Evaluation of soil structure and physical properties influenced by weather conditions during autumn-winter-spring season

Abstract

Physical state of the upper soil layer is susceptible to external factors, including weather conditions. It concerns in particular a soil without plant cover or mulching. Significant soil structure transformations could arise especially due to the globally observed climate change which e.g. increases the possibility of extreme precipitation events. Therefore, we evaluated the seasonal changes of structure of the uncovered 0–5cm soil layer and their effect on other physical properties in relation to precipitation and air temperature. Both the direct evaluation of soil structure by quantitative image analysis and the measurements of structure-dependent parameters as water and air contents and permeabilities were conducted to describe soil physical state in detail. Soil samples were taken on 4 dates during the 2009/2010 season from a Haplic Luvisol developed from loess-like deposits. The largest alterations of soil structure were detected in spring, after the soil had thawed completely and had been affected by the heavy and long-term precipitation. During the season soil structure transformed from aggregate into non-aggregate one and the rearrangement of soil pore size distribution occurred. Soil showed very high available water capacity and mostly medium saturated hydraulic conductivity, but field air capacity and corresponding air permeability decreased below values required for good plant condition. The total volume of pores correlated negatively with precipitation and temperature. Actual water content was strongly positively correlated with the precipitation amount shortly before sampling. There was no statistically valid correlation between saturated hydraulic conductivity and precipitation or temperature. Furthermore, air permeabilities for selected groups of pores showed contrasting trends with precipitation, dependent on the studied span of time. The temperature influenced the intensity of soil drying and freezing-thawing processes. Most of the identified alterations of soil physical state could be attributed however to mechanical impact of rain which remodelled pores and solid phase in the studied soil layer.