Potential of eucalypt trees for remediation of contaminated soils

The use of trees to immobilize contaminants (phytostabilization) is a low-cost and effective method of soil remediation.

Researchers of IRNAS, CSIC and New Zealand have evaluated the potential of red gum (Eucalyptus camaldulensis) to phytostabilize soils contaminated by trace elements (TE). Within the research project RESTECO, the ET concentration in soils and in eucalypt leaves and flowers has been investigated in 7 sites along the Gudiamar River valley. In general, the concentration of elements such as As, Cd, Cu, Pb and Zn in aboveground tissues was relatively low, and lower than toxic levels.

Eucalyptus camaldulensis is a fast-growing tree with a large root system; because of its tolerance to TE contamination and the low transfer of metals towards the aboveground tissues it can be considered suitable for phytoremediation of contaminated soils.

In addition, there was significant correlation between the concentration of Cd, Mn and Zn (but neither for Cu nor Pb) in their leaves and in the rhizosphere. Therefore, the eucalypt´s leaves may serve as bioindicators of the soil contamination for Cd, Mn and Zn.

The study has been published on June 30th 2017 in the open access journal PLOS ONE.

Madejón P, Marañón T, Navarro-Fernández CM, Domínguez MT, Alegre JM, Robinson B, Murillo JM (2017) Potential of Eucalyptus camaldulensis for phytostabilization and biomonitoring of trace-element contaminated soils. PLoS ONE 12(6): e0180240.

 

Evaluation of measures to remediate contaminated soils: European meeting

The RECARE project is focused on preventing and remediating degradation of soils in Europe.

A Plenary Meeting has been held at Hella (Iceland), from May 29th to June 2nd 2017. Each of the 17 study sites participating in the project presented their results.

Photo: Erik van den Elsen

The Group SOIL-PLANT, from the IRNAS, CSIC, presented their results about two measures applied for the remediation of contaminated soils at the Guadiamar Green Corridor: a) amendment addition and b) tree plantation.

Those results are part of a joint work by the projects RECARE and RESTECO.

Copies of the presentation and poster can be consulted at the repository Digital CSIC.

Collaboration with Professor Mark Tibbett on mycorrhizal studies

The symbiosis between plants and mycorrhizal fungi is a fundamental factor for the phytoremediation of contaminated soils in the Guadiamar Valley.

From the 15th to the 18th of May 2017, Professor Mark Tibbett (University of Reading, UK) visited the IRNAS-CSIC to participate in a collaborative work on the effects of contamination by trace elements on soil biodiversity.

Professor Tibbett gave a conference in the IRNAS´ Seminar Cycle, entitled “The mysterious world of mycorrhizas: Unrecognized attributes of the commonest plant-fungal symbiosis”. The role of mycorrhizas and the plant-fungi-soil interface was remarked, as well as their importance in plant nutrition and stress tolerance. “Bare roots does not exist in nature” he stated, remarking the universality of  plant-fungal associations.

The field visit included a general overview of the Aznalcóllar mine complex and the old tailings dams which collapsed, provoking the spill.

In the experimental plot for the long-term study of the effects of amendment addition on soil remediation, the interactions between soil properties (mainly pH), mycorrhizas and colonizing plants were discussed in contaminated and remediated soils.

Lastly, in La Herrería (Sanlúcar la Mayor) field, the relations of different tree species such as stone pine (Pinus pinea), white poplar (Populus alba) and wild olive (Olea europaea) with the soil organic matter underneath, the phytostabilization of trace elements, and the communities of mycorrhizal fungi were discussed.

Conference about ecosystem services in Córdoba University

The RESTECO researcher María T. Domínguez has given the conference “Soil contamination and provision of ecosystem services in the Guadiamar River Basin”, within the Open Classroom program of the University of Córdoba, Spain, on May 9th 2017.

In the conference, the main concepts relative to the role of soil provisioning ecosystem services were introduced. The Guadiamar River Valley was presented as a case study, where many works focused on the impact of soil contamination on the provision of ecosystem services have been carried out.

Functional diversity and stability against climatic change

The functional diversity of a community is a key factor for its stability against climatic change.

Researchers from RESTECO project, in collaboration with University of Córdoba, Autonomous University of Barcelona and EBD-CSIC, have studied the role of functional diversity and soil conditions as main drivers of the stability of woody plant communities in Doñana (south Spain).

The community stability has been assessed as changes in cover, species composition and diversity, in 19 experimental plots during 9 years. The functional diversity was calculated using eight traits (of leaves, stems and roots) for the 16 species comprising the different communities.

Results have proved that shrubland communities were strongly sensitive to inter-annual variability in climate. During colder and drier conditions, total plant cover decreased remarkably, but functional diversity increased; likely because of the expansion of functionally dissimilar species in the new open microsites.

