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Soil infiltration capability is the hot spot topic of soil erosion studies and soil physical and chemical properties have great influence on it. A new infiltration method point - source infiltration method was used to precisely evaluate the infiltration capability in different purple soil land - use types. And correlation analysis on soil physical and chemical properties and soil infiltration capability of different land - use types was performed. Results showed that: (i) there is a large difference among soil physical and chemical properties in different land - use types, soil water content, non - capillary porosity, capillary porosity, content of > 0.25 mm aggregates and organic matter content in the top soil are greater than those in the subsoil; (ii) soil infiltration capability showed differences among different land - use types. Land use showed great effects, in general, the order of decrease on initial infiltration rate and average infiltration rate was: woodland slope > slope farmland > grassland, the order of decrease on steady infiltration rate was : slope farmland > woodland > grassland and the time reaching stable state was : slope farmland > woodland > grassland; (iii) correlation analysis showed that there was a significantly positive correlation between initial infiltration rate and wet sieve MWD value and structural damage rate, and it had a significantly negative correlation with capillary porosity; (iv) steady infiltration rate and non - capillary porosity showed the significantly positive correlation, and it had a significantly negative correlation with the soil bulk density; (v) the average infiltration rate and non - capillary porosity and structural damage rate showed a positive correlation and the correlation coefficient was large and there was a negative correlation between average infiltration rate and soil bulk density and capillary porosity, and the absolute value of correlation coefficient was relatively large. The results of this study can provide the theoretical basis for soil infiltration study in purple soil area. [ABSTRACT FROM AUTHOR]

As a fundamental characteristic of soil physical properties, the soil Particle Size Distribution (PSD) is important in the research on soil moisture migration, solution transformation, and soil erosion. In this research, the PSD characteristics with distinct methods in different land uses are analyzed. The results show that the upper bound of the volume domain of the clay domain ranges from 5.743μm to 5.749μm for all land-use types. For the silt domain of purple soil, the value ranges among 286.852~286.966 μm. For all purple soil land-use types, the order of the volume domain fractal dimensions is DclayDsilt(U)>Dsand (U)>Dsand and Dsilt>Dsilt(U)>Dsand>Dsand(U), respectively. As it is compared with all Dvi, the Dsilt has the most significant correlativity to the soil texture and organic matter in different land uses of the typical purple soil watersheds. Therefore, Dsilt will be a potential indictor for evaluating the proportion of fine particles in the PSD, as well as a key measurement in soil quality and productivity studies. [ABSTRACT FROM AUTHOR]

In this study, the current situation of pluriactivity in mountainous and hilly rural areas of Sichuan province was analyzed using representative sample survey data and natural factor data calculated based on 30 m-resolution DEM and GIS. Moreover, using logistic regression model, a quantitative analysis was conducted on factors influencing pluriactivity in terms of individuals, households, communities and natural environmental conditions. The results showed that, (1) only 17.77% of rural laborers in mountainous and hilly areas of Sichuan province were engaged in pluriactivity. Geographically, pluriactivity was mainly chosen according to the 'proximity principle', and was concentrated in construction and service industries; (2) the following factors have a significant influence on whether rural laborers in hilly areas engage in pluriactivity: gender, number of years of education, marriage, number of laborers and time to towns. Those with little influence include: age, health, family size, arable land per capita and per capita income, whether there are elderly people over 75 years and children less than 3 years. According to the main factors affecting pluriactivity, the government should enhance vocational skills training for rural laborers in mountainous and hilly areas, especially for female laborers, further improve transport accessibility and encourage rural laborers, especially female laborers to move into pluriactivity to increase the income of farm households. [ABSTRACT FROM AUTHOR]

