The fully mulched ridge–furrow(FMRF) system has been widely used on the semi-arid Loess Plateau of China due to its high maize(Zea mays L.) productivity and rainfall use efficiency. However, high outputs under this s...The fully mulched ridge–furrow(FMRF) system has been widely used on the semi-arid Loess Plateau of China due to its high maize(Zea mays L.) productivity and rainfall use efficiency. However, high outputs under this system led to a depletion of soil moisture and soil nutrients, which reduces its sustainability in the long run. Therefore, it is necessary to optimize the system for the sustainable development of agriculture. The development, yield-increasing mechanisms,negative impacts, optimization, and their relations in the FMRF system are reviewed in this paper. We suggest using grain and forage maize varieties instead of regular maize;mulching plastic film in autumn or leaving the mulch after maize harvesting until the next spring, and then removing the old film and mulching new film;combining reduced/notillage with straw return;utilizing crop rotation or intercropping with winter canola(Brassica campestris L.), millet(Setaria italica), or oilseed flax(Linum usitatissimum L.);reducing nitrogen fertilizer and partially replacing chemical fertilizer with organic fertilizer;using biodegradable or weather-resistant film;and implementing mechanized production. These integrations help to establish an environmentally friendly, high quality, and sustainable agricultural system, promote highquality development of dryland farming, and create new opportunities for agricultural development in the semi-arid Loess Plateau.展开更多
In order to study the migration and transformation mechanism of Hg content and occurrence form in subsurface flow zone of gold mining area in Loess Plateau and its influence on water environment,the field in-situ infi...In order to study the migration and transformation mechanism of Hg content and occurrence form in subsurface flow zone of gold mining area in Loess Plateau and its influence on water environment,the field in-situ infiltration test and laboratory test were carried out in three typical sections of river-side loess,alluvial and proluvial strata in Tongguan gold mining area of Shaanxi Province,and the following results were obtained:(1)The source of Hg in subsurface flow zone is mainly caused by mineral processing activities;(2)the subsurface flow zone in the study area is in alkaline environment,and the residual state,iron and manganese oxidation state,strong organic state and humic acid state of mercury in loess are equally divided in dry and oxidizing environment;mercury in river alluvial or diluvial strata is mainly concentrated in silt,tailings and clayey silt soil layer,and mercury has certain stability,and the form of mercury in loess is easier to transform than the other two media;(3)under the flooding condition,most of mercury is trapped in the silt layer in the undercurrent zone where the sand and silt layers alternate with each other and the river water and groundwater are disjointed,and the migration capacity of mercury is far less than that of loess layer and alluvial layer with close hydraulic connection;(4)infiltration at the flood level accelerates the migration of pollutants to the ground;(5)the soil in the undercurrent zone is overloaded and has seriously exceeded the standard.Although the groundwater monitoring results are safe this time,relevant enterprises or departments should continue to pay attention to improving the gold extraction process,especially vigorously rectify the small workshops for illegal gold extraction and the substandard discharge of the three wastes,and intensify efforts to solve the geological environmental problems of mines left over from history.At present,the occurrence form of mercury in the undercurrent zone is relatively stable,but the water and soil layers have been polluted.The risk of disjointed groundwater pollution can not be ignored while giving priority to the treatment of loess and river alluvial landform areas with close hydraulic links.The research results will provide a scientific basis for water conservancy departments to groundwater prevention and control in water-deficient areas of the Loess Plateau.展开更多
