Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Insects as feed and the Sustainable Development Goals
Dicke, M. - \ 2018
Journal of Insects as Food and Feed 4 (2018)3. - ISSN 2352-4588 - p. 147 - 156.
Biodiversity - Climate change - Food security - Health - Welfare

One of the Sustainable Development Goals (SDGs) of the United Nations is to achieve food security and improved nutrition. To be successful in feeding the rapidly growing human population, we need innovative changes in food production. The challenge of safeguarding food security is considerable because many potential solutions are incompatible with solutions for other challenges that we face, including climate change mitigation and halting the biodiversity loss. To produce animal proteins, we currently rely to a large extent on feedstuff for livestock that is either suitable as food for humans (e.g. cereals and soymeal) or on a resource that is becoming scarce due to overfishing of the oceans (fishmeal). To set a first step towards a circular approach to feed production, insects provide interesting opportunities as various species can be reared on organic waste streams, including waste streams of food production and manure. This paper discusses the opportunities for using insects as a valuable feed source for the production of livestock. Insects do not only provide excellent opportunities to replace fishmeal and soymeal, but may also have important additional benefits. These include positive effects on livestock health and welfare with opportunities to reduce antibiotic use in livestock production. This is discussed in the integrated context of five of the sustainable development goals. Recent entrepreneurial and regulatory developments underline the opportunities for employing insects as feed. In this development an important indirect effect may be that consumers get acquainted with insects as a valuable and sustainable component of the food chain. This may result in the acceleration of adopting insects as food and thus of producing mini-livestock as a sustainable source of animal protein.

Landscape planning-paving theway for effective conservation of forest biodiversity and a diverse forestry?
Michanek, Gabriel ; Bostedt, Göran ; Ekvall, Hans ; Forsberg, Maria ; Hof, Anouschka R. ; Jong, Johnny de; Rudolphi, Jörgen ; Zabel, Astrid - \ 2018
Forests 9 (2018)9. - ISSN 1999-4907
Aichi targets - Biodiversity - Birds directive - Boreal forest - Compensation - Fragmentation - Habitat protection - Habitats directive - Landscape planning - Tax-fund

Globally, intensive forestry has led to habitat degradation and fragmentation of the forest landscape. Taking Sweden as an example, this development is contradictory to international commitments, EU obligations, and to the fulfillment of the Parliament's environmental quality objective "Living Forests", which according to Naturvårdsverket (The Swedish Environmental Protection Agency) will not be achieved in 2020 as stipulated. One important reason for the implementation deficit is the fragmented forestry management. In a forest landscape, felling and other measures are conducted at different times on separate forest stands (often relatively small units) by different operators. Consequently, the authorities take case by case decisions on felling restrictions for conservation purposes. In contrast, conservation biology research indicates a need for a broad geographical and strategical approach in order to, in good time, select the most appropriate habitats for conservation and to provide for a functioning connectivity between different habitats. In line with the EU Commission, we argue that landscape forestry planning could be a useful instrument to achieve ecological functionality in a large area. Landscape planning may also contribute to the fulfilment of Sweden's climate and energy policy, by indicating forest areas with insignificant conservation values, where intensive forestry may be performed for biomass production etc. Forest owners should be involved in the planning and would, under certain circumstances, be entitled to compensation. As state resources for providing compensation are scarce, an alternative could be to introduce a tax-fund system within the forestry sector. Such a system may open for voluntary agreements between forest owners for the protection of habitats within a large area.

Farmers show complex and contrasting perceptions on ecosystem services and their management
Teixeira, Heitor Mancini ; Vermue, Ardjan J. ; Cardoso, Irene Maria ; Peña Claros, Marielos ; Bianchi, Felix J.J.A. - \ 2018
Ecosystem Services 33 (2018). - ISSN 2212-0416 - p. 44 - 58.
