Hydrological And Soil Conservation Effects Of Citrus Garden In Red-soil Slope

Citrus reticulata Blanco cv. Ponkan is an important economic fruit tree in Jiangxi Province. Study of the ecosystem effects on hydrological processes of Citrus reticulata Blanco cv. Ponkan is an important part of exploring hydrological processes of regional forest ecosystem. Standard runoff plots are set in the Jiangxi Provincial Soil and Water Conservation Eco-science Park. Through years of observation, testing and experiments, effects of soil and water conservation and hydrological on citrus forest in red soil slope are studied. This research explores the hydrological effects mechanism of the different artificial building models on citrus forest and concludes the means of planting citrus forest to protect water and soil resources which can provide a scientific reference for citrus fruit industry and sustainable development of ecological environment construction. The study includes analysis of rainfall characteristics, canopy interception, soil moisture dynamics, runoff and sediment characteristics of slope, infiltration and runoff model for simulation. The main results are as follows:1. During the year and annual change of rainfall and rainfall intensity in the study areaAccording to the rainfall observation data of study area from 2001 to 2010 shows that the water resource is rich, average rainfall is 1317 mm, the average rainfall intensity is 1.68mm h-1. The total rainfall is 1508 matches from 2001 to 2010.70.9% of annual rainfall concentrated from March to August, the remaining 6 months of rainfall accounted for only 29.4% of annual rainfall. The trend of rainfall is bimodal curve one year, and the highest rainfall is in April, May, June, July gradually fell, and another peak occurred in August, the minimum annual average rainfall is in December. By using Mann-Kendall trend analysis method, rainfall characteristics of interannual rainfall fluctuations remain stable from 2001 to 2010. The difference not decrease significant in spring, autumn and winter, but increase significant in summer. In flood days it shows steady trend, and it shows no significant change in the main flood season and dry season.2. Citrus forest canopy interception and litter characteristicsInterception average rate of citrus canopy is 29.61%, and stem flow rate is 25.67%, and the proportion of through rain is 44.72%. It is that 70.39% of the precipitation will be the second allocation. The relationship between plant outside the forest canopy interception showed significant correlation. But the correlation is strong when rainfall is less than 20mm and poor when rainfall exceeds 20mm. It proves that there is a maximum canopy interception capacity, allowing the maximum interception or canopy interception capacity. The correlation of stem flow and gross rainfall is close in rainfall outside. There are a significant linear relationship between rainfall outside of forest and stem flow. The average stem flow is 4.72mm in 43 rainfall observations, accounting for 25.67% of precipitation outside the forest. Test shows that the largest citrus litter water-holding rate is 325.73%, and is 3.26 times of their litter dry weight.3. Soil moisture characteristics and changes of citrus under different soil and water conservation measuresThe average soil moisture increases with soil depth increasing because surface runoff and subsurface flow effect. The soil moisture increases from 11% to 29% in 0-10cm, from 12% to 31% in 10-20cm, from 14% to 32% in 20-30cm, and from 18% to 38% in 30-40cm. The soil moisture of 6 Cynodon dactylon (L.)Pars. plot(bermudagrass cover band) is highest in 10cm, and of 4 Paspalum natatu plot (bare check) in 20cm and 30cm is highest. In 40cm layer 4 plot (bare check) is the highest and 1 plot (the whole park bahia grass cover) is highest in plots which set measures. Planting grass in citrus forest can effectively intercept-runoff,accumulate,rainfall and surface runoff to accumulate on the slope, not down slope loss. Their water consumption is small in grass cover bands so the water conservation is the best.The seasonal change of soil moisture has a consistent trend. In the 10cm soil layer, the characteristics of soil moisture changes are two valleys and three peaks. The first peak appears in April, and the soil moisture content is maximum in June, reaching a second peak. The soil moisture is lowest in August, and shows the first valley. In October, soil moisture is highest, and third peak. In December, soil water content decreases, shows a second valley. Soil moisture changes in 20cm,30cm and 40cm with the seasons has a similar trend to the 10cm soil layer. Soil and water conservation measures to play an important role in maintaining soil moisture, the higher the vegetation coverage, the smaller the change of soil moisture content.4. Runoff and sediment characteristics of citrus in red soil slope under different soil and water conservation measuresRainfall is the main source of surface runoff.59 separate single rainfall data are selected from the experimental observations from 2001 to 2010, and carried out regression analysis. Runoff increases along with rainfall, rainfall intensity increasing, and the highest correlation with the rainfall is highest, and next is rainfall intensity, and rainfall duration is worst. This shows that rainfall influence runoff significantly.Statistical analysis of rainfall runoff observation data from 2001 to 2010 shows that the soil and water conservation measures can significantly improve effects of runoff reduction. Red soil sediment and rainfall,30min rainfall intensity, rainfall kinetic energy have a significant linear correlation, but the amount of sediment associated with rainfall is generally less than the correlation of runoff and rainfall. Sediment volume with the impact of previous rainfall is more correlative with the previous rainfall, but less than its impact of rainfall. Heavy rain and torrential rain are the major rainfall types which cause soil erosion in citrus of red soil slope. In addition, the amount of sediment and rainfall, runoff are significantly correlated which are more close than the relationship with rainfall, 30min. rainfall intensity, rainfall kinetic energy and the pre-rainfall.5. Characteristics of erosive rainfall and rainfall erosivity under different treatments in citrus forestThe standards variability of erosive rainfall is widely under different treatment in citrus forest. The order of erosive rainfall standard is clean tillage orchard, for 9.8mm, farming groups, for 10.37mm, terraced group, for 11.34mm, and grass measures group, for 14.69mm. The changes of rainfall erosivity and rainfall inter-annual are consistent. 6 Annual variations of runoff and sediment under different treatmentThe characteristics of the inter-annual runoff and sediment show that the runoff and sediment are decreasing trend with time. The soil and water conservation can play a very good role in water and soil conservation effect by plants in the citrus orchards, farming and engineering measures, which can also increase citrus production and improve the local ecological environment.