Arid and semi-arid areas comprise about 30% of the earth's surface. Changes in climate and climate variability will likely have a significant impact on these regions. The Loess Plateau over Northwest China is a speci...Arid and semi-arid areas comprise about 30% of the earth's surface. Changes in climate and climate variability will likely have a significant impact on these regions. The Loess Plateau over Northwest China is a special semi-arid land surface and part of a dust aerosol source. To improve understanding and capture the direct evidence of the impact of human activity on the semi-arid climate over the Loess Plateau, the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) was established in 2005. SACOL consists of a large set of instruments and focuses on: (1) monitoring of long term tendencies in semiarid climate changes; (2) monitoring of the aerosol effect on the water cycle; (3) studies of interaction between land surface and the atmosphere; (4) improving the land surface and climate models; and (5) validation of space-borne observations. This paper presents a description of SACOL objectives, measurements, and sampling strategies. Preliminary observation results are also reviewed in this paper.展开更多
Soil water is an important factor restricting afforestation on the semi-arid Loess Plateau.The microtopography of the loess slope has changed the distribution pattern of soil water on the slope.To improve water utiliz...Soil water is an important factor restricting afforestation on the semi-arid Loess Plateau.The microtopography of the loess slope has changed the distribution pattern of soil water on the slope.To improve water utilization efficiency and optimize afforestation configuration patterns,the relationship between soil water and precipitation at micro-topographic scale must be studied.We used time series analysis to study the temporal variation of soil water and its response to precipitation in four kinds of micro-topographies and undisturbed slope on loess slopes.Micro-topographies significantly influenced soil water distribution and dynamics on the slopes.Soil water stored in the platform,sinkhole,and ephemeral gully influenced subsequent soil water for 4 weeks,whereas soil water stored in the scarp and undisturbed slope could influence soil water for 2 weeks.It took 12 weeks,10 weeks,18 weeks,6 weeks,and 12 weeks for precipitation to reach the deeper soil layer in the platform,sinkhole,scarp,ephemeral gully,and undisturbed slope,respectively.These soil water characteristics in different micro-topographies are vital factors that should be taken into consideration when undertaking afforestation on the Loess Plateau.展开更多
Water harvesting is one of main measures to solve water shortage resulting from less precipitation and erratically seasonal dis- tribution in arid and semi-arid areas. Different types of anti-infiltration treatments i...Water harvesting is one of main measures to solve water shortage resulting from less precipitation and erratically seasonal dis- tribution in arid and semi-arid areas. Different types of anti-infiltration treatments including mechanical and chemical to micro-catchment and their runoff efficiencies had been reported. This paper, through 5 years experiment from 1992 to 1996, is aimed at studying the im- pacts of microcatchment water-harvesting system (MCWHS) with microphytic crust treatment on afforestation on semi-arid Loess Plateau. The results showed that after 3 years of crust inoculation, crust had covered majority of MCWHS and the function of water harvesting had also been demonstrated partially, there were significant difference in soil moisture of shallow soil layer in three typical spring stages be- tween crust cover and control treatments (0.05 level), and about 0.9%-6.04% increase of monthly mean soil moisture within 1m soil layer in spring of late 3 years. The impact of severe spring drought can be alleviated effectively. In the meanwhile, as crust developed on the treated surface, there are significant differences (0.05 level) for tree height (H), diameter at breast height (DBH) and diameter at ground level (DGL) at the end of the study period (1996) with the increases by 22.38%, 17.34%, and 20.49% respectively compared with the con- trol treatment. Microphytic crust, as one of biological infiltration-proof materials, may become the optimized option for revegetation in Chinese Great West Development Strategy due to its self-propagation, non-pollution to water qualities, long use duration and relatively cost effective. Further work should be focused on the selection of endemic crust species and their batch-culture in arid environment.展开更多
