Identity of plant,lichen and moss species connects with microbial abundance and soil functioning in maritime Antarctica

Background and aims

Plant breeding activities shape the rhizosphere microbiome but less is known about the relationship of both with the seed microbiome. We analyzed the composition of bacterial communities of seeds and rhizospheres of Styrian oil pumpkin genotypes in comparison to bulk soil to elucidate specific microbial signatures to support a concept involving plant-microbe interactions in breeding strategies.

Methods

The seed and rhizosphere microbiomes of 14 genotypes of oilseed pumpkin and relatives were analyzed using a 16S rRNA gene amplicon sequencing approach, which was assessed by bioinformatics and statistical methods.

Results

All analyzed microhabitats were characterized by diverse bacterial communities, but the relative proportions of phyla and the overall diversity was different. Seed microbiomes were characterized by the lowest diversity and dominant members of Enterobacteriaceae including potential pathogens (Erwinia, Pectobacterium). Potential plant-beneficial bacteria like Lysobacter, Paenibacillus and Lactococcus contributed to the microbial communities in significant abundances. Interestingly, strong genotype-specific microbiomes were detected for seeds but not for the rhizospheres.

Conclusions

Our study indicates a strong impact of the Cucurbita pepo genotype on the composition of the seed microbiome. This should be considered in breeding of new cultivars that are more capable of exploiting beneficial indigenous microbial communities.

     

Interaction between contrasting rice genotypes and soil physical conditions induced by hydraulic stresses typical of alternate wetting and drying irrigation of soil

Background and aims

Drought events, agricultural practices and plant communities influence microbial and soil abiotic parameters which can feedback to fodder production. This study aimed to determine which soil legacies influence plant biomass production and nutritional quality, and its resistance and recovery to extreme weather events.

Methods

In a greenhouse experiment, soil legacy effects on Lolium perenne were examined, first under optimal conditions, and subsequently during and after drought. We used subalpine grassland soils previously cultivated for two years with grass communities of distinct functional composition, and subjected to combinations of climatic stress and simulated management.

Results

The soil legacy of climatic stress increased biomass production of Lolium perenne and its resistance and recovery to a new drought. This beneficial effect resulted from higher nutrient availability in soils previously exposed to climatic stresses due to lower competitive abilities and resistance of microbial communities to a new drought. This negative effect on microbial communities was strongest in soils from previously cut and fertilized grasslands or dominated by conservative grasses.

Conclusion

In subalpine grasslands more frequent climatic stresses could benefit fodder production in the short term, but threaten ecosystem functioning and the maintenance of traditional agricultural practices in the long term.

     

Litter fingerprint on microbial biomass,activity, and community structure in the underlying soil

Aims

Little is known about how plant leaf litter decomposing on the soil surface is affecting microbial communities in the underlying soil. Here we examined the effects of decomposing leaf litter of different initial chemistry on biomass, stoichiometry, community structure and activity of microorganisms in the soil underneath the decaying litter layer.

Methods

Leaf litter from six different neotropical tree species with contrasted quality decomposed on top of a common tropical soil in a laboratory microcosm experiment over 98 days. At the end of the experiment we determined microbial biomass C, N, and P, microbial community structure (PLFA), and community level physiological profiles (CLPP) from the top soil.

Results

Despite growing in a common soil substrate, soil microorganisms were strongly affected by litter species, especially by the soluble litter fraction. While litters with low soluble C content did not affect the soil microbial community, litters with high soluble C content led to an increase of microbial biomass and to a structural shift to relatively more Gram-negative bacteria. Changing community structure resulted in changes of catabolic capacity of microorganisms to metabolize a range of different C substrates. The large differences in leachate N and P among litter species, in contrast, had no effect on soil microbial parameters.

Conclusions

Our data suggest that plant litter decomposing on the soil surface exhibit a strong and predictable leachate C-control over microbial community biomass, structure and function in the underlying soil.

