Abstract
The study of soil microbial responses to environmental changes is useful to improve simulation models and mitigation strategies for climate change. We here investigated two Alpine forest sites (deciduous forest vs. coniferous forest) situated at different altitudes (altitudinal effect) in spring and autumn (seasonal effect) regarding: (i) bacterial and fungal abundances (qPCR); (ii) diversity and structure of bacterial and fungal communities (amplicon sequencing); and (iii) diversity and composition of microbial functional gene community (Geochip 5.0). Significant altitudinal changes were detected in microbial abundances as well as in diversity and composition of taxonomic and functional communities as a consequence of the differences in pH, soil organic matter (SOM) and nutrient contents and soil temperatures measured between both sites. A network analysis revealed that deciduous forest site (at lower altitude) presented a lower resistance to environmental changes than that of coniferous forest site (at higher altitude). Significant seasonal effects were detected only for the diversity (higher values in autumn) and composition of microbial functional gene community, which was related to the non-significant increased SOM and nutrient contents detected in autumn respect to spring and the presumable high capacity of soil microbial communities to respond in functional terms to discreet environmental changes.
Highlights
Forests, which cover 38 million square kilometers of the planet and contain more than three trillions of trees, have a crucial role on the climate, the geochemical cycles and especially on the global carbon (C) cycling since they act as important C sinks[1]
Integrative studies investigating abundance, taxonomy and functionality of soil microbial communities are important for understanding the response of microorganisms to changing environmental conditions and the ecosystem functioning[1]
We have demonstrated that soil bacterial and fungal communities from two Alpine forest sites differing in altitude and vegetation cover type, significantly differed in terms of abundance as well as taxonomic and functional gene diversity and composition
Summary
Forests, which cover 38 million square kilometers of the planet and contain more than three trillions of trees, have a crucial role on the climate, the geochemical cycles and especially on the global carbon (C) cycling since they act as important C sinks[1]. Our recent investigations have been focused on the characterization of altitudinal and/or seasonal (spring to autumn comparisons) shifts in soil microbial communities using different methodological approaches at four Alpine forest sites (representing a climosequence) located over an altitudinal gradient from 545 to 2,000 m above sea level (asl) Using this altitudinal gradient: (i) Siles & Margesin[17] confirmed the significance of altitude determining changes in abundance and Illumina-based analysis of diversity and composition of bacterial and fungal communities (with no significant changes in the case of archaeal communities) and elucidated the main driving factors of those changes considering only one season; (ii) França, et al.[29] reported for the first time culturable bacterial and yeast diversity of Alpine forest soils and discovered distinct differences between culturable bacterial and yeast diversity related to altitude, season and isolation temperature; and (iii) Siles, et al.[30] described significant altitudinal and seasonal shifts in some soil physicochemical properties and PLFA (phospholipid fatty acid)-based abundance and structure of soil microbial communities as well as altitudinal variations (with limited seasonal effects) in soil microbial functionality (determined through measurement of potential enzyme activities and characterization of community level physiological profiles). Notwithstanding all these works, there is still a lack of detailed information regarding the altitudinal and seasonal shifts in taxonomic diversity and composition of both bacterial and fungal communities as well as their functional traits in the aforementioned forest ecosystems using comprehensive and state-of-the-art tools
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