Soil organic carbon (SOC) has great impacts on global warming, land degradation and food security. Classic statistical and geostatistical methods were used to characterize and compare the spatial heterogeneity of SOC ...Soil organic carbon (SOC) has great impacts on global warming, land degradation and food security. Classic statistical and geostatistical methods were used to characterize and compare the spatial heterogeneity of SOC and related factors, such as topography, soil type and land use, in the Liudaogou watershed on the Loess Plateau of North China. SOC concentrations followed a log-normal distribution with an arithmetic and geometric means of 23.4 and 21.3 g kg-1, respectively, were moderately variable (CV = 75.9%), and demonstrated a moderate spatial dependence according to the nugget ratio (34.7%). The experimental variogram of SOC was best-fitted by a spherical model, after the spatial outliers had been detected and subsequently eliminated. Lower SOC concentrations were associated with higher elevations. Warp soils and farmland had the highest SOC concentrations, while aeolian sand soil and shrublands had the lowest SOC values. The geostatistical characteristics of SOC for the different soil and land use types were different. These patterns were closely related to the spatial structure of topography, and soil and land use types.展开更多
A total of 60 VES （geo-electrical resistivity soundings） and ten exploratory core holes （boreholes） were carried out along the axis of a proposed earth dam site as part of an overall geotechnical investigation for...A total of 60 VES （geo-electrical resistivity soundings） and ten exploratory core holes （boreholes） were carried out along the axis of a proposed earth dam site as part of an overall geotechnical investigation for the design and construction of an earth dam along Dansak River, Shemankar River Basin, Jos Plateau, Nigeria. The geophysical interpretation revealed four to five geo-electric layers corresponding to lithologic units （1） topsoil from 0-2 m with a resistivity value of 〈 100-320 ohm-m, （2） weathered/slightly weathered basalt fi＇om 0.6 m to 20 m characterized by resistivity value of 27-130 ohm-m, followed by （3） basalt/fractured basalts with resistivity value of 130-400 ohm-m and （4） the basement rocks with resistivity value 〉 320 ohm-m to 3,021 ohm-m. Exploratory borehole drilling encountered a series of lithologic units viz： overburden （clay, silt and sand） weathered basalt, slightly weathered basalt, fresh/fractured basalts, weathered migmatite and migmatites/migmatite gneiss. Exploratory core analysis in terms of CR （core recovery） and RQD （rock quality designation） revealed an average of 70%-90% and 75%-90%, respectively. Lugeon test gave Lugeon values of 1-5 for the ten core holes. However, fractures with Lugeon value from 〉 5-15 lugeon were encountered on borehole numbers BH 1, 7, 8, 9 and 10. Grouting is recommended to seal this shallow to medium depth （0-15 m） fractures to reduce or eliminate possible seepage when the dam is constructed. The rock mass index grading for the dam axis ranges from good to excellent.展开更多
Habitat quality assessments are of great significance for protecting biodiversity.This study analyzes the changing habitat quality of Lashihai watershed based on SPOT satellite images.We extracted the land use data fo...Habitat quality assessments are of great significance for protecting biodiversity.This study analyzes the changing habitat quality of Lashihai watershed based on SPOT satellite images.We extracted the land use data for Lashihai watershed in Yunnan province for the years 2000 and 2015,and then used an INVEST model to evaluate habitat degradation,habitat quality and habitat scarcity in the study area from 2000 to 2015.Spatial statistical methods were used to determine changes to spatial dynamics.Results indicate that the number of areas with habitat degradation was generally small,and that both the number of areas with habitat degradation and the degree of degradation had fallen noticeably during the fifteen-year study period.In general,the quality of habitats was main- tained or improved,while the quality of habitats decreased in only a few areas.The scarcity of habitats for cultivated land had increased,the tension between people and land use was relatively prominent.The reason habitat quality in Lashihai watershed has improved can be attributed to three factors:1)The policy of returning farmland to forests since 2000 has been well implemented and has achieved remarkable results.Loss of forests from logging and deforestation has basically been eliminated,and great progress has been made restoring the ecological environment.2)High background value of quality habitat suitability benefits from the research area's high vegetation coverage.3)The development of the local tourism economy has transformed the area's ecological advantages into an economic bonus,greatly increasing the income level and living standards of residents.At the same time,the ecological resource bonus has increased the enthusiasm of residents for ecological protection and has helped to promote the protection of local eco-systems,both reducing ecological degradation and improving habitat quality.At the same time,increasing conflicts between land and people should be addressed.Support is needed to promote development of the ecological economy while continuously reducing ecological degradation and further increasing residents'income.There must be less reliance on industry and less pressure on both land and people,all the while ensuring that the local economy and ecology can more forward together in a sustainable way.展开更多