     

Grass vs. tree origin of soil organic carbon under different land-use systems in the Brazilian Cerrado

Aims

This study aimed at assessing whether patch type (i.e., under-shrub soil patch and inter-shrub soil patch) has an effect on soil microbes and how different shrub species altered the soil microbes through understanding soil microbial activity, biomass, and community structure.

Methods

We characterized the soil microbes in under-shrub and inter-shrub soil patches in three shrublands (Artemisia ordosica, Salix psammophila, and Caragana microphylla), respectively, in the Mu Us Desert, China, using microbial activity indicators, chloroform fumigation-extraction analysis, and high-throughput 16S rRNA gene sequencing.

Results

Members of the phyla Proteobacteria, Actinobacteria, Acidobacteria, Planctomycetes, Bacteroidetes, Chloroflexi, Firmicutes, and Gemmatimonadetes were dominant. Inter-shrub soil patch differed from under-shrub soil patch in soil bacterial composition, microbial enzyme activity, and biomass, but not in diversity. Soil collected in A. ordosica shrubland exhibited the highest microbial enzyme activity, biomass, and diversity. Shrub species had significant effects on community structure, primarily the relative abundance of Proteobacteria, Actinobacteria, and Bacteroidetes.

Conclusions

The results indicated that both shrub species and patch type had effects on soil microbial communities. In shrub-dominated desert ecosystems, spatial heterogeneity of soil nutrients and moisture might not be the main factors underlying variations in bacterial diversity. The different compositions of microbial communities in various shrublands provide a foundation for further research into the mechanisms of soil organic carbon accumulation.

     

Holm oak decline triggers changes in plant succession and microbial communities,with implications for ecosystem C and N cycling

Background and aims

The occurrence of drought-induced forest die-off events is projected to increase in the future, but we still lack complete understanding of its impact on plant-soil interactions, soil microbial diversity and function. We investigated the effects of holm oak (Quercus ilex) decline (HOD) on soil microbial community and functioning, and how these effects relate to changes in the herbaceous community.

Methods

We selected 30 holm oak trees with different defoliation degrees (healthy, affected and dead) and analyzed soil samples collected under the canopy (holm oak ecotype) and out of the influence (grassland ecotype) of each tree.

Results

HOD increased potential nitrogen (N) mineralization and decreased inorganic N concentrations. These results could be partially explained by changes in the herbaceous composition, an increased herbaceous abundance and changes in soil microbial functional diversity and structure, with HOD favoring bacteria against fungi. Moreover, herbaceous abundance and microbial functional diversity of holm oak and grassland ecotypes converged with HOD.

Conclusions

Our results show that HOD triggers a cascade effect on plant understory and soil microbial communities, as well as a plant succession (savannization) process, where understory species colonize the gaps left by dead holm oaks, with important implications for ecosystem C and N budgets.

     

Total and active microbial communities and <Emphasis Type="Italic">phoD</Emphasis> as affected by phosphate depletion and pH in soil

Background and Aims

Soil microbial communities contribute to organic phosphorus cycling in a variety of ways, including secretion of the PhoD alkaline phosphatase. We sampled a long-term grassland fertilization trial in Switzerland characterized by a natural pH gradient. We examined the effects of phosphate depletion and pH on total and active microbial community structures and on the structure and composition of the total and active phoD-harboring community.

Methods

Archaeal, bacterial and fungal communities were investigated using T-RFLP and phoD-harboring members of these communities were identified by 454-sequencing.

Results

Phosphate depletion decreased total, resin-extractable and organic phosphorus and changed the structure of all active microbial communities, and of the total archaeal and phoD-harboring communities. Organic carbon, nitrogen and phosphorus increased with pH, and the structures of all total and active microbial communities except the total fungal community differed between the two pH levels. phoD-harboring members were affiliated to Actinomycetales, Bacilliales, Gloeobacterales, Planctomycetales and Rhizobiales.

