Attending the 12th International Conference on Mine Closure

Last September, the 12th International Conference on Mine Closure was celebrated in Leipzig (Germany). This conference, organized by the Technical University Bergakademie Freiberg, is one of the world`s reference events among the mine closure professionals. The main conference topics that were discussed and that have been found as the main issues were:  establishing integrated life of mine planning, design sustainable land uses from the social and environmental perspective, increasing the post-mining assets value, and establishing  stable and self-regenerating ecosystems, among others.

Due to the urgent necessity of improving reclamation of mining areas, abandoned and/ or in transition to close, researchers from IRNAS-CSIC, University of Seville, University of Reading and Haute École Condorcet have collaborated to present a paper and an oral communication in this conference.

Gil-Martínez M, Domínguez MT, Navarro-Fernández CM, Crompot H, Tibbett M , Marañón T (2018). Long-term effects of trace elements contamination on soil microbial biomass and enzyme activities, in C Drebenstedt, F von Bismarck, A Fourie & M Tibbett (eds), Proceedings of the 12th International Conference on Mine Closure, Technical University Bergakademie Freiberg, Germany, pp. 633-644.

Results from the applied strategy of phytostabilisation on mining areas contaminated by heavy metals were presented. In our study area known as Guadiamar Green Corridor, where phytostabilisation have happened over 19 years, forestation has been found to improve soil fertility and microbial biomass, which is an indicator of improved soil quality. Moreover, different tree species have been found to affect soil chemistry and biology in different ways. White poplar was found to increase soil pH and to recover nutrients levels. However, stone pine was found to acidify the soil, increasing heavy metal availability and reducing microbial communities. In conclusion, previous to forestation is recommended to select the most suitable species for the specific conditions of the mining area to reclaim.

In this conference, Marta Gil-Martínez, predoctoral researcher from IRNAS-CSIC, had the opportunity to visit the Wismut Uranium Tailings Remediation Project , which started back in 1991 and currently clean-up, re-contouring and implementation of covers tasks are still in place. Last cover consists in revegetation to establish some forest and pastures areas, in order to maximize biodiversity.


Soil contamination and colonization by ectomycorrhizal fungi associated with holm oak

The environmental disaster caused by the breakdown of the decanting basin of the Aznalcóllar mine, Seville (in 1998), left behind hectares of contaminated land. The tasks of decontamination and restoration of the ecosystem led to the establishment of a green and environmentally protected area, the Guadiamar Green Corridor. The restoration was carried out through plantations of native trees, however, the restoration of the microbial flora of the soil, a crucial component for the functioning of terrestrial ecosystems, was not included.

A research group from IRNAS, CSIC, in collaboration with the EEZ, CSIC, the University of Seville and the University of Copenhagen (Denmark) have assessed the status of the ectomycorrhizal fungi (ECM) community associated with the roots of the holm oak (Quercus ilex) in the contaminated and recovered Guadiamar soils. Ectomycorrhizal fungi form symbiotic associations mainly with trees. These fungi develop a hyphal sheath, known as the mantle, around the roots tips of trees where the exchange of nutrients (carbohydrates for nitrogen, mainly) is developed inherent in this type of symbiosis. A single tree can be colonized, at the same time, by several species of fungi. However, within the group of fungal species capable of developing this type of symbiosis, there are functional differences, both at the level of nutrient intake and exchange with the plant, and at the plant protection against trace elements contamination. These differences can be inferred, in part, from the morphology of these fungi, but few studies have been based on the characterization of individual mycorrhizal root tips to infer the effects of an environmental impact on ectomycorrhizal fungal communities.

The molecular and morphological characterization of the ectomycorrhizal fungi associated with holm oak in a pollution gradient in the Guadiamar Green Corridor allowed us to discover that contamination is in fact affecting the functional composition of the ECM community. In the most contaminated areas, there was a reduction in the abundance of fungi capable of exploring the substrate at long and medium distances, which could, consequently, affect the nutritional status of trees at contaminated sites.

The study has been published in the journal Soil Biology and Biochemistry:

López-García, Á., Gil-Martínez, M., Navarro-Fernández, C. M., Kjøller, R., Azcón-Aguilar, C., Domínguez, M. T., Marañón, T. (2018). Functional diversity of ectomycorrhizal fungal communities is reduced by trace element contamination. Soil Biology and Biochemistry, 121: 202-211.