Quantification of soil spatial and temporal variability at watershed scale is important in ecological modeling, precision agriculture, and natural resources management. The spatio-temporal variations of soil nitrogen under different land uses in a small watershed (12.10 km) in the hilly area of purple soil at the upper reaches of the Yangtze River in southwestern China were investigated by using conventional statistics, geostatistics, and a geographical information system in order to provide information for land management and control of environmental issues. A total of 552 soil samples (0 to 15 cm) from 276 sites within the watershed were collected in April and August of 2011, and analyzed for soil total nitrogen (STN) and nitrate nitrogen (NO3-N). We compared spatial variations of STN and NO3-N under different land uses as well as the temporal variations in April (dry season) and August (rainy season). Results showed that STN contents were deeply affected by land-use types; median STN values ranged from 0.94 to 1.27 g·kg, and STN contents decreased in the following order: paddy field > forestland > sloping cropland. No significant difference was found for STN contents between April and August under the same land use. However, NO3-N contents were 23.26, 10.58, and 26.19 mg·kg in April, and 1.34, 8.51, and 3.00 mg·kg in August for the paddy field, sloping cropland and forestland, respectively. Nugget ratios for STN indicated moderate spatial dependence in the paddy field and sloping cropland, and a strong spatial dependence in forestland. The processes of nitrogen movement, transformation, absorption of plant were deeply influenced by land use types; as a result, great changes of soil nitrogen levels at spatial and temporal scales were demonstrated in the studied watershed. [ABSTRACT FROM AUTHOR]

Abstract: Determining soil nutrient distribution is critical to identify sites which are at risk of N and P loading. Equally important are determining factors that influence such distribution (e.g. land use, land management, topography, etc.). In this research, soil nutrient distribution and its influencing factors were studied in a small-scaled watershed in the purple soil region of Sichuan Province, China. The watershed is 1.3km2 with a complex land management system including agriculture and forestry. Surface soil samples (0–20cm) from 48 sites within the watershed were collected in the spring of 1999 and analysed for chemical properties. When spatial distribution patterns of soil organic matter and soil nutrients were considered, several patterns were evident. Soil organic matter and total nitrogen coincided with high soil nutrients in the center of the watershed. Total phosphorus was linked to low soil nutrient contents on hilltops, while total potassium was characterized by low variability and high soil nutrient content throughout the watershed. Water-soluble nutrients in soils were highly variable throughout the watershed. Results of this study indicate that land use, topography and other variables play important roles in controlling the spatial distribution of most soil nutrients. However, the relative roles of these indices were nutrient specific. The relationship was therefore complex. Land use, silt, and sand content contributed to a high level of heterogeneity for soil organic matter and total nitrogen with the former being the dominant factor. Land use, particle size distribution (silt and sand) and topographic factors (slope and elevation) contributed to the variability of total phosphorus. However, particle size distribution and topographic factors were the dominant factors affecting total phosphorus. Elevation influenced the concentration of total potassium and land use controlled the concentration of dissolved phosphorous. No significant relationship was found between the studied characteristics and nitrate nitrogen. [Copyright &y& Elsevier]

Abstract: Bedload sediment is not only a major pollutant, but can also act as a transporter of pollutants. Sediment flow behavior often reflects the characteristics of a watershed, such as land use and management. To clarify the behavior of sediment flow under different spatial scales and storm types in the Chinese purple soil area, the sediment flow behavior in three small agro-watersheds with different catchment areas, physical characteristics and land use types was investigated during natural rainfall events from 1999 to 2000. The results showed that there were three types of sediment hydrographs, waveform or linear with a low sediment concentration (1.13±0.58gl−1), logarithmic decrease (3.41±4.13gl−1), and compound linear and logarithmic decrease (9.58±10.90gl−1). During PP-type rainfall events (high-intensity rainfall occurred during the prophase of the rainfall process) and ML-type rainfall events (high intensity rainfall occurred during the middle of the rainfall event), the waveform or linear type sediment hydrographs or the logarithmic decrease type hydrographs were generated in each of the three agro-watersheds. However, sediment hydrographs produced by IM-type rainfall events (discontinuous rainfall with obvious segments) depended on the spatial scale of the watershed. As the spatial scale decreased, the hydrographs were transformed from the logarithmic decrease type to the compound type. In addition, it was found that the S = aQ b model could effectively simulate the sediment hydrologic process of a single rainfall event. The information provided in this study will help evaluate and prevent soil and water loss and non-point source pollution in the purple soil region. [Copyright &y& Elsevier]