Fungal endophytes affect plant response to leaf litter with contrasting chemical traits

Abstract Plant litter decomposition is a crucial process of nutrient cycling within ecosystems. However, many studies have shown that, apart from its several beneficial effects, organic matter decomposition can be disadvantageous to seed germination, seedling growth, and physiological activity of plants. Litter decomposition was reported to affect both plants and their associated soil microbial communities. The aim of this work was to test the relationships between seed-associated endophytic fungi on the either positive or negative plant's response to different litter types. Leaf material of four species was collected and used in a decomposition experiment inside a growth chamber for 120 days. The plant growth experiment was set in a greenhouse using Trifolium repens and Triticum durum with and without their associated endophytic fungi in the presence of the different litter species at two decay levels (fresh litter and after 120 days of decomposition). Results demonstrated that fresh litter exerted a strong inhibition effect on the plant total biomass when compared to decomposed litter. Moreover, seed-associated endophytic fungi enhanced the inhibitory effect of litter in the observed experimental conditions. The removal of seed-associated endophytic fungi improved the capacity of tested plants to resist to litter inhibitory effect

Decomposition and temperature sensitivity of fine root and leaf litter of 43 mediterranean species

Aims: Data on the decomposition of fine roots are scarce for the Mediterranean basin. This work aims to compare chemical traits, decomposition rate, and temperature sensitivity (Q10) for root and leaf litter of 43 Mediterranean species. Methods: We carried out a two-years litterbag decomposition experiment using 43 fine roots litter and leaf litter types incubated in laboratory conditions at three different temperatures, i.e. 4 °C, 14 °C, and 24 °C. Litter was characterized for carbon (C), nitrogen (N), lignin and cellulose concentration, C/N, and lignin/N ratios. Results: Fine root litter had lower N content but higher lignin concentration, lignin/N, and C/N ratios compared to leaf litter. The decay rate of fine root litter was slower than leaf litter. For both tissues, the decay rate was negatively associated with lignin concentration, lignin/N, and C/N ratios but positively with N concentration. Q10 was higher for fine root than leaf litter, with a positive correlation with lignin while negative with N concentration. Conclusions: Our findings demonstrate a higher Q10 accompanied by a slower decomposition rate of fine root litter compared to leaf litter in Mediterranean ecosystems. These results must be considered in modeling organic C at the ecosystem scale

Basil essential oil: Composition, antimicrobial properties, and microencapsulation to produce active chitosan films for food packaging

The essential oil (EO) from basil—Ocimum basilicum—was characterized, microencapsu-lated by vibration technology, and used to prepare a new type of packaging system designed to extend the food shelf life. The basil essential oil (BEO) chemical composition and antimicrobial activity were analyzed, as well as the morphological and biological properties of the derived BEO microcapsules (BEOMC). Analysis of BEO by gas chromatography demonstrated that the main component was linalool, whereas the study of its antimicrobial activity showed a significant inhibitory effect against all the microorganisms tested, mostly Gram-positive bacteria. Moreover, the prepared BEOMC showed a spheroidal shape and retained the EO antimicrobial activity. Finally, chitosan-based edible films were produced, grafted with BEOMC, and characterized for their physicochemical and biological properties. Since their effective antimicrobial activity was demonstrated, these films were tested as packaging system by wrapping cooked ham samples during 10 days of storage, with the aim of their possible use to extend the shelf life of the product. It was demonstrated that the obtained active film can both control the bacterial growth of the cooked ham and markedly inhibit the pH increase of the packaged food

Negative plant-soil feedback in Arabidopsis thaliana: Disentangling the effects of soil chemistry, microbiome, and extracellular self-DNA

Nutrient deficiency, natural enemies and litter autotoxicity have been proposed as possible mechanisms to explain species-specific negative plant-soil feedback (PSF). Another potential contributor to negative PSF is the plant released extracellular self-DNA during litter decay. In this study, we sought to comprehensively investigate these hypotheses by using Arabidopsis thaliana (L.) Heynh as a model plant in a feedback experiment. The experiment comprised a conditioning phase and a response phase in which the conditioned soils underwent four treatments: (i) addition of activated carbon, (ii) washing with tap water, (iii) sterilization by autoclaving, and (iv) control without any treatment. We evaluated soil chemical properties, microbiota by shotgun sequencing and the amount of A. thaliana extracellular DNA in the differently treated soils. Our results showed that washing and sterilization treatments mitigated the negative PSF effect. While shifts in soil chemical properties were not pronounced, significant changes in soil microbiota were observed, especially after sterilization. Notably, plant biomass was inversely associated with the content of plant self-DNA in the soil. Our results suggest that the negative PSF observed in the conditioned soil was associated to increased amounts of soilborne pathogens and plant self-DNA. However, fungal pathogens were not limited to negative conditions, butalso found in soils enhancing A.thaliana growth. In-depth multivariate analysis highlights that the hypothesis of negative PSF driven solely by pathogens lacks consistency. Instead, we propose a multifactorial explanation for the negative PSF buildup, in which the accumulation of self-DNA weakens the plant's root system, making it more susceptible to pathogens

