elapsed time is (1730±50) ～ (1802±52) a BP.展开更多
基金Supported by the Fundamental Research for the Central Welfare Scientific Research Institutes,China(BRF090202)~~
文摘[Objective] This study aimed to accomplish a biome classification of helophytes at Maqu,the first bend of the Yellow River.[Method] Helophgtes in the Maqu wetland were investigated using quadrat sampling method with references to plant specimens.[Result] The helophyte communities at Maqu wetland could be divided into two categories：sedge marshes and non-sedge marshes,which can be further subdivided into 4 biomes.The constructive species mainly included Blysmus sinocompressus,Blysmocarex nudicarpa,Eleocharis valleculosa and Polygonum amphibian.The sub-constructive species consisted mainly of Carex brunnescens,Catabrosa aquatica,Kobresia kansuensis,Polygonum amphibium and Leontopodium alpinum.The total coverage of communities ranged from 5% to 90%,which were commonly found in areas permanently ponded with water,such as watercourse depressions,floodplains,valley depressions,terrace scarp depressions and riverhead depressions,with the underground water depth of 20-30 cm.[Conclusion] The biome classification of helophyte communities provided scientific basis for the ecological restoration and control of Maqu wetland prairie.
基金support of the Natural Science Foundation of China(41472178)the China Geological Survey projects(1212011120167,12120114002211)
文摘The Late Quaternary slip rate along the Maqu segment of the eastern Kunlun Fault was estimated using a combination of high-resolution remote sensing imagery interpretation, field observations and differential Global Positioning System（GPS） measurements of offset river terraces, and 14 C dating of snail shells collected from offset risers. The results show that the left-slip rate along the segment is 3–5 mm/a, and that the vertical slip rate is 0.3–0.5 mm/a. Both the horizontal and vertical slips on the segment remain consistent over a distance of ~100 km. It means that no slip gradient as previously suggested occurred along the Maqu segment, and which thus might behave as an independent seismogenic fault. Judging from multiple relationships among young terrace offsets, we infer that co-seismic surface rupture produced by a characteristic earthquake with a magnitude of Ms7.0–7.5 on the Maqu fault could generate a horizontal slip of 4.5–5 m and a vertical slip of 0.45–0.5 m, with a corresponding ratio（Dh/Dv） of about 9. Two surface rupture events must have occurred over the past 3300 years, the latest one possibly between 1485 cal BP and 1730 cal BP.
基金the funding received from the Natural Science Foundation of China (41301003, 41371026, and 31470480)the Technology of the People's Republic of China (No. 2013CB956000)
文摘Maqu County is located in the northeast Qinghai-Tibetan Plateau, and it is the main watershed for the Yellow River. The ecosystem there is extremely vulnerable and sensitive to climate change and human activities, which have caused significant deterioration of the eco-environment in this region. In order to restore the ecological environment, a government project to restore the grazing areas to grassland was implemented in Maqu County in early 2004. This study evaluates the effects of that restoration project on land use and land cover change （LUCC）, and explores the driving forces of LUCC in Maqu County. In the study we used Landsat images obtained in 1989, 2004, 2009, and 2014 to establish databases of land use and land cover. Then we derived LUCC information by overlaying these layers using GIS software. Finally, we analyzed the main forces responsible for LUCC. The results showed that forests, high-coverage grasslands, and marshes experienced the most significant decreases during 1989–2004, by 882.8 ha, 35,250.4 ha, and 2,753.4 ha, respectively. However, moderate- and low-coverage grasslands and sand lands showed the opposite trend, increasing by 12,529.7 ha, 25,491.0 ha, and 577.5 ha, respectively. LUCC in 2004–2009 showed that ecological degradation slowed compared with 1989？2004. During 2009–2014, high- and moderate-coverage grasslands increased obviously, but low-coverage grasslands, marshes, unused lands, sand lands, and water areas showed the opposite trend. These results suggested that the degradation of the eco-environment was obvious before 2009, showing a decrease in the forests, grasslands, and water areas, and an increase in unused lands. The ecological degradation was reversed after 2009, as was mainly evidenced by increases in high- and mod-erate-coverage grasslands, and the shrinkage rate of marshes decreased obviously. These results showed that the project of restoring grazing lands to grassland had a positive effect on the LUCC. Other major factors that influence the LUCC include increasing temperature, variation in the seasonal frozen soil environment, seasonal overgrazing, and pest and rodent damage.
基金the Project of the Youth Talent Development Fund of the Northwest Institute of Eco−Environment and ResourcesChinese Academy of Science(CAREERI)(Y851C81001)+1 种基金the National Natural Science Foundation of China(41877162)the Instrument Functional Development Project from the Technology Service Center of CAREERI(Y429C51007).
文摘Carex brunnescens(Pers.)Poir.is considered to be the only clonal herb found to date that can develop and form fixed dunes in Maqu alpine degraded grasslands of northwestern China.However,due to strong dormant characteristics of C.brunnescens seeds,the sand-fixing effect of the plant is severely limited.This study explores a technique that can rapidly promote the seed germination of C.brunnescens,and also investigates the adaptation and sand-fixing effect by cultivating C.brunnescens seedlings to establish living sand barriers in the sand ridges of moving sand dunes.Results show that the seed germination rate obtained a maximum of 63.7%or 65.1%when seeds were treated with 150 mg/L gibberellic acid(GA3)for 24 h followed by soaking in sulfuric acid(98%H2SO4)for 2.5 min or sodium hydroxide(10%NaOH)for 3.5 h,and then germinated(25°C in daytime and 5°C at nighttime)in darkness for 10 d.After breaking seed dormancy of C.brunnescens,the living sand barrier of C.brunnescens(plant spacing 15−20 cm;sand barrier spacing 10−20 m)was established in the perpendicular direction to the main wind in the middle and lower parts of the sand ridges on both sides of the moving sand dunes.When the sand ridges were leveled by wind erosion,the living sand barrier(plant spacing 15−20 cm;sand barrier spacing 0.5−1.0 m)of C.brunnescens was reestablished on the wind-eroded flat ground.Finally,a stable sand-fixing surface can be formed after connecting the living sand barriers on both sides,thus achieving a good sand-fixing effect.These findings suggest that rapid seed germination technology combined with the sand−fixing method of C.brunnescens can shorten the seed germination period and make the seedling establishment become much easier which may be an effective strategy to restore and reconstruct Maqu degraded grasslands.
基金The project wasjointlysupported bythefollow-up projectsof moderately strong earthquake prediction of the North-South earthquake zone of China Earthquake Administration,theJoint Earthquake Science Foundation of CEA (104073) and the National Natural science Foundation of China(40372086) .Contribution No.LC20060016 of Lanzhou Institute of Seismology of CEA
文摘The East Kunlun active fault is an important NWW-trending boundary fault on the northeastern margin of the Qinghai-Xizang (Tibet) Plateau. The Maqu fault is the easternmost segment of the East Kunlun active fault. Based on three trenches, four Holocene palaeo-earthquake events are identified along the Maqu fault. The latest palaeo-earthquake event is (1730±50) ～ (1802±52) a BP, the second is (3736±57) ～ (4641±60) a BP, the third is (8590±70) a BP, and the earliest is (12200±1700) ka BP. The time of the first and second palaeo-earthquake events is more reliable than that of the third and last ones. As a result, the recurrence interval of the palaeo-earthquakes on the easternmost segment of the East Kunlun active fault is approximately 2400 a, and the palaeo-earthquake elapsed time is (1730±50) ～ (1802±52) a BP.