Changes in the distribution of soil aggregate sizes and concentrations of aggregate-associated organic carbon (OC) and nitrogen (N) in response to the fertilization of grasslands are not well understood. Understan...Changes in the distribution of soil aggregate sizes and concentrations of aggregate-associated organic carbon (OC) and nitrogen (N) in response to the fertilization of grasslands are not well understood. Understanding these changes is essential to the sustainable development of artificial grasslands. For understanding these changes, we collected soil samples at 0-20 and 20-40 cm depths from a semi-arid artificial alfalfa grassland after 27 years of applications of phosphorus (P) and nitrogen+phosphorus+manure (NPM) fertilizers on the Loess Pla- teau of China. The distribution of aggregate sizes and the concentrations and stocks of OC and N in total soils were determined. The results showed that NPM treatment significantly increased the proportions of 〉2.0 mm and 2.0-0.25 mm size fractions, the mean geometric diameter (MGD) and the mean weight diameter (MWD) in the 0-20 cm layer. Phosphorous fertilizer significantly increased the proportion of 〉2.0 mm size fractions, the MGD and the MWD in the 0-20 cm layer. Long-term application of fertilization (P and NPM) resulted in the accumulation of OC and N in soil aggregates. The largest changes in aggregate-associated OC and N in the 0-20 cm layer were found at the NPM treatment, whereas the largest changes in the 20-40 cm layer were found at the P treatment. The results suggest that long-term fertilization in the grassland leads to the accumulation of OC and N in the coarse size fractions and the redistribution of OC and N from fine size fractions to coarse size fractions.展开更多
Pollen records from the Chinese Loess Plateau revealed a detailed history of vegetation variation and associated climate changes during the last 13.0 ka BP. Before 12.1 ka BP, steppe or desert-steppe vegetation domina...Pollen records from the Chinese Loess Plateau revealed a detailed history of vegetation variation and associated climate changes during the last 13.0 ka BP. Before 12.1 ka BP, steppe or desert-steppe vegetation dominated landscape then was replaced by a coniferous forest under a generally wet climate (12.1-11.0 ka BP). The vegetation was deteriorated into steppe landscape and further into a desert-steppe landscape between 11.0 and 9.8 ka BP. After a brief episode of a cool and wet climate (9.8-9.6 ka BP), a relatively mild and dry condition prevailed during the early Holocene (9.6-7.6 ka BP). The most favourable climate of warm and humid period occurred during mid-Holocene (7.6-4.0 ka BP) marked by forest-steppe landscape and vegetation alternatively changed between steppe and desert-steppe from -4.0 to -1.0 ka BP.展开更多
Vegetation near-soil-surface factors can protect topsoil from erosion,however,their contributions to the reduction of soil erosion,especially under natural rainfall events,have not been systematically recognized.This ...Vegetation near-soil-surface factors can protect topsoil from erosion,however,their contributions to the reduction of soil erosion,especially under natural rainfall events,have not been systematically recognized.This study was performed to quantify the effects of near-soil-surface factors on runoff and sediment under natural rainfall events on grasslands dominated by Bothriochloa ischaemum(Linn.)Keng(BI grassland)and Artemisia gmelinii Thunb.(AG grassland)in two typical watersheds on the Loess Plateau,China in 2018.By successive removal of the plant canopy,litter,biological soil crusts(BSCs)and plant roots,we established five treatments including plant roots,plant roots+BSCs,plant roots+BSCs+litter,intact grassland and bare land in each grassland type.In total,twenty runoff plots(5 m×3 m)with similar slopes and aspects were constructed in the two types of grasslands.Results showed that plant canopy,litter and roots reduced runoff,while BSCs,which swelled in the presence of water,increased runoff.In contrast,all of these factors reduced sediment yield.In addition,the reductions in runoff and sediment yield increased with I30(maximum 30-min rainfall intensity)for each vegetation near-soil-surface factor except for BSCs.Among these factors,plant canopy had the largest contribution to runoff reduction,accounting for 48.8% and 39.9% in the BI and AG grasslands,respectively.The contributions of these vegetation near-soil-surface factors to sediment yield reduction were similar(21.3%-29.9%)in the two types of grasslands except for BSCs in the AG grassland(10.3%).The total reduction in runoff in the BI grassland(70.8%)was greater than that in the AG grassland(53.1%),while the reduction in sediment yield was almost the same in both grasslands(97.4%and 96.7%).In conclusion,according to the effects of different vegetation near-soil-surface factors on runoff and sediment production,our results may provide more complete insight and scientific basis into the effects of various vegetation related factors in controlling soil erosion.展开更多