Conclusions

Our results suggest that pH and associated soil factors are important determinants of microbial and phoD-harboring community structures. These associated factors include organic carbon and total nitrogen, and to a lesser degree phosphorus status, and active communities are more responsive than total communities. Key players in organic P mineralization are affiliated to phyla that are known to be important in organic matter decomposition.

     

Effects of phosphorus-mobilizing bacteria on tomato growth and soil microbial activity

Aims

The aim of our study was to clarify whether inoculating a soil with Pseudomonas sp. RU47 (RU47) bacteria would stimulate the enzymatic cleavage of organic P compounds in the rhizosphere and bulk soil, promoting plant growth. Adding either viable or heat treated RU47 cells made it possible to separate direct from indirect effects of the inoculum on P cycling in soil and plants.

Methods

We performed a rhizobox experiment in the greenhouse with tomato plants (Solanum lycopersicum) under low P soil conditions. Three inoculation treatments were conducted, using unselectively grown soil bacteria (bacterial mix), heat treated (HT-RU47) and viable RU47 (RU47) cells, and one not inoculated, optimally P-fertilized treatment. We verified plant growth, nutrient availability, enzyme activities and microbial community structure in soil.

Results

A plant growth promotion effect with improved P uptake was observed in both RU47 treatments. Inoculations of RU47 cells increased microbial phosphatase activity (PA) in the rhizosphere.

Conclusions

Plant growth promotion by RU47 cells is primarily associated with increased microbial PA in soil, while promotion of indigenous Pseudomonads as well as phytohormonal effects appear to be the dominant mechanisms when adding HT-RU47 cells. Thus, using RU47 offers a promising approach for more efficient P fertilization in agriculture.

     

Towards understanding the traits contributing to performance of pearl millet open-pollinated varieties in phosphorus-limited environments of West Africa

Background and aims

Arbuscular mycorrhizal (AM) hyphae represent an important route for input of plant-derived C to soil, but impacts of these inputs on microbial communities and processes are poorly understood. In this study we characterised pathways of C-flow through microbial communities associated with AM hyphae and quantified impacts on mineralisation of native SOM.

Methods

Continuous, steady-state ¹³CO₂ labelling was applied throughout the growth period (60 d) of Lolium perenne. Exclusion meshes were used to control access of roots and AM hyphae to soil, and plant-derived C was quantified within microbial PLFA and NLFA, and soil CO₂ efflux was partitioned into plant- and soil organic matter (SOM) derived components.

Results

Pathways of C-flow through hyphosphere and mycorrhizosphere communities were distinct, as was the fate of plant-derived C from AM hyphae accessing soil through 37 and 1 μm meshes. Mineralisation of native SOM was increased in all treatments, relative to unplanted controls, and this priming effect was largest for AM hyphae accessing soil through the 1 μm mesh size.

Conclusions

We demonstrated that AM hyphae can strongly increase mineralisation of native SOM and identified distinct pathways of C-flow through hyphosphere communities. Our results suggest that, in addition to affecting rates of litter decomposition, AM hyphae may have a significant influence on turnover of native SOM.

     

Responses of switchgrass soil respiration and its components to precipitation gradient in a mesocosm study

Aims

The objective of this study was to investigate the effects of the precipitation changes on soil, microbial and root respirations of switchgrass soils, and the relationships between soil respiration and plant growth, soil moisture and temperature.

Methods

A mesocosm experiment was conducted with five precipitation treatments over two years in a greenhouse in Nashville, Tennessee. The treatments included ambient precipitation, ?50%, ?33%, +33% and +50% of ambient precipitation. Soil, microbial, and root respirations were quantified during the growing seasons.

