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  • Guo, Qingxue; Yan, Lijuan; Korpelainen, Helena; Niinemets, Ülo; Li, Chunyang (2019)
    The impact of conspecific and heterospecific neighboring plants on soil bacterial and fungal communities has never been explored in a forest ecosystem. In the present study, we first investigated soil microbial communities in three plantations: Larix kaempferi monoculture, L. olgensis monoculture and their mixture. Then, a two-year growth experiment was conducted to investigate the effects of intra- and inter-specific interactions of L. kaempferi and L. olgensis on rhizosphere microbial communities at two different nitrogen levels. The results demonstrated clear differences in the beta-diversity and composition of bacteria and fungi among the three plantations, which implied the presence of different effects of plant-plant interactions on soil microbial communities. The results of the pot experiment showed that L. kaempferi suffered from greater neighbor effects from its conspecific neighbor regardless of N fertilization, although the effect declined when L. kaempferi was grown with L. olgensis under N fertilization. Changes in intra- and inter-specific plant interactions significantly impacted the chemical and biological properties of soil under N fertilization, with lower concentrations of NH4+, and lower soil microbial biomass (C-Mic) and soil carbon nitrogen biomass (N-Mic) under intra-specific plant interactions of L. kaempferi (KK) compared to inter-specific interactions of L. kaempferi and L. olgensis (KO). N fertilization increased bacterial and fungal alpha diversities in the rhizosphere soil of KO. For the beta diversity, the PERMANOVA results demonstrated that there was a significant impact of intra- and inter-specific plant interactions on soil microbial communities, with KK significantly differing from intra-specific plant interactions of L. olgensis (OO) and KO. The two plant species and N fertilization showed specific effects on the soil microbial composition, particularly on the fungal community. Both L. olgensis and N fertilization increased the abundance of Ascomycota but reduced that of Basidiomycota, and even shifted the dominance from Basidiomycota to Ascomycota under KO combined with N fertilization.
  • Mantzouki, Evanthia; Lurling, Miquel; Fastner, Jutta; Domis, Lisette de Senerpont; Wilk-Wozniak, Elzbieta; Koreiviene, Judita; Seelen, Laura; Teurlincx, Sven; Verstijnen, Yvon; Krzton, Wojciech; Walusiak, Edward; Karosiene, Jurate; Kasperoviciene, Jurate; Savadova, Ksenija; Vitonyte, Irma; Cillero-Castro, Carmen; Budzynska, Agnieszka; Goldyn, Ryszard; Kozak, Anna; Rosinska, Joanna; Szelag-Wasielewska, Elzbieta; Domek, Piotr; Jakubowska-Krepska, Natalia; Kwasizur, Kinga; Messyasz, Beata; Pelechata, Aleksandra; Pelechaty, Mariusz; Kokocinski, Mikolaj; Garcia-Murcia, Ana; Real, Monserrat; Romans, Elvira; Noguero-Ribes, Jordi; Parreno Duque, David; Fernandez-Moran, Elisabeth; Karakaya, Nusret; Haggqvist, Kerstin; Demir, Nilsun; Beklioglu, Meryem; Filiz, Nur; Levi, Eti E.; Iskin, Ugur; Bezirci, Gizem; Tavsanoglu, Ulku Nihan; Ozhan, Koray; Gkelis, Spyros; Panou, Manthos; Fakioglu, Ozden; Yang, Yang; Salmi, Pauliina; Arvola, Lauri (2018)
    Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.
  • Faiola, C. L.; Buchholz, A.; Kari, E.; Yli-Pirila, P.; Holopainen, J. K.; Kivimäenpää, M.; Miettinen, P.; Worsnop, D. R.; Lehtinen, K. E. J.; Guenther, A. B.; Virtanen, A. (2018)
    Secondary organic aerosol (SOA) impact climate by scattering and absorbing radiation and contributing to cloud formation. SOA models are based on studies of simplified chemical systems that do not account for the chemical complexity in the atmosphere. This study investigated SOA formation from a mixture of real Scots pine (Pinus sylvestris) emissions including a variety of monoterpenes and sesquiterpenes. SOA generation was characterized from different combinations of volatile compounds as the plant emissions were altered with an herbivore stress treatment. During active herbivore feeding, monoterpene and sesquiterpene emissions increased, but SOA mass yields decreased after accounting for absorption effects. SOA mass yields were controlled by sesquiterpene emissions in healthy plants. In contrast, SOA mass yields from stressed plant emissions were controlled by the specific blend of monoterpene emissions. Conservative estimates using a box model approach showed a 1.5- to 2.3-fold aerosol enhancement when the terpene complexity was taken into account. This enhancement was relative to the commonly used model monoterpene, "alpha-pinene". These results suggest that simplifying terpene complexity in SOA models could lead to underpredictions in aerosol mass loading.