Land Use Change and Anthropogenic Driving Forces:A Case Study in Yanhe River Basin

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.

Research on the gully forming in the gully region of Yanhe River Basin and process of geological disasters

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.

Effects of Robinia pseudoacacia on the undergrowth of herbaceous plants and soil properties in the Loess Plateau of China

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.