European Journal of Soil Biology最新文献

Body size is a crucial functional trait that influences the environmental filtering processes of animal communities. However, the role of intraspecific variations in soil invertebrate communities remains poorly understood. In this study, we investigated the influence of environmental changes on intraspecific body size variations in Collembola communities along an elevational gradient in northern Japan, using potential body length in the literature cited and realized body length actually measured. Our hypothesis posits that environmental conditions selectively filtered out smaller nymphs while sparing larger adults of Collembola, as stress tolerance, survival and mortality are directly influenced by body size in response to environmental severity. Calculating size quantiles based on observed realized individual body lengths, we found a stable size hierarchy among species across elevational sites. Species composition was significantly related with elevational gradient, with community-weighted means of smaller quantiles in body length increasing at higher elevations, while those of larger quantiles and adult body size remained unaffected. This suggests that environmental filtering predominantly influences the body size of smaller individuals, such as nymphs, but not larger adults within species. Our findings reveal asymmetric size selection among different life stages in soil animal communities.

Phosphorus (P) is a non-replaceable, finite component of fertilizers. The imbalanced resource distribution and possible depletion of P impose challenges on current crop production worldwide. The aim of this study was to assess the impact of poultry litter biochar on plant growth and P mobilizing capability of the microbiome in comparison to a mineral fertilizer application. Spring barley (Hordeum vulgare) was grown in microcosms using a P-limited soil, fertilized with 0 (control), 50 (fertilizer) kg P ha⁻¹ or a poultry litter biochar amendment (biochar, 2% w/w). Biochar amended rhizospheres had significantly higher phosphonate-utilizing bacteria, phoC and phoD gene (acid and alkaline phosphatase) copy numbers and improved P availability. Spring barley dry matter yields were significantly higher for biochar and fertilizer over control; however, P uptake with biochar was higher than with fertilizer. Furthermore, biochar had higher arbuscular mycorrhizal colonization and significantly raised soil pH. Fingerprint-analysis showed significant differences between all treatments for bacterial and fungal communities. 16S rRNA gene-based sequencing analysis revealed increased relative abundance of the phyla Actinobacteriota and Chloroflexi in biochar compared to control, potentially contributing to the ameliorated plant growth conditions. Pearson correlations of both phyla was positive with a range of P cycling variables as well as Morgan's P but negative with acid phosphatase activity. FAPROTAX analysis revealed positive correlations of aromatic compound degradation with phoC and phoD gene abundance, highlighting a possible link between biodegradation and P release. In conclusion, poultry litter biochar could potentially replace mineral P fertilizer for sustainable plant growth in P depleted soil environments.

Lumbricus terrestris is an epi-anecic earthworm, normally occupying a 1–2 m deep, vertical burrow. Some observations suggest that population persistence in much shallower burrows could be possible in a mild and humid climate. This was further investigated at an ex-industrial site in NW England, with a topsoil less than 0.15 m deep, above inert subsoil formed from semi-weathered Leblanc waste. L. terrestris were collected from an adjacent woodland soil and introduced into unoccupied areas. After four days, settlement and survival were studied by targeted sampling of half of the individuals, and depth of burrows were measured by resin casting. After 14 months, the second half of inoculated areas were studied and after another four years a further general survey occurred. After four days, 41 % of targeted worms were recovered, with 0.11 m mean burrow depth and burrows ending at the subsoil interface. After 14 months, all age classes of L. terrestris were present and burrow depth had not changed. After five years, adult, juvenile and hatchling L. terrestris were present, demonstrating establishment of a breeding population. In a parallel laboratory experiment, with site topsoil and subsoil in Evans’ boxes, L. terrestris avoided subsoil and constructed U-shaped burrows. The results show that through flexible burrow construction, L. terrestris can survive above highly constraining subsoil conditions. This is likely to be only possible where severe droughts are uncommon, and topsoil does not freeze in winter.