基金supported by the Major Special Research projects in Gansu Province, China (22ZD6NA009)the National Key R&D Program of China (2022YFD1900300)+4 种基金the State Key Laboratory of Aridland Crop Science, Gansu Agricultural University, China (GSCS-2022-Z02)the Fostering Foundation for the Excellent Ph.D. Dissertation of Gansu Agricultural University, China (YB2020002)the Innovation Star Project for Excellent Graduate Student of Department of Education of Gansu Province, China (2021CXZX-369)the Young Instructor Fund Project of Gansu Agricultural University, China (GAU-QDFC-2020-03)the Science and Technology Project of Gansu Province, China (20JR5RA033)。
文摘The fully mulched ridge–furrow(FMRF) system has been widely used on the semi-arid Loess Plateau of China due to its high maize(Zea mays L.) productivity and rainfall use efficiency. However, high outputs under this system led to a depletion of soil moisture and soil nutrients, which reduces its sustainability in the long run. Therefore, it is necessary to optimize the system for the sustainable development of agriculture. The development, yield-increasing mechanisms,negative impacts, optimization, and their relations in the FMRF system are reviewed in this paper. We suggest using grain and forage maize varieties instead of regular maize;mulching plastic film in autumn or leaving the mulch after maize harvesting until the next spring, and then removing the old film and mulching new film;combining reduced/notillage with straw return;utilizing crop rotation or intercropping with winter canola(Brassica campestris L.), millet(Setaria italica), or oilseed flax(Linum usitatissimum L.);reducing nitrogen fertilizer and partially replacing chemical fertilizer with organic fertilizer;using biodegradable or weather-resistant film;and implementing mechanized production. These integrations help to establish an environmentally friendly, high quality, and sustainable agricultural system, promote highquality development of dryland farming, and create new opportunities for agricultural development in the semi-arid Loess Plateau.
基金This study was funded by the survey projects initiated by the Ministry of Natural Resources of the People’s Republic of China(1212010741003,1212011220224,and 121201011000150022)China Geological Survey(DD20189220,DD20211317)+2 种基金the public welfare scientific research project launched by the Ministry of Natural Resources of the People’s Republic of China(201111020)the project of 2015 Natural Science Basic Research Plan of Shaanxi Province of China(2015JM4129)the project of 2016 Fundamental Research Funds for the Central Universities of China(an open-end fund)(310829161128).
文摘In order to study the migration and transformation mechanism of Hg content and occurrence form in subsurface flow zone of gold mining area in Loess Plateau and its influence on water environment,the field in-situ infiltration test and laboratory test were carried out in three typical sections of river-side loess,alluvial and proluvial strata in Tongguan gold mining area of Shaanxi Province,and the following results were obtained:(1)The source of Hg in subsurface flow zone is mainly caused by mineral processing activities;(2)the subsurface flow zone in the study area is in alkaline environment,and the residual state,iron and manganese oxidation state,strong organic state and humic acid state of mercury in loess are equally divided in dry and oxidizing environment;mercury in river alluvial or diluvial strata is mainly concentrated in silt,tailings and clayey silt soil layer,and mercury has certain stability,and the form of mercury in loess is easier to transform than the other two media;(3)under the flooding condition,most of mercury is trapped in the silt layer in the undercurrent zone where the sand and silt layers alternate with each other and the river water and groundwater are disjointed,and the migration capacity of mercury is far less than that of loess layer and alluvial layer with close hydraulic connection;(4)infiltration at the flood level accelerates the migration of pollutants to the ground;(5)the soil in the undercurrent zone is overloaded and has seriously exceeded the standard.Although the groundwater monitoring results are safe this time,relevant enterprises or departments should continue to pay attention to improving the gold extraction process,especially vigorously rectify the small workshops for illegal gold extraction and the substandard discharge of the three wastes,and intensify efforts to solve the geological environmental problems of mines left over from history.At present,the occurrence form of mercury in the undercurrent zone is relatively stable,but the water and soil layers have been polluted.The risk of disjointed groundwater pollution can not be ignored while giving priority to the treatment of loess and river alluvial landform areas with close hydraulic links.The research results will provide a scientific basis for water conservancy departments to groundwater prevention and control in water-deficient areas of the Loess Plateau.
