Liding Chen

The relationships between land use and soil conditions in the hilly area of the loess plateau in northern Shaanxi, China

Abstract Inappropriate land use is one of the main reasons for soil erosion and nutrient loss in the hilly loess area. In the Yangjuangou catchment, which has typical hill and gully topography, the effects of land use changes on soil erosion and the distribution of soil nutrients and moisture were studied at the three spatial scales of total catchment, transect and land use type. Between 1984 and 1996, forest and grassland increased by 36% and 5%, respectively, and slope farmland decreased by 43%. The land use changes decreased annual soil erosion by 24%. The amounts of total N, total P, available N, available P and organic matter of surface soil (0–20 cm) and of moisture in the 0–70 cm soil suggest that a farmland/grassland/forest land use structure from hill foot to hill top has a better capacity for soil conservation and retention of nutrients than other land use structures. The contents of soil nutrients are in the order forest>grassland>slope farmland, and those of soil water are forest

Soil moisture variation in relation to topography and land use in a hillslope catchment of the Loess Plateau, China

The profile characteristics and the temporal dynamics of soil moisture variation were studied at 26 locations in Da Nangou catchment (3.5 km(2)) in the loess area of China. Soil moisture measurements were performed biweekly at five depths in the soil profile(0-5, 10-15, 20-25, 40-45 and 70-75 cm) from May to October 1998 using Delta-T theta probe. Soil moisture profile type and temporal variation type and their relationship to topography and land use were identified by detrended canonical correspondence analysis (DCCA) and correlation analysis. The profile distribution of time-averaged soil moisture content can be classified into three types i.e. decreasing-type, waving-type and increasing-type. The profile features of soil moisture (e.g. profile gradient and profile variability) are influenced by different environmental factors. The profile type of soil moisture is only attributed to land use while profile gradient and profile variability of soil moisture is mainly related to land use and topography (e.g. landform type and slope). The temporal dynamics of layer-averaged soil moisture content is grouped into three types including three-peak type, synchro-four-peak type and lagged-four-peak type. These types are controlled by topography rather than by land use. The temporal dynamic type of soil moisture shows significant correlation with relative elevation, slope, aspect, while temporal variance displays significant relation with slope shape. The mean soil moisture is related to both the profile and dynamics features of soil moisture and is controlled by both land use and topography (e.g. aspect, position, slope and relative elevation). The spatial variability of soil moisture across landscape varies with both soil depths and temporal evolution

The effects of land use on soil moisture variation in the Danangou catchment of the Loess Plateau, China

Abstract Soil moisture plays a critical role in both crop growth and vegetation restoration in semiarid environments. Its spatial and temporal variability results from topography, soils, vegetation and land uses. However, little knowledge exists about the effects of land use structure on soil moisture variability. In order to analyze soil moisture variations in relation to land use patterns, five land use structures and seven land use types were selected to monitor soil moisture. Soil moisture measurements were performed biweekly at 26 locations in a small catchment on the Loess Plateau of China from May to October 1998. The measurements were taken using a Theta-Probe at five depths of soil profile (0–5, 15–20, 25–30, 45–50 and 70–75 cm). These data were analyzed for soil moisture variations in space and time for seven land use types. Three peaks and three troughs of soil moisture variations during the growing season were found. The influence of shrubland on mean soil moisture within 0–70 cm was significantly different from that of cropland, orchard and intercropping land. Three types of soil moisture changes in profile were classified as increasing, decreasing and waving types. An analysis of the differences in soil moisture for five land use structures indicated that the influences of land use patterns on soil moisture were complex. This study provides an insight into the implications for hydrological modeling, runoff and erosion control in this area.