Topoclimate effect on treeline elevation depends on the regional framework: A contrast between Southern Alps (New Zealand) and Apennines (Italy) forests

Deciphering the spatial patterns of alpine treelines is critical for understanding the ecosystem processes involved in the persistence of tree species and their altitudinal limit. Treelines are thought to be controlled by temperature, and other environmental variables but they have rarely been investigated in regions with different land-use change legacies. Here, we systematically investigated treeline elevation in the Apennines (Italy) and Southern Alps (New Zealand) with contrasting human history but similar biogeographic trajectories, intending to identify distinct drivers that affect their current elevation and highlight their respective peculiarities. Over 3622 km of Apennines, treeline elevation was assessed in 302 mountain peaks and in 294 peaks along 4504 km of Southern Alps. The major difference between the Southern Alps and Apennines treeline limit is associated with their mountain aspects. In the Southern Alps, the scarcely anthropized Nothofagus treeline elevation was higher on the warmer equator-facing slopes than on the pole-facing ones. Contrary to what would be expected based on temperature limitation, the elevation of Fagus sylvatica treelines in the Apennines was higher on colder, pole-facing slopes than on human-shaped equator-facing, warmer mountainsides. Pervasive positive correlations were found between treeline elevation and temperature in the Southern Alps but not in the Apennines. While the position of the Fagus and Nothofagus treelines converge on similar isotherms of annual average temperature, a striking isothermal difference between the temperatures of the hottest month on which the two taxonomic groups grow exists. We conclude that actual treeline elevation reflects the ecological processes driven by a combination of local-scale topoclimatic conditions, and human disturbance legacy. Predicting dynamic processes affecting current and future alpine treeline position requires further insight into the modulating influences that are currently understood at a regional scale

Impact of prescribed burning, mowing and abandonment on a Mediterranean grassland: A 5-year multi-kingdom comparison

Mediterranean grasslands are semi-natural, fire-prone, species-rich ecosystems that have been maintained for centuries through a combination of fire, grazing, and mowing. Over the past half century, however, grasslands have faced numerous threats, including the abandonment of traditional agro-pastoral practices. Our hypothesis was that mowing and prescribed burning are management practices potentially effective in counteracting the reduction of plant diversity triggered by land abandonment. However, the long-term effects of such management practices on plant communities and soil microbiota in Mediterranean grassland remain poorly studied. Here, we conducted a 5-year field experiment comparing prescribed fire, vegetation mowing, and abandonment in a fire-prone Mediterranean grassland in southern Italy in order to evaluate the capability of such management strategies to counteract the detrimental impacts of land abandonment on plant diversity and the associated increase of wildfire. We combined vegetation analysis and soil chemical characterization and several microbiota analyses, including microbial biomass and respiration, arthropod community, and high-throughput sequencing of bacterial and eukaryotic rRNA gene markers. Burning and mowing significantly increased plant species richness and diversity compared to abandonment plots, reducing the abundance of perennial tall grasses in favour of short-lived species. Standing litter followed the same trend, being 3.8-fold greater and largely composed of grass remains in the abandoned compared to burnt and mowed plots. In the soil, prescribed burning caused significant increase in pH, a reduction in organic carbon, total N, and cation exchange capacity. Diversity and taxonomic composition of bacterial and fungal microbiota was affected by burning and mowing treatments. Abandonment caused shifts of microbiota towards a fungal-dominated system, composed of late successional fungi of the Basidiomycota. Fast-growing and putative fungal pathogens were more abundant under burnt and mowed treatments. Soil arthropods were influenced by vegetation and microbiota changes, being strongly reduced in mowed plots. Our study demonstrated that grassland abandonment promotes the spread of tall grasses, reducing plant diversity and increasing the risk of wildfire, while prescribed burning and mowing are effective in counteracting such negative effects

Dieback of the cushion plant Silene acaulis at its southern limit of distribution in the Apennines

Here, we quantified the dieback of Silene acaulis subsp. bryoides along a 500 m elevational transect from 1900 to 2400 m a.s.l. in the Sibillini Group (Apennines). We also investigated the role of the 2022 summer heat wave that affected the Apennines as a putative cause. The intensity of the dieback was not uniformly distributed across the elevational gradient, but was widespread at 1900 and 2000 m a.s.l. and decreased with increasing elevation. Specifically, 40.7% and 38.4% of plants were affected by dieback at 1900 and 2000 m a.s.l., respectively, but less than 1% at elevations above 2300 m a.s.l. Regarding climate, the maximum air temperature in 2022 was 3.7, 4.5, and 3.4 degrees C above the respective long-term average in May, June, and July. A similar trend was observed for the minimum temperature. The monthly maximum (21.5 degrees C) and minimum (14.6 degrees C) temperatures in July were the highest ever recorded since the monitoring station was commissioned in 2005. In terms of daily maximum temperatures, three consecutive days with temperatures above 25 degrees C were recorded in July 2022, an upper limit that has only been reached on four days in the last 17 years. Regarding precipitation, 180 mm of precipitation fell during the May-August growing season compared to the long-term average of 255 mm, a decrease of 30%. More importantly, only 15.2 mm of rain fell in July 2022, compared to a long-term average of 54.3 mm. The sudden dieback of Silene highlights the vulnerability of high elevation vegetation to climate change. Moreover, the loss of Silene cushions is alarming for the survival of the species, which is long lived but very slow growing

