•Some earthworm species were assigned to two or more ecological categories by different researchers.•Marcel Bouché defined ecological categories using earthworm traits but without assignment ...rules.•Using PCA and random forest classification on Bouché’s data, we redefined categories and the most influential traits.•Each species is now defined by three percentages of membership to the three main categories.
In the early 70s, the soil biologist Marcel Bouché classified French earthworms species into defined ecological categories. This classification system was immensely successful and is still widely used to describe earthworm functional groups even outside of Europe. Bouché used morpho-anatomical traits to differentiate three main categories: epigeic, anecic and endogeic. However, the way species are assigned to a category was not explicitly described in Bouché’s work. Thus, some earthworm species can still be assigned to two categories depending on the way researchers interpret Bouché’s description. To solve these issues and avoid unnecessary controversies, we applied PCA and random forest models to the seminal data of Marcel Bouché (earthworm morpho-anatomical traits). Their assignment to Bouché’s three main categories allowed us to statistically redefine the different categories and determine which traits are the most influential. We found that the three main traits were skin pigmentation (from none to black), body length (mean of the minimal and maximal values) and skin coloration (yes or no), followed by 10 other morphological and anatomical traits. We then used this approach to assign a likely category to all of the species studied by Bouché, resulting in a new triangular graph including other categories such as epi-anecic, endo-anecic, epi-endogeic and intermediate. Finally, we calculated the percentage that each species belongs to each main ecological category. This represents a paradigm shift and may change our vision of earthworm communities enabling the computation of the percentage of anecic, endogeic and epigeic species at the community level and thus overcoming the limits and debate about fixed ecological categories for each species.
Background
Agroforestry systems have enhanced diversity of cultivated plants compared to monocultures, and are expected to affect associated biodiversity. Despite a growing body of literature on the ...importance of soil fauna, the known effects of different agroforestry types on soil fauna communities and functions have not yet been synthesized.
Scope
We scanned publications on soil fauna in agroforestry systems. Our aim was to give an overview of strengths and weaknesses of the existing data, in terms of spatial coverage and representation of diverse agroforestry types and soil fauna groups and functions.
Conclusions
Our database includes sixty-seven articles, mostly focusing on tropical regions and perennial crop agroforestry systems. Soil macrofauna are the most studied fauna group. The most common question addressed is the comparison of the effect of land use types on communities. Effects on fauna abundance and diversity are mainly positive when agroforestry is compared to cropland, and neutral or negative when compared to forests. Few publications actually measure soil fauna functions, or characterize their interactions and evolution in time and space depending on system design and management. Further work on soil fauna in agroforestry should harness ecological theory and address questions of spatial structure and scale, temporal dynamics and ecological interaction networks and how they determine ecosystem functioning.
Summary
Trait‐based approaches are increasingly being used to test mechanisms underlying species assemblages and biotic interactions across a wide range of organisms including terrestrial arthropods ...and to investigate consequences for ecosystem processes. Such an approach relies on the standardized measurement of functional traits that can be applied across taxa and regions. Currently, however, unified methods of trait measurements are lacking for terrestrial arthropods and related macroinvertebrates (terrestrial invertebrates hereafter).
Here, we present a comprehensive review and detailed protocol for a set of 29 traits known to be sensitive to global stressors and to affect ecosystem processes and services. We give recommendations how to measure these traits under standardized conditions across various terrestrial invertebrate taxonomic groups.
We provide considerations and approaches that apply to almost all traits described, such as the selection of species and individuals needed for the measurements, the importance of intraspecific trait variability, how many populations or communities to sample and over which spatial scales.
The approaches outlined here provide a means to improve the reliability and predictive power of functional traits to explain community assembly, species diversity patterns and ecosystem processes and services within and across taxa and trophic levels, allowing comparison of studies and running meta‐analyses across regions and ecosystems.
This handbook is a crucial first step towards standardizing trait methodology across the most studied terrestrial invertebrate groups, and the protocols are aimed to balance general applicability and requirements for special cases or particular taxa. Therefore, we envision this handbook as a common platform to which researchers can further provide methodological input for additional special cases.
A lay summary is available for this article.
Lay Summary
Pesticides and earthworms. A review Pelosi, Céline; Barot, Sébastien; Capowiez, Yvan ...
Agronomy for sustainable development,
2014, 1-2014, 2014-1-00, 20140101, Letnik:
34, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Earthworms provide key soil functions that favour many positive ecosystem services. These services are important for agroecosystem sustainability but can be degraded by intensive cultural practices ...such as use of pesticides. Many literature reports have investigated the effect of pesticides on earthworms. Here, we review those reports to assess the relevance of the indicators of earthworm response to pesticides, to assess their sensitivity to pesticides, and to highlight the remaining knowledge gaps. We focus on European earthworm species and products authorised in Europe, excluding natural compounds and metals. We consider different organisation levels: the infra-individual level (gene expression and physiology), the individual and population levels (life-history traits, population density and behaviour) and the community level: community biomass and density. Our analysis shows that earthworms are impacted by pesticides at all organisation levels. For example, pesticides disrupt enzymatic activities, increase individual mortality, decrease fecundity and growth, change individual behaviour such as feeding rate and decrease the overall community biomass and density. Insecticides and fungicides are the most toxic pesticides impacting survival and reproduction, respectively.
