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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Impact of the blue mussel Mytilus edulis on the microbial food web in the western Wadden Sea, the Netherlands
Jacobs, P. ; Riegman, R. ; Meer, J. van der - \ 2015
Marine Ecology Progress Series 527 (2015). - ISSN 0171-8630 - p. 119 - 131.
suspension-feeding bivalves - phytoplankton growth - dilution experiments - plankton communities - upwelling system - microzooplankton - carbon - bacterioplankton - protists - rates
To study the impact of juvenile blue mussels Mytilus edulis on the microbial food web in the Dutch Wadden Sea, natural sea water was first exposed to mussel filtration. Subsequently, filtered plankton communities were used in a dilution experiment to establish mussel-induced changes in bacterial, pico- and nanophytoplankton growth rates as well as heterotrophic nanoflagellates (HNAN) and ciliate-induced grazing mortality rates. During the experimental period, from July to September, mussel filtration had a size-selective impact on the plankton community; on average, nanophytoplankton, HNAN and ciliates biomasses were removed at equal rates, while bacterial and picophytoplankton biomasses were affected to a much lower extent. The reduction in HNAN predators by mussels significantly lowered the grazing mortality rates for picophytoplankton. For bacteria, grazing mortality did not change, while specific growth rates almost doubled (from 0.65 to 1.16 d-1). There was an increase in HNAN biomass following the enhanced bacterial production. Single exposure to mussel filtration thus led to a stimulation of the bacterial-HNAN pathway. HNAN biomass, although seriously reduced by mussel filtration, recovered to pre-filtration levels within 24 h. Nanophytoplankton and ciliates did not recover completely within 24 h. The results from this study reveal potentially important effects of mussel filtration on the pelagic food web not disclosed when considering phytoplankton biomass alone.
Homo erectus at Trinil on Java used shells for tool production and engraving
Joordens, J.C.A. ; d’Errico, F. ; Wesselingh, F.P. ; Munro, S. ; Vos, J. de; Wallinga, J. ; Ankjaergaard, C. ; Reimann, T. ; Wijbrans, J.R. ; Kuiper, K.F. ; Mücher, H.J. ; Coqueugniot, H. ; Prié, V. ; Joosten, I. ; Os, B. van; Schulp, A.S. ; Panuel, M. ; Haas, V. van der; Lustenhouwer, W. ; Reijmer, J.J.G. ; Roebroeks, W. - \ 2015
Nature 518 (2015). - ISSN 0028-0836 - p. 228 - 231.
quartz osl ages - luminescence signals - south-africa - indonesia - sediments - reliability - sangiran - record - rates
The manufacture of geometric engravings is generally interpreted as indicative of modern cognition and behaviour1. Key questions in the debate on the origin of such behaviour are whether this innovation is restricted to Homo sapiens, and whether it has a uniquely African origin1. Here we report on a fossil freshwater shell assemblage from the Hauptknochenschicht (‘main bone layer’) of Trinil (Java, Indonesia), the type locality of Homo erectus discovered by Eugène Dubois in 1891 (refs 2 and 3). In the Dubois collection (in the Naturalis museum, Leiden, The Netherlands) we found evidence for freshwater shellfish consumption by hominins, one unambiguous shell tool, and a shell with a geometric engraving. We dated sediment contained in the shells with 40Ar/39Ar and luminescence dating methods, obtaining a maximum age of 0.54 ± 0.10 million years and a minimum age of 0.43 ± 0.05 million years. This implies that the Trinil Hauptknochenschicht is younger than previously estimated. Together, our data indicate that the engraving was made by Homo erectus, and that it is considerably older than the oldest geometric engravings described so far4, 5. Although it is at present not possible to assess the function or meaning of the engraved shell, this discovery suggests that engraving abstract patterns was in the realm of Asian Homo erectus cognition and neuromotor control.
Plant species richness leaves a legacy of enhanced root litter-induced decomposition in soil
Cong, W. ; Ruijven, J. van; Werf, W. van der; Deyn, G.B. de; Mommer, L. ; Berendse, F. ; Hoffland, E. - \ 2015
Soil Biology and Biochemistry 80 (2015). - ISSN 0038-0717 - p. 341 - 348.
