Pedobiologia最新文献

Arbuscular mycorrhizal (AM) associations are multifunctional. Two important functions they perform are facilitating nutrient uptake in host plants and protecting plants from biotic stress, among other functions. AM fungal taxa vary in how capably they perform these functions and can also respond differently to environmental selection. Therefore, there is a need to better understand how particular environmental variables might alter the response of AM fungal communities. Here, we analysed data from a DNA-based survey of fungal communities in soils collected throughout Australia to observe relationships among soil nitrogen and phosphorus availability and the abundance of two AM fungal taxa that reportedly vary in function – the Gigasporaceae (putatively more important for nutrient uptake) and Glomeraceae (putatively more important for biotic stress). Relationships were assessed in three vegetation types – grasslands, forests and woodlands – to assess whether associations with soil nutrition varied depending on carbon availability for AM fungi. Fungi from the Gigasporaceae decreased in frequency as available phosphorus increased, while those from the Glomeraceae increased or were unresponsive as available phosphorus increased. Similar patterns were observed for nitrate availability, although only in woodlands. These patterns are consistent with expectations that AM fungi from the Gigasporaceae, in general, are better suited to alleviate nutrient limitation in hosts as soil chemical fertility decreases. This knowledge may aid in implementing optimal strategies involving AM fungal inoculum best suited to the local conditions of future land management and agricultural projects.

To date, a paucity of studies have examined bacterial communities in tuberospheres. However, the function of these bacterial communities in healthy potato plants is still largely unknown. Here, we aimed to describe the structure and composition of tuberosphere bacteriomes and its capability to make organosulfur plant available using the rhizosphere and bulk soil bacterial community characteristics as a reference. Rhizosphere, tuberosphere and bulk soil was collected from two field grown potato varieties. Bacterial communities were characterized by 16S rRNA gene amplicon sequencing. Bacterial organosulfur mobilization indicators were evaluated with cultivation dependent and independent methods and were correlated (Spearman) with the relative abundance of bacterial families. The structure of tuberosphere bacterial communities either overlapped with the bulk soil or had similarities with the rhizosphere. Relative abundance of specific bacterial families were distinct between bulk soil, tuberosphere and rhizosphere. Tuberospheres had a tendency for higher arylsulfonate utilization compared to bulk soil. The families Sphingomonadaceae, Sphingobacteriaceae and Rhizobiaceae which presented a decline in their relative abundances from the rhizosphere to tuberosphere and bulk soil had positive correlations with organosulfur mobilizing indicators. Potato variety and soil characteristics played a role in structuring the tuberosphere bacterial communities. Tuberospheres represent an environment in-between bulk soil and rhizosphere indicative from the intermediate relative abundances of specific bacterial families. A moderately higher bacterial organosulfur mobilization activity in tuberospheres suggests that this microbial function may serve specific biological roles for potato tubers.

The ratio of β-glucosidase (BG) to phosphomonoesterase (PME) activity (BG:PME) is often used to predict the intensity of microbial phosphorus (P) shortage, with lower BG:PME indicating stronger P shortage (enzymatic stoichiometry theory). Here, we demonstrated that 10-year continuous P fertilization as high as 150 kg P ha⁻¹ yr⁻¹ in the form of NaH₂PO₄ solution did not elevate the BG:PME up to the level of other terrestrial ecosystems. The BG:PME of primary, secondary, and planted forests were 0.094, 0.067, and 0.089, respectively in P-fertilized plots, which were much lower than global average (0.62 ± 0.04), despite the fact that Bray-extracted P contents were substantially elevated (more than 600 times). Thus, the findings of the current study suggest that BG:PME overestimates P shortage in our P-enriched forests, implying that the enzymatic stoichiometry theory may not be universally applicable.

Investment in non-native species management should be informed by knowledge of impact, including on native biodiversity and ecosystem function. Oribatid soil mites may be useful to evaluate the impacts of plant invasions since they are bioindicators of disturbance and soil ecosystem health. Still, more research is needed to characterize their responses to plant invasion, especially at the species level. Our objective was to determine the effect of invasion of urban forest understories by an allelopathic weed (garlic mustard, Alliaria petiolata (Brassicaceae)) on belowground oribatid mite species and communities. At two sites in central Alberta (Canada), over two years, we examined adult oribatid (≥ 300 µm) community assemblages, species richness, evenness, diversity, and abundance in plots invaded with garlic mustard and uninvaded plots with native vegetation. Environmental covariates known to be associated with soil invertebrate communities were also evaluated. Results suggest that the spatial extent of the garlic mustard invasion (patch area) mediates its impact on oribatid mite communities. However, there were no community-level impacts when considering invasion as binary (garlic mustard vs. native vegetation). Garlic mustard patch area influenced oribatid community composition and was positively related to species richness and several abundance metrics. The oribatid species we observed benefiting from garlic mustard invasion have been previously associated with disturbed soils. The mechanisms driving these patterns need more research, but we hypothesize they may relate to patch-specific resident times. Site was also a dominant factor influencing oribatid mite communities, and impacts of year, litter depth, and canopy cover were also detected at the species and/or community level. These findings contribute to our understanding of the impact of an invasive weed on bioindicating soil mite communities and species and highlight the importance of considering invasion context, including spatial extent when evaluating the impacts of invasive species on belowground invertebrate communities.

