Human activities alter land use patterns and affect landscape sustainability. It is therefore very important to investigate the relationship between land use change and human activities. This study focuses on the dete...Human activities alter land use patterns and affect landscape sustainability. It is therefore very important to investigate the relationship between land use change and human activities. This study focuses on the detection of changing land use patterns in the Yanhe River Basin in northern Loess Plateau of China between 1995 and 2008. Landscape metrics were used to analyze the changing land use patterns and to explore the related anthropogenic driving forces. Results show that:1) Totally, 186 590 ha of croplands were converted into alternate land-use types (equivalent to 61.7% of the original cropland area). The majority of cropland areas were found to be converted into grassland and woodland areas (accounting for 55.9% and 4.9% respectively of the original cropland areas). 2) Both cropland and woodland demonstrated an increasing fragmentation tendency while grasslands showed a decreasing fragmentation tendency. 3) Multiple driving forces of land use change were thought to act together to changes in landscape metrics in the Yanhe River Basin. The anthropogenic driving forces were analyzed from four perspectives:ecological conservation policy, labor force transfer, industrial development, and rural settlement. The policy of the GfG (Grain for Green) project was the main driving factor which expedited the conversion from cropland to woodland and grassland. Industrial development was also found to affect land use change through the direct impact of economic activities such as oil exploration and agricultural production, or through indirect impacts such as the industrial structures readjustment. Labor force transfer from rural to urban areas was found to follow the industrial structure readjustment and further drove land use change from cropland to off-farm land use. Establishment of new tile-roofed houses instead of cave-type dwellings in rural settlements has helped to aggregate the original scattered land-use type of construction.展开更多
In recent years, the frequency of geological disasters gradually increases in the gully region of the Loess Plateaus centred with Yanhe River Basin. The research on the forming of the geological disasters in gully reg...In recent years, the frequency of geological disasters gradually increases in the gully region of the Loess Plateaus centred with Yanhe River Basin. The research on the forming of the geological disasters in gully region and the disaster process will help us further understand the development of geological disasters and the disaster process. According to the detailed survey of geological disasters in Yan’an City, the river and gully erosion is the main natural predisposing factor that caused the geological disasters in the river gully region. In the forming of ditches and gullies, the surface water system changes the stress form of the original slope and reduces the strength combination of the slope in ways of water erosion and gravity erosion. Gully’s forming stage and stratigraphic contact form have some influence on the geological disasters and disaster process.展开更多
[Objective] The aim was to study the climate changes of Yanhe watershed during 1974-2004. [Method] The monthly temperature and precipitation during 1974-2004 in seven representative stations in Yanhe watershed were ch...[Objective] The aim was to study the climate changes of Yanhe watershed during 1974-2004. [Method] The monthly temperature and precipitation during 1974-2004 in seven representative stations in Yanhe watershed were chosen. By dint of climate statistics analysis method, accumulated anomaly and signal/noise ratio method, the regional temperature and precipitation changes in recent 31 years were expounded and its changes features and the year having climate mutation were found out. [Result] The climate changes in Yanhe watershed in recent 31 years rose at a speed of 0.44 ℃/10 a. The temperature increase range enlarged after 1990s. Precipitation decreased at a speed of 26.3 mm/10 a. Precipitation reduced most distinctly in summer and autumn, and the reduction range enlarged in 1990s. 1996 was the year of abrupt temperature changes year in the region. 1993 was the year of temperature transition year. 1994 was the year of precipitation mutation year. 1990 was the year of precipitation transition year. [Conclusion] The study provided references for the agricultural production, life and disaster pre-warning in Yanhe watershed.展开更多
Aims The introduction of Robinia pseudoacacia(RP)has some effects on undergrowth herbaceous plants(UH),soil properties and their relationships,which may be related to the vegetation zone.However,few studies have teste...Aims The introduction of Robinia pseudoacacia(RP)has some effects on undergrowth herbaceous plants(UH),soil properties and their relationships,which may be related to the vegetation zone.However,few studies have tested effects of RP on UH and soil over a large-scale area of the Loess Plateau.Methods The study area consisted of three vegetation zones(the steppe,forest-steppe and forest zone).Two canopy plant types were selected:RP stands and adjacent native vegetation.We measured five leaf functional traits:leaf carbon content(LC),leaf nitrogen content(LN),leaf phosphorus content(LP),specific leaf area(SLA)and leaf tissue density(LTD).The functional diversity,species diversity and community-weighted mean(CWM)traits were calculated.Important Findings(i)CWM.LN,CWM.LP and CWM.SLA increased significantly,whereas CWM.LC and CWM.LTD decreased significantly in the three vegetation zones,compared with the native communities.(ii)Species diversity,functional diversity and community biomass decreased in the steppe zone,increased in the forest zone,and did not differ significantly in the forest-steppe zone.(iii)We found only soil organic carbon(P<0.05)and soil total nitrogen(P<0.05)in the forest zone decreased significantly compared with the native plots.(iv)The relationship between UH and soil properties was affected by RP and the vegetation zone.Overall,the effect of RP on UH and soil properties was associated with the vegetation zone.This result is of great significance to the planning of restoration and reconstruction of artificial forests in the Loess Plateau.展开更多
基金Under the auspices of National Natural Science Foundation of China(No.40930528)State Forestry Administration of China(No.201004058)External Cooperation Program of Chinese Academy of Sciences(No.29GJHZ0948)
文摘Human activities alter land use patterns and affect landscape sustainability. It is therefore very important to investigate the relationship between land use change and human activities. This study focuses on the detection of changing land use patterns in the Yanhe River Basin in northern Loess Plateau of China between 1995 and 2008. Landscape metrics were used to analyze the changing land use patterns and to explore the related anthropogenic driving forces. Results show that:1) Totally, 186 590 ha of croplands were converted into alternate land-use types (equivalent to 61.7% of the original cropland area). The majority of cropland areas were found to be converted into grassland and woodland areas (accounting for 55.9% and 4.9% respectively of the original cropland areas). 2) Both cropland and woodland demonstrated an increasing fragmentation tendency while grasslands showed a decreasing fragmentation tendency. 3) Multiple driving forces of land use change were thought to act together to changes in landscape metrics in the Yanhe River Basin. The anthropogenic driving forces were analyzed from four perspectives:ecological conservation policy, labor force transfer, industrial development, and rural settlement. The policy of the GfG (Grain for Green) project was the main driving factor which expedited the conversion from cropland to woodland and grassland. Industrial development was also found to affect land use change through the direct impact of economic activities such as oil exploration and agricultural production, or through indirect impacts such as the industrial structures readjustment. Labor force transfer from rural to urban areas was found to follow the industrial structure readjustment and further drove land use change from cropland to off-farm land use. Establishment of new tile-roofed houses instead of cave-type dwellings in rural settlements has helped to aggregate the original scattered land-use type of construction.