Agroecology - Agroecosystems - Biodiversity - Brazil - Fuzzy cognitive maps

Agricultural systems are complex socio-ecological systems that are managed by farmers to achieve desired outcomes, including food production and other ecosystem services (ES). While farm management is a key factor for ES provision, farmers may widely differ in their awareness, ambition and skills to manage their systems. Currently there is a lack of understanding of farmers’ perception on ES, and how this is related to their management. We studied the management and perception of large scale farmers, conventional family farmers and agroecological family farmers in the Zona de Mata region in Brazil. Farmers were interviewed and constructed fuzzy cognitive maps (FCM) of their perception on ES. The FCM analysis revealed that in general, the perception of farmers on ES is highly complex and interconnected. Yet, agroecological family farmers showed a more complex perception on ES, which is associated with more diversified and autonomous agroecosystems. Both agroecological and conventional family farmers had a strong peasant identity, recognising more cultural ecosystem services than large scale farmers and relied more on production for consumption. Initiatives that aim to strengthen on-farm ecosystem services provision should be sensitive to farmer's perceptions and may need to consider using specific strategies for different farmer types.

Integrating quantitative morphological and qualitative molecular methods to analyse soil nematode community responses to plant range expansion
Geisen, Stefan ; Snoek, L.B. ; Hooven, Freddy C. ten; Duyts, Henk ; Kostenko, Olga ; Bloem, Janneke ; Martens, Henk ; Quist, Casper W. ; Helder, Johannes A. ; Putten, Wim H. van der - \ 2018
Methods in Ecology and Evolution 9 (2018)6. - ISSN 2041-210X - p. 1366 - 1378.
Biodiversity - High-throughput sequencing - Microscopy - Molecular approaches - Nematodes - QPCR - Soils
Below-ground nematodes are important for soil functioning, as they are ubiquitous and operate at various trophic levels in the soil food web. However, morphological nematode community analysis is time consuming and requires ample training. qPCR-based nematode identification techniques are well available, but high-throughput sequencing (HTS) might be more suitable for non-targeted nematode community analyses. We compared effectiveness of qPCR- and HTS-based approaches with morphological nematode identification while examining how climate warming-induced plant range expansion may influence below-ground nematode assemblages. We extracted nematodes from soil of Centaurea stoebe and C. jacea populations in Slovenia, where both plant species are native, and Germany, where C. stoebe is a range expander and C. jacea is native. Half of each nematode sample was identified morphologically and the other half was analysed using targeted qPCR and a novel HTS approach. HTS produced the highest taxonomic resolution of the nematode community. Nematode taxa abundances correlated between the methods. Therefore, especially relative HTS and relative morphological data revealed nearly identical ecological patterns. All methods showed lower numbers of plant-feeding nematodes in rhizosphere soils of C. stoebe compared to C. jacea. However, a profound difference was observed between absolute and relative abundance data; both sampling origin and plant species affected relative abundances of bacterivorous nematodes, whereas there was no effect on absolute abundances. Taken together, as HTS correlates with relative analyses of soil nematode communities, while providing highest taxonomic resolution and sample throughput, we propose a combination of HTS with microscopic counting to supplement important quantitative data on soil nematode communities. This provides the most cost-effective, in-depth methodology to study soil nematode community responses to changes in the environment. This methodology will also be applicable to nematode analyses in aquatic systems.
On the Opportunity Cost of Crop Diversification
Ang, Frederic ; Mortimer, Simon M. ; Areal, Francisco J. ; Tiffin, Richard - \ 2018
Journal of Agricultural Economics 69 (2018)3. - ISSN 0021-857X - p. 794 - 814.
Biodiversity - CAP greening measures - Crop diversification - Duality - Non-convexity - Shadow price - Shannon index

Distance functions are increasingly being augmented, with environmental goods treated as conventional outputs. A common approach to evaluate the opportunity cost of providing an environmental good is the exploitation of the distance function's dual relationship to the value function. This implies that the opportunity cost is assumed to be non-negative. This approach also requires a convex technology set. Focusing on crop diversification for a balanced sample of 44 cereal farms in the East of England for the years 2007-2013, this paper develops a novel opportunity cost measure that does not depend on these strong assumptions. We find that the opportunity cost of crop diversification is negative for most farms.

Low probability of a dilution effect for Lyme borreliosis in Belgian forests
Ruyts, Sanne C. ; Landuyt, Dries ; Ampoorter, Evy ; Heylen, Dieter ; Ehrmann, Steffen ; Coipan, Elena C. ; Matthysen, Erik ; Sprong, Hein ; Verheyen, Kris - \ 2018
Ticks and Tick-borne Diseases 9 (2018)5. - ISSN 1877-959X - p. 1143 - 1152.
