Intensive agriculture reduces soil biodiversity across Europe
Tsiafouli, M.A. ; Thébault, E. ; Sgardelis, S. ; Ruiter, P.C. de; Putten, W.H. van der; Birkhofer, K. ; Hemerik, L. ; Vries, F.T. de; Bardgett, R.D. ; Brady, M. ; Bjornlund, L. ; Bracht Jörgensen, H. ; Christensen, S. ; Herfelt, T. D'; Hotes, S. ; Hol, W.H.G. ; Frouz, J. ; Liiri, M. ; Mortimer, S.R. ; Setälä, H. ; Stary, J. ; Tzanopoulos, J. ; Uteseny, C. ; Wolters, V. ; Hedlund, K. - \ 2015
Global Change Biology 21 (2015)2. - ISSN 1354-1013 - p. 973 - 985.
food-web structure - land-use intensity - taxonomic distinctness - community structure - phylogenetic diversity - arthropod communities - temporal variability - 7-year period - ecosystem - management
Soil biodiversity plays a key role in regulating the processes that underpin the delivery of ecosystem goods and services in terrestrial ecosystems. Agricultural intensification is known to change the diversity of individual groups of soil biota, but less is known about how intensification affects biodiversity of the soil food web as a whole, and whether or not these effects may be generalized across regions. We examined biodiversity in soil food webs from grasslands, extensive, and intensive rotations in four agricultural regions across Europe: in Sweden, the UK, the Czech Republic and Greece. Effects of land-use intensity were quantified based on structure and diversity among functional groups in the soil food web, as well as on community-weighted mean body mass of soil fauna. We also elucidate land-use intensity effects on diversity of taxonomic units within taxonomic groups of soil fauna. We found that between regions soil food web diversity measures were variable, but that increasing land-use intensity caused highly consistent responses. In particular, land-use intensification reduced the complexity in the soil food webs, as well as the community-weighted mean body mass of soil fauna. In all regions across Europe, species richness of earthworms, Collembolans, and oribatid mites was negatively affected by increased land-use intensity. The taxonomic distinctness, which is a measure of taxonomic relatedness of species in a community that is independent of species richness, was also reduced by land-use intensification. We conclude that intensive agriculture reduces soil biodiversity, making soil food webs less diverse and composed of smaller bodied organisms. Land-use intensification results in fewer functional groups of soil biota with fewer and taxonomically more closely related species. We discuss how these changes in soil biodiversity due to land-use intensification may threaten the functioning of soil in agricultural production systems.
Trophic niche-space imaging, using resource and consumer traits
Nagelkerke, L.A.J. ; Rossberg, A.G. - \ 2014
Theoretical Ecology 7 (2014)4. - ISSN 1874-1738 - p. 423 - 434.
food-web structure - lake tana ethiopia - interaction strengths - fish assemblage - barbs barbus - body-size - ecological networks - species flock - general-model - patterns
The strength of trophic (feeding) links between two species depends on the traits of both the consumer and the resource. But which traits of consumer and resource have to be measured to predict link strengths, and how many? A novel theoretical framework for systematically determining trophic traits from empirical data was recently proposed. Here we demonstrate this approach for a group of 14 consumer fish species (Labeobarbus spp., Cyprinidae) and 11 aquatic resource categories coexisting in Lake Tana in northern Ethiopia, analysing large sets of phenotypic consumer and resource traits with known roles in feeding ecology. We systematically reconstruct structure and geometry of trophic niche space, in which link strengths are predicted by the distances between consumers and resources. These distances are then represented graphically resulting in an image of trophic niche space and its occupancy. We find trophic niche to be multi-dimensional. Among the models we analysed, one with two resource and two consumer traits had the highest predictive power for link strength. Results further suggest that trophic niche space has a pseudo-Euclidean geometry, meaning that link strength decays with distance in some dimensions of trophic niche space, while it increases with distance in other dimensions. Our analysis not only informs theory and modelling, but may also be helpful for predicting trophic link strengths for pairs of other, similar species.
Diet of harbor porpoises along the Dutch coast: A combined stable isotope and stomach contents approach
Jansen, O.E. ; Michel, L. ; Lepoint, G. ; Das, K. ; Couperus, A.S. ; Reijnders, P.J.H. - \ 2013
Marine Mammal Science 29 (2013)3. - ISSN 0824-0469 - p. E295 - E311.
