How various surface covers affect soil structure and hydraulic properties

Different land uses significantly affect the soil water and temperature regimes. Very different modifications of the soil surface are found especially in the urban environment, where different materials, which are used in gardening and civil engineering, are used to cover soil surface. Alternations of these regimes due to modifications of soil covers may lead to changes in soil properties. Therefore, the goal of this study was to find out how soil properties, particularly soil structure and soil hydraulic properties changed during our experiment, which has been mainly focused on the monitoring of soil water and thermal regimes under five different surface covers (bare soil, bark chips, concrete, mown grass, and unmown grass). The surface of a Haplic Chernozem (which was originally coverd by grass) was modified in the autumn 2012. Since then, climatic conditions are monitored, and soil water contents and temperatures are measured at the depths of 10, 20, 30, 40, 60, and 80 cm. In the summer 2020, after removal of the surface over, intact soil samples were taken, on which the hydraulic properties were measured using the multistep outflow method. Another set of the undisturbed soil samples was used to study soil structure using the X-Ray computer tomography. In addition, these samples were next used to prepare thin soil slides for micromorphological analyses. Along with soil sampling, the measurement of some characteristics took place directly in the field. The mini disk tension infiltrometer with a disk radius of 2.22 cm was used to measure unsaturated hydraulic conductivities for pressure head of –2 cm. The net CO2 and net H2O efflux were measured using the LCi-SD portable photosynthesis system with a Soil Respiration Chamber. The CT and micromorphological analyzes showed that while the soil under the bare surface showed small aggregates and small interaggregate pores, the soil under the grass cover was formed by large aggregates with large pores formed by roots and organisms living in soils. Soil structure under concrete or bark chips was compact with thin fractures and few pores created by organisms living in soils. However, porosity under bark chips was larger than that under concrete likely due to better conditions, i.e., larger amount of the organic matter content due to the decomposition of organic mulch. Measured soil properties reflected character of soil structure.

Acknowledgement: Study was supported by the European Structural and Investment Funds, projects NutRisk (No. CZ.02.1.01/0.0/0.0/16_019/0000845).