Bayesian belief network - Biodiversity - Borrelia afzelii - Ixodes ricinus - Tick - Vector-borne disease
An increasing number of studies have investigated the consequences of biodiversity loss for the occurrence of vector-borne diseases such as Lyme borreliosis, the most common tick-borne disease in the northern hemisphere. As host species differ in their ability to transmit the Lyme borreliosis bacteria Borrelia burgdorferi s.l. to ticks, increased host diversity can decrease disease prevalence by increasing the proportion of dilution hosts, host species that transmit pathogens less efficiently. Previous research shows that Lyme borreliosis risk differs between forest types and suggests that a higher diversity of host species might dilute the contribution of small rodents to infect ticks with B. afzelii, a common Borrelia genospecies. However, empirical evidence for a dilution effect in Europe is largely lacking. We tested the dilution effect hypothesis in 19 Belgian forest stands of different forest types along a diversity gradient. We used empirical data and a Bayesian belief network to investigate the impact of the proportion of dilution hosts on the density of ticks infected with B. afzelii, and identified the key drivers determining the density of infected ticks, which is a measure of human infection risk. Densities of ticks and B. afzelii infection prevalence differed between forest types, but the model indicated that the density of infected ticks is hardly affected by dilution. The most important variables explaining variability in disease risk were related to the density of ticks. Combining empirical data with a model-based approach supported decision making to reduce tick-borne disease risk. We found a low probability of a dilution effect for Lyme borreliosis in a north-western European context. We emphasize that under these circumstances, Lyme borreliosis prevention should rather aim at reducing tick-human contact rate instead of attempting to increase the proportion of dilution hosts.
Identifying barriers and levers of biodiversity mainstreaming in four cases of transnational governance of land and water
Karlsson-Vinkhuyzen, S.I.S.E. ; Boelee, E. ; Cools, J. ; Hoof, L.J.W. van; Hospes, O. ; Kok, M. ; Peerlings, J.H.M. ; Tatenhove, J.P.M. van; Termeer, C.J.A.M. ; Visseren-Hamakers, I.J. - \ 2018
Environmental Science & Policy 85 (2018). - ISSN 1462-9011 - p. 132 - 140.
Biodiversity - Mainstreaming - Integration - Values-based leadership - Governance - Certification - Economic sectors - Fisheries - Palm Oil - FDI - Land - Mangroves
Mainstreaming biodiversity into the governance of economic sectors such as agriculture, forestry and fisheries is required to reverse biodiversity loss and achieve globally adopted conservation targets. Governments have recognized
this but little progress has been made. This paper addresses the following research question: What are the barriers and levers for mainstreaming biodiversity into economic sectors that exert high pressure on biodiversity?
This question is approached through applying an analytical framework developed from literature on mainstreaming and Environmental Policy Integration as well as governance theory and practice to four cases in
agriculture, agro-forestry and fisheries covering multi-level and transnational governance contexts. Decisionmaking and governance in these cases look quite different compared to the kind of public policy machinery of governmental bureaucracies that much EPI literature has focused on. Our analysis demonstrates mainstreaming efforts in some of our cases at the degree of harmonization and even coordination among key actors. It further identifies a number of ‘additional’ barriers and levers that from an Environmental Policy Integration perspective would be considered as external factors out of reach for mainstreaming efforts. The results are pertinent for the evaluation of EPI performance because the governance perspective expands the borders of who can initiate, enable and sustain mainstreaming, what scope of regulatory norms they can use and the potentially useful resources for the process.
Soil microbes promote complementarity effects among co-existing trees through soil nitrogen partitioning
Luo, Shan ; Schmid, Bernhard ; Deyn, Gerlinde B. De; Yu, Shixiao - \ 2018
Functional Ecology 32 (2018)7. - ISSN 0269-8463 - p. 1879 - 1889.