Study of the characteristics of the crustal magnetic anomaly in the Qinghai-Tibet Plateau and the adjacent areas helps better understand the lithospheric structure and evolution, as well as the regional geodynamic pro...Study of the characteristics of the crustal magnetic anomaly in the Qinghai-Tibet Plateau and the adjacent areas helps better understand the lithospheric structure and evolution, as well as the regional geodynamic processes. Here we analyze the distri- bution laws of the crustal magnetic anomaly and its vertical gradient, the decay characteristics of the anomaly, the contribu- tions from different wavelength bands to the anomaly, and the relationship between the anomaly and the crustal regional tec- tonics in the plateau and nearby, based on a new and higher degree geomagnetic model NGDC-EMM-720-V3 constructed from the surface, aeromagnetic, marine and satellite survey data. The results reveal that the positive and negative anomalies in the Qinghai-Tibet Plateau are weak, while those of the surrounding areas are strong. The boundary agrees well with the border of the plateau regional tectonics. The anomaly is nearly east-west in the central and western plateau, arc-shaped in the south- western and eastern, and nearly north-south in the southeastern, consistent with the tectonic trends. There are strong negative anomaly loci in the east and west syntaxis, whereas no significant differences exist among the Cenozoic blocks in the plateau interior. No direct correspondence exists between the anomaly and the crustal depth. On the background of a weak magnetic anomaly in the plateau, relatively stronger short wavelength fields from the shallower crust are overlapped in the Lhasa, Qilian, Qaidam, and Sichuan-Yunnan rhombic blocks. A strong negative anomaly in the east-west direction is distributed along the Himalayas, mainly caused by the middle and long wavelength bands in the deep and central crust. The magnetic structural lay- ers are stable in the Sichuan and Tarim basins. The anomalies at different altitudes over the southern plateau vary strongly, showing a drastic variation in the magnetic structure from the deep crust to the shallow crust.展开更多
The paper analyzes the sediment source of watershed by means of studying watershed in westernShanxi of the Losses Plateau. On the basis of watersheds classification, 7 typical watersheds were chosen andobserved for 11...The paper analyzes the sediment source of watershed by means of studying watershed in westernShanxi of the Losses Plateau. On the basis of watersheds classification, 7 typical watersheds were chosen andobserved for 11 years. The result shows that the sediment at the small watershed mainly comes from gullies,which is 60% of the total sediment. Erosion modulus of valley (including gully head, gully bed, valley side)is 1.28~2.48 times as that of the area between channels(including hill slope and mound of the Loess Plateau).The main sediment source of slope erosion is cultivated land on slope without water and soil conservationmeasures.展开更多
基金Project supported by the National Key Basic Research Program (973 Program) of China (No.2007CB106803)the National Programs for Science and Technology Development of China (No.2006BAD09B06)the Scientific ResearchInnovation Team Support Program of the Northwest A&F University, China
文摘Soil organic carbon (SOC) has great impacts on global warming, land degradation and food security. Classic statistical and geostatistical methods were used to characterize and compare the spatial heterogeneity of SOC and related factors, such as topography, soil type and land use, in the Liudaogou watershed on the Loess Plateau of North China. SOC concentrations followed a log-normal distribution with an arithmetic and geometric means of 23.4 and 21.3 g kg-1, respectively, were moderately variable (CV = 75.9%), and demonstrated a moderate spatial dependence according to the nugget ratio (34.7%). The experimental variogram of SOC was best-fitted by a spherical model, after the spatial outliers had been detected and subsequently eliminated. Lower SOC concentrations were associated with higher elevations. Warp soils and farmland had the highest SOC concentrations, while aeolian sand soil and shrublands had the lowest SOC values. The geostatistical characteristics of SOC for the different soil and land use types were different. These patterns were closely related to the spatial structure of topography, and soil and land use types.
文摘A total of 60 VES （geo-electrical resistivity soundings） and ten exploratory core holes （boreholes） were carried out along the axis of a proposed earth dam site as part of an overall geotechnical investigation for the design and construction of an earth dam along Dansak River, Shemankar River Basin, Jos Plateau, Nigeria. The geophysical interpretation revealed four to five geo-electric layers corresponding to lithologic units （1） topsoil from 0-2 m with a resistivity value of 〈 100-320 ohm-m, （2） weathered/slightly weathered basalt fi＇om 0.6 m to 20 m characterized by resistivity value of 27-130 ohm-m, followed by （3） basalt/fractured basalts with resistivity value of 130-400 ohm-m and （4） the basement rocks with resistivity value 〉 320 ohm-m to 3,021 ohm-m. Exploratory borehole drilling encountered a series of lithologic units viz： overburden （clay, silt and sand） weathered basalt, slightly weathered basalt, fresh/fractured basalts, weathered migmatite and migmatites/migmatite gneiss. Exploratory core analysis in terms of CR （core recovery） and RQD （rock quality designation） revealed an average of 70%-90% and 75%-90%, respectively. Lugeon test gave Lugeon values of 1-5 for the ten core holes. However, fractures with Lugeon value from 〉 5-15 lugeon were encountered on borehole numbers BH 1, 7, 8, 9 and 10. Grouting is recommended to seal this shallow to medium depth （0-15 m） fractures to reduce or eliminate possible seepage when the dam is constructed. The rock mass index grading for the dam axis ranges from good to excellent.