experimental grassland ecosystems - leaf-litter - functional composition - microbial communities - biodiversity loss - carbon storage - diversity - productivity - nitrogen - rates
Increasing plant species richness generally enhances plant biomass production, which may enhance accumulation of carbon (C) in soil. However, the net change in soil C also depends on the effect of plant diversity on C loss through decomposition of organic matter. Plant diversity can affect organic matter decomposition via changes in litter species diversity and composition, and via alteration of abiotic and/or biotic attributes of the soil (soil legacy effect). Previous studies examined the two effects on decomposition rates separately, and do therefore not elucidate the relative importance of the two effects, and their potential interaction. Here we separated the effects of litter mixing and litter identity from the soil legacy effect by conducting a factorial laboratory experiment where two fresh single root litters and their mixture were mixed with soils previously cultivated with single plant species or mixtures of two or four species. We found no evidence for litter-mixing effects. In contrast, root litter-induced CO2 production was greater in soils from high diversity plots than in soils from monocultures, regardless of the type of root litter added. Soil microbial PLFA biomass and composition at the onset of the experiment was unaffected by plant species richness, whereas soil potential nitrogen (N) mineralization rate increased with plant species richness. Our results indicate that the soil legacy effect may be explained by changes in soil N availability. There was no effect of plant species richness on decomposition of a recalcitrant substrate (compost). This suggests that the soil legacy effect predominantly acted on the decomposition of labile organic matter. We thus demonstrated that plant species richness enhances root litter-induced soil respiration via a soil legacy effect but not via a litter-mixing effect. This implies that the positive impacts of species richness on soil C sequestration may be weakened by accelerated organic matter decomposition.
Glycemic control and all-cause mortality risk in type 1 diabetes patients: the EURODIAB prospective complications study
Schoenaker, D.A.J.M. ; Simon, D. ; Chaturvedi, N. ; Fuller, J.H. ; Soedamah-Muthu, S.S. - \ 2014
Journal of Clinical Endocrinology and Metabolism 99 (2014)3. - ISSN 0021-972X - p. 800 - 807.
vascular complications - cardiovascular-disease - severe hypoglycemia - hba(1c) - trials - cohort - accord - rates - death - a1c
Context: Glycemic targets and the benefit of intensive glucose control are currently under debate because intensive glycemic control has been suggested to have negative effects on mortality risk in type 2 diabetes patients. Objective: We examined the association between glycated hemoglobin (HbA1c) and all-cause mortality in patients with type 1 diabetes mellitus. Design, Setting, and Patients: A clinic-based prospective cohort study was performed in 2764 European patients with type 1 diabetes aged 15–60 years enrolled in the EURODIAB Prospective Complications Study. Outcome Measure: Possible nonlinearity of the association between HbA1c and all-cause mortality was examined using multivariable restricted cubic spline regression using three (at HbA1c 5.6%, 8.1%, and 11.8%) and five knots (additionally at HbA1c 7.1% and 9.5%). Mortality data were collected approximately 7 years after baseline examination. Results: HbA1c was related to all-cause mortality in a nonlinear manner after adjustment for age and sex. All-cause mortality risk was increased at both low (5.6%) and high (11.8%) HbA1c compared with the reference (median HbA1c: 8.1%) following a U-shaped association [P overall effect = .008 and .04, P nonlinearity = .03 and .11 (three and five knots, respectively)]. Conclusions: Results from our study in type 1 diabetes patients suggest that target HbA1c below a certain threshold may not be appropriate in this population. We recognize that these low HbA1c levels may be related to anemia, renal insufficiency, infection, or other factors not available in our database. If our data are confirmed, the potential mechanisms underlying this increased mortality risk among those with low HbA1c will need further study.
Carbon accumulation in peat deposits from northern Sweden to northern Germany during the last millennium
Linden, M. van der; Heijmans, M.M.P.D. ; Geel, B. van - \ 2014
Holocene 24 (2014)9. - ISSN 0959-6836 - p. 1117 - 1125.
climate-change - human impact - bog - sphagnum - temperature - rates - vegetation - peatlands - growth - ams
Historic carbon accumulation rates in four bogs on a north to south transect from Sweden to Germany were calculated by using the bulk densities and carbon concentrations of 1-cm peat layers and a fine-resolution radiocarbon chronology. Carbon accumulation rates were compared to environmental data to explore the effects of climatic factors. Carbon accumulation rates in a period without clear human impact on the bog ecosystems ( 1700–ad 1800) ranged from 25 g C/m2/yr in the most northern site to 50 g C/m2/yr in the southernmost site, which coincided with increasing annual temperatures from north to south. This suggests that temperature or growing season length is a major factor influencing carbon accumulation rates at different geographical sites. The temporal variations in carbon accumulation rates within the sites tentatively suggest that carbon accumulation rates may still increase with further warming in northern peat bogs, but decrease in southern peat bogs.