Biodiversity - Complementarity - Ecosystem functioning - Mycorrhizal fungi - Nitrogen partitioning - Plant-soil interactions - Soil microbes
Plant resource partitioning is a mechanism promoting species coexistence and ecosystem functioning. Yet, we still have limited understanding of how soil microbes, especially plant symbiotic microbes, influence resource partitioning. We hypothesized that soil-borne microbes, in particular mycorrhizal fungi, facilitate differential performance of tree species depending on different nitrogen sources and that this leads to a positive plant diversity-community productivity relationship. We conducted two complementing glasshouse experiments. In a "monoculture experiment," we supplied nitrogen as ammonium, nitrate or glycine and tested the growth response of three tree species associated with different root symbionts: one associated with ectomycorrhizal fungi, one associated with arbuscular mycorrhizal fungi, and the third associated with both arbuscular mycorrhizal fungi and N-fixing bacteria. In an "intermixed experiment," we grew the tree species at three richness levels (one, two or three species) in soil supplied with a mix of the three nitrogen forms or no added nitrogen, and with or without soil microbes. The monoculture experiment showed that in the presence of soil microbes, the ectomycorrhizal plant species grew best when supplied with glycine and the two arbuscular mycorrhizal plant species grew best with either nitrate or ammonium addition. When the different forms of nitrogen were mixed in the intermixed experiment, plant mixtures produced more biomass than plant monocultures in the presence of soil microbes, with positive complementarity effects indicating microbe-mediated plant resource partitioning. Our results suggest that co-existing tree species can partition soil nitrogen when grown with their particular mycorrhizal symbionts or other soil microbes, resulting in positive biodiversity effects in complex resource environments. A plain language summary is available for this article.
Species and structural diversity affect growth of oak, but not pine, in uneven-aged mature forests
Vanhellemont, Margot ; Bijlsma, Rienk Jan ; Keersmaeker, Luc De; Vandekerkhove, Kris ; Verheyen, Kris - \ 2018
Basic and Applied Ecology 27 (2018). - ISSN 1439-1791 - p. 41 - 50.
Biodiversity - Ecosystem functioning - Pinus sylvestris - Productivity - Quercus petraea - Quercus robur - Temperate forest
The effects of mixing tree species on tree growth and stand production have been abundantly studied, mostly looking at tree species diversity effects while controlling for stand density and structure. Regarding the shift towards managing forests as complex adaptive systems, we also need insight into the effects of structural diversity. Strict forest reserves, left for spontaneous development, offer unique opportunities for studying the effects of diversity in tree species and stand structure. We used data from repeated inventories in ten forest reserves in the Netherlands and northern Belgium to study the growth of pine and oak. We investigated whether the diversity of a tree's local neighbourhood (i.e., species and structural diversity) is important in explaining its basal area growth. For the subcanopy oak trees, we found a negative effect of the tree species richness of the local neighbours, which - in the studied forests - was closely related to the share of shade-casting tree species in the neighbourhood. The growth of the taller oak trees was positively affected by the height diversity of the neighbour trees. Pine tree growth showed no relation with neighbourhood diversity. Tree growth decreased with neighbourhood density for both species (although no significant relationship was found for the small pines). We found no overall diversity-growth relationship in the studied uneven-aged mature forests; the relationship depended on tree species identity and the aspect of diversity considered (species vs. structural diversity).
Complementarity and synergisms among ecosystem services supporting crop yield
Garibaldi, Lucas A. ; Andersson, Georg K.S. ; Requier, Fabrice ; Fijen, Thijs P.M. ; Hipólito, Juliana ; Kleijn, David ; Pérez-Méndez, Néstor ; Rollin, Orianne - \ 2018
Global Food Security 17 (2018). - ISSN 2211-9124 - p. 38 - 47.
Biodiversity - Ecosystem functioning - Pest control - Pollination - Regulatory services - Soil fertility
Understanding how ecosystem services interact to support crop yield is essential for achieving food security. Here we evaluate the interactions among biotic pest regulation, pollination, and nutrient cycling. We found only 16 studies providing 20 analyses of two-way interactions. These studies show that multiple services limit crop yield simultaneously. Complementary effects (no interactions) between ecosystem services were the most common, followed by synergistic effects (positive interactions), while evidence for negative interactions was weak. Most studies evaluated two levels of service delivery, thus did not quantify the functional response of crop yield. Although this function is expected to be non-linear, most studies assume linear relations. We conclude that the lack of evidence for negative interactions has important implications for agricultural management.