Results

Mean soil and root respirations in the +50% treatment were the highest (2.48 and 0.93 μmol CO₂ m^?2 s^?1, respectively) among all treatments. Soil microbial respiration contributed more to soil respiration, and had higher precipitation sensitivity mostly than root respiration. Increases in precipitation mostly enhanced microbial respiration while decreases in precipitation reduced both microbial and root respirations. Across precipitation treatments, soil respiration was significantly influenced by soil moisture, soil temperature, and aboveground biomass.

Conclusions

Our results showed that microbial respiration was more sensitive to precipitation changes, and precipitation regulated the response of soil respiration to soil temperature. The information generated in this study will be useful for model simulation of soil respiration in switchgrass fields under precipitation changes.

     

Assembly of seed-associated microbial communities within and across successive plant generations

Background and aims

Seeds are involved in the transmission of microorganisms from one plant generation to another and consequently may act as the initial inoculum source for the plant microbiota. In this work, we assessed the structure and composition of the seed microbiota of radish (Raphanus sativus) across three successive plant generations.

Methods

Structure of seed microbial communities were estimated on individual plants through amplification and sequencing of genes that are markers of taxonomic diversity for bacteria (gyrB) and fungi (ITS1). The relative contribution of dispersal and ecological drift in inter-individual fluctuations were estimated with a neutral community model.

Results

Seed microbial communities of radish display a low heritability across plant generations. Fluctuations in microbial community profiles were related to changes in community membership and composition across plant generations, but also to variation between individual plants. Ecological drift was an important driver of the structure of seed bacterial communities, while dispersal was involved in the assembly of the fungal fraction of the seed microbiota.

Conclusions

These results provide a first glimpse of the governing processes driving the assembly of the seed microbiota.

     

Machine learning analysis of microbial flow cytometry data from nanoparticles,antibiotics and carbon sources perturbed anaerobic microbiomes

Background

Flow cytometry, with its high throughput nature, combined with the ability to measure an increasing number of cell parameters at once can surpass the throughput of prevalent genomic and metagenomic approaches in the study of microbiomes. Novel computational approaches to analyze flow cytometry data will result in greater insights and actionability as compared to traditional tools used in the analysis of microbiomes. This paper is a demonstration of the fruitfulness of machine learning in analyzing microbial flow cytometry data generated in anaerobic microbiome perturbation experiments.

Results

Autoencoders were found to be powerful in detecting anomalies in flow cytometry data from nanoparticles and carbon sources perturbed anaerobic microbiomes but was marginal in predicting perturbations due to antibiotics. A comparison between different algorithms based on predictive capabilities suggested that gradient boosting (GB) and deep learning, i.e. feed forward artificial neural network with three hidden layers (DL) were marginally better under tested conditions at predicting overall community structure while distributed random forests (DRF) worked better for predicting the most important putative microbial group(s) in the anaerobic digesters viz. methanogens, and it can be optimized with better parameter tuning. Predictive classification patterns with DL (feed forward artificial neural network with three hidden layers) were found to be comparable to previously demonstrated multivariate analysis. The potential applications of this approach have been demonstrated for monitoring the syntrophic resilience of the anaerobic microbiomes perturbed by synthetic nanoparticles as well as antibiotics.

Conclusion

Machine learning can benefit the microbial flow cytometry research community by providing rapid screening and characterization tools to discover patterns in the dynamic response of microbiomes to several stimuli.

     

The impact of <Emphasis Type="Italic">Carpobrotus</Emphasis> cfr. <Emphasis Type="Italic">acinaciformis</Emphasis> (L.) L. Bolus on soil nutrients,microbial communities structure and native plant communities in Mediterranean ecosystems

Background and aims

Carpobrotus spp. are amongst the most impactful and widespread plant invaders of Mediterranean habitats. Despite the negative ecological impacts on soil and vegetation that have been documented, information is still limited about the effect by Carpobrotus on soil microbial communities. We aimed to assess the changes in the floristic, soil and microbial parameters following the invasion by Carpobrotus cfr. acinaciformis within an insular Mediterranean ecosystem.

