Initial recovery of compacted soil—planting and technical treatments decrease CO2 concentrations in soil and promote root growth

The combination of technical treatments and planting of alder trees in a compacted forest soil improves the circulation of air and water through the pore system. This leads to decreases in CO2concentrations and increases in root growth in the soil. Both are indicative of an initial recovery of soil structure.

Context. The compaction of forest soils, caused by forest machinery, has as a principal consequence: the destruction of soil structure and thus the reduction of the soil aeration status. Thus, the gas exchange between soil and atmosphere is reduced and the depth propagation of roots is limited, resulting in the shortage of water and nutrient supplies for trees.
Aims. This research aimed at detecting the first stages of recovery of soil structure in a compacted forest soil, which was treated with a combination of techniques (i.e., planting tree species, mulching, addition of lime), which could presumably accelerate the regeneration of soil structure.
Methods. The variation of CO2 concentrations and the dynamics of root growth were repeatedly measured. Linear mixed models were developed in order to test the effects of the treatments and the planting of trees on soil aeration, as well as to identify the influence of the different environmental effects on CO2 concentration in soil.
Results. The planting of root-active trees showed significant effects on decreases in CO2 concentrations. However, during the short-term observation, some negative effects occurred especially for the mulched sites. Nevertheless, all applied technical treatments promoted an improved soil aeration and a higher root growth compared to untreated sites which points to an initial enhanced recovery of soil structure. Pronounced seasonal and interannual variations of soil respiration were highly influenced by soil temperature and soil water content variations.
Conclusion. An initial regeneration of soil structure is indicated by distinct changes of the soil aeration status. This regeneration is partially enhanced by the applied treatments. The quantitative potential of the regeneration techniques needs a longer observation period for mid- and long-term soil recoveries.

Compacted forest soils, CO2 concentrations, Root growth, Rhizotron window, Soil temperature, Soil water tension

Flores Fernández, J.L., Hartmann, P., Schäffer, J. et al. Annals of Forest Science (2017) 74: 73.

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