Biotic interactions enhance survival and fitness in the caddisfly Micropterna sequax (Trichoptera : Limnephilidae)
Westveer, Judith J. ; Verdonschot, Piet F.M. ; Verdonschot, Ralf C.M. - \ 2018
Hydrobiologia 818 (2018)1. - ISSN 0018-8158 - p. 31 - 41.
Biodiversity - Ecosystem functioning - Interspecific facilitation - Macroinvertebrates - Niche complementarity
Patches of coarse particulate organic matter in lowland streams are inhabited by many different macroinvertebrate species, yet knowledge of interactions among the members of these assemblages is scarce. In a mesocosm experiment we aimed to determine the effect of interspecific interactions on species survival and fitness of two caddisfly species. It was hypothesized that, as a result of positive interactions, mixed species populations would yield higher survival and fitness than single species populations. Larvae of two caddisfly species, Micropterna sequax and Potamophylax rotundipennis, were reared in single species and mixed species populations. Emergence rate was recorded and adult fitness was measured in terms of wingspan and biomass. We found that in mixed populations, emergence rate, wing length and biomass of M. sequax were higher than in single species populations. P. rotundipennis was only significantly, yet negatively, affected in terms of biomass of the male individuals. This study showed that occurring together with other species holds advantages for M. sequax, and emphasizes the importance of species diversity in streams. Furthermore, the observed positive effects on survival and fecundity might influence population sizes of the interacting species, in turn affecting macroinvertebrate-mediated ecosystem processes such as leaf litter decomposition.
The benefits of self-governance for nature conservation : A study on active citizenship in the Netherlands
Mattijssen, Thomas ; Buijs, Arjen ; Elands, Birgit - \ 2018
Journal for Nature Conservation 43 (2018). - ISSN 1617-1381 - p. 19 - 26.
Active citizenship - Biodiversity - Co-benefits - Governance - Nature conservation - Self-governance
An increased involvement of citizens in the management of European green spaces raises questions about its contributions to nature conservation. In this research, we study the effects of different types of active citizenship in green space. Combining qualitative and quantitative methods, we look at the benefits of 50 green self-governance practices in which citizens aim to realize, manage or protect green space in the Netherlands. While most of these practices contribute to nature conservation (80%) and/or the conservation of cultural landscapes (50%), our analysis shows that the benefits of green self-governance are much broader. This includes so called ‘co-benefits’, social, cultural and economic benefits such as the use function of green for human activity (78%), environmental education (88%) and social cohesion (50%). The benefits and co-benefits of green self-governance strongly depend on the type of practice. Using a typology of green self-governance, we show that a majority of practices focuses on direct benefits to nature conservation through hands-on activities and/or political actions. However, we also show that this focus is regularly combined with efforts to realize co-benefits. Practices with an explicit focus on co-benefits often also produce benefits - and vice-versa. In this way, co-benefits can provide a first step towards the realization of more direct benefits to nature conservation. Even so, there are also tensions between benefits and co-benefits, for example when an increase of recreation negatively affects biodiversity values or when ‘wild’ nature is being replaced by a cultivated garden. Relating to co-benefits can be an effective strategy for governments or environmental NGO's, but we have to be aware that the benefits generated by green self-governance are generally of a much smaller scale than those realized by ‘traditional’ managers of green space such as authorities.
Soil ecology and ecosystem services of dairy and semi-natural grasslands on peat
Deru, Joachim G.C. ; Bloem, Jaap ; Goede, Ron de; Keidel, Harm ; Kloen, Henk ; Rutgers, Michiel ; Akker, Jan van den; Brussaard, Lijbert ; Eekeren, Nick van - \ 2018
Applied Soil Ecology 125 (2018). - ISSN 0929-1393 - p. 26 - 34.