The most functionally diverse communities, and those inhabiting resource-limited environments were the most stable over time in terms of species diversity. This could be explained because they were mainly constituted by a large diversity of slow-growth, stress-tolerant species that are potentially better adapted to harsh climatic conditions.

We could infer that the increased frequency of extreme climatic events (predicted by climatic models) will alter the functional structure of shrubland communities, with potential repercussions for ecosystem functioning.

This study has been published in the Journal of Ecology (on line since February 28, 2017).

Pérez‐Ramos, I. M., Díaz‐Delgado, R., de la Riva, E. G., Villar, R., Lloret, F., Marañón, T. (2017). Climate variability and community stability in Mediterranean shrublands: the role of functional diversity and soil environment. Journal of Ecology doi: 10.1111/1365-2745.12747

Data can be consulted at the free access DRYAD repository.

Regulation about polluted soils in Andalusia

The management of polluted soils in Andalusia (South Spain) is regulated by the Decree-Law 18/2015 which includes “Recognized Documents”. Those are technical documents providing guide and promotion of good practices for natural or legal persons responsible of potentially contaminants activities.

During a Workshop on March 15th 2017 three recognized documents were discussed:

Guide for the research of potentially contaminated soils

Guide for the classification of potentially contaminated soils according to the risk

Guide for the evaluation of risks for human health in potentially contaminated soils

Contributions to those documents can be submitted, before March 31st 2017, at:

sueloscontaminados.cmaot@juntadeandalucia.es

Master students visit the Guadiamar study site

On Friday February 10th 2017 a group of students from the Master in Advanced Biology: Research and Application (University of Seville) visited the Guadiamar Green Corridor. That was a field practice of the subject Environmental Contamination, Ecotoxicology and Phytoremediation.

The visit was guided by the RESTECO researcher María T. Domínguez (IRNAS, CSIC). She showed the experimental plots where the measures for remediation of contaminated soils are evaluated. In particular, the demonstration was focused on the amendment addition and the phytostabilization of trace elements by the planted trees.

Photo: Marta Gil

International Congress of mediterranean Ecosystems

Researchers of the RESTECO project have presented their results in the International Congress of Mediterranean-type Ecosystems – XIV MEDECOS – which was held at Sevilla, Spain, on February 2017.

In particular, three oral communications were presented within the Symposium “Filling current knowledge gaps: understanding the role of plant-soil interactions on the functioning and resilience of Mediterranean ecosystems in a changing world”:

Marta Gil-Martínez et al. “Understanding feedback processes between holm oak (Quercus ilex) and their ectomycorrhizal fungal symbionts in trace-element polluted soils in Mediterranean ecosystems”.

Álvaro López García et al. “Assessment of the recovery of functional diversity of ectomycorrhizal fungal communities in metal polluted soils”.

Teodoro Marañón et al. “Soil functioning and ecosystem services: using trees to remediate contaminated soils”.

Three poster communications, also related to the project, were presented in other sessions:

María Teresa Domínguez Núñez et al. “Soil contamination and the provision of ecosystem services in Mediterranean lands: implications for livestock and bionergy uses”.

Sara Muñoz Valdés et al. “Modelling resilience and ecosystem services of soils contaminated by heavy metals under remediation measures and Climate Change scenarios: The Case Study of Guadiamar”.

Carmen M. Navarro-Fernández et al. “A functional approach to explore the drivers of mycorrhizal trait variability in Mediterranean plant communities”

Diversity of ectomycorrhizal fungi associated with holm oaks in the Guadiamar

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Ectomycorrhizal (ECM) fungi associate with plants to conform one of the most important symbioses in terrestrial ecosystems, with important incidence in the provision of some ecosystem services.

Álvaro López García presented on December 6, 2016, the seminar “Taxonomic and functional diversity of ectomycorrhizal fungal communities in metal polluted soils” within the Cycle of seminars of Section for Terrestrial Ecology, Deptartment of Biology, University of Copenhagen, Denmark.

To deepen in how anthropogenic disturbance affect the taxonomic and functional diversity of ECM, we characterized the ECM fungal communities associated with holm oak trees used in the restoration of the Aznalcóllar toxic mine spill (SW Spain). The comparison between contaminated and control (non-contaminated) sites showed no differences in terms of taxonomic diversity. However a certain clustering in key traits of ECM fungi was found in communities exposed to higher levels of heavy metal pollution. This finding is in agreement with what expected from an environmental filtering process, i.e. species in a community tend to be more similar between them than expected by chance, and indicates that the functional diversity of ECM in contaminated sites is lower than in control sites.