Methods

Within three study areas a paired-site approach, comparing an invaded vs. a non-invaded plot, was established. Within each plot biodiversity indexes, C and N soil content, pH and microbial biomass and structure (bacterial and fungal) were assessed.

Results

Invaded plots showed a decrease of α-species richness and diversity. The least represented plant species in invaded plots were those related to grassland habitats. In all invaded soils, a significant increase of carbon and nitrogen content and a significant decrease of pH were registered. Carpobrotus significantly increased bacterial and fungal biomass and altered soil microbial structure, particularly favoring fungal growth.

Conclusions

Carpobrotus may deeply impact edaphic properties and microbial communities and, in turn, these strong modifications probably increase its invasive potential and its ability to overcome native species, by preventing their natural regeneration.

     

Phylogenetically structured traits in root systems influence arbuscular mycorrhizal colonization in woody angiosperms

Background

Rhizodeposition is the release of organic compounds from plant roots into soil. Positive relationships between rhizodeposition and soil microbial biomass are commonly observed. Rhizodeposition may be disrupted by increasing drought however the effects of water stress on this process are not sufficiently understood.

Scope

We aimed to provide a synthesis of the current knowledge of drought impacts on rhizodeposition. The current scarcity of well-defined studies hinders a quantitative meta-analysis, but we are able to identify the main effects of water stress on this process and how changes in the severity of drought may produce different responses. We then give an overview of the links between rhizodeposition and microbial communities, and describe how drought may disrupt these interactions.

Conclusions

Overall, moderate drought appears to increase rhizodeposition per gram of plant, but under extreme drought rhizodeposition is more variable. Concurrent decreases in plant biomass may lessen the total amount of rhizodeposits entering the soil. Effects on rhizodeposition may be strongly species-dependant therefore impacts on soil communities may also vary, either driving subsequent changes or conferring resilience in the plant community. Advances in the study of rhizodeposition are needed to allow a deeper understanding of this plant-soil interaction and how it will respond to drought.

     

Heterogeneity in arbuscular mycorrhizal fungal communities may contribute to inconsistent plant-soil feedback in a Neotropical forest

Background and aims

Plant-soil feedback may vary across host species and environmental gradients. The relative importance of these biotic versus abiotic drivers of feedback will determine the stability of plant and microbial communities across environments. If plant hosts are the main driver of soil microbial communities, plant-soil feedback may be stable across changing environments. However, if microbial communities vary with environmental gradients, feedback may also vary, limiting its capacity to predict plant distributions.

Methods

We characterized arbuscular mycorrhizal (AM) fungi across tree plantations and a primary Neotropical rainforest. We then performed a plant-soil feedback pot experiment of AM fungi from these plantations on three plant species and related feedback and AM fungal communities in the field.

Results

In the field, temporal and spatial variation in AM fungal composition was similar in magnitude to variation across plant host species. Composition of AM fungi in the pot experiment significantly differed from the field plots. Furthermore, differential feedback was explained by shifts in AM fungal composition only for one plant host species (Hyeronima alchorneoides) in the pot experiment.

Conclusions

Natural AM fungal communities were temporally and spatially heterogeneous and AM fungal communities in the greenhouse did not reflect natural soils. These factors led to heterogeneous and unpredictable feedback responses, which suggests that applying greenhouse derived plant-soil feedback trends to predict plant coexistence in natural systems may be misleading.

     

The bacterial community associated with rose-scented geranium (<Emphasis Type="Italic">Pelargonium graveolens</Emphasis>) leaves responds to anthracnose symptoms

Background

The fungus Colletotrichum is a plant pathogen that causes the anthracnose disease, resulting in huge losses in various crops including the rose-scented geranium (Pelargonium graveolens). Although the bacterial community associated with plants has an important role in the establishment of plant diseases, little is known about what happens in P. graveolens.

