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The XXXII Reunión Nacional de Suelos organized by researchers from the field of edaphology belonging to the University of Seville and the Institute of Natural Resources and Agrobiology of Seville (IRNAS-CSIC) took place in Seville (Spain) on 10-13 September 2019. This meeting is an initiative of the Spanish Society of Soil Science (SECS) that has been taking place since 1973 as they organize excursions to get to know different Spanish soils.

The meeting began with a session of posters and presentations framed within different themes (see Abstracts Book). Within the theme of “Study and recovery of contaminated soils” Marta Gil Martínez, predoctoral researcher at IRNAS-CSIC, presented a study on the fungal functional diversity in trace element contaminated soils from the Guadiamar Green Corridor.

In this study, the soil fungal communities were analyzed with a methodology of next generation sequencing in soils with different levels of contamination by trace elements and with different plant covers. The results showed that the phytoremediation plan established after the Aznalcóllar mining accident has favored the development of fungal communities by increasing their species richness and diversity. Both the type of vegetation covers and the properties of the soil determine the structure of the fungal communities. Under the poplar and pine trees, the communities of ectomycorrhizal fungi dominate, and under the wild olive and herbaceous species dominate arbuscular mycorrhizal fungi, due to the specific symbiosis of each type of vegetation with the fungi.

Access to the poster in this link:

Gil-Martínez M, López-García Á, Navarro-Fernández CM, Domínguez MT, Marañón T (2019). Fungal functional diversity in trace element contaminated soils from the Guadiamar Green Corridor. XXXII Reunión Nacional de Suelos (Seville).

In the following days we made three diverse and representative itineraries of the main soils and landscapes of Western Andalusia: 1) a protected and unique space in Europe, Doñana National Park; 2) a global example of restoration such as the Guadiamar Green Corridor, a protected area after the Aznalcóllar mining disaster, and finally 3) the Mediterranean soils of the valley and countryside of Carmona.

In the Doñana National Park, the researcher Luis Clemente (IRNAS-CSIC) explained the types of soils and the various ecosystems that Doñana include. In the Guadiamar Green Corridor we visited the Aznalcóllar mine and the researchers María Teresa Domínguez (University of Seville) and Engracia Madejón (IRNAS-CSIC) explained the details of the accident and the studies that have been carried out since then. In Carmona, we study two soil profiles with the help of Antonio Jordán (University of Seville).

 

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).

The Iberian Ecological Society SIBECOL has just been established to gather professional scientist from Portugal and Spain from all ecology areas: theoretical, terrestrial, marine and continental waters. Its main aim is promoting ecology and to give visibility to scientific works in all these fields.

To celebrate the establishment of the society and to share the scientific progress in ecology, last 4th -7th of February the First SIBECOL Congress, as well as the XIV AEET Meeting, were celebrated. The venue selected was the Faculty of Biology at the University of Barcelona (Spain).

This congress was celebrated in an emblematic time and place due to the commemoration, this year 2019, of the centenary of Professor Ramon Margalef. Margalef became one of the most relevant ecologist of the XX century and the first professor of Ecology in Spain at the University of Barcelona, where all the Iberian ecologist had the opportunity to meet.

INTARSU Project did not want to miss this important event for ecology and we had the opportunity of presenting our last study in a poster titled: “Phytostabilisation of trace elements with different tree species revealed a species-specific effect on soil functioning”. This work has been possible thanks to the collaboration between researchers from IRNAS-CSIC, University of Sevilla and University of Reading (United Kingdom). The poster was presented in the Thematic Session 14 “Organisms and ecosystem responses to global change in soils and sediments”, organized by the Group of Plant-Soil Interactions of AEET.

