Earthworms and mesofauna from an isolated, alkaline chemical waste site in Northwest England

Post-industrial sites across Europe may have developed over periods in excess of a century, often leading to poor nutrient soils with noxious constituents and extreme pH values. One such site, Nob End (Bolton, UK), a toxic tip created in the 1800s from a sodium carbonate factory, represents an “island of alkalinity in an acidic sea” where the weathering process (from pH 12) has provided a suitable environment for a rich alkali-loving flora and hence, deserving its designation as a Site of Special Scientific Interest. Despite their importance, the belowground communities have not been investigated and for this reason, in this study, we explored how soil macro- and mesofauna communities respond to extreme pH values in a system that has also experienced recent changes in management practices. As expected, earthworms, mites, insects and woodlice numbers were significantly higher and the community diversity enriched at the (now pH 8) alkaline sites, whereas in areas where acidic boiler waste was historically deposited, enchytraeids, collembolans and dipteran larvae populations dominated the soil communities. Surprisingly, site management (cutting back of scrub) in the alkaline soil areas had a significant positive effect on soil macro-fauna by promoting numbers and biomass, but severely reduced the microarthropod populations. A transect investigation across an increasing pH gradient (from 4.5 to 8.0) was mirrored by a rise in earthworm numbers and species richness. Earthworms were further investigated surrounding the site, seeking potential sources of colonisation, with the majority of species at Nob End also present in adjacent non-industrially-influenced areas. This work demonstrates that soil fauna can ultimately colonise extreme edaphic conditions and these extreme environments have not prompted the development of specific faunal communities. As management of above-ground communities significantly influenced soil invertebrate communities, this could represent an important restoration practice to improve soil structure and fertility at this polluted site

Extracting DNA from soil or directly from isolated nematodes indicate dissimilar community structure for Europe-wide forest soils

Nematodes are numerous in soils and play a crucial role in soil food-webs. DNA metabarcoding offers a time-effective alternative to morphology-based assessments of nematode diversity. However, it is unclear how different DNA extraction methods prior to metabarcoding could affect community analysis. We used soils with woody vegetation from a European latitudinal gradient (29 sites, 39 to 79°N, ∼4500 km, covering six biomes) to systematically evaluate the effect of two sources of nematode DNA either directly extracted from soils vs. extracted from nematodes previously isolated from soils hypothesizing that the DNA source material may produce different diversities, community structures and abundances of feeding types. Nematode-sample DNA exhibited a higher richness, while no difference in Shannon diversity was found between the approaches. The DNA sources also created significantly different community structures, with greater differences observed across soil-extracted DNA than nematode-sample DNA. The most overrepresented species in nematode-sample DNA were Heterocephalobus elongatus, Eucephalobus striatus and Hexatylus sp., whereas Phasmarhabditis sp. and Eumonhystera filiformis were overrepresented in soil-extracted DNA. Read abundances of feeding types significantly differed between the DNA sources and across sites, with a significant effect of biome on both ecto- and endoparasitic herbivores in soil-extracted DNA and for ectoparasitic herbivores only in nematode-sample DNA. Collectively, our data suggest that choice of the DNA source material may lead to different patterns of nematode community composition across space and environmental conditions. Improving the sensitivity of the soil-extracted DNA method by developing protocols using larger amounts of soil and designing nematode-specific primers will make this approach an efficient screening tool to analyse nematode diversity and community structure complementing the labour-intensive isolation of intact nematodes from soils (nematode-sample DNA)

Global data on earthworm abundance, biomass, diversity and corresponding environmental properties

Publisher Copyright: © 2021, The Author(s).Earthworms are an important soil taxon as ecosystem engineers, providing a variety of crucial ecosystem functions and services. Little is known about their diversity and distribution at large spatial scales, despite the availability of considerable amounts of local-scale data. Earthworm diversity data, obtained from the primary literature or provided directly by authors, were collated with information on site locations, including coordinates, habitat cover, and soil properties. Datasets were required, at a minimum, to include abundance or biomass of earthworms at a site. Where possible, site-level species lists were included, as well as the abundance and biomass of individual species and ecological groups. This global dataset contains 10,840 sites, with 184 species, from 60 countries and all continents except Antarctica. The data were obtained from 182 published articles, published between 1973 and 2017, and 17 unpublished datasets. Amalgamating data into a single global database will assist researchers in investigating and answering a wide variety of pressing questions, for example, jointly assessing aboveground and belowground biodiversity distributions and drivers of biodiversity change.Peer reviewe