Biodiversity - C mineralization - Grassland - Histosols - N mineralization - Water infiltration
Peat wetlands are of major importance for ecosystem services such as carbon storage, water regulation and maintenance of biodiversity. However, peat drainage for farming leads to CO2 emission, soil subsidence and biodiversity losses. In the peat areas in the Netherlands, solutions are sought in reducing drainage, adapting farming to wetter soils, and converting productive dairy grasslands to less intensively managed semi-natural grasslands. Our objective was to compare the soil ecology and related ecosystem services of dairy and semi-natural grasslands on peat soils (Terric Histosols). Soil biotic and abiotic parameters were measured in twenty dairy and twenty semi-natural sites, with particular focus on (i) soil faunal diversity (ecosystem service "maintenance of biodiversity"), (ii) CO2 emission ("climate regulation"), (iii) water infiltration ("water regulation") and (iv) soil fertility ("grass production"). Mean soil faunal taxonomic richness per site (alpha diversity) was higher in dairy grasslands compared to semi-natural grasslands. However, the total observed number of taxa (gamma diversity) in dairy grassland was 13% lower for soil fauna and 21% lower when including plant species. Potential C mineralization rate in the topsoil - used as a proxy for CO2 emission - was not influenced by land use but was limited by drought. Additionally, potential C mineralization depended on different C sources and microbial groups in the two grassland types. Water infiltration rate differed by a factor of five between land use types (dairy > semi-natural), and correlated with soil porosity. As expected, soil fertility was higher in dairy than in semi-natural grasslands. However, potential N mineralization was similar in dairy and semi-natural grasslands and was correlated negatively with bacterial biomass apparently indicating N immobilization, and positively with bacterial growth that depended on labile C and N in soil. Our study on peat soils shows that dairy versus semi-natural grassland use influences biodiversity, climate regulation, water regulation and (potential for) grassland production. We conclude with recommendations for land management to optimize the delivery of those ecosystem services.
The need for standardisation : Exemplified by a description of the diversity, community structure and ecological indices of soil nematodes
Griffiths, B.S. ; Groot, G.A. de; Laros, I. ; Stone, D. ; Geisen, S. - \ 2018
Ecological Indicators 87 (2018). - ISSN 1470-160X - p. 43 - 46.
Biodiversity - DNA extraction - Metabarcoding - Microscopy - Molecular approaches - Nematodes - Standardisation
Molecular approaches are offering a supplement to, or even the possibility of replacing morphological identification of soil fauna, because of advantages for throughput, coverage and objectivity. We determined ecological indices of nematode community data from four sets of duplicate soil cores, based on morphological identification of nematodes after elutriation from 200 g soil and high throughput sequencing (HTS) targeting nematodes both after being elutriated from soils and DNA extracted directly from 10 g soil. HTS (at genus and species level) increased the taxonomic resolution compared to morphology (at family level). DNA extracted from elutriated nematodes identified more nematode taxa than when extracted from soil, due to an enrichment in nematode sequences. Each method also gave a different ecological footprint for the nematode community. Standardisation to previously determined indices based on morphological identification is needed in order to provide more meaningful information about soil quality and for ecological monitoring.
Feasibility of coupled empirical and dynamic modeling to assess climate change and air pollution impacts on temperate forest vegetation of the eastern United States
McDonnell, T.C. ; Reinds, G.J. ; Sullivan, T.J. ; Clark, C.M. ; Bonten, L.T.C. ; Mol-Dijkstra, J.P. ; Wamelink, G.W.W. ; Dovciak, M. - \ 2018
Environmental Pollution 234 (2018). - ISSN 0269-7491 - p. 902 - 914.
Acidification - Biodiversity - Climate change - Forest understory - Nitrogen
Changes in climate and atmospheric nitrogen (N) deposition caused pronounced changes in soil conditions and habitat suitability for many plant species over the latter half of the previous century. Such changes are expected to continue in the future with anticipated further changing air temperature and precipitation that will likely influence the effects of N deposition. To investigate the potential long-term impacts of atmospheric N deposition on hardwood forest ecosystems in the eastern United States in the context of climate change, application of the coupled biogeochemical and vegetation community model VSD+PROPS was explored at three sites in New Hampshire, Virginia, and Tennessee. This represents the first application of VSD+PROPS to forest ecosystems in the United States. Climate change and elevated (above mid-19th century) N deposition were simulated to be important factors for determining habitat suitability. Although simulation results suggested that the suitability of these forests to support the continued presence of their characteristic understory plant species might decline by the year 2100, low data availability for building vegetation response models with PROPS resulted in uncertain results at the extremes of simulated N deposition. Future PROPS model development in the United States should focus on inclusion of additional foundational data or alternate candidate predictor variables to reduce these uncertainties. Climate change and elevated N deposition were simulated to be important factors for determining habitat suitability for plants, and are expected to interact with changes in soil chemistry.