Earthworms play a key role as soil bioengineers, but livestock farming and croplands can impact on the composition, structure, and functioning of earthworm communities. This study aimed to quantify the effects of replacing natural grasslands with crop rotations on the seasonal dynamics of key attributes of earthworm communities and explore soil physicochemical properties as mechanisms behind these effects. We conducted paired samplings on seven sites across Uruguay, comparing earthworm communities in soils under grazed natural grasslands and adjacent croplands, considering earthworm species composition, richness, diversity, and evenness, biomass, density, and mean body weight, over five consecutive seasons. Results revealed a clear negative impact of croplands on earthworm communities, showing substantial reductions in all considered attributes. Observed changes were attributed to environmental filters limiting the occurrence of larger exotic earthworm species in croplands, and variations in soil physicochemical properties were identified as potentially mediating some of these effects, including soil water regime (particularly affecting juvenile individuals) and soil organic matter content. These impacts resulted in a shift to dominance of r strategists (smaller, surface-feeding species such as Microscolex spp. in croplands compared to larger deeper-burrowing species in grasslands) and reduced functional composition of earthworm communities. Furthermore, seasonal dynamics revealed that differences between land uses were more pronounced during wetter periods, underscoring the relevance of seasonal variations when evaluating land use impacts on earthworm communities. Earthworms mean body weight resulted a useful attribute to be included in earthworm's assessments, allowing to identify impacts in community functional composition and suggesting size dependent mechanisms. Additional research is required to comprehensively understand the mechanisms behind these patterns and to develop more sustainable agricultural practices by considering soil fauna.

In no-till agroecosystems, presence of the earthworm Lumbricus terrestris L. can be a key driver in the replenishment of soil organic matter stocks post-harvest, through surface residue foraging and incorporation. The impact on such systems under different climatic conditions is, however, still unquantified. A field experiment was designed to determine incorporation of cereal harvest residues at three no-till agricultural sites in boreal conditions (SW Finland) focusing on L. terrestris impacts over the period from autumn harvest to spring sowing. Either spring barley, wheat or oats were cultivated at the sites. Following the harvests, representative masses of residues were applied on small experimental plots (0.25 m²) with cleaned soil surfaces in areas of inherently high (LT+: 10.6 ± 2.1 ind. 0.25 m^-2) and low (LT-: 1.8 ± 0.7 ind. 0.25 m^-2) L. terrestris density within the fields. Residues were covered with metal mesh caging and left until spring sowing, when changes in residue mass were recorded and plots sampled for earthworms. The reduction of straw residue mass varied between sites, from no difference between the LT+ and LT- treatments to 19 % and 59 % higher mass reduction in LT+. Amount of earthworm castings on the residues was also quantified and findings indicated a positive correlation with earthworm (also endogeic) density. For L. terrestris, earthworm species abundance relationships indicated competitive interaction with epigeics and positive interaction with endogeics. Results showed that L. terrestris foraging can enhance the incorporation of cereal surface residues outside of the boreal growing season and that earthworm surface casting also has a role in residue burial. However, the increase of incorporation by L. terrestris activity, interrupted by winter conditions, was moderate and did not lead to marked exposition of the soil surface by experimental end, even at those plots with the highest L. terrestris foraging. The incorporation rate estimates may have been unrepresentative due to the exceptionally late harvest during the study period. Investigations covering the whole year from multiple growing seasons are needed for a comprehensive assessment of earthworm impacts on crop surface residue dynamics.

Acquiring knowledge of the patterns of soil microbial diversity along elevational gradients and the driving factors of these patterns is important for understanding the dynamics of global nutrient elements. In this study, we analyzed the soil bacterial community composition and diversity using Illumina high-throughput sequencing along an elevational gradient from 670 to 1780 m on Huangshan including 6 vegetation types from base to summit. We found that the dominant phyla were Proteobacteria, Acidobacteria, Actinobacteria and Chloroflexi, accounting for more than 75 % of the sequences. We observed significant variation in soil bacterial community composition across different elevations (ANOSIM P = 0.001). In addition, the soil bacterial diversity increased with increasing elevation from 875 m to 1165 m and decreased with increasing elevation from 1280 m to 1370 m, showing a humpbacked relationship with elevations. Soil pH had the strongest effect on bacterial community composition. In conclusion, soil properties, especially soil pH was the primary factor controlling the elevational distribution of soil bacterial communities on Huangshan.

