Methods For Estimation Of Mean Annual Soil Temperature In China

Mean annual soil temperature is an important physical property of soil and of great significance to regional agricultural production.The data of domestic study is few and previous.The identical estimation model is used to estimate mean annual soil temperature and it's short of compare of different methods.Ground meteorological data accumulated in the 895 meteorological stations in China during the period from 1980 to 2010 were collated,mean annual soil temperature analyzed and estimation model with meteorological and environment factors and mean difference between mean annual soil and air temperature based on zoning by Grade I standard farming system in China through Spssl8.0 and Arcgis 10.2.Results show:Mean annual soil temperature in various soil layers 5 to 40cm in depth in all the regions was higher than the mean annual air temperature monitored at the meteorological stations of corresponding regions.From north to south,mean annual air temperature,precipitation and soil temperature rising all.From east to west,that is,from Norteast China to Northwest China,mean annual air and soil temperature rising,mean annual precipitation declining;from the Middle and Lower Reaches of Yangtze River to Sichuan Basin,mean annual air temperature and precipitation declining slightly,mean annual soil temperature changes smally.;from Jiangnan region to Yunnan-Guizhou Plateau,mean annual air temperature,precipitation and soil temperature declining slightly.In the same meteorological zone,regardless of meteorological stations,mean annual soil temperature varied with soil depth within 5?40 cm,but the variation didn't follow the same trend.Mean annual soil and air temperatures differed in the range of ? 0.1? in all the soil layers from 5 to 20cm in depth,but varied more,significantly in the soil layers from 20 to 40cm in depth,and the difference in some individuals zones reached 0.4?.In some zones the difference varied in the range of 1.4?3.9 ? at 20 cm in soil depth and in the range of 1.1?4.3 ? at 40cm in soil depth.Comparison between meteorological zones shows that 5?40 cm mean difference between mean annual soil and air temperature varied regionally,that is,declining first and then rising from north to south,and gradually increasing from east to west.Around the country,mean annual soil temperature is significantly negative relative with latitude,longitude and altitude at 0.01.Latitude has the greatest impact,followed by altitude,longitude has the least impact.The estimation of mean annual soil temperature using the mean annual soil and air temperature difference method is quite low in accuracy and the method is recommended for use only in the Middle and Lower Reaches of the Yangtze River,Inner Mongolia and zone along the Great Wall,Sichuan Basin and Yunnan-Guizhou Plateau and Qinghai-Tibet Plateau;The estimation of mean annual soil temperature using meteorological and environment factors method is quite high in accuracy in all the zones of Grade I standard farming system,except for Qinghai-Tibet Plateau.In fanning zones where the distribution of meteorological stations is dense and little in elevation variation.In the soil layers 5?40cm in depth,mean annual soil temperature varied in the range of<0.1 ? at 5cm and the max variation is 0.3 ?,much less in the soil layers 20?40cm in depth.Based on a single estimation site,the estimated mean soil temperature in the soil layer at 50 cm differed from the value at 40 cm to the extreme by? 0.4?.It is advisable to use the soil temperature at 40cm to replace that at 50cm in the prevailing "Chinese Soil Taxonomy".