Soil bacteria show different tolerance ranges to an unprecedented disturbance
Nunes, Inês ; Jurburg, Stephanie ; Jacquiod, Samuel ; Brejnrod, Asker ; Falcão Salles, Joana ; Priemé, Anders ; Sørensen, Søren J. - \ 2018
Biology and Fertility of Soils 54 (2018)2. - ISSN 0178-2762 - p. 189 - 202.
Bet-hedging - Biodiversity - Disturbance - Functional response group - RNA - Soil bacteria
Soil microbial communities have remarkable capacities to cope with ceaseless environmental changes, but little is known about their adaptation potential when facing an unprecedented disturbance. We tested the effect of incremental dose of microwaving on soil bacteria as a model of unprecedented stress. 16S rRNA gene qPCR at both the DNA and cDNA levels was used to characterize the total (DNA) and transcriptionally active (cDNA) fractions of the bacterial community. Amplicon sequencing of 16S rRNA gene transcripts was performed to decipher tolerance ranges within the community using the concept of functional response groups (FRGs). Increasing microwaving doses resulted in 90% loss in total and transcriptionally active bacterial communities after 6.8 and 4.7 min, respectively. Four distinct FRGs with peculiar phylogenetic signatures were identified, revealing a link between taxonomy and increasing stress doses. FRG1, the most sensitive group, was dominated by Actinobacteria. FRG2 and FRG3, with intermediate tolerance, displayed prevalence of Proteobacteria, while FRG4, the most resistant group, was driven by Firmicutes. While the most sensitive FRGs showed predictable responses linked to changes in temperature and soil water content associated with microwaving, more tolerant FRG4 members exhibited a stochastic response nested within the Firmicutes phylum, potentially revealing bet-hedging strategists. The concept of FRGs based on 16S rRNA gene transcripts stood as an efficient tool for unraveling bacterial survival strategies and tolerance ranges triggered by incremental doses of an unprecedented stress, with regard to phylogeny linkages.
Effects of crown architecture and stand structure on light absorption in mixed and monospecific Fagus sylvatica and Pinus sylvestris forests along a productivity and climate gradient through Europe
Forrester, David Ian ; Ammer, Christian ; Annighöfer, Peter J. ; Barbeito, Ignacio ; Bielak, Kamil ; Bravo-Oviedo, Andrés ; Coll, Lluis ; Río, Miren del; Drössler, Lars ; Heym, Michael ; Hurt, Václav ; Löf, Magnus ; Ouden, Jan den - \ 2018
Journal of Ecology 106 (2018). - ISSN 0022-0477 - p. 746 - 760.
Allometric equation - Biodiversity - Complementarity - Maestra model - Plant-plant interactions - Resource availability - Tree height
When tree-species mixtures are more productive than monocultures, higher light absorption is often suggested as a cause. However, few studies have quantified this effect and even fewer have examined which light-related interactions are most important, such as the effects of species interactions on tree allometric relationships and crown architecture, differences in vertical or horizontal canopy structure, phenology of deciduous species or the mixing effects on tree size and stand density. In this study, measurements of tree sizes and stand structures were combined with a detailed tree-level light model (Maestra) to examine the contribution of each light-related interaction on tree- and stand-level light absorption at 21 sites, each of which contained a triplet of plots including a mixture and monocultures of Fagus sylvatica and Pinus sylvestris (63 plots). These sites were distributed across the current distribution of these species within Europe. Averaged across all sites, the light absorption of mixtures was 14% higher than the mean of the monocultures. At the whole community level, this positive effect of mixing on light absorption increased as canopy volume or site productivity increased, but was unrelated to climate. At the species population or individual tree levels, the mixing effect on light absorption resulted from light-related interactions involving vertical canopy structure, stand density, the presence of a deciduous species (F. sylvatica), as well as the effects of mixing on tree size and allometric relationships between diameter and height, crown diameter and crown length. The mixing effects on light absorption were only correlated with the mixing effects on growth for P. sylvestris, suggesting that the mixing effects on this species were driven by the light-related interactions, whereas mixing effects on F. sylvatica or whole community growth were probably driven by non-light-related interactions. Synthesis. The overall positive effect of mixing on light absorption was the result of a range of light-related interactions. However, the relative importance of these interactions varied between sites and is likely to vary between other species combinations and as stands develop.
