Search

Ectomycorrhizas (ECM) are a common symbiotic association between fungi and various plant species in forest ecosystems, affecting community assemblages at the landscape level. ECMs benefit host plants by increasing the surface area for nutrient uptake, defending against pathogens, and decomposing organic matter in the soil. ECM-symbiotic seedlings are also known to perform better in conspecific soils than other species unable to carry the symbiosis, in a process referred to as plant-soil feedback (PSF). In this study, we tested the effects of different leaf litter amendments on ECM and non-ECM seedlings of Quercus ilex inoculated with Pisolithus arrhizus and how they altered the litter-induced PSF. Our experiment showed that the ECM symbiont induced a shift from negative PSF to positive PSF in Q. ilex seedlings by analysing plant and root growth parameters. However, non-ECM seedlings performed better than ECM seedlings in a no-litter condition, indicating an autotoxic effect when litter is present without ECM symbionts. Conversely, ECM seedlings with litter performed better at different decomposition stages, suggesting a possible role of the symbiosis of P. arrhizus and Q. ilex in recycling autotoxic compounds released from conspecific litter, transforming them into nutrients that are transferred to the plant host. [ABSTRACT FROM AUTHOR]

Question: Cushion‐forming vascular plants are adapted to alpine environments and act as ecosystem engineers by moderating microclimate and creating a fertility island under their canopy. Most of the available studies on cushion ecology have been devoted to plant facilitation, but none used a holistic approach that considers the response of co‐existing plant species with other key ecosystem players. Here, we quantified the biogenic effect and facilitation capacity of Astragalus siculus, a spiny nitrogen‐fixing cushion plant, and test the hypothesis that the facilitation effect would increase with elevation as stress gradient. Location: Mount Etna, the highest active volcano in the Mediterranean Basin. Methods: We combined chemical characterization of the soil with a description of the soil microbiota by high‐throughput sequencing of bacterial and eukaryotic rRNA gene markers carried out at three elevations, that is 1650, 1900 and 2210 m a.s.l. In addition, we analysed the microclimate outside and inside the Astragalus canopy to assess the linkages between above‐ and below‐ground ecosystem compartments and quantified the occurrence of co‐existing vascular plants. Results: Astragalus cushions have strong biogenic effects on above‐ and below‐ground conditions by dramatically increasing soil organic carbon and total nitrogen stocks at 1900 and 2210 m elevation. Moreover, a buffering of soil temperature and moisture regimes was recorded, with lower temperatures in summer but higher in winter inside the cushions. Cushions harbour a specific bacterial and fungal microbiota compared to external bare soil. Stem density and cushion height increase significantly with altitude, as does the nurse effect of the cushion on the growth and survival of co‐existing vascular plants. Conclusions: As a result of cushion biogenic environmental changes, the effect of Astragalus on some of the co‐existing species shifted from negative or null at 1650 m to facilitative along the elevation gradient. Furthermore, our data show a relationship between Astragalus morphological traits and soil biogenic changes related to soil chemistry and microbiota that affect plant interaction and coexistence. [ABSTRACT FROM AUTHOR]

The use of soil fumigants and fungicides to control soilborne pathogens is reduced due to awareness of their negative drawbacks. Long‐term application of such agrochemicals negatively affects soil microbiota and reduces natural soil suppressiveness. We investigated long‐term impacts of biochar and not‐pyrogenic organic amendment (OAs: manure, alfalfa straw and glucose), on disease suppression compared with conventional management in three pathosystems: Fusarium oxysporum f. sp. lactucae (FOL)–lettuce, Rhizoctonia solani–tomato and Sclerotinia sclerotiorum–lettuce, by conditioning soil for 2 years. Soil analyses included pH, electrical conductivity, organic carbon, total nitrogen, C:N ratio, N‐NO3−, N‐NH4+, cation exchange capacity, available phosphorus, Ca2+, Mg2+, K+, Na+, fluorescein diacetate (FDA), and total and active limestone. Soil microbiota was characterized by combining BIOLOG EcoPlates with next‐generation sequencing of 16S and 18S rRNA genes. Soil amended with OAs generally suppressed disease by S. sclerotiorum and FOL compared to fumigants and synthetic fertilizers. However, the incidence of R. solani infection was lower in soil treated with synthetic fertilizers than soil amended with OAs. EC, pH, C:N, N‐NO3−, N‐NH4+, FDA and BIOLOG were significantly correlated with disease, depending on pathosystem. Bacterial richness and diversity, presence of some genera like Acidobacteria, Chloracidobacteria, Solibacteres, Anaerolineae, Nitrospira and Deltaproteobacteria were negatively related to disease incidence of FOL and S. sclerotiorum, whereas damping‐off caused by R. solani was negatively affected by the presence of Flavobacterium and Chitinofagha. Therefore, we concluded that long‐term application of OAs can effectively improve soil suppressiveness and reduce disease incidence against root pathogens, although the effects vary considerably depending upon pathosystem. [ABSTRACT FROM AUTHOR]