Abstract
Increasing evidence suggests that agricultural intensification is a threat to many groups of soil biota, but how the impacts of land-use intensity on soil organisms translate into changes in ...comprehensive soil interaction networks remains unclear. Here for the first time, we use environmental DNA to examine total soil multi-trophic diversity and food web structure for temperate agroecosystems along a gradient of land-use intensity. We tested for response patterns in key properties of the soil food webs in sixteen fields ranging from arable crops to grazed permanent grasslands as part of a long-term management experiment. We found that agricultural intensification drives reductions in trophic group diversity, although taxa richness remained unchanged. Intensification generally reduced the complexity and connectance of soil interaction networks and induced consistent changes in energy pathways, but the magnitude of management-induced changes depended on the variable considered. Average path length (an indicator of food web redundancy and resilience) did not respond to our management intensity gradient. Moreover, turnover of network structure showed little response to increasing management intensity. Our data demonstrates the importance of considering different facets of trophic networks for a clearer understanding of agriculture-biodiversity relationships, with implications for nature-based solutions and sustainable agriculture.
The three main ecological categories of earthworms (anecic, endogeic, epigeic) are often used as proxies for functional groups. This is troublesome since they were not designed for this purpose and ...thus the relevance of such a use was never tested nor proven. How earthworms influence the different soil functions is tightly linked to their bioturbating behavior and thus they are considered as physical ecosystem engineers. Here, we characterized the different facets of this behavior (burrow creation, production of casts below and above ground, and litter consumption) for 50 species or subspecies of European earthworms under standardized laboratory conditions. Using PCA and K-means methods, we defined six new functional groups of earthworms, i.e. intense tunnelers, burrowers, shallow bioturbators, deep bioturbators, litter dwellers and intermediates. Intense tunnelers and burrowers build continuous and vertically oriented burrows, the first however burrow more and consume less litter. Deep bioturbators live deeply in the soil, make very discontinuous burrows and consume no litter. They could be seen as a novel group but they can be linked to the hypo-endogeics ecological categories defined 50 years ago. Litter-dwellers and shallow bioturbators can be respectively linked to the epidegeics and endogeics ecological categories. However, the new groups only partially overlap with the traditional ecological categories. We assume that their use, based on quantitative behavioral assessments, will improve the study of the relationships between earthworm communities and the associated provision of ecosystem services by minimizing the overlooked variability within the three main ecological categories regarding their behavior.
Conventional agriculture strongly alters soil quality due to industrial practices that often have negative effects on soil life. Alternative systems such as conservation agriculture and organic ...farming could restore better conditions for soil organisms. Improving soil life should in turn improve soil quality and farming sustainability. Here, we have compared for the first time the long-term effects of conservation agriculture, organic farming, and conventional agriculture on major soil organisms such as microbes, nematofauna, and macrofauna. We have also analyzed functional groups. Soils were sampled at the 14-year-old experimental site of La Cage, near Versailles, France. The microbial community was analyzed using molecular biology techniques. Nematofauna and macrofauna were analyzed and classified into functional groups. Our results show that both conservation and organic systems increased the abundance and biomass of all soil organisms, except predaceous nematodes. For example, macrofauna increased from 100 to 2,500 %, nematodes from 100 to 700 %, and microorganisms from 30 to 70 %. Conservation agriculture showed a higher overall improvement than organic farming. Conservation agriculture increased the number of many organisms such as bacteria, fungi, anecic earthworms, and phytophagous and rhizophagous arthropods. Organic farming improved mainly the bacterial pathway of the soil food web and endogeic and anecic earthworms. Overall, our study shows that long-term, no-tillage, and cover crops are better for soil biota than periodic legume green manures, pesticides, and mineral fertilizers.