Soil N mineralization in a dairy production system with grass and forage crops
Verloop, J. ; Hilhorst, G.J. ; Oenema, J. ; Keulen, H. van; Sebek, L.B.J. ; Ittersum, M.K. van - \ 2014
Nutrient Cycling in Agroecosystems 98 (2014)3. - ISSN 1385-1314 - p. 267 - 280.
net nitrogen mineralization - in-situ methods - organic-matter - field measurement - incubation method - pasture soils - cover crops - rates - denitrification - netherlands
This paper describes the dynamics of soil N mineralization in the experimental intensive dairy farming system ‘De Marke’ on a dry sandy soil in the Netherlands. We hypothesized that knowledge of the effects of crop rotation on soil N mineralization and of the spatial and temporal variability of soil N mineralization in a farming system can be used to better synchronize N application with crop N requirements, and hence to increase the recovery of applied N and to reduce N losses. Soil N mineralization was recorded continuously in the soil layer 0–0.30 m, from 1992 to 2005, using a sequential in situ coring technique on six observation plots, of which two were located in permanent grassland and four in crop rotations with a 3 year grassland phase and an arable phase of 3 or 5 years, dominated by maize. Average annual soil N mineralization was highest under permanent grassland: 381 kg ha-1 and lowest under =3rd years arable crops: 184 kg ha-1. In temporary grassland, soil N mineralization increased in the order: 1st year, 2nd year, 3rd year grassland and in arable crops after grassland mineralization decreased in the order: 1st year, 2nd year, =3rd years. Total mineral N input, i.e. the sum of N mineralization and mineral N supply to soil, exceeded crop N requirements in 1st year maize and was lower than the requirements in 1st year temporary grassland. N mineralization in winter, outside the growing season, was 77 kg ha-1 in maize and 60 kg ha-1 in grassland. This points at the importance of a suitable catch crop to reduce the susceptibility to N leaching. Temporal and spatial variability of soil N mineralization was high and could not be related to known field conditions. This limits the extent to which N fertilization can be adjusted to soil N mineralization. Variability increased with the magnitude of soil N mineralization. Hence, situations with high soil N mineralization may be associated with high risks for N losses and to reduce these risks a strong build-up of soil organic N should be avoided. This might be achieved, for instance, by fermenting slurry before application on farmland to enhance the fraction mineral N in slurry at the expense of organic N.
Nutrient regeneration by mussel Mytilus edulis spat assemblages in a macrotidal system
Broekhoven, W. van; Troost, K. ; Jansen, H.M. ; Smaal, A.C. - \ 2014
Journal of Sea Research 88 (2014). - ISSN 1385-1101 - p. 36 - 46.
la-madeleine quebec - seasonal-variation - biogeochemical fluxes - oosterschelde estuary - carrying-capacity - nitrogen - rates - phytoplankton - aquaculture - budgets
Besides exercising grazing control over phytoplankton populations, suspension-feeding bivalves can also stimulate carrying capacity by regeneration of nutrients. This study provides new data on nutrient uptake and release dynamics, and potential implications for availability and stoichiometry of nutrients, for Mytilus edulis spat collectors in the Netherlands. Uptake and release rates were measured in situ on intact spat collector ropes in a eutrophic macrotidal system in relation to development of ropes in terms of mussel biomass and associated components (fauna, flora, and organic material). There was a good fit between uptake/release rates and mussel weight based on allometric scaling functions, despite the occurrence of a substantial biomass of associated fauna, flora and organic matter on ropes. On a unit biomass basis, nutrient release rates were much higher than reported in other studies, which we attribute to greater activity of small mussels. Accounting for greater weight-specific activity of small mussels, spat collectors released more P than reported for other systems. We show that spat collectors can affect relative availabilities of N, P and Si, and we show that SMCs (Seed Mussel Collectors) likely stimulated phytoplankton production through regeneration of N and of Si, which were at limiting concentrations at different points in time. In the case of Si, stimulation would be restricted to diatoms. We conclude that SMCs are able to stimulate phytoplankton production rates, and thereby carrying capacity, and are able to influence phytoplankton composition.
Biochars produced from individual grassland species differ in their effect on plant growth
Voorde, T.F.J. van de; Noppen, F. van; Nachenius, R.W. ; Prins, W. ; Mommer, L. ; Bezemer, T.M. ; Groenigen, J.W. van - \ 2014
Basic and Applied Ecology 15 (2014)1. - ISSN 1439-1791 - p. 18 - 25.
litter decomposition - soil - chemistry - jacobaea - vulgaris - quality - traits - rates - biota
Biochar, pyrolyzed biomass, has been shown to be a promising way to improve plant productivity and soil quality. Biochar characteristics and its effect on plant performance depend strongly on the type of feedstock from which it is made. However, whether biochars produced from individual grassland species differ in their characteristics and effects on plant growth when applied to soil is poorly understood. The aim of this study was to examine how soil application of pyrolyzed and non-pyrolyzed biomass originating from different grassland species influences plant performance. We measured the growth of the forb Jacobaea vulgaris in soil amended with pyrolyzed or non-pyrolyzed biomass of seven different plant species, and in control soil without amendments. The characteristics (nutrient content, C:N) and effects on plant growth of both pyrolyzed and non-pyrolyzed biomass differed significantly between species from which the biomass originated (‘feedstock species’). For most feedstock species there was no relationship between the effects that the pyrolyzed and the non-pyrolyzed biomass had on plant performance. Our results show that pyrolyzed grassland species differ in their characteristics and their effect on plant growth when amended to soil. This shows that it is important to test what the effect of pyrolysing a chosen feedstock is on a species before applying it on a larger scale and that potentially biochar with predefined effects could be designed for specific purposes.
