| Soil water is the limiting factor for vegetation restoration and ecological reconstruction, in order to solve the question of ecological construction and economic development on the Loess Plateau, three kinds of micro-irrigation technology and supporting technology were used to reform the irrigation measure in Mengcha village of Mizhi county in 2006, maintenance costs of micro-irrigation facilities increased with the aging of micro-irrigation projects and facilities, the useful measures need to be supplied urgently to ensure the jujube trees getting enough water in the jujube forests came form the northern of Shaanxi, Therefore, Bamboo-shaped rainwater harvesting ditch (BRHD) technique which is a new soil water conservation measure is practiced. It could be highly appropriate for specific geographical conditions in the Hilly Loess Plateau Region of China. This study can help to create new patterns and ways of water efficiency from mountain jujube forests in the northern of Shaanxi.This study based on the combination of field tests and indoor experiment and the analysis of soil samples indoor.The study foucus on the response of soil water on Bamboo-shaped rainwater harvesting ditch (BRHD) of mountain jujube forests in the northern of Shaanxi. The objectives of the study were to understand the water storage capacity and impounding capacity and water retention capacity of BRHD system and study the influence of BRHD system to soil moisture spatial and temporal distribution and transport law and analyse soil physical properties in the soil profile of each BRHD, according to the actual observed data, the evapotranspiration model of the mountain jujube forest in the northern of Shaanxi was anaylised comparatively.The main results are as follows:1. The BRHD with the best size and filling material was selected because of the biggest water storage capacityUnder three different water flow rates, the BRHD when the size was 1×0.3×0.3m showed the largest water storage capacity. The BRHD with the size of 1×0.3×0.3m was selected to study the influence of fillers of BRHD; the BRHD filled with straw has shown the best water storge capacity than other materials of filler in the three kinds of water flow. The order of water storage capacity of the BRHD wirh different filler is:straw>branch>gravel.2. The water-holding capacity of different filling materials and water interception capacity of BRHD have the significant differenceThe water-holding capacity was studied under the condition of the four kinds of materials immersion to water, the results have showed that the water-holding capacity of wood chips is almost 2.5 times than straw; the stone almost doesn’t hold water. Water interception capacity of BRHD under 0.6 mm/min rainfall intensity is mare than 0.92 mm/min rainfall intensity.3. The effects of BRHD on soil physical properties existedThe BRDH filled with substrate and soybean hulls can reduce soil bulk density, enhance soil porosity and improve the ability of water retention and moisture diffusion. The BRDH filled with substrate and soybean is effected mainly concentrating on the soil layer form 20cm to 40cm, the soil porosity of the BRDH filled with substrate and soybean were enhance 6.08% and 2.26%, the saturated moisture content and saturated hydraulic conductivity were increased in different degrees.4. The BRHD has a certain effect on soil moisture increaseDifferent materials the BRDH systems filled with were not significantly affect the soil moisture around the BRDH systems, the soil moisture around the BRDH systems is higher than flat bench-terraces (FBT) system about 12% and it suggests that water retention effect of BRDH systems is better than flat bench-terraces (FBT) system. In the period of jujube dormancy, the soil water storage capacity of BRDH systems decreased 24mm after the period of jujube dormancy, the soil water storage capacity of FBT systems decreased up to 50 mm, it suggests that BRDH systems has good inhibitory effect of water evaporation and hold soil moistureAccording to locating observation about the jujubes for three consecutive years, the BRDH systems can help to increase the yield of jujube about 10.13%.5. Significant differences of the moisture change with time and space between BRHD and FBT systems(1) Soil moisture changes greatly in the BRHD filled different materialsSoil water storage under the treatments gradually decreased from May to August. It then increased significantly after August as the rainfall increased. Clearly, water storage capacity of the BRHD system is higher than that of the FBT system on October.(2) Different soil moisture recovery deep in BRHD filled different materialsThe depths of soil water restoration in October under the GD, SD and BD systems were 110 cm,140 cm and 140 cm, respectively. However, soil water restoration depth under the FBT system was only 80 cm. Below the 80 cm soil layers, however, different degrees of soil water loss (discharge) were noted in the study area.(3) Different materials the BRDH systems filled with have different saturated time under simulated rainfall conditionsThe BD treatment was the first get saturated, SD had the longest time to reach saturation. The needed time of water intercepted under the BRHD systems were in the order of SD (68min)> GD (59min)> BD (47min)(4) High soil water area can developed on the BRHD conditionUnder the rainfall intensity of 0.92mm/min, after rain 30min, soil moisture diffusion about 0.3m, rain diffusion reach lm after 24 hours, while soil moisture in the soil at a depth of 2 m did not change significantly, the results showed high soilwater area is conducive to the growth of jujube trees.6. The Shuttleworth-Wallace model can effectively estimate the mountain jujube water consumptionThe accuracy of Shuttleworth-Wallace model in transpiration estimation met the evaluation criteria, but was affected by the weather condition, specifically, sunny days> rainy days. In the stand of sparsely cultivated jujube forest, the reliability of Shuttleworth-Wallace was comprehensively validated. Therefore, huttleworth-Wallace model could be the promising model applied in ET estimation to grasp the law of water consumption for jujube forest and similar stand. Over the whole growing season, Shuttleworth-Wallace model performed better than Penman-Monteith model in ET estimation. Their accuracy was the poorest in the germination and leaf expansion stage and changed following the growth seasons. The accuracy of Shuttleworth-Wallace model in ET estimation met the evaluation criteria but Penman-Monteith model did not. |
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