Skip to content

This past June, from 23-28, the 8th International Symposium on Interactions of Soil Minerals with Organic Components and Microorganisms was held in the city of Seville. This symposium was organized by Division 2.5 belonging to the International Union of Soil Sciences (IUSS). The specific theme chosen for this symposium was “Understanding Soil Interfacial Reactions for Sustainable Soil Management and Climate Change Mitigation”.

From the INTARSU Project we had the opportunity to participate in this symposium in the scientific session entitled “Dynamics of pollutants at soil interfaces – What is new and how can environmental biotechnology be beneficial for soil restoration and bioremediation?”

Marta Gil Martínez gave an oral presentation entitled “Tree species effect on soil organic matter and soil microorganisms in trace element contaminated soils” where she presented the latest results obtained from the study about the effects of phytoremediation in soils contaminated by trace elements, after the mining spill of Aznacólllar in 1998. In this study, an exhaustive study of the changes in soil organic matter was carried out under three tree species: olive, white poplar and pine, and in a treeless area dominated by herbaceous species. In addition, two zones located 15 and 30 km from the discharge point were sampled to study, as well as, how the effects of these trees vary according to the physical and chemical properties of the soils.

The objectives of this study were:

- Evaluating the effect of these species on different fractions of soil organic matter, after 15 years of tree growth, as part of the phytoremediation program.

- Analysing the influence of microbial activity in two contrasted areas with different degradation status.

The results obtained from this study showed that the North zone (closer to the mine) has greater availability of trace elements due to the acidic pH and the low content of soil organic matter. Among the species studied, the pine had an acidifying effect in this zone but not in the South zone (farther from the mine) due to the neutral pH and greater buffering power of these soils. This effect of the pine is explained by infrared analysis, which showed its litter and underneath soils some characteristic peaks of acidic functional groups (pectins, resins and waxes), which did not appear in other species infrared analysis.

The effects of phytoremediation had a positive effect on the amount of organic matter, compared to treeless areas, and this was reflected in a greater microbial biomass.

Among the conclusions of this study, we highlight the potential of pine trees to acidify the soil, however this species also generates a large amount of litter, increasing the organic matter of the soil. It has also been found that reforestation has increased microbial biomass, therefore, new functionalities are being recovered in soils.

You can access the presentation in this link:

Gil-Martínez M, Fernández Boy ME, Marañón T, Montero González JF, Navarro-Fernández CM, Domínguez MT (2019). Tree species effect on soil organic matter and soil microorganisms in trace element contaminated soils. 8th International Symposium on Interactions of Soil Minerals with Organic Components and Microorganisms (Sevilla).