In addition to well-known effects on species ecophysiology, phenology, and distributions, climate change is widely predicted to impact essential ecosystem services such as decomposition and nutrient cycling. While temperature and soil moisture are thought to influence litter decomposition, elucidating consistent soil process responses to observed or predicted shifts in climate have proven difficult to evidence. Here we investigated how aspect (i.e., north-south orientation), a natural model for variation in soil temperature, influenced soil physico-chemical conditions and decomposition of two standardised litter types (Green tea and Rooibos teabags) in Pole-facing (PF) and Equator-facing (EF) roadside verges spanning a 3000 km and 27° latitudinal gradient across Europe. Despite average daily temperatures being 1.5 - 3.0 °C warmer on EF than PF slopes, there were only minor region-specific differences in initial soil physico-chemical conditions and short-term variation in litter decomposition (i.e., litter mass loss was higher in EF-verges for the first month of deployment only) associated with aspect. We conclude that previously observed differences in soil environments and the decomposition process associated with slope orientation, is largely litter or environment specific, although medium-term soil-decomposition in semi-natural grassland ecosystems may also be insensitive to the magnitude of temperature variation within the range predicted by the IPCC SSP1–2.6 emissions scenario. Nonetheless, consistent average and extreme temperature differences between adjacent PF- and EF-aspects along roadside verges provides a model system to explore exactly how resilient the soil environment and the micro-organisms responsible for decomposition, are to temperature variation.

Applications of mineral fertilizer to grasslands have become more frequent in recent decades to increase forage production. However, the impacts of mineral fertilizer on the soil microbiome is poorly understood in cold semiarid grassland ecosystems of Southern Patagonia, Argentina. Therefore, our objective was to analyze experimentally the influence of mineral nutrient fertilization (N, P, K, and NPK in combination) on soil microbial community attributes, such as microbial biomass carbon (MBC) and nitrogen (MBN), soil basal respiration (SBR), microbial metabolic coefficients, the colonization of endophytic fungi such as arbuscular mycorrhizal (AM) fungi, and dark septate endophytes (DSE), and aboveground plant productivity. Mineral fertilization with macronutrients (N, P, K, and NPK) decreased the SBR, qCO₂, AM fungi and DSE fungi, but did not generate changes in MBC and MBN. The magnitude of these responses depends on years after fertilization. We found that soil microbiome was strongly dependent on a range of biotic and abiotic factors, such as growing season precipitation, aboveground plant biomass the relationship between the microbial biomass and microbial respiration, and between endophytic fungi and plants. This work improved our understanding of the soil microorganisms’ response to mineral fertilizer application and provides new insights into soil nutrient dynamics and ecosystem functioning.

Purpose

Soil invertebrates are abundant and diverse members of forest ecosystems, contributing in large parts to ecosystem functioning. Understanding drivers of soil invertebrate diversity, density, and community composition is critical to inform management practices as forests face rapid changes in land use and climate. Tree community metrics may help predict invertebrate communities due to their large role in shaping microhabitat and soil conditions. Ground beetles are a large family of soil-dwelling invertebrates comprised of multiple functional groups ideal for tying tree communities to invertebrate communities broadly. Methods Here, we evaluated the effects of tree diversity, density, and functional groups on ground beetle (Carabidae) diversity, density, and community composition in four eastern US temperate forest sites in the National Ecological Observatory Network. Results We found little evidence to support our hypothesis that higher tree diversity and density would, respectively, lead to higher diversity and density ground beetle communities. Instead, evergreen tree abundance strongly shaped ground beetle density and community composition. Specifically, evergreen stands contained a lower density of ground beetles than deciduous stands. Similarly, the relative abundance of predatory ground beetles increased as the relative abundance of evergreen trees increased. Conclusions Our results show that the resource environments created by trees with varying leaf habits are a dominant force driving ground beetle community diversity and density patterns and suggest that future research exploring mechanisms driving this pattern could improve our understanding of plant-soil interactions.