Héloïse Crompot Master’s Thesis on evaluation of microbial activities in the soils of the Guadiamar Green Corridor

Between February and May 2017, the student Héloïse Crompot of the Haute École Condorcet (Belgium) has collaborated with the group Sustainable Use of the Soil-Plant System at IRNAS-CSIC in an evaluation study of the microbial activities under soils contaminated by trace elements.

Héloïse obtained her Master’s title in Industrial Engineering Sciences in Agronomy after presenting her Master’s Thesis titled “Evaluation of soil chemical status, microbial biomass and enzyme activities under three tree species, in soils contaminated by trace elements, in the Green Corridor of the Guadiamar (Seville, Spain) “.

Thanks to this study we found out that in areas covered by trees there is a greater stabilization of the trace elements, and a greater enzymatic activity and microbial growth, than in open areas in the Guadiamar Green Corridor. We have also observed that there is a disturbance in the decomposition cycle of organic matter, which could be an effect of soil contamination.

International Conference on Mycorrhiza

Last August, the 9th International Conference on Mycorrhiza was held in Prague (Czech Republic). This conference, organised by the International Mycorrhiza Society, provided a global platform for exchanging the latest mycorrhizal symbiosis knowledge (anatomy, molecular mechanisms, mycorrhizal ecology and functioning) as well as its implications for the ecosystems and for the human society.

Researchers from RESTECO Project, together with collaborators, presented their last results in the session “Advances in biological conservation through a better understanding of mycorrhizal ecology”.  A poster was presented with the study of the functional traits of ectomycorrhizal fungi (ECM) in holm oak (Quercus ilex) tree species in trace elements contaminated soils of the Guadiamar Green Corridor (Seville, Spain). In this study, two hypotheses were validated: soil contamination affects ECM species composition and their functionality, and ECM functional traits mediate in the effect of soil contamination on plant status.

Link to the poster: Marta Gil-Martínez et al. “Ectomycorrhizal functional traits mediate plant-soil feedback processes in trace elements contaminated soils”.

Biology degree students visit the Guadiamar River

On March 24th, the students of the subject “Ecology of Global Change: Current Transition of the Biosphere” visited the Guadiamar River basin. The subject belongs to the Biology degree of the University of Seville (US).

The objective of the excursion was to carry out an ecological and environmental analysis of the landscape and ecosystem transformations produced by the anthropic action during centuries in the outskirts of the city of Seville. The Guadiamar River, because of its ancestral importance as a source of water and resources, is a good example of these transformations that can be observed from its birth in the Sierra Norte until its mouth in the Guadalquivir River, in the marshes of the Doñana Park.

The professors María Cruz Díaz Antúnez-Barradas (US) and María José Leiva Morales (US) described the different ecosystems where the Guadiamar River flows. In its high part, in the mountain range, the Guadiamar River crosses forests and plantations of eucalyptus trees. In the middle section, the amplitude of the fluvial valley appears increasing riverside vegetation in the borders and meadows in the high zones. Further down, the river enters the Protected Landscape of the Guadiamar Green Corridor where the forest of the alluvial plains was reforested with Mediterranean shrubs and trees (oaks, olive trees, brooms, etc.), while the forest gallery shows poplars, ash trees and willows. Finally, in the low section, it ends in the marshes of Doñana, where crops of rice and brackish pastures appear.

At the Doblas stop (Sanlúcar la Mayor), Marta Gil Martínez (IRNAS-CSIC) was invited to talk about the consequences and restoration measures after the Aznalcóllar mine spill to the Guadiamar River, as well as the results of the investigations which is carried out by IRNAS-CSIC researchers in the Green Corridor (RECARE and RESTECO projects). Soil contamination by heavy metals, such as lead, zinc, cadmium and copper, affects the growth and health of plants, soil organisms and, in general, the ecosystem food web. Soil-plant-microorganism interaction is being investigated in soils with different levels of contamination. The ability of plants and their associated microbes to stabilize heavy metals in the soil (a technique known as phytostabilization) and thus reduce the risk of toxicity in the ecosystem is studied.