Sort by: Order: Results:

Now showing items 1-3 of 3
  • Yan, Lijuan; Penttinen, Petri; Mikkonen, Anu; Lindstrom, Kristina (2018)
    We investigated bacterial community dynamics in response to used motor oil contamination and perennial crop cultivation by 16S rRNA gene amplicon sequencing in a 4-year field study. Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria, and Gemmatimonadetes were the major bacterial phyla, and Rhodococcus was the most abundant genus. Initially, oil contamination decreased the overall bacterial diversity. Actinobacteria, Betaproteobacteria, and Gammaproteobacteria were sensitive to oil contamination, exhibiting clear succession with time. However, bacterial communities changed over time, regardless of oil contamination and crop cultivation. The abundance difference of most OTUs between oil-contaminated and non-contaminated plots remained the same in later sampling years after the initial abundance difference induced by oil spike. The abundances of three oil-favored actinobacteria (Lysinimonas, Microbacteriaceae, and Marmoricola) and one betaproteobacterium (Aquabacterium) changed in different manner over time in oil-contaminated and non-contaminated soil. We propose that these taxa are potential bio-indicators for monitoring recovery from motor oil contamination in boreal soil. The effect of crop cultivation on bacterial communities became significant only after the crops achieved stable growth, likely associated with plant material decomposition by Bacteroidetes, Armatimonadetes and Fibrobacteres.
  • Jiang, Yonglei; Lei, Yanbao; Yang, Yan; Korpelainen, Helena; Niinemets, Ulo; Li, Chunyang (2018)
    Despite the ubiquitous distributions and critical ecological functions of microorganisms in pedogenesis and ecosystem development in recently deglaciated areas, there are contrasting successional trajectories among bacteria and fungi, but the driving forces of community assembly still remain poorly resolved. In this study, we analyzed both bacterial and fungal lineages associated with seven different stages in the Hailuogou Glacier Chronosequence, to quantify their taxonomic composition and successional dynamics, and to decipher the relative contribution from the bottom-up control of soil nutrients and altered vegetation as well as top-down pressures from nematode grazers. Co-occurrence networks showed that the community complexity for both bacteria and fungi typically peaked at the middle chronosequence stages. The overlapping nodes mainly belonged to Proteobacteria and Acidobacteria in bacteria, and Ascomycota and Basidiomycota in fungi, which was further supported by the indicator species analysis. Variation in partitioning and structural equation modeling suggested that edaphic properties were the primary agents shaping microbial community structures, especially at the early stages. The importance of biotic factors, including plant richness and nematode feeding, increased during the last two stages along with the establishment of a coniferous forest, eventually governing the turnover of fungal communities. Moreover, bacterial communities exhibited a more compact network topology during assembly, thus supporting determinism, whereas the looser clustering of fungal communities illustrated that they were determined more by stochastic processes. These pieces of evidence collectively reveal divergent successional trajectories and driving forces for soil bacterial and fungal communities along a glacier forefield chronosequence.
  • TeaComposition Network; Kwon, TaeOh; Shibata, Hideaki; Kepfer-Rojas, Sebastian; Schmidt, Inger K.; Larsen, Klaus S.; Beier, Claus; Berg, Björn; Verheyen, Kris; Lamarque, Jean-Francois; Hagedorn, Frank; Eisenhauer, Nico; Djukic, Ika (2021)
    Litter decomposition is a key process for carbon and nutrient cycling in terrestrial ecosystems and is mainly controlled by environmental conditions, substrate quantity and quality as well as microbial community abundance and composition. In particular, the effects of climate and atmospheric nitrogen (N) deposition on litter decomposition and its temporal dynamics are of significant importance, since their effects might change over the course of the decomposition process. Within the TeaComposition initiative, we incubated Green and Rooibos teas at 524 sites across nine biomes. We assessed how macroclimate and atmospheric inorganic N deposition under current and predicted scenarios (RCP 2.6, RCP 8.5) might affect litter mass loss measured after 3 and 12 months. Our study shows that the early to mid-term mass loss at the global scale was affected predominantly by litter quality (explaining 73% and 62% of the total variance after 3 and 12 months, respectively) followed by climate and N deposition. The effects of climate were not litter-specific and became increasingly significant as decomposition progressed, with MAP explaining 2% and MAT 4% of the variation after 12 months of incubation. The effect of N deposition was litter-specific, and significant only for 12-month decomposition of Rooibos tea at the global scale. However, in the temperate biome where atmospheric N deposition rates are relatively high, the 12-month mass loss of Green and Rooibos teas decreased significantly with increasing N deposition, explaining 9.5% and 1.1% of the variance, respectively. The expected changes in macroclimate and N deposition at the global scale by the end of this century are estimated to increase the 12-month mass loss of easily decomposable litter by 1.1-3.5% and of the more stable substrates by 3.8-10.6%, relative to current mass loss. In contrast, expected changes in atmospheric N deposition will decrease the mid-term mass loss of high-quality litter by 1.4-2.2% and that of low-quality litter by 0.9-1.5% in the temperate biome. Our results suggest that projected increases in N deposition may have the capacity to dampen the climate-driven increases in litter decomposition depending on the biome and decomposition stage of substrate.