Spatially structured environmental filtering of collembolan traits in late successional salt marsh vegetation

Both the environment and the spatial configuration of habitat patches are important factors that shape community composition and affect species diversity patterns. Species have traits that allow them to respond to their environment. Our current knowledge on environment to species traits relationships is limited in spite of its potential importance for understanding community assembly and ecosystem function. The aim of our study was to examine the relative roles of environmental and spatial variables for the small-scale variation in Collembola (springtail) communities in a Dutch salt marsh. We used a trait-based approach in combination with spatial statistics and variance partitioning, between environmental and spatial variables, to examine the important ecological factors that drive community composition. Turnover of trait diversity across space was lower than for species diversity. Most of the variation in community composition was explained by small-scale spatial variation in topography, on a scale of 4-6 m, most likely because it determines the effect of inundation, which restricts where habitat generalists can persist. There were only small pure spatial effects on species and trait diversity, indicating that biotic interactions or dispersal limitation probably were less important for structuring the community at this scale. Our results suggest that for springtails, life form (i.e. whether they live in the soil or litter or on the surface/in vegetation) is an important and useful trait to understand community assembly. Hence, using traits in addition to species identity when analysing environment-organism relationships results in a better understanding of the factors affecting community composition

The Updated version of SF Box: A method for soil quality classification as a basis for applicable site-specific environmental risk assessment of contaminated soils

This technical note summarises major changes in the updated version of SF Box, which is part of the SCORE – the Multi-Criteria Decision Analysis method for decision support in soil remediation projects. SCORE stands for the Sustainable Choice Of REmediation and SF Box stands for Soil Function toolBox. The SF Box tool has been developed for soil function assessment to complement environmental risk assessments, in order to increase awareness of decision-makers for inherent soil qualities other than concentration of contaminants and their availability/mobility, which are critical for proper soil functioning, e.g. availability of water and nutrients for soil organisms, but often ignored in remediation projects (driven by protection of the soil environment with ambition to recover ecosystem functions) in Sweden. The tool is based on a scoring method using soil quality indicators (SQIs) for assessing (I) the soil’s capacity to perform its functions in its own reference state of being ‘clean’, i.e. “what can this soil do and can it perform its functions well, assuming that it is free of contaminants?”, and (II) the effects of the remedial actions themselves on soil functions, i.e. “can the remediated soil continue to perform these functions well?”. The earlier version of SF Box addresses the soil functions associated with Primary Production. By (i) taking into consideration the perspectives of soil microbiology, soil fauna and vegetation, (ii) slightly modifying the set of SQIs (consisting of soil texture, content of coarse material, organic carbon/matter, available water, C/N ratio, pH and available phosphorus), and (iii) revisiting the curves for scoring of soil performances on each SQI, the SF Box tool has been updated to assess the soils’ capacity to function as a basis for Life and Habitat of flora and fauna. This updated version is therefore aimed to provide an improved basis for site-specific environmental risk assessment by means of (1) differentiating between the effects of contamination on soil biota and the effects of soil capability to function as a host to these species in its own reference state free from contaminants, and (2) classification of the soils (usually characterized by heterogeneity at contaminated sites) in accordance with their overall performance on the selected SQIs for further analysis of ecotoxicological risks in each soil class

Changes in Plant Species Richness Induce Functional Shifts in Soil Nematode Communities in Experimental Grassland

Changes in plant diversity may induce distinct changes in soil food web structure and accompanying soil feedbacks to plants. However, knowledge of the long-term consequences of plant community simplification for soil animal food webs and functioning is scarce. Nematodes, the most abundant and diverse soil Metazoa, represent the complexity of soil food webs as they comprise all major trophic groups and allow calculation of a number of functional indices.We studied the functional composition of nematode communities three and five years after establishment of a grassland plant diversity experiment (Jena Experiment). In response to plant community simplification common nematode species disappeared and pronounced functional shifts in community structure occurred. The relevance of the fungal energy channel was higher in spring 2007 than in autumn 2005, particularly in species-rich plant assemblages. This resulted in a significant positive relationship between plant species richness and the ratio of fungal-to-bacterial feeders. Moreover, the density of predators increased significantly with plant diversity after five years, pointing to increased soil food web complexity in species-rich plant assemblages. Remarkably, in complex plant communities the nematode community shifted in favour of microbivores and predators, thereby reducing the relative abundance of plant feeders after five years.The results suggest that species-poor plant assemblages may suffer from nematode communities detrimental to plants, whereas species-rich plant assemblages support a higher proportion of microbivorous nematodes stimulating nutrient cycling and hence plant performance; i.e. effects of nematodes on plants may switch from negative to positive. Overall, food web complexity is likely to decrease in response to plant community simplification and results of this study suggest that this results mainly from the loss of common species which likely alter plant-nematode interactions

Plant Diversity Surpasses Plant Functional Groups and Plant Productivity as Driver of Soil Biota in the Long Term