Soil quality regime in relation to land cover and slope position across a highly modified slope landscape

Vegetation and land-use mosaics of shrub land, grassland, farmland and reforested land are characteristic for residential areas of the Wolong nature reserve in Sichuan province, southwest China. The patterns represent a stage in long-term human disturbance and natural secondary succession since deforestation. The aim of this paper was to elucidate the soil-land cover types, soil-slope position relationships on a typical disturbed slope in the humid mountainous region. Soils were taken from four typical land cover types (shrub land, grassland, farmland and reforested land) under four slope positions (upper slope, middle slope, lower slope, foot slope) to study the distribution of soil nutrients and moisture on the transect scales of the slope. To elucidate the influence of land-use and slope position on soil quality, two integrated quantitative indexes were developed to compare soil quality under different land-use types (QI) and under different slope positions (PI). The results showed shrub land had the highest QI value, while the QI of reforested land and farmland had lower values. Foot slopes and upper slopes had higher soil quality levels compared to middle slopes and lower slopes. The results indicated that on the slope scale shrub land had high soil quality levels. The results also suggested that in the area of China where the climate favors secondary succession, ‘leave nature as it is’ is a better choice than the policy ‘change farmland to forest land’.

Analysis on soil nutrient characteristics for sustainable land use in Danangou catchment of the Loess Plateau, China

Understanding of the characteristics of soil organic matter (SOM) and soil nutrients at the field and catchment scale is important for refining agricultural management practices and for improving sustainable land use. In order to analyze on SOM and nutrient differences among different land use types and their relationships between land use, landscape position and slope aspect, 94 sampling sites including 7 land uses were selected along 6 transects in the Danangou catchment with an area of 3.5 km(2) on the Loess Plateau of China. Significant differences in SOM, total N (TN), available N (AN) and available P (AP) among these land uses were found.. Higher values in SOM, TN and AN were measured in soils from woodland and grassland, but lower values in the soils from fallow land and cropland. Compare SOM and TN with cropland, intercropping land had high contents. The adjusted R-2 values of regression models for SOM and nutrients with land use, landscape position and slope aspect ranged from 0.501 (SOM) to 0.134 (AP). A comparison between average predicted and measured values for SOM and each soil nutrient revealed that the predicted values in TP and AN for each land use, in SOM and TN except for fallow land and in AP except for intercropping land, shrub land and woodland, fell with in a 95% confidence interval about the measured values. The simplified predicted models of soil nutrients combined with the key value of SOM for soil quality can serve to improve agricultural practices and to provide useful information on sustainable land use. Improvement in SOM and nutrients would be expected from more C inputs including manure and crop residues and alternative cultivation practices such as developing intercropping system, building terrace for soil and water conservation, return the cropland with SOM content less than a key value of 0.44% to the grassland and woodland on the hilly areas similar to the Loess Plateau of China. At the same time, it is recommended that nitrogen fertilization addition could be decreased in the foot slope and increased on the upper slope

The effect of land use structure on the distribution of soil nutrients in the hilly area of the Loess Plateau, China

The irrational land use is one of the main reasons for the soil erosion and nutrienloss in the loess hilly area of China. In this project, 4 types of typical land use structure of sustain ment for about 15 years in the loess hill slope are selected to study the effect of land use structure on the distribution of soil nutrients. From hill bottom to hill top, the patterns of land use types are: grassland-slope farmland-forest, slope farmland-grassland-forest, terrace-grasslandforest and slope farmland-forest-grassland. By measuring the contents of the total N, total P, available N, available P and organic matter of soils, the results show that the land use structure types of slope farmland-grassland-forest and terrace-grassland-forest have a better capacity to maintain the soil nutrients.

A framework for evaluating the effectiveness of protected areas: the case of Wolong Biosphere Reserve

To evaluate the effectiveness of protected areas, we developed a general framework to integrate necessary steps into an operational system. In this case study, we applied the framework to the Wolong Biosphere Reserve in Sichuan Province (southwestern China), the largest reserve of Giant Pandas (Ailuropoda melanoleuca). We collected data through questionnaire surveys and employed fuzzy modeling to analyze and integrate the data collected. The results revealed that Wolong Biosphere Reserve was moderately effective in nature conservation, especially in the protection of Giant Pandas. But the overall effectiveness of Wolong Biosphere Reserve was not as high as expected because its functions in environmental education, social development and economic development were only marginally effective. Both the overall effectiveness of Wolong Biosphere Reserve and the effectiveness of nature conservation need to be improved. First, efforts should be directed towards improving nature conservation and more specifically on improving the protection of forest ecosystems. To achieve this objective, local farmers in Wolong Biosphere Reserve should become the main group improving nature conservation. In addition, more effective measures should be developed to raise the living standards and the socio-economic status of the local farmers in an environmentally compatible way. Second, environmental education for local people and outsiders should be increased. Furthermore, we need to strengthen basic research and build cooperation among the reserve administration bureau, researchers and other organizations at the local, national and international levels. Finally, we need to improve the living conditions of the local population through education, family planning and healthcare