scottish north-sea - food-web structure - phocoena-phocoena - laboratory experiments - sandeel consumption - trophic ecology - carbon isotopes - animal-tissues - marine mammals - southern bight
High stranding frequency of porpoises, Phocoena phocoena, along the Dutch coast since 2006 has led to increased interest in the ecology of porpoises in the North Sea. Stranded porpoises were collected along the Dutch coast (2006–2008) and their diet was assessed through stomach content and stable isotope analysis (d13C and d15N) of porpoise muscle and prey. Stable isotope analysis (SIAR) was used to estimate the contribution of prey species to the porpoises' diet. This was compared to prey composition from stomach contents, to analyze differences between long- and short-term diet. According to stomach contents, 90.5% of the diet consisted of gobies, whiting, lesser sandeel, herring, cod, and sprat. Stable isotope analysis revealed that 70-83% of the diet consisted of poor cod, mackerel, greater sandeel, lesser sandeel, sprat, and gobies, highlighting a higher importance of pelagic, schooling species in the porpoises' diet compared to stomach contents. This could be due to prey distribution as well as differences in behavior of porpoises and prey between the coastal zone and offshore waters. This study supports the need for multi-method approaches. Future ecological and fishery impact assessment studies and management decisions for porpoise conservation should acknowledge this difference between the long- and short-term diet. High stranding frequency of porpoises, Phocoena phocoena, along the Dutch coast since 2006 has led to increased interest in the ecology of porpoises in the North Sea. Stranded porpoises were collected along the Dutch coast (2006–2008) and their diet was assessed through stomach content and stable isotope analysis (d13C and d15N) of porpoise muscle and prey. Stable isotope analysis (SIAR) was used to estimate the contribution of prey species to the porpoises' diet. This was compared to prey composition from stomach contents, to analyze differences between long- and short-term diet. According to stomach contents, 90.5% of the diet consisted of gobies, whiting, lesser sandeel, herring, cod, and sprat. Stable isotope analysis revealed that 70-83% of the diet consisted of poor cod, mackerel, greater sandeel, lesser sandeel, sprat, and gobies, highlighting a higher importance of pelagic, schooling species in the porpoises' diet compared to stomach contents. This could be due to prey distribution as well as differences in behavior of porpoises and prey between the coastal zone and offshore waters. This study supports the need for multi-method approaches. Future ecological and fishery impact assessment studies and management decisions for porpoise conservation should acknowledge this difference between the long- and short-term diet.
The ecological and evolutionary implications of merging different types of networks
Fontaine, C. ; Guimaraes, P.R. ; Kéfi, S. ; Loeuille, N. ; Memmott, J. ; Putten, W.H. van der; Veen, F.J. ; Thébault, E. - \ 2011
Ecology Letters 14 (2011)11. - ISSN 1461-023X - p. 1170 - 1181.
food-web structure - animal mutualistic networks - positive interactions - plant-communities - phylogenetic constraints - species extinctions - stability - pollination - coevolution - ecosystems
Interactions among species drive the ecological and evolutionary processes in ecological communities. These interactions are effectively key components of biodiversity. Studies that use a network approach to study the structure and dynamics of communities of interacting species have revealed many patterns and associated processes. Historically these studies were restricted to trophic interactions, although network approaches are now used to study a wide range of interactions, including for example the reproductive mutualisms. However, each interaction type remains studied largely in isolation from others. Merging the various interaction types within a single integrative framework is necessary if we want to further our understanding of the ecological and evolutionary dynamics of communities. Dividing the networks up is a methodological convenience as in the field the networks occur together in space and time and will be linked by shared species. Herein, we outline a conceptual framework for studying networks composed of more than one type of interaction, highlighting key questions and research areas that would benefit from their study
Stability of Ecological Communities and the Architecture of Mutualistic and Trophic Networks
Thebault, E.M.C. ; Fontaine, C. - \ 2010
Science 329 (2010)5993. - ISSN 0036-8075 - p. 853 - 856.
food-web structure - biodiversity - pollination - competition - modularity - diversity
Research on the relationship between the architecture of ecological networks and community stability has mainly focused on one type of interaction at a time, making difficult any comparison between different network types. We used a theoretical approach to show that the network architecture favoring stability fundamentally differs between trophic and mutualistic networks. A highly connected and nested architecture promotes community stability in mutualistic networks, whereas the stability of trophic networks is enhanced in compartmented and weakly connected architectures. These theoretical predictions are supported by a meta-analysis on the architecture of a large series of real pollination (mutualistic) and herbivory (trophic) networks. We conclude that strong variations in the stability of architectural patterns constrain ecological networks toward different architectures, depending on the type of interaction.
Effects of intraspecific variation in white cabbage (Brassica oleracea var. Capitata) on soil ogranisms
Kabouw, P. ; Putten, W.H. van der; Dam, N.M. van; Biere, A. - \ 2010
Plant and Soil 336 (2010)1-2. - ISSN 0032-079X - p. 509 - 518.
enzymatic-hydrolysis products - gradient gel-electrophoresis - food-web structure - body-surface area - community structure - glucosinolate - root - oligochaeta - enchytraeidae - biodiversity
Intraspecific variation in plants can affect soil organisms. However, little is known about whether the magnitude of the effect depends on the degree of interaction with the roots. We analyzed effects of plant intraspecific variation on root herbivores and other soil organisms that interact directly with living plant roots, as well as on decomposer organisms that interact more indirectly with roots. We used four different white cabbage (Brassica oleracea var. capitata) cultivars exhibiting a high degree of intraspecific variation in root glucosinolate profiles. Intraspecific variation affected root-feeding nematodes, whereas decomposer organisms such as earthworms and Collembola were not affected. Root-feeding nematodes were most abundant in one of the cultivars, Badger Shipper, which lacked the glucosinolate gluconasturtiin. The effect of the intraspecific variation in glucosinolate composition may have been restricted to root-feeding nematodes due to the rapid degradation of glucosinolates and their breakdown products in the soil. Additionally, the low biomass of root-feeding nematodes, relative to other soil organisms, limits the possibility to affect higher trophic level organisms. Our results show that variation in root chemistry predominantly affects belowground herbivores and that these effects do not extend into the soil food web.