In this study, we presented the effects of different tree species (white poplar, wild olive and stone pine) on biotic and abiotic soil properties. The study area, known as Guadiamar Green Corridor (Seville), suffered in 1998 a serious contamination due to Aznalcóllar mine-spill. After a remediation plan in the whole affected area, different tree and shrubs species were planted, and 15 years after these trees have generated soil changes. In relation to soil nutrients, we have found that the tree coverage has increased fertility in soils underneath compared to soils covered by herbaceous plants. Among the studied species, white poplar trees have helped to neutralize soil pH; however, stone pine trees have acidified the soil which is undesirable as acidity increases soil trace element availability. Soil microbial activity presented differences among tree species and we found that enzyme activities with an important role in C, N and P cycles were highly dependent on soil pH. To summarise, we have found a tree species effect on abiotic and biotic soil properties with direct consequences on soil functioning.

Gil-Martínez, Marta; Domínguez, María Teresa; Navarro-Fernández, Carmen María; Tibbett, Mark; Marañón, Teodoro (2019). Phytostabilisation of trace elements with different tree species revealed a species-specific effect on soil functioning. In: Abstract book. 1st Meeting of the Iberian Ecological Society & XIV AEET Meeting. Ecology: an integrative science in the Anthropocene. February 4-7, 2019, Barcelona (Spain), page 269. AEET, Madrid, DOI: 10.7818/SIBECOLandAEETmeeting.2019.

Soil abiotic properties, such as texture, nutrient availability and water, are essential in the development of terrestrial plants. Mycorrhizal fungi, which are fungi living in symbiosis with plants roots, are also key for plant growing. This symbiosis enhances a trade-off of carbohydrates and nutrients beneficial for both plant and fungi. Therefore, it is expected that different mycorrhizal fungal communities (in terms of species and their morphological traits) would affect plant development (in terms of plant chemical and morphological traits) in different ways.

In order to understand this mycorrhizal fungi-plant relationship, researchers from IRNAS-CSIC and Universidad de Sevilla (Spain), in collaboration with researchers from the University of Copenhagen (Denmark) and the University of Reading (United Kingdom), developed a study on holm oak trees and their symbiotic ectomycorrhizal fungi. The area selected for this study, known as the Guadiamar Green Corridor (Seville), suffered a mine spill leaving behind hectares of land contaminated by trace elements. Twenty years after the accident and the phytoremediation of the affected area, trace elements are still present and the role of ectomycorrhizal fungi might be especially important in this stressful environment.

In this study, we found that ectomycorrhizal fungi explained more than soil abiotic properties for most of the measured plant traits, especially root functional traits. The symbiosis with abundant species of ectomycorrhizal fungi (Hebeloma cavipes and Thelephora terrestris) was related to conservative positions into the root economics spectrum. Conservative traits, like denser roots and higher dry matter content, allow tree survival under adverse conditions. Hebeloma cavipes and Thelephora terrestris were characterised with a high rhizomorph formation, a fungal trait that enhances water and phosphate uptake through a long-distance exploration mechanism. It may be possible that this specific tree-fungi symbiosis was established as a consequence of resource limitations.

Trace element mobility through the soil-root-leaf continuum was analysed and despite soil trace elements concentrations in our environmental gradient was relatively large, accumulation of trace elements in oak leaves was relatively low. This confirms that holm oak is a suitable species for the phytostabilisation of contaminated soils, given its ability to prevent trace element accumulation into aboveground biomass. However, it is not the role of the tree alone, as trace element transfer was highly explained by its associated ectomycorrhizal fungal communities, which suggests that interactions with fungi play an important role at determining the capacity of this tree species to retain trace elements into its roots.

These findings support that ectomycorrhizal fungal community composition and their functional traits mediate plant performance in trace element contaminated soils, and have a high influence on plant capacity for phytoremediation of contaminants.

The study has been published in the journal Frontiers in Plant Science:

Gil-Martínez, M., López-García, Á., Domínguez, M. T., Navarro-Fernández, C. M., Kjøller, R., Tibbett, M., & Marañón, T. (2018). Ectomycorrhizal Fungal Communities and Their Functional Traits Mediate Plant–Soil Interactions in Trace Element Contaminated Soils. Frontiers in Plant Science, 9, 1682.