Higher taxa vs. functional guilds vs. trophic groups as indicators of soil nematode diversity and community structure (original) (raw)
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Nematode community indices for microhabitat type and large scale landscape properties
Ecological Indicators, 2017
Nematode community indices have been broadly used to assess and monitor soil conditions. Most studies focused on agricultural or other disturbed soils and were usually applied at local-field scale. In this study, we focused on the variation of nematode community indices across fine (among microhabitats) and landscape level scales with the aim to identify indices or combinations of indices that are efficient at distinguishing microhabitats and landscape properties. We calculated nematode community indices in five microhabitats to account for variability in basal resources/organic input (soils, mosses on soil, mosses on rocks, as well as mosses on the lower and the upper part of trees trunks). The different microhabitats were located across the landscape in sites that differed in vegetation cover type (forested and nonforested), altitude (low, high) and aspect (North, East, South). Results of our models showed that microhabitat type could be predicted by all indices except the Maturity Index (MI) and the Fungivore/Bacterivore (F/B) ratio. Soil could be distinguished from mosses by the higher Plant Parasitic Index (PPI) and Enrichment Index (EI) and the lower Channel Index (CI). The different moss microhabitats could be distinguished from each other by the Summed Maturity Index (SMI) the Structure Index (SI) as well as the Basal Index (BI). At the larger scale, among landscape properties, variation by altitude was more pronounced compared to vegetation cover type and aspect. Samples originated from low altitudes were characterized by higher EI and F/B ratio. Indices for predicting landscape properties of the site a sample was taken from were more efficient when analyzed separately within each microhabitat. The interaction of the BI and the F/B ratio was able to predict vegetation cover type in soils while the same holds for BI, SI and their interaction in mosses. We conclude that nematode community structure is strongly shaped by variation in basal resources in the different microhabitats and microhabitats can be well predicted by most nematode community indices. Landscape properties constitute gradients of exposure of basal resources to ambient conditions, which affects basal resource transformations and availability. This variation across the landscape can also be predicted by some nematode community indices.
Ecosystem type affects interpretation of soil nematode community measures
Applied Soil Ecology, 2005
A better understanding of performance among major ecosystem types is necessary before nematode community indices can be applied at large geographic scales, ranging from regional to global. The objectives of this study were to: (1) determine the inherent variability in soil properties among and within wetland, forest and agricultural ecosystems; (2) compare nematode community composition among and within ecosystem types and report genera detected in wetland soils; (3) determine if community composition or composite indices are able to differentiate type and magnitude of disturbance; (4) identify seasonal responses of nematode communities and indices to disturbance; (5) quantify variance components of nematode community measures at the land resource region (LRR) and ecosystem scale. Nematode communities were extracted from soils in relatively undisturbed and disturbed wetland, forest and agricultural soils in three LRR (coastal plain, piedmont and mountain) in North Carolina (n = 18 sites), seven to eight times per year for 2 years, starting in March 1994 and ending in November 1995. Overall, 48, 44 and 45 nematode families were observed in wetland, forest and agricultural soils, respectively. This inventory totaling 110 genera represents the richest nematode fauna reported from wetlands. After adjusting for soil properties as covariables, nematode maturity index (MI) values were inconsistent among ecosystems in their ability to distinguish levels of disturbance. The magnitude of disturbance was greater between relatively undisturbed and disturbed wetland than forest or agricultural soil. Nematode family composition differentiated levels of disturbance and ecosystems better than community indices, and current efforts indicate that taxonomic resolution at the level of genus is necessary for interpretation of ecosystem function. Deviation between disturbance levels in all ecosystems was greatest in July. For use in large-scale environmental monitoring programs, it is more cost-effective and easier to calibrate and interpret indices if variance is greatest at larger rather than at smaller spatial scales, e.g., variance is progressively smaller from among regions, among ecosystems and disturbance within ecosystems. This preferred order of ranking of variance by spatial scale occurred for nematode community indices MI, MI25, SMI25, and SI and abundance of predaceous nematodes. Variance was greater at smaller than at larger spatial scales for nematode community www.elsevier.com/locate/apsoil Applied Soil Ecology 30 (2005) 47-64
Biology and Fertility of Soils, 1992
Nematodes are the most abundant metazoans in soil, and are exceeded in species diversity only by the arthropods. Estimates of nematode diversity in natural and agroecosystems have been based on both species-level taxonomy and trophic-level guilds. Because trophic groups do not act in a unitary manner with respect to environmental alterations, species-level analysis is more meaningful and should be preferred for most kinds of investigations. Nematodes of a biotope have often been considered as mere assemblages, but there is increasing evidence that certain plant associations have characteristic groups of species. This concept has been used by Bongers to develop a maturity index relating nematode families and site stability, and to identify assemblages that colonize disturbed soils. Major constraints on detailed ecological studies of soil nematode faunas are an incomplete understanding of trophic groups and their subsets, the need for repeated sampling of seasonally variable populations, and a severe shortage of taxonomycompetent persons, especially for microbial feeders.
