基于不同估算方法的贵州省土壤温度状况

Soil Temperature Regime in Guizhou Province Relative to Assessment Method

土壤温度状况是土壤系统分类重要的土壤诊断特性,是土壤某些分类单元的划分依据。以贵州省86个气象站点(1951/71—1980)地面气候资料为基础,应用不同的土壤温度估算方法(土温内插法、土温直接估算、纽荷模型估算、气温回归估算法、纬度海拔回归估算法),判定贵州省各县(市)的土壤温度状况。结果表明,5种方法的估算结果基本一致,"不同海拔的贵州省经纬度海拔回归估算"方法在贵州省土壤温度状况估算中的应用更为广泛。贵州省土壤温度状况包括温性、热性和高热性三种土壤温度状况类型;有80个县(市)的估算结果属于热性土壤温度状况;威宁、大方属于温性土壤温度状况;有4个县(市)估算结果处在不同土壤温度状况临界值附近,存在两种土壤温度状况,其中水城、开阳和习水存在温性和热性两种土壤温度状况,而罗甸则存在高热性和热性两种土壤温度状况。将贵州省土壤温度状况作为诊断特性应用于土壤系统分类时,应综合考虑成土环境条件。

Soil temperature regime refers generally to soil temperature at 50 cm（T50）in soil depth or at the interface between lithic or paralithic substance and soil in soil profiles thinner than 50 cm. It is an important parameter charactering soil properties and a diagnostic feature and basis in modern soil classification systems for dividing soil classification units. However,so far none of the existing observatory stations is capable of providing observatory data all by itself sufficient for dividing attributes of soil temperature. Fortunately,as soil temperature at any observatory station is closely related to geographic position（coordinates,altitude,etc.）,meteorological conditions and some other environmental elements of the locality the station sits in,some researchers have built up several models by making use of these obtainable environmental indexes for assessing soil temperature regime. Currently the following five methods are commonly used in researches on soil temperature regime in China：＂Soil temperature interpolation method＂,＂Direct estimation method＂,＂Newhall model-based estimation＂,＂National air temperaturebased regression estimation＂and＂Coordinates and elevation-based regression estimation＂. These methods have been extensively applied to researches on soil temperature regime in various regions of the country with some good results. However,little has been reported on the work In Guizhou Province. In this paper,based on the ground climatic data（1951/71~1980）pooled from 86 meteorological observatory stations all over Guizhou Province,the five methods were either used directly or modified in the light of the actual situation in Guizhou. With the soil temperature interpolation method,T50 is deduced from the soil temperatures measured at 40 cm and 80 cm in depth,with interpolation,namely,mean annual T50 =mean annual soil temperature at 40cm＋[mean annual soil temperature at 80 cm-mean annual soil temperature at 40 cm]/4. With the direct estimation method,the mean annual soil temperature at 20 cm in depth is deemed as T50. With the Newhall simulation model method,some modification has been made of the model in the light of the close relationship between soil temperature and air temperature in Guizhou,like assuming that the mean annual T50 is 1.8 ℃ higher than the mean annual air temperature. The air temperature-based regression estimation method is developed by Feng Xueming,using the mean annual air temperatures of 150 meteorological stations scattered in 30 provinces of China as（x）and mean annual T50（y）namely y=2.900 1＋0.951 3x（r=0.988 9）.On the basis of the Feng Xueming method,a multiple regression equation is put forward and used to reflect the influence of latitude（x1）and elevation（x2）besides the air temperature,namely y=40.25-0.716 6x1-0.002 389x2（r=0.9515）. Direct use of the coordinates-based regression estimation method may have some deviation. It is,therefore,modified into y=132.979-0.54×latitude（x1）-0.005×elevation（x2）-0.9×longitude（x3）（r=0.910）. In the end,in view of the special terrains of Guizhou,a series of regression estimation models are established to fit regions different in elevation,namely,for regions ≤ 800 m in elevation,the model of y=129.57-0.551x1-0.006x2-0.864x3（r=0.910）is used;for regions between 800 m and 1 400 m in elevation,the model of y=133.693-0.514x1-0.005x2-0.916x3（r=0.864）is;and for regions above 1 400 m in elevation,the model of y=141.454-0.724x1-0.005x2-0.945x3（r=0.976）is,separately. Results show that the five methods,some of which have been modified,may yield basically similar estimations,which indicates that they are all applicable to estimation of soil temperature regimes in Guizhou. But for regions lacking sufficient soil or air temperature data the method of longitude-latitudeelevation based regression estimation method is more commonly used. The soil temperature regimes in Guizhou can be sorted into three categories：hyperthermic,thermic and mesic;Guizhou has 80 counties（cities）in the category of thermic temperature regime;Weining and Dafang of Bijie in the category of mesic temperature regime;and four counties in between the two categories,like Shuicheng,Kaiyang and Xishui counties where both mesic and thermic temperature regimes exist,and Luodian where both thermic and hyperthermic temperature regimes do. Besides,when temperature regime is used as diagnostic feature in soil classification in Guizhou,attention should be paid to the fact that the meteorological stations may represent most of the areas under the influence of the atmosphere,but not the maintain areas where variations along vertical zones and microrelieves exist. As two categories of soil temperature regimes exist in Shuicheng,Kaiyang,Xishui and Luodian counties,it is essential to take into account soil forming environmental conditions,especially topographic conditions,in applying the methods to estimation of soil temperature regimes.