Spatial variability of soil temperature in Poland

Abstract

The aim of the study was to determine the spatial variability of monthly mean soil temperature at a depth of 5 cm in Poland. Soil temperature data from 88 meteorological stations in the years 1961-1975 were used. The measurement data were analyzed using statistical and geostatistical methods. Spatial variability of soil temperature was recognized based on the empirical semivariograms, adjusted models and semivariogram parameters i.e. values of nugget, sill, range of spatial dependency and calculated fractal dimensions. The spatial distribution of surface soil temperature was determined from measurement points data, using the kriging method. Significant and strong spatial dependence of soil temperature with a range from 290 to 880 km was found, and the shape of this relationship was spherical. The values of the nugget, sill and fractal dimension increased during the summer period and decreased from autumn to spring and were the lowest at the end of autumn and at the beginning of winter. These data indicate that during the spring and summer the spatial variability of the soil temperature is mostly modified by diversified precipitation and a higher content of sand fraction in the central part of Poland. Surface semivariograms indicate the occurrence of anisotropy in the soil temperature distribution that changed with time. Spatial distributions of soil temperature show significant diversification in the territory of Poland with longitudinal orientation in autumn and winter and latitudinal in spring and summer.

Keywords

• soil temperature
• spatial variability
• geostatistics
• anisotropy
• fractal dimension
• spatial distribution