Seasonal dynamic of yeast fungi in soils along land use gradients of beech forests
Final Report Abstract
Alteration of natural ecosystems by human activity is one of the most serious concerns nowadays. This is also true for forest sites as they are repeatedly affected by environmental change and land management. Forestry and agriculture cause biodiversity losses in many functional groups. Previous studies showed that forest management induces pronounced shifts in soil yeast communities. It remained, however, uncertain whether these changes are found throughout the vegetative season. In this project, we studied seasonal changes in soil yeast communities in natural and managed beech forests in order to distinguish forest management effects from seasonal changes. We analysed soil samples collected in two regions, Hainich and Schwäbische Alb. Using advances of our previous studies, we have further optimized cultivation approach and tested several common additives to cultivation media. We found that application of Rose Bengal substantially changes yeast species composition recovered from soil samples. Unlike plates supplemented with lactate and kanamycin, plates containing Rose Bengal yielded dimorphic fungi of the genus Trichosporon only. Despite reports on antifungal activity of soil yeasts Trichosporon porosum, we found no negative effect of media acidification with lactate on yeast species compositions. Also, plates supplemented with lactate yielded as many different species as plates containing kanamycin. In contrast to our expectations, our project revealed minor contribution of plant-related yeasts to the soil community. Specifically, pigmented phylloplane-related species have been found in the end of the vegetative season only. These were abundant in areas exposed to forest litter making up to 30% of the total abundance but did not exceed 5% in probes protected from litter fall, i.e. samples collected underneath wood logs. This project revealed substantial changes in soil yeast community composition and structure throughout the vegetative season and supported previous observations regarding effects of forest management on yeast community parameters. Abundance of ascomycetous yeasts reflects well the forest management. In the same time, fermenting ascomycetes from genera Candida, Kazachstania, Schwanniomyces were present in high quantity in soil communities in spring and summer, and were replaced by fermenting basidiomycetes, Mrakia spp. in autumn. Thereby, our results display an interesting successional trend in soil microbial communities but also suggest that yeasts likely to provide an important community service. Another interesting seasonal trend is the increasing number and diversity of psychrophilic yeasts in the end of the vegetative season. Specifically, we have isolated yeasts, which were previously found in Antarctica and glaciers in Alps. This observation suggests that so-called cold-adopted yeasts are not restricted to extreme habitats but are present in forest soils during cold periods. Although yeast communities reflected forest properties (management intensity), their diversity and biomass patterns did not depend on basic soil properties such as pH, clay content, total nitrogen, C/N ratio, nitrate, ammonium and plant-available phosphorus concentrations. Because the regular presence of large wood logs is typical for unmanaged forests, we assessed the impact of aboveground wood log deposition in forests on yeast communities. We found that dead wood deposition (and the associated leaching organic carbon) promoted development of several soil-borne species and is likely to account for larger productivity of soil ecosystems. This project has also established molecular barcodes for the most frequent soil yeasts. The lack of taxonomic annotation and errors in taxonomic assignments of environmental sequences deposited in public databases limit application of culture-independent techniques for biodiversity assessments of Fungi, including soil yeasts. Our project revealed two novel species within reference strains retrieved from culture collections. Analysis of sequence data generated in this project showed low variability of the rRNA ITS and suggests additional DNA-barcode to be used in Tremellomycetes. Molecular barcodes (rRNA SSU, LSU, ITS; RPB1) obtained in this project will serve as the reference database to reassess the distribution of yeasts from the analysis of environmental sequences available in public databases.
Publications
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(2012) Assessment of yeast diversity in soils under different management regimes. Fungal Ecology, 5: 24-35
Yurkov AM, Kemler M & Begerow D
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(2012) General relationships between abiotic soil properties and soil biota across spatial scales and different land-use types. PLoS ONE, 7: e43292
Birkhofer K, Schöning I, Alt F, Herold N, Klarner B, Marhan S, Oelmann Y, Wubet T, Yurkov A, Begerow D, Berner D, Buscot F, Daniel R, Diekötter T, Ehnes RB, Erdmann G, Fischer C, Foesel B, Groh J, Gutknecht J, Kandeler E, Lang C, Lohaus G, Meyer A, Nacke H, Näther A, Overmann J, Polle A, Pollierer MM, Scheu S, Schloter M, Schulze ED, Schulze W, Weinert J, Weisser WW, Wolters V & Schrumpf M
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(2012) Nuclear ribosomal internal transcribed spacer (ITS) region as a universal DNA barcode marker for Fungi. Proceedings of the National Academy of Sciences of the United States of America (PNAS), 109: 6241-6246
Schoch CL, Seifert KA, Huhndorf S, Robert V, Spouge JL, Levesque CA, Chen W& Fungal Barcoding Consortium (149 Collaborators)