Spatiotemporal prediction of soil moisture content using multiple-linear regression in a small catchment of the Loess Plateau, China

Abstract Three basic multiple-linear regression models with different sets of more readily observed environmental variables (land use, topographic and meteorological factors) were developed for the prediction of soil moisture content in space and time. The model performances were evaluated in the Danangou catchment (3.5 km2) on the Loess Plateau, China, with soil moisture content measurements. The soil moisture content measurements were performed biweekly at five depths in the soil profile (0–5, 10–15, 20–25, 40–45 and 70–75 cm) from May to October 1998 and from May to September 1999, using a Delta-T theta probe. It was indicated that the regression models could describe the relationships of soil moisture content with environmental attributes. It was found that the spatiotemporal-SM model showed the best goodness of fit since it explained the greatest fraction of soil moisture variation in both space and time, and the predicted mean, standard deviation, minimum and maximum soil moisture were closest to the observed values. This model was also either the most precise or the most economical in prediction of soil moisture content in space and time since it gives the lowest values in mean absolute error of prediction (MAE) and Akaike information criterion (AIC). There is little difference in performance and cost-benefit between the spatial-GM model and landuse-GM model. The superior robustness of the spatiotemporal-SM model over the other two models is most significant in the prediction of soil moisture content at 0–5 cm, and decreases with increasing soil depth.

Soil conditions in a small catchment on the Loess Plateau in China

Abstract This article presents the results from soil surveys carried out within the framework of a soil conservation research project with several components: soil erosion modelling, land evaluation and participatory planning. The study area was a small catchment (3.5 km2), ranging in altitude between 1085 and 1370 m, in the vast Loess Plateau area in northern China. It is continuously affected by soil erosion by water, to a certain extent due to the unprotected slopes resulting from cultivation of subsistence food by the land users. The information on variability of soil properties in the study catchment was required as a basis for development of land use scenarios opting for ecological and economical sustainable production for the land users in the future. Soil profiles to 1-m depth were described, using FAO guidelines, at 17 sites along two transects covering the different facets of the morphology: hilltop, hillslope, valley bottom. Samples were collected from each horizon in the soil profiles for laboratory determination of physical and chemical properties. It was found that the nutrient status of the soils was poor, with ranges in contents of: sand=6.5–30.0%, silt=53.5–74.5%, clay=11.1–29.0%, organic matter=0.11–1.32%, available P=0.1–11 ppm, available N=5–56 ppm. The extremely high pH values, ranging between 8.7 and 9.3, effectively restricted the availability of nutrients. The soils have a high available water storage capacity so that, during years with a good supply of rain water, fair yields of crops can be achieved if the soil is fertilised. However, during dry years, when the soil dries out, the soils are vulnerable to drought and the crops fail. A divide at approximately 1200 to 1225 m above sea level was found between stratified and unstratified loessial soils. Above this altitude, the soils were yellowish, homogeneous silt loams with no or few restrictions for tillage, root penetration or water percolation. Below this altitude, layers that were more reddish (due to soil processes during climatically wetter periods), slightly cemented or higher in clay content, although still having a silt loam texture, were found in the soil profiles. These layers could cause problems at tillage, and could give rise to some restrictions to root penetration and water percolation, thereby increasing the erosion risk. A partitioning into characteristic soil types is proposed, to be used in the other parts of the project: erosion modelling, land evaluation and participatory planning.

Greening China Naturally

China leads the world in afforestation, and is one of the few countries whose forested area is increasing. However, this massive “greening” effort has been less effective than expected; afforestation has sometimes produced unintended environmental, ecological, and socioeconomic consequences, and has failed to achieve the desired ecological benefits. Where afforestation has succeeded, the approach was tailored to local environmental conditions. Using the right plant species or species composition for the site and considering alternatives such as grassland restoration have been important success factors. To expand this success, government policy should shift from a forest-based approach to a results-based approach. In addition, long-term monitoring must be implemented to provide the data needed to develop a cost-effective, scientifically informed restoration policy.