Evaluation of the Effect of Aeration Tubes and Holes on Soil Gas Exchange Using a Simulation Model

Abstract

A prevalent strategy to mitigate the negative impacts of soil compaction or sealing on urban trees involves installing aeration tubes, aeration holes or near surface aeration horizons to enhance gas exchange between the soil air and the atmosphere. Despite their widespread use, there is currently no scientific evidence confirming their effectiveness. In this study, gas exchange between the atmosphere and soils that were aerated using different methods was modelled and evaluated in the laboratory and in the field. Both the laboratory and field measurements could be modelled well with the simulation model. The research showed that the effectiveness of aeration tubes and holes is highly dependent on the air-filled porosity of the soil. The more gas exchange can take place via the soil pores, the lesser the influence of the aeration equipment. Thus, the use of aeration tubes is not necessary when using tree substrates in unsealed tree pits but could mitigate disturbances in soil aeration in compacted and fine-grained soils with low air capacity. However, modelling shows that the effect of aeration tubes and holes is less than expected and that near-surface aeration layers are generally more effective than vertical aeration systems. With the help of the modelling of gas exchange as presented here, it is possible to optimise the level of aeration of the soil depending on the existing degree of compaction and/or the planned surface sealing.