No evidence for increased loss of old carbon in a temperate organic soil after 13 years of simulated climatic warming despite increased CO2 emissions

Determining the temperature sensitivity of terrestrial carbon (C) stores is an urgent priority for predicting future climate feedbacks. A key aspect to solve this long‐standing research gap is to determine whether warmer temperatures will increase autotrophic activities leading to greater C storage or promote heterotrophic activities that will drive these systems to become C sources. We experimentally addressed this critical question by subjecting intact plant‐soil systems in a UK upland ecosystem to simulated climate warming under natural field conditions. We report the results of a 13‐year field‐based climate manipulation experiment combining in situ respiration measurements with radiocarbon (14C) analyses of respired CO2, dissolved organic carbon (DOC), soil and the tissue contents of the dominant soil fauna (enchytraeids). We found that warming during the growing season produced the largely expected increases in ecosystem respiration (63%) and leaching of DOC (19%) with no evidence for thermal acclimation or substrate exhaustion over the whole 13‐year experimental period. Contrary to expectations, we found no evidence to support an increased release of old soil C after more than a decade of simulated climatic change, and indeed, 14C analyses indicated that warming caused a significant shift towards mineralisation of more recent plant‐derived C inputs. Further support came from the radiocarbon analyses of the enchytraeid tissues, which showed a greater assimilation of the more recent (plant‐derived) C sources following warming. Therefore, in contrast to subarctic ecosystems, our results suggest that changes in C storage in this UK upland soil are strongly coupled to plant activities and that increasing temperatures will drive the turnover of organic material fixed only within recent years, without resulting in the loss of existing old carbon stores

A critical review of current methods in earthworm ecology: From individuals to populations.

Earthworms play an important role in the functioning of many terrestrial ecosystems, and while their importance is frequently acknowledged significant challenges still remain in determining their operant roles within the soil. This lack of knowledge becomes increasingly important as the spatial scale of analysis increases from individuals to populations within the landscape. To effectively develop understanding, research techniques must be able to determine the effects that earthworms have on the soil system, as well as to establish how many and which species are present. A range of techniques are required to facilitate meaningful analysis from the micro-scale within a soil profile (e.g. drilosphere effects) to a field scale or landscape scale. Furthermore, an additional framework of understanding is required to investigate the role of earthworms in the biogeochemical cycles. By critically evaluating recent advances in methods and data analysis techniques in three areas of earthworm research we highlight that combinations of common approaches often offer the most significant insights into the functional roles of earthworms within a soil system. Through particular reference to earthworm sampling and identification, biochemical functions and persistent pollutant ecotoxicology of temperate ecosystems we emphasise how a range of investigation methods can be a hindrance to developing a whole-system level understanding. The complex and diverse nature of soil systems means that a traditional compartmentalised approach studying single species using a single research technique is no longer sufficient to gain further insights into the earthworm contribution to ecosystemgoods and services delivered at the whole landscape scale. The integration of technologically advanced methods in combination with systems based modelling will be critical to develop landscape scale understanding of the functions of earthworms as individuals and as populations within in their ecosystems

More frequent droughts slow down litter decomposition across European agroecosystems and increase the importance of earthworm functional diversity

Effects of increasing rainfall variability and weather extremes on litter decomposition are still uncertain, especially in agroecosystems, where the functional structure of soil communities is already affected. We conducted a mesocosm experiment to evaluate the impacts of different rain regimes and land management on litter mass loss and earthworm ecological groups (epigeic, endogeic and anecic) across European agroecosystems. We also tested if the effects of different rainfall regimes (normal, drought, flooding, intermittent) on earthworm functional diversity (FD) or community-weighted mean (CWM) of earthworm ecological groups (particularly anecic species in the case of CWM), affected litter mass loss across land-use types. We found that drought was the main factor retarding litter mass loss across European agroecosystems irrespective of management type. The effects of the rain regime on litter mass loss were coupled with the pedoclimatic conditions that were different among the studied European land-use types. Across land-use types the importance of earthworm communities for litter decomposition was higher under water depletion. These results also suggest that FD, as a proxy of niche complementarity, is crucial for the stability of the decomposition process under environmental disturbances. The FD values under drought regimes strongly indicated that climatic changes may slow down litter decomposition as a result of FD alterations that could compromise the long-term maintenance of litter mass loss. This result may be especially relevant for the European soils that are already under hydric stress, such as in most Mediterranean agroecosystems.</p

More frequent droughts slow down litter decomposition across European agroecosystems and increase the importance of earthworm functional diversity