Functional diversity in nematode communities across terrestrial ecosystems
Functional diversity can be defined as the distribution of trait values within a community. Hence, functional diversity can be an indicator of habitat filtering and a reliable environmental predictor of ecosystem functioning. However, there is a serious lack of studies that test how functional diversity indices change depending on the environmental conditions. The aim of this study is to provide such evidence by analyzing the distribution and variation of continuous body-mass values (i.e. functional diversity) and related shifts in body length and width in a nematode community. We used a large online dataset on nematode traits to analyze: (i) the distribution of body mass using three functional diversity indices, i.e. functional richness, functional divergence and functional evenness; (ii) the shifts in body-size traits (length and width); and (iii) the body-mass distributions of five trophic groups and of the entire nematode community. Managed grasslands exhibited the widest range of body-mass values while body-mass distribution in arable fields covered the greatest area in comparison to the other ecosystem types. The shift in body size revealed environmental filters that could not have been identified by the study of functional diversity indices per se. We found low values of functional evenness to be associated with high values of functional richness. We provide novel empirical evidence that body-mass distribution within a trophic group mirrors the effects of habitat filtering more than the distribution in the community as a whole. Hence, our trait-based approach, more than functional diversity itself, disclosed soil food-web structure and identified community responses.
Soil Biology & Biochemistry, 2004
Variability in the spatial distribution of nematode communities in relation to the structural heterogeneity of the environment was studied in nine different microhabitats within a relatively small area of a natural oak forest in Bulgaria. Maturity and diversity indices, trophic structure and the distribution of colonizer-persister groups were applied to analyze the quality of substrate and ecological processes involved from a functional point of view. Two main groups of nematode communities, below-and above-ground, were distinguished in terms of the location of the microhabitats. Our results indicated a higher percentage similarity between nematode communities inhabiting microhabitats with a higher resemblance in substrate structure, and abiotic and biotic conditions than between microhabitats with more dissimilar microenvironmental conditions. The application of Detrended Correspondence Analysis helped to reveal two ecological gradients. The first one was from microhabitats characterized by smaller fluctuations in microclimatic conditions and nutrient supply to microhabitats with more adverse abiotic conditions and dynamics of food resources. Along this gradient from below-to above-ground microhabitats, the proportion of general opportunists (cp 2 taxa) increased, whereas the diversity, MI and the proportions of persisters (cp (3 -5) taxa), decreased. Along the second gradient a gradual decrease in the decomposition rate within above-ground microhabitats was revealed, which was indicated by the proportion of enrichment opportunists (cp 1 taxa). The nematode communities of decaying wood had the most specific cp groups' distribution characterized by a high proportion of enrichment opportunists (colonizers). Each microhabitat has developed nematode communities with a characteristic trophic structure that was related to the relative importance of primary production and decomposition processes occurring within the microhabitat. The nematode communities of mosses growing on soil, stones and tree trunks had similar trophic structure dominated by bacterial-feeding nematode taxa. Our results supported the role of nematode communities as potential indicators of environmental conditions. q
The use of nematodes in ecological soil classification and assessment concepts
Although there has been extensive applied agricultural research (research on plant-parasitic species has a long tradition), insufficient taxonomical knowledge, especially of free-living nematodes, is a serious problem concerning the use of nematodes in soil classification and assessment. However, due to their essential and various roles in ecosystem functioning and their high diversity and abundance, interest in using these organisms for the assessment of soil quality is increasing. In particular in The Netherlands, but also in other countries (e.g., Germany, United Kingdom), progress in taxonomy is being achieved and evaluation strategies are being elaborated. While examples exist for the successful use of nematodes as part of a community approach comprising several organism groups, much work concerning the establishment of an adequate reference database remains to be done. This article is a general overview of the suitability and application of soil nematodes in soil assessments.
2023
This work evaluates the diversity, and abundance of nematodes and their use as indicators of soil health in an area strongly influenced by industrial wastes (food, metal and paper industries). The relationships between trophic groups, coloniser-persister scale and nematode community indices as well as nematode indicators of soil elements and the relationships of soil elements with different habitats were investigated. Nematodes were recovered from the soil samples of fifty sites from five different habitats. The trophic groups, colonizer-persister scale, and nematode community indices were analysed and compared. To test the significance of the dataset, bivariate linear regression; several samples repeated measure test of Analysis of Variance (ANOVA) have been performed. The Canonical Correspond Analysis (CCA); Principal Component Analysis (PCA), and clustering of habitats were performed to know the relationships between such variables among different habitats. Bacterial feeders with 15,582 individuals were found to be a highly diverse and most abundant group. The results indicated that the nematode diversity and abundance, trophic groups and coloniser-persister ratio were adversely affected by organically enriched habitats to food, metal and paper industries as compared to natural habitats. The habitats contaminated by industrial wastes were mainly dominated by bacterivores and fungivores of c-p2 class. Few colonizer genera were observed to be cosmopolitan and prevalent in all habitats. However, some genera showed specificity towards a particular set of conditions and were more or less endemic for specific habitats.
a global database of soil nematode abundance and functional group composition
as the most abundant animals on earth, nematodes are a dominant component of the soil community. they play critical roles in regulating biogeochemical cycles and vegetation dynamics within and across landscapes and are an indicator of soil biological activity. Here, we present a comprehensive global dataset of soil nematode abundance and functional group composition. This dataset includes 6,825 georeferenced soil samples from all continents and biomes. For geospatial mapping purposes these samples are aggregated into 1,933 unique 1-km pixels, each of which is linked to 73 global environmental covariate data layers. Altogether, this dataset can help to gain insight into the spatial distribution patterns of soil nematode abundance and community composition, and the environmental drivers shaping these patterns.
PloS one, 2011
Background: 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.