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Wide-scale application of biochar to soil has been suggested as a mechanism to offset increases in CO 2 emissions through the long-term sequestration of a carbon rich and inert substance to the soil, but the implications of this for soil diversity and function remain to be determined. Biochar is capable of inducing changes in soil bacterial communities, but the exact impacts of its application are poorly understood. Using three European sites [UK SRC, short rotation coppice, French grassland (FR) and Italian SRF, short rotation forestry (IT)] treated with identical biochar applications, we undertook 16S and ITS amplicon DNA sequencing. In addition, we carried out assessments of community change over time and N and P mobilization in the UK. Significant changes in bacterial and community structure occurred due to treatment, although the nature of the changes varied by site. STAMP differential abundance analysis showed enrichment of Gemmatimonadete and Acidobacteria in UK biochar plots 1 year after application, whilst control plots exhibited enriched Gemmataceae, Isosphaeraceae and Koribacteraceae. Increased mobility of ammonium and phosphates was also detected after 1 year, coupled with a shift from acid to alkaline phosphomonoesterase activity, which may suggest an ecological and functional shift towards a more copiotrophic ecology. Italy also exhibited enrichments, in both the Proteobacteria (driven by an increase in the order Rhizobiales) and the Gemmatimonadetes. No significant change in the abundance of individual taxa was noted in FR, although a small significant change in unweighted UNIFRAC occurred, indicating variation in the identities of taxa present due to treatment. Fungal b diversity was affected by treatment in IT and FR, but was unaffected in UK samples. The effects of time and site were greater than that of biochar application in UK samples. Overall, this report gives a tantalizing view of the soil microbiome at several sites across Europe and suggests that although application of biochar has significant effects on microbial communities, these may be small compared with the highly variable soil microbiome that is found in different soils and changes with time.

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Global warming accelerates land surface drying, increasing the incidence of extreme climatic events such as severe droughts with detrimental effects on ecosystem functions and structure. We investigated the effects of an imposed severe drought (24 days) on fully established synthesized grassland communities with three species richness (S) levels (one, three or nine species), grown for 3 years at either ambient air temperatures (unheated) or ambient +3°C (heated). Since water supply during these 3 years was equal in all treatments, heated communities experienced more frequent, short mild droughts, but it was unknown whether this conferred greater or smaller resistance for facing prolonged droughts. During the 24-day drought period, soil matric potential decreased in a similar way over time in both temperature treatments and was lower at increasing S-levels. Although green vegetation cover was significantly reduced by the drought in both temperature treatments, the decrease was higher in heated than unheated communities indicating a lower resistance of heated communities to the drought. After only 13 days of recovery, green vegetation cover of both temperature treatments approached values similar to those observed before the imposed drought, suggesting similar resilience in both treatments. Above-ground biomass was reduced by elevated temperature, consistently in all S-levels, showing that the drought period did not change the biomass production patterns observed in the treatments before the imposed drought. Our results suggest that, regardless of the continuous exposure to elevated temperatures and associated short mild droughts, heated communities had not developed clear mechanisms to better cope with extended summer droughts.

The aims of our experiment were to evaluate the uptake and translocation of cerium and titanium oxide nanoparticles and to verify their effects on the growth cycle of barley (Hordeum vulgare L.). Barley plants were grown to physiological maturity in soil enriched with either 0, 500 or 1000 mg·kg−1 cerium oxide nanoparticles (nCeO2) or titanium oxide nanoparticles (nTiO2) and their combination. The growth cycle of nCeO2 and nTiO2 treated plants was about 10 days longer than the controls. In nCeO2 treated plants the number of tillers, leaf area and the number of spikes per plant were reduced respectively by 35.5%, 28.3% and 30% (p ≤ 0.05). nTiO2 stimulated plant growth and compensated for the adverse effects of nCeO2. Concentrations of Ce and Ti in aboveground plant fractions were minute. The fate of nanomaterials within the plant tissues was different. Crystalline nTiO2 aggregates were detected within the leaf tissues of barley, whereas nCeO2 was not present in the form of nanoclusters.