Methodological advances to study the diversity of soil protists and their functioning in soil food webs
Geisen, Stefan ; Bonkowski, Michael - \ 2018
Applied Soil Ecology 123 (2018). - ISSN 0929-1393 - p. 328 - 333.
Biodiversity - Functional diversity - High throughput sequencing - Soil food web - Soil protists

Soils host the most complex communities of organisms, which are still largely considered as an unknown 'black box'. A key role in soil food webs is held by the highly abundant and diverse group of protists. Traditionally, soil protists are considered as the main consumers of bacteria in soils. However, recent insights obtained using new methodologies, provide clear evidence for the trophic diversity of microbial eukaryotes, showing that non-bacterivorous soil protists (fungivores, omnivores, predators of other protists and nematodes), photosynthetic taxa and plant-as well as animal parasites might be equally important.Here we provide an overview of methodologies to study these important soil organisms. Major gaps of knowledge are highlighted, which can be addressed using a combination of now available methods These studies will undeniably reveal an even higher functional diversity of protists and likely raise awareness of their ecological importance in soils.

Taking stock of the spectrum of arguments for biodiversity
Howard, Bruce ; Braat, Leon C. ; Bugter, Rob J.F. ; Carmen, Esther ; Hails, Rosemary S. ; Watt, Allan D. ; Young, Juliette C. - \ 2018
Biodiversity and Conservation 27 (2018)7. - ISSN 0960-3115 - p. 1561 - 1574.
Arguments - Biodiversity - Ecosystem services - Valuation

This paper provides an analysis of the spectrum of arguments associated with the term biodiversity, as expressed in the literature. Through sampling of the grey and peer-review literature, and testing of results through semi-structured interviews, this review presents a total of 31 different instrumental and non-instrumental premises used in arguments for biodiversity. Based on the identified premise statements, this review offers a simple classification by which to understand the complex public discourse associated with arguments for biodiversity, and outlines the current frequency of use of arguments in the literature. Although a wide range of premise statements were identified, the majority of arguments were instrumental with the most frequently used ones putting forward economic perspectives as well as emphasising the role of biodiversity in underpinning ecosystem services. Results from interviews with decision-makers emphasise the need to combine arguments in order to strengthen biodiversity conservation generally, and minimise possible risks associated with individual arguments.

Biodiversity and food web indicators of community recovery in intertidal shellfish reefs
Christianen, M.J.A. ; Heide, T. van der; Holthuijsen, S.J. ; Reijden, K.J. van der; Borst, A.C.W. ; Olff, H. - \ 2017
Biological Conservation 213 (2017). - ISSN 0006-3207 - p. 317 - 324.
Biodiversity - Ecological networks - Facilitation - Foundation species - Habitat modification - Trophic interactions
In conservation strategies of marine ecosystems, priority is given to habitat-structuring foundation species (e.g. seagrasses, mangroves and reef-building corals, shellfish) with the implicit goal to protect or restore associated communities and their interactions. However, the number and accuracy of community level metrics to measure the success of these strategies are limited. Using intertidal shellfish reefs as a model, we tested to what extent foundation species alter community and food web structure, and explored whether basic metrics of food web structure are useful indicators of ecosystem complexity compared to other often-used indices. We found that shellfish reefs strongly modified community and food web structure by modifying habitat conditions (e.g. hydrodynamics, sediment grain size). Stable isotope-based food web reconstruction captured important differences between communities from bare mudflat and shellfish reefs that did not emerge from classic abundance or diversity measures. On shellfish reefs, link density and the number of top predators were consistently higher, while both connectance and the richness of intermediate species was lower. Species richness (+ 42%), species density (+ 79%) and total biomass of benthos, fish and birds (+ 41%) was also higher on shellfish reefs, but this did not affect the Shannon diversity or Evenness. Hence, our results showed that basic food web metrics such as link density and number of top consumers and intermediate species combined with traditional measures of species richness can provide a robust tool to measure conservation and restoration success. We therefore suggest that these metrics are included as Essential Biodiversity Variables (EBV), and implemented as ecosystem health indicators in legislative frameworks such as the Marine Strategy Framework Directive (MSFD).
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