基金SACOL was sponsored by Lanzhou University through 985 Programthe National Basic Research Program of China under Grant No. 2006CB400501the National Natural Science Founda- tion of China under Grant Nos. 40633017 and 40725015
文摘Arid and semi-arid areas comprise about 30% of the earth's surface. Changes in climate and climate variability will likely have a significant impact on these regions. The Loess Plateau over Northwest China is a special semi-arid land surface and part of a dust aerosol source. To improve understanding and capture the direct evidence of the impact of human activity on the semi-arid climate over the Loess Plateau, the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) was established in 2005. SACOL consists of a large set of instruments and focuses on: (1) monitoring of long term tendencies in semiarid climate changes; (2) monitoring of the aerosol effect on the water cycle; (3) studies of interaction between land surface and the atmosphere; (4) improving the land surface and climate models; and (5) validation of space-borne observations. This paper presents a description of SACOL objectives, measurements, and sampling strategies. Preliminary observation results are also reviewed in this paper.
基金financially supported by Forestry Industry Research Special Funds for Public Welfare Projects(201104002-2)China National Scientific and Technical Innovation Research Project for 12th Five Year Plan(2015BAD07B0201)
文摘Soil water is an important factor restricting afforestation on the semi-arid Loess Plateau.The microtopography of the loess slope has changed the distribution pattern of soil water on the slope.To improve water utilization efficiency and optimize afforestation configuration patterns,the relationship between soil water and precipitation at micro-topographic scale must be studied.We used time series analysis to study the temporal variation of soil water and its response to precipitation in four kinds of micro-topographies and undisturbed slope on loess slopes.Micro-topographies significantly influenced soil water distribution and dynamics on the slopes.Soil water stored in the platform,sinkhole,and ephemeral gully influenced subsequent soil water for 4 weeks,whereas soil water stored in the scarp and undisturbed slope could influence soil water for 2 weeks.It took 12 weeks,10 weeks,18 weeks,6 weeks,and 12 weeks for precipitation to reach the deeper soil layer in the platform,sinkhole,scarp,ephemeral gully,and undisturbed slope,respectively.These soil water characteristics in different micro-topographies are vital factors that should be taken into consideration when undertaking afforestation on the Loess Plateau.
文摘Water harvesting is one of main measures to solve water shortage resulting from less precipitation and erratically seasonal dis- tribution in arid and semi-arid areas. Different types of anti-infiltration treatments including mechanical and chemical to micro-catchment and their runoff efficiencies had been reported. This paper, through 5 years experiment from 1992 to 1996, is aimed at studying the im- pacts of microcatchment water-harvesting system (MCWHS) with microphytic crust treatment on afforestation on semi-arid Loess Plateau. The results showed that after 3 years of crust inoculation, crust had covered majority of MCWHS and the function of water harvesting had also been demonstrated partially, there were significant difference in soil moisture of shallow soil layer in three typical spring stages be- tween crust cover and control treatments (0.05 level), and about 0.9%-6.04% increase of monthly mean soil moisture within 1m soil layer in spring of late 3 years. The impact of severe spring drought can be alleviated effectively. In the meanwhile, as crust developed on the treated surface, there are significant differences (0.05 level) for tree height (H), diameter at breast height (DBH) and diameter at ground level (DGL) at the end of the study period (1996) with the increases by 22.38%, 17.34%, and 20.49% respectively compared with the con- trol treatment. Microphytic crust, as one of biological infiltration-proof materials, may become the optimized option for revegetation in Chinese Great West Development Strategy due to its self-propagation, non-pollution to water qualities, long use duration and relatively cost effective. Further work should be focused on the selection of endemic crust species and their batch-culture in arid environment.
基金funded by the Program for New Century Excellent Talents in University (NCET-13-0487)the Program from Northwest A&F University (2014YQ007)+4 种基金the National Basic Research Program of China (2009CB118604)the National Science and Technology Support for Major Projects of China (2011BAD31B01)the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-JC408)Science and Technology Generalized Program for the Overall Development of Agriculture in Ningxia (NTKJ-2014-01)the Scientific Research Program from Education Department of Shaanxi Province (11JK0650).
