Study On Fish-scale Pits Of Different Specification In Semi-arid Loess Plateau Of Northern Shaanxi Province

Soil moisture is the main restricted factor in the construction of vegetation restoration and ecological environment in Loess Plateau.This research paper seeks to explore the fish-scale pits of different specifications in the semi-arid Loess Plateau of northern Shaanxi province under the different influence of environmental factors. And this study can provide a theory, scientific basis and policy support to afforestation key technology under difficult site conditions. This thesis has Wuqi County in Yan'an in Shaanxi Province as the experimental region, explore the fish-scale pits of different specifications in the semi-arid Loess Plateau of northern Shaanxi province by stratified sampling of soil samples, determination of soil water content and mathematical analysis. The major conclusions are as follows:By studying the distribution of precipitation of Wuqi County indicated the average annual precipitation decreased in the past 50 years, annual precipitation had the large amplitude, the more water and less water in precipitation can have a difference of 1 to 3 times. During the each year,the distribution curve of the precipitation had mostly typical single peak. Rainfall mainly concentrated in the growing season (5 to 9 months), the precipitation for each month are not the same in the growing season, rainfall was accounted for 58% of the precipitation in growing season between 7 to 8 months, and it was accounted for only 24% of the precipitation in growing season between 5 to 6 months. Seasonal distribution of precipitation was uneven, precipitation distribution ratio of the four seasons as followed:the precipitation in spring (3 to 5 months) was accounted for 15% of the year, the rainfall in summer(6 to 8 months) was accounted for 51% of the year,the rainfall in autumn (9 to 11 months) was accounted for 22% of the year, the precipitation in winter was accounted for only 12% of the year. To ensure that 80% of the precipitation rate was the 306mm in growing season (4 to 9 months), which was accounting for 76.0% of average precipitation over the same period.The variability of precipitation in rainy season was more larger than in spring,but the guarantee rate of precipitation in rainy season was more less than in spring.Fish-scale pit could effectively intercept surface runoff and reduced soil erosion in slope, and it also played an important role in improving soil moisture, so it created favorable water conditions for vegetation. The seasonal variation trend of soil moisture in fish-scale pits of different specifications overall performance as " two litres of two drop," accordingly, the dynamic changes of soil water in fish-scale pits of different specifications was divided into four stages:soil moisture slow recovery (October to next spring), soil moisture decline period (4 to 6 months), soil moisture complement recovery (6 to 8 months) and soil moisture subsidise period (8 to 10 months). The soil moisture content in fish-scale pits of different specifications was relatively large in October 2009 and 2010 June and October, and in April and August 2010 the soil moisture content in fish-scale pits of different specifications was smaller or similar.In the gentle slope, the soil moisture increases with the specifications of fish-scale pits, the big fish-scale pits improve soil moisture content was 2.1% in half-sunny slope, the big fish-scale pits which in half negative slope increase soil moisture content was 1.85%, the large scale pits to raise the soil moisture content was 2.56%; in terms of soil water on steep and extremely steep slopes, specifications may be ranked in the descendant order of middle, large, small and smaller, on semi-sun to steep slopes, the soil moisture of middle fish-scale pits improved 1.59%, semi-sunny to the extremely steep slopes, the middle fish-scale pits improved soil moisture content was 1.92%.Rainfall, slope and aspect on the variation of soil moisture in fish-scale pits had a significant impact, while the size of the fish-scale pits was not significant to the variation of soil moisture. In terms of the influence on rainfall to the soil moisture, in the descendant order of small, smaller, middle and large. The variation of soil moisture in fish-scale pits of different specifications correlation with slope was increased with increasing specifications. In terms of soil water that was influenced by aspect, specifications may be ranked in the descendant order of large, small, middle, and smaller.