Suolo, tartufo, comunità vivente animale: un intricato microcosmo naturale
Author(s)
Pinto, Stefania
Date Issued
June 28, 2016
Type
Doctoral Thesis
Abstract
Scientific research to find out the secret of truffles date back to the 19th century but to date many aspects are still unkown. Tuber aestivum Vitt., or summer truffle, and Tuber melanosporum Vitt., or black truffle, are hypogeus ectomycorrhizal fungi that create symbiosis with plants, such as Quercus (spp.), Corylus avellana L., Pinus (spp.). Both species of truffle create an area around the trunk of the host plant that is covered with little or no vegetation at all, called “pianello” in Italian or brûlé in French. The ecological importance of this area, e.g. the dynamics of the organisms living there, is still partly unknown. The main aim of the study presented here was to investigate any direct or indirect relationships between the soil fauna and the fungi of the genus Tuber, with particular emphasis on the brûlé area, namely by:
- studying the intricate relationships between truffles and soil fauna, focusing on microarthropods and the basic group of Collembola. Identifying which of them are involved in the ecology of truffles and influence or are influenced by it;
- investigating whether and how the specific chemical features of the soil of a brûlé have an impact on the soil fauna community, by using two different species of truffle that create a brûlé;
- ascertaining whether the effect of truffle is greater during fructification, by conducting an analysis throughout the entire biological cycle of the truffle;
- assessing whether the grazing on mycelium by fungivorous organisms, such as some collembolan species can favour the dissemination of truffle spores;
- determining whether the collembolan species Folsomia candida Willem (ISO 11267-99) can recognize the presence of truffle in standard soil assessing potential attraction (feeding preference tests).
The study was conducted in natural brûlés of T. aestivum and T. melanosporum. We chose nine brûlés of T. aestivum located in the province of Piacenza (Italy) and twenty brûlés of T. melanosporum in the province of Guadalajara (Spain). Soil samples were collected to perform chemical and biogical analyses. In Italy we collected samples every first week of the month, from June 2013 to May 2014 (with the only exception of February when sampling was impossible due to bad weather conditions). In Spain, all the samples were collected on the same day, i.e. 20 May 2014, at the end of the truffle fructification period and the dry season.
Moisture content, pH, organic matter and total organic carbon were determined on T. aestivum samples. pH value, calcium carbonate and active carbonate were determined on T. melanosporum
samples. The microarthropod community was analyzed for both truffle species, with particular focus on Collembola and Folsomia genus, and biodiversity and soil quality indices were applied.
Between June and September 2015, feeding preference tests were also performed with both truffle species and the Collembola F.candida.
The area inside T. aestivum brûlé was characterized by lightly alkaline pH values, compared to the outside area, with low organic matter and organic carbon. The area inside T. melanosporum brûlé was characterized by lightly alkaline pH values and small differences in terms of calcium carbonate and active lime. Well-developed and diversified microarthropod community was found for both species, with the main groups of organisms well adapted to soil. No clear differences were noted between the inside and the outside of the brûlés, though the outside was characterized by higher densities and a greater number of groups. Some groups seems to prefer the area outside the brûlé, where they probably find a more favourable environment to their development, while the Folsomia genus seems to prefer the brûlé area, only in T. aestivum. This group probably find in this area greater food resource and hence a more suitable environment. Biodiversity and soil biological quality indices showed the same trend. Finally, feeding preference tests showed a preference for truffles especially at the end of the test.
The study contributes to demonstrate that truffles create a modified area inside the brûlé. These differences in chemical parameters could influence and modify the community structure (in terms of edaphic fauna) inside the brûlé. In conclusion, the study contributes to clarify the particular conditions created inside the brûlé, in terms of both chemical parameters and microarthropod community. Nevertheless, some aspects relating to the relationship between soil fauna and truffles still need to be investigated. Research could be extended to other Tuber species, including those not producing a brûlé, and other soil organisms. An analysis of the effect of truffles on earthworms and nematodes would be of great interest, especially for their important role in soil ecosystems. Research could also be improved by recognizing organisms to species level in order to verify whether there are further differences at higher taxonomic levels.
Additional information
Dottorato di ricerca in Scienze e tecnologie per la gestione forestale e ambientale
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