The international 4 per 1000 initiative aims at supporting states and non-governmental stakeholders in their efforts towards a better management of soil carbon (C) stocks. These stocks depend on soil ...C inputs and outputs. They are the result of fine spatial scale interconnected mechanisms, which stabilise/destabilise organic matter-borne C. Since 2016, the CarboSMS consortium federates French researchers working on these mechanisms and their effects on C stocks in a local and global change setting (land use, agricultural practices, climatic and soil conditions, etc.). This article is a synthesis of this consortium’s first seminar. In the first part, we present recent advances in the understanding of soil C stabilisation mechanisms comprising biotic and abiotic processes, which occur concomitantly and interact. Soil organic C stocks are altered by biotic activities of plants (the main source of C through litter and root systems), microorganisms (fungi and bacteria) and ‘ecosystem engineers’ (earthworms, termites, ants). In the meantime, abiotic processes related to the soil-physical structure, porosity and mineral fraction also modify these stocks. In the second part, we show how agricultural practices affect soil C stocks. By acting on both biotic and abiotic mechanisms, land use and management practices (choice of plant species and density, plant residue exports, amendments, fertilisation, tillage, etc.) drive soil spatiotemporal organic inputs and organic matter sensitivity to mineralisation. Interaction between the different mechanisms and their effects on C stocks are revealed by meta-analyses and long-term field studies. The third part addresses upscaling issues. This is a cause for major concern since soil organic C stabilisation mechanisms are most often studied at fine spatial scales (mm–μm) under controlled conditions, while agricultural practices are implemented at the plot scale. We discuss some proxies and models describing specific mechanisms and their action in different soil and climatic contexts and show how they should be taken into account in large scale models, to improve change predictions in soil C stocks. Finally, this literature review highlights some future research prospects geared towards preserving or even increasing C stocks, our focus being put on the mechanisms, the effects of agricultural practices on them and C stock prediction models.
Structural equation models (SEM) are increasingly used in ecology as multivariate analysis that can represent theoretical variables and address complex sets of hypotheses. Here we demonstrate the ...interest of SEM in ecotoxicology, more precisely to test the three-step concept of metal bioavailability to earthworms. The SEM modeled the three-step causal chain between environmental availability, environmental bioavailability and toxicological bioavailability. In the model, each step is an unmeasured (latent) variable reflected by several observed variables. In an exposure experiment designed specifically to test this SEM for Cd, Pb and Zn, Aporrectodea caliginosa was exposed to 31 agricultural field-contaminated soils. Chemical and biological measurements used included CaC12-extractable metal concentrations in soils, free ion concentration in soil solution as predicted by a geochemical model, dissolved metal concentration as predicted by a semi-mechanistic model, internal metal concentrations in total earthworms and in subcellular fractions, and several biomarkers. The observations verified the causal definition of Cd and Pb bioavailability in the SEM, but not for Zn. Several indicators consistently reflected the hypothetical causal definition and could thus be pertinent measurements of Cd and Pb bioavailability to earthworm in field-contaminated soils. SEM highlights that the metals present in the soil solution and easily extractable are not the main source of available metals for earthworms. This study further highlights SEM as a powerful tool that can handle natural ecosystem complexity, thus participating to the paradigm change in ecotoxicology from a bottom-up to a top-down approach.
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•Bioavailability is a complex concept for which no indicator is fully generic•Robustness of some indicators of metal bioavailability to earthworms was investigated•SEM modeled the causal relations between the three steps of metal bioavailability•Soil metal availability, earthworm metal contents and biomarkers were assessed•SEM highlighted which indicators were pertinent for Cd and Pb bioavailability
Collembola are a widespread class of arthropods that live mostly in the soil or on its surface. Communities of Collembola have notably been used as bioindicators of several environmental factors such ...as pollution or land use. Recently, they have also opened perspectives for monitoring the effects of projected climate change on soil biodiversity, in particular through the responses of their traits. Collembola are known to exhibit several morphological variations throughout their lifecycle (other than growth and sexual dimorphism). One of these phenomena, ecomorphosis, has been described as a survival strategy mainly triggered by elevated temperature. This could be of interest in analysing collembolan adaptation to climate change, yet studies on this are - to date - sparse in international literature in English. To begin to address this gap, we conducted a literature review that enabled us to: (i) identify the concepts behind the ecomorphosis strategy, (ii) list the collembolan species known to display ecomorphosis, (iii) summarize its consequences on individuals; and (iv) analyse its theoretical implications for community ecology and functional ecology. We then discussed its potential use as a proxy for climate adversity. We thus suggested using the ability of a species to display ecomorphosis as a trait, and in the future test its responses in collembolan communities along climatic gradients. Considering the recent inputs of taking into account intraspecific trait variability in community ecology, we advocate for a better understanding of such eco-physiological strategies in order to improve our hypotheses-based approaches in trait-environment relationships. In a context of rapid global climate change, our findings may provide insights into functional responses to climatic gradients in Collembola, and hopefully contribute to stimulate discussion in other soil fauna biological models.
•We reviewed literature on ecomorphosis in Collembola.•Ecomorphosis is a reversible polymorphism, induced by climatic factors.•Ecomorphosis modifies a wide and consistent set of functional traits.•Displaying ecomorphosis strategy improves survival against adverse temperature rise.•We investigate the potential use of ecomorphosis as a trait in future studies.
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