文摘Changes in the distribution of soil aggregate sizes and concentrations of aggregate-associated organic carbon (OC) and nitrogen (N) in response to the fertilization of grasslands are not well understood. Understanding these changes is essential to the sustainable development of artificial grasslands. For understanding these changes, we collected soil samples at 0-20 and 20-40 cm depths from a semi-arid artificial alfalfa grassland after 27 years of applications of phosphorus (P) and nitrogen+phosphorus+manure (NPM) fertilizers on the Loess Pla- teau of China. The distribution of aggregate sizes and the concentrations and stocks of OC and N in total soils were determined. The results showed that NPM treatment significantly increased the proportions of 〉2.0 mm and 2.0-0.25 mm size fractions, the mean geometric diameter (MGD) and the mean weight diameter (MWD) in the 0-20 cm layer. Phosphorous fertilizer significantly increased the proportion of 〉2.0 mm size fractions, the MGD and the MWD in the 0-20 cm layer. Long-term application of fertilization (P and NPM) resulted in the accumulation of OC and N in soil aggregates. The largest changes in aggregate-associated OC and N in the 0-20 cm layer were found at the NPM treatment, whereas the largest changes in the 20-40 cm layer were found at the P treatment. The results suggest that long-term fertilization in the grassland leads to the accumulation of OC and N in the coarse size fractions and the redistribution of OC and N from fine size fractions to coarse size fractions.
基金National Science Fund for Distinguished Young Scholars, 40025105 National Natural Science Foundation of China, No. 40331012+3 种基金 NSF Project, No.EAR 0402509 No.BCS 00-78557 Doctoral Fund from Southwest University, No. 104220-20710904 CSTC, No.2009BB7112
文摘Pollen records from the Chinese Loess Plateau revealed a detailed history of vegetation variation and associated climate changes during the last 13.0 ka BP. Before 12.1 ka BP, steppe or desert-steppe vegetation dominated landscape then was replaced by a coniferous forest under a generally wet climate (12.1-11.0 ka BP). The vegetation was deteriorated into steppe landscape and further into a desert-steppe landscape between 11.0 and 9.8 ka BP. After a brief episode of a cool and wet climate (9.8-9.6 ka BP), a relatively mild and dry condition prevailed during the early Holocene (9.6-7.6 ka BP). The most favourable climate of warm and humid period occurred during mid-Holocene (7.6-4.0 ka BP) marked by forest-steppe landscape and vegetation alternatively changed between steppe and desert-steppe from -4.0 to -1.0 ka BP.
基金funded by the Chinese Academy of Sciences(CAS)"Youth Scholar of West China"Program(XAB2019A04)the National Natural Science Foundation of China(42130717).
文摘Vegetation near-soil-surface factors can protect topsoil from erosion,however,their contributions to the reduction of soil erosion,especially under natural rainfall events,have not been systematically recognized.This study was performed to quantify the effects of near-soil-surface factors on runoff and sediment under natural rainfall events on grasslands dominated by Bothriochloa ischaemum(Linn.)Keng(BI grassland)and Artemisia gmelinii Thunb.(AG grassland)in two typical watersheds on the Loess Plateau,China in 2018.By successive removal of the plant canopy,litter,biological soil crusts(BSCs)and plant roots,we established five treatments including plant roots,plant roots+BSCs,plant roots+BSCs+litter,intact grassland and bare land in each grassland type.In total,twenty runoff plots(5 m×3 m)with similar slopes and aspects were constructed in the two types of grasslands.Results showed that plant canopy,litter and roots reduced runoff,while BSCs,which swelled in the presence of water,increased runoff.In contrast,all of these factors reduced sediment yield.In addition,the reductions in runoff and sediment yield increased with I30(maximum 30-min rainfall intensity)for each vegetation near-soil-surface factor except for BSCs.Among these factors,plant canopy had the largest contribution to runoff reduction,accounting for 48.8% and 39.9% in the BI and AG grasslands,respectively.The contributions of these vegetation near-soil-surface factors to sediment yield reduction were similar(21.3%-29.9%)in the two types of grasslands except for BSCs in the AG grassland(10.3%).The total reduction in runoff in the BI grassland(70.8%)was greater than that in the AG grassland(53.1%),while the reduction in sediment yield was almost the same in both grasslands(97.4%and 96.7%).In conclusion,according to the effects of different vegetation near-soil-surface factors on runoff and sediment production,our results may provide more complete insight and scientific basis into the effects of various vegetation related factors in controlling soil erosion.