The Study Of Microclimate Effects On Several Typical Patterns Of Farmland Of Loess Plateau

There was serious soil erosion in Loess Plateau region, the implementations of the Grain for Green Project have obvious improved the local natural conditions. It have studied about the impact of returning farmland to forests on many of the natural environment in the region, but the study about the whole micro-climate impact on small observation after returning farmland to forest areas was little. The study selected several typical patterns of farmland, in northern of in the county of Ansai in Shaanxi of Loess Plateau, though the small climate of observations in spring, summer and autumn of 2009, found the characteristics of forest areas micro-climate in some typical patterns of farmland after returning farmland to Forests, provided a basis for the data of the further implementation of the research, started a discussion.The study selected four plots in the west side of the hill of the Soil and Water Conservation Experiment Station Chinese Academy of Sciences in the County of Ansai, all the four plots was farmland in 1998, including forest, shrub forest, artificial forests and a bare control without vegetation cover, the small climate was observed in April, July, September, and also selected the air temperature, relative humidity, soil temperature, light intensity as the four indicators to analysis. Through research the main conclusions were draw as following:1. The characteristics of the changes of atmospheric temperature in different patterns of farmland:From 8:00, the air temperature gradually increased, from13:00 to 14: 00 get to reach the highest, and then gradually decreased. The same law was in different patterns of farmland. The air temperature of the same season in different patterns of farmland is different t, this difference is mainly caused by the cover of different vegetation. The turbulence advection has a certain extent impact on the temperature of different modes. T was half of the temperature measurements, the value of temperature of four modes can be expressed as: T bare> T shrub forest> T artificial forest> T forest.2. The characteristics of the changes of air relative humidity in different patterns of farmland:The relative humidity of the air in different patterns of farmland shows two high-middle- low "V" shaped features. The characteristics was negative correlation with air temperature, when solar radiation was the strongest, temperature was the highest .Because of the temperature, the temperature led to the near-surface transpiration increasing, making relative humidity lowest. About 14:00-15:00, the relative humidity in four kinds of patterns of farmland reached a minimum value, one hand because transpiration loss of water caused by solar radiation, on the other hand because when the solar radiation was strongest, the plant stomata was closure, the respiration suspended, reduced drainage. Relative humidity shows a pattern: artificial shrubbery > mixed forest> artificial forest> bare land.3. The characteristic of the changes of soil temperature in different patterns of farmlands:The soil temperature at the same depth in the same patterns of different seasons, in order of July> September> in April, the soil temperature in the same pattern in the same season at different depths, in order of 5cm> 10cm> 15cm> 20cm> 25cm, the temperature in the same season in different patterns at the same depth, in order of bare land > artificial shrubbery> artificial forest> mixed forest. The solar radiation and vegetation cover mainly affected by the soil temperature.4. The characteristic of the changes of light intensity in different patterns of farmlandFrom8:00 to 19:00 in the determination time during the day, starting from 8:00, when time goes by, the light intensity increased gradually to reach the maximum value at around 12:00, and then declined. This law between the different patterns of farmland shows obvious differences, such differences were mainly caused by the cover of different vegetation.