One of the most significant consequences of contemporary global change is the rapid decline of biodiversity in many ecosystems. Knowledge of the consequences of biodiversity loss in terrestrial ecosystems is largely restricted to single ecosystem functions. Impacts of key plant functional groups on soil biota are considered to be more important than those of plant diversity; however, current knowledge mainly relies on short-term experiments.We studied changes in the impacts of plant diversity and presence of key functional groups on soil biota by investigating the performance of soil microorganisms and soil fauna two, four and six years after the establishment of model grasslands. The results indicate that temporal changes of plant community effects depend on the trophic affiliation of soil animals: plant diversity effects on decomposers only occurred after six years, changed little in herbivores, but occurred in predators after two years. The results suggest that plant diversity, in terms of species and functional group richness, is the most important plant community property affecting soil biota, exceeding the relevance of plant above- and belowground productivity and the presence of key plant functional groups, i.e. grasses and legumes, with the relevance of the latter decreasing in time.Plant diversity effects on biota are not only due to the presence of key plant functional groups or plant productivity highlighting the importance of diverse and high-quality plant derived resources, and supporting the validity of the singular hypothesis for soil biota. Our results demonstrate that in the long term plant diversity essentially drives the performance of soil biota questioning the paradigm that belowground communities are not affected by plant diversity and reinforcing the importance of biodiversity for ecosystem functioning

Soil nematode assemblage responds weakly to grazer exclusion on a nutrient-rich seabird island

The effects of aboveground herbivores on plant-soil interactions are highly context dependent and a key underlying factor controlling this is thought to be nutrient availability. Here, we tested whether the effects of vertebrate grazing on the soil food web varied with nutrient availability and hypothesised that soil food web structure would be driven more by the exclusion of vertebrate grazers than by nutrient enrichment. An 8-year long grazer exclusion experiment was performed in grasslands on a small Scottish island near soil nutrient-enriching seabird colonies at the coast and in less fertile conditions inland. We investigated the trophic structure of the soil nematode assemblage as a proxy for soil food web structure. Across all eight study sites the bacterial energy channel was predominant over the fungal channel. Grazer exclusion strongly enhanced plant biomass accumulation and although this tended to be associated with a somewhat lower abundance of bacterial-feeders, this effect was non-significant and surprisingly weak given the observed changes aboveground. Indeed, plant species identity, diversity and dominance were, just as any other vegetation descriptor, weak predictors of nematode trophic structure. Instead, site specific conditions were important, despite the small island area and apparently homogenous sampling conditions

Helminths associated with terrestrial slugs in Swedish agricultural fields

Slugs are important agricultural pests causing yearly yield losses. However, parasitizing helminths potentially could affect the size of the slug population. Here, a survey of terrestrial slug-parasitic helminths (nematodes and trematodes) was conducted for the first time in Sweden. In total, 268 terrestrial slugs were collected from 27 agricultural field edges in three seasons over 2020 and 2021 and dissected for presence of helminth parasites. Slugs belonging to the genus Arion were molecularly identified by mitochondrial DNA cytochrome c oxidase subunit I (COI) while parasites were identified using ribosomal RNA (18S). Overall, 13% of the collected slugs had helminth parasites and the likelihood of a slug being parasitized was highest in autumn. Slugs identified as Arion vulgaris were more likely to be parasitized than native slug species. The prevalence of nematodes and trematodes were similar; the dominant species found were Alloionema appendiculatum and Brachylaima thompsoni, respectively. This is the first record of the presence of these two species in Sweden

Helminths associated with terrestrial slugs in Swedish agricultural fields

Abstract Slugs are important agricultural pests causing yearly yield losses. However, parasitizing helminths potentially could affect the size of the slug population. Here, a survey of terrestrial slug-parasitic helminths (nematodes and trematodes) was conducted for the first time in Sweden. In total, 268 terrestrial slugs were collected from 27 agricultural field edges in three seasons over 2020 and 2021 and dissected for presence of helminth parasites. Slugs belonging to the genus Arion were molecularly identified by mitochondrial DNA cytochrome c oxidase subunit I (COI) while parasites were identified using ribosomal RNA (18S). Overall, 13% of the collected slugs had helminth parasites and the likelihood of a slug being parasitized was highest in autumn. Slugs identified as Arion vulgaris were more likely to be parasitized than native slug species. The prevalence of nematodes and trematodes were similar; the dominant species found were Alloionema appendiculatum and Brachylaima thompsoni, respectively. This is the first record of the presence of these two species in Sweden.</jats:p

Above-and belowground insect herbivory modifies the response of a grassland plant community to nitrogen eutrophication

Understanding the role that species interactions play in determining the rate and direction of ecosystem change due to nitrogen (N) eutrophication is important for predicting the consequences of global change. Insects might play a major role in this context. They consume substantial amounts of plant biomass and can alter competitive interactions among plants, indirectly shaping plant community composition. Nitrogen eutrophication affects plant communities globally, but there is limited experimental evidence of how insect herbivory modifies plant community response to raised N levels. Even less is known about the roles of above‐ and belowground herbivory in shaping plant communities, and how the interaction between the two might modify a plant community's response to N eutrophication. We conducted a 3‐yr field experiment where grassland plant communities were subjected to above‐ and belowground insect herbivory with and without N addition, in a full‐factorial design. We found that herbivory modified plant community responses to N addition. Aboveground herbivory decreased aboveground plant community biomass by 21%, but only at elevated N. When combined, above‐ and belowground herbivory had a stronger negative effect on plant community biomass at ambient N (11% decrease) than at elevated N (4% decrease). In addition, herbivory shifted the functional composition of the plant community, and the magnitude of the shifts depended on the N level. The N and herbivory treatments synergistically conferred a competitive advantage to forbs, which benefited when both herbivory types were present at elevated N. Evenness among the plant species groups increased when aboveground herbivory was present, but N addition attenuated this increase. Our results demonstrate that a deeper understanding of how plant–herbivore interactions above and below ground shape the composition of a plant community is crucial for making reliable predictions about the ecological consequences of global change