Aims

To increase the knowledge about the bacterial community associated with P. graveolens and its relationship with anthracnose disease symptoms.

Methods

Quantitative PCR and high-throughput sequencing were combined to determine the presence of the fungus Colletotrichum and to reveal the bacterial communities associated with different plant parts – root, stem and leaf – and in the rhizosphere and bulk soil, and also to determine the respective bacterial communities associated with P. graveolens leaves symptomatic and asymptomatic for anthracnose disease.

Results

The fungus Colletotrichum was detected in all plant parts and in the surrounding soil. Bacterial communities varied spatially in plants, and the disease symptoms also influenced the composition of the bacterial community. Abundances of operational taxonomic units (OTUs) assigned to the phylum Actinobacteria and to the genus Streptococcus were greatly increased in asymptomatic leaves.

Conclusions

The bacterial community associated to geranium leaves responds to anthracnose symptoms.

     

Performance and diversity of polyvinyl alcohol-degrading bacteria under aerobic and anaerobic conditions

Objectives

To compare the degradation performance and biodiversity of a polyvinyl alcohol-degrading microbial community under aerobic and anaerobic conditions.

Results

An anaerobic–aerobic bioreactor was operated to degrade polyvinyl alcohol (PVA) in simulated wastewater. The degradation performance of the bioreactor during sludge cultivation and the microbial communities in each reactor were compared. Both anaerobic and aerobic bioreactors demonstrated high chemical oxygen demand removal efficiencies of 87.5 and 83.6 %, respectively. Results of 16S rDNA sequencing indicated that Proteobacteria dominated in both reactors and that the microbial community structures varied significantly under different operating conditions. Both reactors obviously differed in bacterial diversity from the phyla Planctomycetes, Chlamydiae, Bacteroidetes, and Chloroflexi. Betaproteobacteria and Alphaproteobacteria dominated, respectively, in the anaerobic and aerobic reactors.

Conclusions

The anaerobic–aerobic system is suitable for PVA wastewater treatment, and the microbial genetic analysis may serve as a reference for PVA biodegradation.

     

Phosphorus availability and microbial community in the rhizosphere of intercropped cereal and legume along a P-fertilizer gradient

Background and aims

Positive below-ground interactions (facilitation) should be more pronounced when resources limit crop growth, according to the stress-gradient hypothesis. Our aim was to test this hypothesis for intercropped durum wheat and faba bean along a P-fertilizer gradient.

Methods

A field experiment was conducted in a long-term P-fertilizer trial with three rates of P-fertilization (No, Low and High P). Microbial biomass was assessed by chloroform fumigation-extraction. Quantitative PCR was applied to evaluate the abundance of relevant microbial groups.

Results

Phosphorus availability and microbial biomass systematically increased in the rhizosphere compared to bulk soil. P-fertilization resulted in higher abundance of targeted bacterial phyla, whole bacterial and fungal communities, and depressed mycorrhizal colonization of durum wheat, but not faba bean. Microbial biomass carbon significantly increased in the rhizosphere only in P-fertilized treatments, pointing to P limitation of microbial communities. Intercropping yielded a significant effect on rhizosphere microbial properties only at High P. Microbial biomass P increased in the rhizosphere of intercropped faba bean only at No P level, and was thus the sole finding supporting the stress-gradient hypothesis.

Conclusions

P-fertilization was the main driver of microbial communities in this field trial, and P-fertilizer application modulated the species-specific effect in the intercrop. Plant performance did not validate the stress-gradient hypothesis as positive plant-plant interactions occurred regardless of the level of P-fertilization.

     

Microbial community and associated enzymes activity influence soil carbon chemical composition in <Emphasis Type="Italic">Eucalyptus urophylla</Emphasis> plantation with mixing N<Subscript>2</Subscript>-fixing species in subtropical China

Background and aims

Microbial communities and their associated enzyme activities affect the quantity and chemical quality of carbon in soil. We aimed to evaluate the biochemical mechanisms underlying how N₂-fixing species influences soil organic carbon chemical composition through soil microbial functional groups and enzyme activities.