Soil mixing by earthworms can have a large impact on the fate of nutrients and pollutants and on the soil's ability to sequester carbon. Nevertheless, methods to quantify earthworm ingestion and egestion under field conditions are largely lacking. Soils of the Fennoscandian tundra offer a special possibility for such quantifications, as these soils commonly lack burrowing macrofauna and exhibit a well-defined O horizon with low bulk density on top of a mineral soil with higher density. Since ingestion-egestion mixes the two soil layers, the temporal changes in the bulk density profile of such soils may be useful for estimating field ingestion rates. In this study, we applied a model for earthworm burrowing through soil ingestion to observed changes in soil densities occurring in a mesocosm experiment carried out in the arctic during four summers with intact soil. The earthworms present in the mesocosms were Aporrectodea trapezoides, Aporrectodea tuberculata, Aporrectodea rosea, Lumbricus rubellus and Lumbricus Terrestris (fourth season only). We show that changes in soil density profiles can indeed be used to infer earthworm ingestion rates that are realistic in comparison to literature values. Although uncertainties in parameter values were sometimes large, the results from this study suggest that soil turnover rates and endogeic earthworm soil ingestion rates in tundra heath and meadow soils may be as high as those reported for temperate conditions. Such large ingestion rates can explain observed large morphological changes in arctic soils where dispersing earthworms have resulted in complete inmixing of the organic layer into the mineral soil. Our approach is applicable to soil profiles with marked vertical differences in bulk density such as the soils of the Fennoscandian tundra where earthworms are currently dispersing into new areas and to layered repacked soil samples that are incubated in the field.

As an economically important fruit crop, continuous cropping of grapes can potentially impact soil health resulting in decreased yields. However, the mechanism of how soil microecological environment affects grape quality at different growth stages is not fully understood. A field experiment was conducted to investigate the effects of continuous grape cultivation for 0, 7, and 12 (CK, G7Y and G12Y) years on soil physicochemical properties and microbial community at different growth periods and soil depths, as well as on grape yield and quality. The results showed that grape yield, aroma compound contents, soil and grape leaf nutrients decreased significantly with the increase of planting years, soil acidification and secondary salinization intensified. Compared to G7Y, the relative abundance of the beneficial soil microorganisms Mortierella, Bacillus and Pseudomonas decreased significantly in G12Y, while the relative abundance of the potential pathogenic fungi Pseudaleuria and Aspergillus increased significantly. In addition, the nutrient content and biomarkers in the subsoil were lower than those in the topsoil. Particularly, the fruit setting stage appeared to be more sensitive to shifts in soil microbial communities over different planting years. Correlation analysis showed that grape yield was positively correlated with Bacillus and Mortierella, and negatively correlated with Fusarium. Grape yield was more sensitive to phosphorus and potassium fertilizers than to nitrogen fertilizer. In conclusion, continuous cropping reduced the content of soil nutrients and the number of soil beneficial microorganisms, increased the abundance of soil pathogenic microorganisms, and jointly caused changes in grape yield and quality. Therefore, it is necessary to optimize the management strategies to improve the soil microbial diversities especially beneficial microbial diversity to maintain the soil health and then to promote sustainable production of vineyards.

Species interactions exert important influences on biodiversity and ecosystem stability. In complex natural communities, species interactions have gone beyond pairwise mechanisms, as interactions between two species can be regulated by one or more other species (higher-order species interactions). However, few studies consider higher-order interactions among organisms that are indirectly contacted, particularly under high soil nutrient conditions. Here, we performed a common garden experiment to investigate how natural herbivory (aboveground weevil) and simulated herbivory (leaf clipping) affect plant (Triadica sebifera) interactions with soil antagonists (root-knot nematodes) and mutualists (arbuscular mycorrhizal fungi; AMF) under nitrogen and phosphorus addition. We also tested the effects of nitrogen, phosphorus, and herbivory-stimuli on T. sebifera leaf extrafloral nectary (EFN) production. We found that T. sebifera can compensate for biomass loss caused by clipping or weevil feeding, moreover, high nitrogen availability caused plant biomass to outpace herbivory-stimuli. Plant–antagonist (root-knot nematodes) interactions were not affected by clipping or weevil feeding under ambient nitrogen condition but were reduced by clipping or weevil feeding under high nitrogen supply, however, we did not find the same pattern under phosphorus addition. Aboveground herbivory-stimuli did not affect plant–mutualist (AMF) interactions, whether fertilized or not. In addition, nitrogen addition stimulated plants to secrete more EFN against clipping but did not increase EFN production against weevil feeding. Clipping and weevil feeding exhibited consistent effects on both plant–antagonist (root-knot nematodes) interactions and plant–mutualist (AMF) interactions. These results suggest that aboveground antagonists mainly mitigate belowground plant–antagonist interactions but not affect plant–mutualist interactions, and higher-order species interactions depend on nitrogen addition but not phosphorus addition.