Microbiota management for effective disease suppression: A systematic comparison between soil and mammals gut

Both soil and the human gut support vast microbial biodiversity, in which the microbiota plays critical roles in regulating harmful organisms. However, the functional link between microbiota taxonomic compositions and disease suppression has not been explained yet. Here, we provide an overview of pathogen regulation in soil and mammals gut, highlighting the differences and the similarities between the two systems. First, we provide a review of the ecological mechanisms underlying the regulation of soil and pathogens, as well as the link between disease suppression and soil health. Particular emphasis is thus given to clarifying how soil and the gut microbiota are associated with organic amendment and the human diet, respectively. Moreover, we provide several insights into the importance of organic amendment and diet composition in shaping beneficial microbiota as an efficient way to support crop productivity and human health. This review also discusses novel ways to functionally characterize organic amendments and the proper operational combining of such materials with beneficial microbes for stirring suppressive microbiota against pathogens. Furthermore, specific examples are given to describe how agricultural management practices, including the use of antibiotics and fumigants, hinder disease suppression by disrupting microbiota structure, and the potentiality of entire microbiome transplant. We conclude by discussing general strategies to promote soil microbiota biodiversity, the connection with plant yield and health, and their possible integration through a “One Health” framework

Microclimate, soil chemistry, and microbiota fail to explain Euphorbia dendroides Janzen‐Connell pattern in a shrubland

Abstract Negative plant–soil feedback can cause density and distance effects that lead to Janzen–Connell (JC) distribution. The JC hypothesis has been proposed to explain the high species diversity in tropical forests, but it has been rarely tested in species‐rich Mediterranean shrublands. In this study, we assessed whether the JC hypothesis could explain Euphorbia dendroides recruitment pattern under conspecific conditions, that is, mother plant and the canopy of Pistacia lentiscus, Juniperus phoenicea, Myrtus communis, Rosmarinus officinalis, and Olea europaea. We examined whether soil chemistry and/or soil microbiota, characterized by both bacterial and fungal communities, explained the observed JC pattern. We also explored differences in microclimate among shrub species by monitoring air temperature and light availability at different times of the year. Euphorbia recruits were almost absent under the canopy of conspecifics, being more abundant at the edge of the canopy, which fits the JC pattern. Interestingly, we also found a high density of Euphorbia recruitment under heterospecific canopies, that is, O. europaea and J. phoenicea, but a very low density under other heterospecific canopies, for example, R. officinalis and P. lentiscus. Although shrubs have a species‐specific microbiota signature under their canopy, neither the accumulation of species‐specific pathogens nor soil chemical properties explain the observed JC pattern. Despite finding that shrubs buffer high temperatures in summer, the observed microclimatic difference failed to explain the recruitment pattern. We conclude that JC is prevalent in this species‐rich Mediterranean shrubland, but the underlying mechanism remains to be investigated and clarified

Distribution and vegetation of Pinus mugo subsp. mugo dieback patches in Maiella massif (Central Italy)

Forest dieback in the last decade has been reported all over the world and not only causes a significant loss of forest yield but also affects successional trajectories. Here, we investigate the plant communities associated with Pinus mugo subsp. mugo dieback patches in Maiella massif. Dieback patches were examined by using satellite images to describe the occurrences and distribution. According to dieback patch size, we identified three ontogenetic stages: small, medium and large. To assess the effect of P. mugo on coexisting species, patch was divided into four belts according to P. mugo healthy status: OUT, FRONT, DEAD and IN zone. Within the four belt zones for each of the three ontogenetic stages, a vegetation analysis was conducted. Overall, 35 dieback patches were recorded and all are characterized by a circular shape and a size ranging from a few meters to 76.1 m. The linear correlation between the width of the inner regeneration belt and the total diameter of the patch suggests that the dieback area expands centrifugally due to the death of standing P. mugo. The increased resources, in terms of light availability caused by dieback, contribute to higher plants diversity in DEAD belts with the highest cover of hemicryptophytes. Contrariwise, in the OUT belts, not affected by dieback, plant diversity was the lowest with the highest cover of phanerophytes and a good contingent of nemoral species. Dieback affects forest structure and leads to sudden vegetation shifts that play an important role in maintaining biodiversity by allowing alternation between forest and grassland ecosystems