Methods

We examined the effects of N₂-fixing species mixed with Eucalyptus on soil carbon storage, and the chemical composition of an 8-year-old pure Eucalyptus urophylla plantation (PP) and a mixed E.urophylla and Acacia mangium plantation (MP).

Results

The soil carbon stock and recalcitrant carbon chemical component significantly increased in surface soil in MP. The total PLFAs and bacterial PLFAs increased by 29.1% and 27.0% in cool-dry season, while in the warm-wet season, the total PLFAs and bacterial PLFAs increased by 13.1% and 27.3%, respectively. However, the fungal PLFAs decreased significantly in warm-wet season in MP. The total activity of the cellulose-degrading enzyme β-glucosidase was significantly greater with mixed N₂-fixing species in both dry-cool and wet-warm season. The increase in the Alk-C/O-Alk-C ratio and SOC was strongly associated with both C-acquisition activity and bacterial community.

Conclusions

Our findings highlight the importance of N₂-fixing species in regulating both soil microbial communities and their functioning in association with soil extracellular enzyme activities, which contribute to the increased soil carbon storage and recalcitrant carbon composition in Eucalyptus plantations.

     

“Preferential” ammonium uptake by sugarcane does not increase the <Superscript>15</Superscript>N recovery of fertilizer sources

Aims

Human activities can dramatically alter natural plant communities which, after disturbance cessation, undergo secondary succession. In arid environments plant succession is quite slow, and its link to the carbon (C) cycle is not well known. We assessed changes in C balance on a semiarid plant community along a chronosequence spanning ca. 100 years after land abandonment in an arid environment in SE Spain to examine temporal changes in C following human disturbance.

Methods

We selected 5 individuals of the dominant plant species along five plant community stages differing in the time since land abandonment occurred, and we used a closed-chamber infrared gas analyzer method to estimate the contribution of whole plants and bare soil to community C exchange. We estimated CO₂ fluxes for each plant community stage and calculated temporal differences along the chronosequence.

Results

Plant community composition and plant cover changed throughout the chronosequence. Carbon balance was related to changes in plant photosynthesis and plant and soil respiration along the chronosequence. Overall, community C exchange shifted from source to sink as plant colonization progressed. It took 65 years for the system to recover the equivalent C sink capacity of the undisturbed site.

Conclusions

Recovery of arid plant communities after land abandonment may enhance long-term C sequestration and significantly contribute to C balance at the global level.

     

Seed weight affects shoot and root growth among and within soybean genotypes beyond the seedling stage: implications for low P tolerance screening

Background and aims

Invasive plants have been associated with alterations to soil properties, functions, and organisms, with the potential to impact ecosystem processes. An observational study was conducted to determine how the invasive plant Frangula alnus affects soil microbial communities and biogeochemical processes in Wisconsin forests.

Methods

Paired invaded/non-invaded sites (n = 10), including high (n = 5) and low (n = 5) density invasions, were sampled in spring, summer, and fall. Soil was analyzed for extractable and total nitrogen (N), N mineralization rate, total carbon, microbial biomass carbon and N, and microbial community structure using terminal restriction fragment length polymorphisms.

Results

Linear regression analysis with robust variance estimation revealed higher N mineralization rates in invaded sites than non-invaded sites in summer, and in high density invaded sites than non-invaded sites overall (p < 0.05). There was not a corresponding increase in extractable N. No differences between invaded and non-invaded sites were observed for other variables.

Conclusions

Nitrogen-rich F. alnus leaf litter (3.2 % of dry mass) may contribute to elevated N mineralization at these sites, though pre-existing conditions may be responsible. Results suggest that F. alnus alters N cycling but has little impact on soil carbon pools and microbial communities.