基金“Twelfth National Five-Year Plan” for science in 2013 “Research and demonstration of key technology of engineering construction in loess hill-gully area” (Item number: 2013BAJ06B03, 2013BAJ06B04)Science and technology co-ordinating innovative engineering projects in Shaanxi Province in 2013 “Research on geological and geotechnical engineering construction in loess hill-gully area of Yan’an City” (Item number: 2012KTZD03-04, 07)
文摘In recent years, the frequency of geological disasters gradually increases in the gully region of the Loess Plateaus centred with Yanhe River Basin. The research on the forming of the geological disasters in gully region and the disaster process will help us further understand the development of geological disasters and the disaster process. According to the detailed survey of geological disasters in Yan’an City, the river and gully erosion is the main natural predisposing factor that caused the geological disasters in the river gully region. In the forming of ditches and gullies, the surface water system changes the stress form of the original slope and reduces the strength combination of the slope in ways of water erosion and gravity erosion. Gully’s forming stage and stratigraphic contact form have some influence on the geological disasters and disaster process.
基金Supported by National Natural Science Youth Fund (41001374)Basic Scientific Research Business of Central Universities and Basic Research Support Fund of Chang'an University (CHD2009JC167)Basic Science and Research Business of Central University (Human Social Science Fund) (Y1014)
文摘[Objective] The aim was to study the climate changes of Yanhe watershed during 1974-2004. [Method] The monthly temperature and precipitation during 1974-2004 in seven representative stations in Yanhe watershed were chosen. By dint of climate statistics analysis method, accumulated anomaly and signal/noise ratio method, the regional temperature and precipitation changes in recent 31 years were expounded and its changes features and the year having climate mutation were found out. [Result] The climate changes in Yanhe watershed in recent 31 years rose at a speed of 0.44 ℃/10 a. The temperature increase range enlarged after 1990s. Precipitation decreased at a speed of 26.3 mm/10 a. Precipitation reduced most distinctly in summer and autumn, and the reduction range enlarged in 1990s. 1996 was the year of abrupt temperature changes year in the region. 1993 was the year of temperature transition year. 1994 was the year of precipitation mutation year. 1990 was the year of precipitation transition year. [Conclusion] The study provided references for the agricultural production, life and disaster pre-warning in Yanhe watershed.
基金This study was supported by the National Natural Science Foundation of China(41671289,41601586).
文摘Aims The introduction of Robinia pseudoacacia(RP)has some effects on undergrowth herbaceous plants(UH),soil properties and their relationships,which may be related to the vegetation zone.However,few studies have tested effects of RP on UH and soil over a large-scale area of the Loess Plateau.Methods The study area consisted of three vegetation zones(the steppe,forest-steppe and forest zone).Two canopy plant types were selected:RP stands and adjacent native vegetation.We measured five leaf functional traits:leaf carbon content(LC),leaf nitrogen content(LN),leaf phosphorus content(LP),specific leaf area(SLA)and leaf tissue density(LTD).The functional diversity,species diversity and community-weighted mean(CWM)traits were calculated.Important Findings(i)CWM.LN,CWM.LP and CWM.SLA increased significantly,whereas CWM.LC and CWM.LTD decreased significantly in the three vegetation zones,compared with the native communities.(ii)Species diversity,functional diversity and community biomass decreased in the steppe zone,increased in the forest zone,and did not differ significantly in the forest-steppe zone.(iii)We found only soil organic carbon(P<0.05)and soil total nitrogen(P<0.05)in the forest zone decreased significantly compared with the native plots.(iv)The relationship between UH and soil properties was affected by RP and the vegetation zone.Overall,the effect of RP on UH and soil properties was associated with the vegetation zone.This result is of great significance to the planning of restoration and reconstruction of artificial forests in the Loess Plateau.