Effects of increasing rainfall variability and weather extremes on litter decomposition are still uncertain, especially in agroecosystems, where the functional structure of soil communities is already affected. We conducted a mesocosm experiment to evaluate the impacts of different rain regimes and land management on litter mass loss and earthworm ecological groups (epigeic, endogeic and anecic) across European agroecosystems. We also tested if the effects of different rainfall regimes (normal, drought, flooding, intermittent) on earthworm functional diversity (FD) or community-weighted mean (CWM) of earthworm ecological groups (particularly anecic species in the case of CWM), affected litter mass loss across land-use types. We found that drought was the main factor retarding litter mass loss across European agroecosystems irrespective of management type. The effects of the rain regime on litter mass loss were coupled with the pedoclimatic conditions that were different among the studied European land-use types. Across land-use types the importance of earthworm communities for litter decomposition was higher under water depletion. These results also suggest that FD, as a proxy of niche complementarity, is crucial for the stability of the decomposition process under environmental disturbances. The FD values under drought regimes strongly indicated that climatic changes may slow down litter decomposition as a result of FD alterations that could compromise the long-term maintenance of litter mass loss. This result may be especially relevant for the European soils that are already under hydric stress, such as in most Mediterranean agroecosystems.</p

The soil food web ontology: Aligning trophic groups, processes, resources, and dietary traits to support food-web research

International audienceAlthough soil ecology has benefited from recent advances in describing the functional and trophic traits of soil organisms, data reuse for large-scale soil food-web reconstructions still faces challenges. These obstacles include: (1) most data on the trophic interactions and feeding behaviour of soil organisms being scattered across disparate repositories, without well-established standard for describing and structuring trophic datasets; (2) the existence of various competing terms, rather than consensus, to delineate feeding-related concepts such as diets, trophic groups, feeding processes, resource types, leading to ambiguities that hinder meaningful data integration from different studies; (3) considerable divergence in the trophic classification of numerous soil organisms, or even the lack of such classifications, leading to discrepancies in the resolution of reconstructed food webs and complicating the reuse and comparison of food-web models within synthetic studies. To address these issues, we introduce the Soil Food Web Ontology, a novel formal conceptual framework designed to foster agreement on the trophic ecology of soil organisms. This ontology represents a collaborative and ongoing endeavour aimed at establishing consensus and formal definitions for the array of concepts relevant to soil trophic ecology. Its primary objective is to enhance the accessibility, interpretation, combination, reuse, and automated processing of trophic data. By harmonising the terminology and fundamental principles of soil trophic ecology, we anticipate that the Soil Food Web Ontology will improve knowledge management within the field. It will help soil ecologists to better harness existing information regarding the feeding behaviours of soil organisms, facilitate more robust trophic classifications, streamline the reconstruction of soil food webs, and ultimately render food-web research more inclusive, reusable and reproducible

ES1406 COST Action: Soil fauna: Key to Soil Organic Matter Dynamics and Fertility. How far have we got?

EGU2018-18437201

Research trends in ecosystem services provided by insects.

Insects play akeyrole in the regulation and dynamics of many ecosystem services (ES). However, this role is often assumed, withlimited or no experimental quantification of itsreal value.We examine publication trends in the research on ES provided by insects, ascertainingwhich ESand taxa were more intensivelyinvestigated,and with which methodological approaches,with particular emphasison experimental approaches. We performed a systematicliterature search to identify which EShave been attributed to insects. Thenweclassifiedthereferences retrieved according to theES, taxonomic group and ecosystem studied, as well as to the method applied to quantify the ES(in four categories:no quantification, proxies, direct quantificationand experiments). Pollination, biological control, food provisioning and recycling organic matter are the most studied ES. However, the majority of papers do not specify theES under consideration, and from those that do it, most do not quantifythe ESprovided. From the rest, alarge number of publications use proxies as indicators for ES, assuming or inferringtheir provision through indirect measurementssuch as species abundances, species richness, diversity indices, species density or the number of functional groups. Pollinators, predators, parasitoids, herbivores and decomposers are the most studied functional groups, while Hymenoptera, Coleoptera andDiptera arethe most studiedtaxa. Experimental studies are relatively scarceandthey mainly focus onbiological control, pollination,and decompositionperformed in agroecosystems. These results suggest that our current knowledge on the ES provided by insects is relatively scarce andbiased, and showsobvious gaps in the least-studied functional and taxonomic groups. An ambitious research agenda to improve the empirical and experimental evidence of the role played byinsects in ES provision is essential to fully assess synergies between functional ecology and biodiversity conservatio