基金Supported by fund for building world-class universities(disciplines) of Renmin University of China(2018)
文摘Habitat quality assessments are of great significance for protecting biodiversity.This study analyzes the changing habitat quality of Lashihai watershed based on SPOT satellite images.We extracted the land use data for Lashihai watershed in Yunnan province for the years 2000 and 2015,and then used an INVEST model to evaluate habitat degradation,habitat quality and habitat scarcity in the study area from 2000 to 2015.Spatial statistical methods were used to determine changes to spatial dynamics.Results indicate that the number of areas with habitat degradation was generally small,and that both the number of areas with habitat degradation and the degree of degradation had fallen noticeably during the fifteen-year study period.In general,the quality of habitats was main- tained or improved,while the quality of habitats decreased in only a few areas.The scarcity of habitats for cultivated land had increased,the tension between people and land use was relatively prominent.The reason habitat quality in Lashihai watershed has improved can be attributed to three factors:1)The policy of returning farmland to forests since 2000 has been well implemented and has achieved remarkable results.Loss of forests from logging and deforestation has basically been eliminated,and great progress has been made restoring the ecological environment.2)High background value of quality habitat suitability benefits from the research area's high vegetation coverage.3)The development of the local tourism economy has transformed the area's ecological advantages into an economic bonus,greatly increasing the income level and living standards of residents.At the same time,the ecological resource bonus has increased the enthusiasm of residents for ecological protection and has helped to promote the protection of local eco-systems,both reducing ecological degradation and improving habitat quality.At the same time,increasing conflicts between land and people should be addressed.Support is needed to promote development of the ecological economy while continuously reducing ecological degradation and further increasing residents'income.There must be less reliance on industry and less pressure on both land and people,all the while ensuring that the local economy and ecology can more forward together in a sustainable way.
基金sponsored by National Natural Science Foundation of China (Grant Nos. 40464001 and 40864002)
文摘Study of the characteristics of the crustal magnetic anomaly in the Qinghai-Tibet Plateau and the adjacent areas helps better understand the lithospheric structure and evolution, as well as the regional geodynamic processes. Here we analyze the distri- bution laws of the crustal magnetic anomaly and its vertical gradient, the decay characteristics of the anomaly, the contribu- tions from different wavelength bands to the anomaly, and the relationship between the anomaly and the crustal regional tec- tonics in the plateau and nearby, based on a new and higher degree geomagnetic model NGDC-EMM-720-V3 constructed from the surface, aeromagnetic, marine and satellite survey data. The results reveal that the positive and negative anomalies in the Qinghai-Tibet Plateau are weak, while those of the surrounding areas are strong. The boundary agrees well with the border of the plateau regional tectonics. The anomaly is nearly east-west in the central and western plateau, arc-shaped in the south- western and eastern, and nearly north-south in the southeastern, consistent with the tectonic trends. There are strong negative anomaly loci in the east and west syntaxis, whereas no significant differences exist among the Cenozoic blocks in the plateau interior. No direct correspondence exists between the anomaly and the crustal depth. On the background of a weak magnetic anomaly in the plateau, relatively stronger short wavelength fields from the shallower crust are overlapped in the Lhasa, Qilian, Qaidam, and Sichuan-Yunnan rhombic blocks. A strong negative anomaly in the east-west direction is distributed along the Himalayas, mainly caused by the middle and long wavelength bands in the deep and central crust. The magnetic structural lay- ers are stable in the Sichuan and Tarim basins. The anomalies at different altitudes over the southern plateau vary strongly, showing a drastic variation in the magnetic structure from the deep crust to the shallow crust.
文摘The paper analyzes the sediment source of watershed by means of studying watershed in westernShanxi of the Losses Plateau. On the basis of watersheds classification, 7 typical watersheds were chosen andobserved for 11 years. The result shows that the sediment at the small watershed mainly comes from gullies,which is 60% of the total sediment. Erosion modulus of valley (including gully head, gully bed, valley side)is 1.28~2.48 times as that of the area between channels(including hill slope and mound of the Loess Plateau).The main sediment source of slope erosion is cultivated land on slope without water and soil conservationmeasures.