A toolkit for the mzIdentML standard: the ProteoIDViewer, the mzidLibrary and the mzidValidator.
Ghali, F. ; Krishna, R. ; Lukasse, P.N.J. ; Martínez-Bartolomé, S. ; Reisinger, F. ; Hermjakob, H. ; Vizcaíno, J.A. ; Jones, A.R. - \ 2013
Molecular and Cellular Proteomics 12 (2013). - ISSN 1535-9476 - p. 3026 - 3035.
tandem mass-spectrometry - proteomics - software - parser - miape - rates
The Proteomics Standards Initiative has recently released the mzIdentML data standard for representing peptide and protein identification results, for example, created by a search engine. When a new standard format is produced, it is important that software tools are available that make it straightforward for laboratory scientists to use it routinely and for bioinformaticians to embed support in their own tools. Here we report the release of several open-source Java-based software packages based on mzIdentML: ProteoIDViewer, mzidLibrary, and mzidValidator. The ProteoIDViewer is a desktop application allowing users to visualize mzIdentML-formatted results originating from any appropriate identification software; it supports visualization of all the features of the mzIdentML format. The mzidLibrary is a software library containing routines for importing data from external search engines, post-processing identification data (such as false discovery rate calculations), combining results from multiple search engines, performing protein inference, setting identification thresholds, and exporting results from mzIdentML to plain text files. The mzidValidator is able to process files and report warnings or errors if files are not correctly formatted or contain some semantic error. We anticipate that these developments will simplify adoption of the new standard in proteomics laboratories and the integration of mzIdentML into other software tools. All three tools are freely available in the public domain.
Measuring gas emissions from livestock buildings: A review on uncertainty analysis and error sources
Calvet, S. ; Gates, R.S. ; Zhang, G. ; Estelles, F. ; Ogink, N.W.M. ; Pedersen, S. ; Berckmans, D. - \ 2013
Biosystems Engineering 116 (2013)3. - ISSN 1537-5110 - p. 221 - 231.
measuring ammonia emissions - fattening pig house - ventilation rate - carbon-dioxide - broiler houses - air-flow - rates - poultry - manure - performance
Measuring gaseous and particulate emissions from livestock houses has been the subject of intensive research over the past two decades. Currently, there is general agreement regarding appropriate methods to measure emissions from mechanically ventilated buildings. However, measuring emissions from naturally ventilated buildings remains an elusive target primarily because there is no reference method for measuring building ventilation rate. Ventilation rates and thus building emissions estimates for naturally ventilated buildings are likely to contain greater errors compared with those from mechanically ventilated buildings. This work reviews the origin and magnitude of errors associated with emissions from naturally ventilated buildings as compared to those typically found in mechanical ventilation. Firstly, some general concepts of error analysis are detailed. Then, typical errors found in the literature for each measurement technique are reviewed, and potential sources of relevant systematic and random errors are identified. The emission standard uncertainty in mechanical ventilation is at best 10% or more of the measured value, whereas in natural ventilation it may be considerably higher and there may also be significant unquantifiable biases. A reference method is necessary to obtain accurate emissions estimates, and for naturally ventilated structures this suggests the need for a new means of ventilation measurement. The results obtained from the analysis of information in this review will be helpful to establish research priorities, and to optimize research efforts in terms of quality of emission measurements.
Modeling environmental and human health risks of veteriary medicinal products applied in pond aquaculture
Rico Artero, A. ; Geng, Y. ; Focks, A. ; Brink, P.J. van den - \ 2013
Environmental Toxicology and Chemistry 32 (2013)5. - ISSN 0730-7268 - p. 1196 - 1207.
organic-chemicals - biological products - rate constants - pharmaceuticals - water - antibiotics - rates
A model called ERA-AQUA was developed to assess the risks posed by the use of veterinary medicinal products (VMPs) applied in aquaculture ponds for the targeted produce, surrounding aquatic ecosystems, consumers, and trade of the aquaculture produce. The model calculates risks by following a risk quotient approach, calculating predicted exposure concentrations (exposure assessment) and predicted no-effect concentrations (effect assessment) for the endpoint under study. The exposure assessment is performed by combining information on the environmental characteristics of the aquaculture pond, characteristics of the cultured species, aquaculture management practices, and physicochemical properties of the compound under study. The model predicts concentrations of VMPs in the pond water, pond sediment, cultured species, and watercourse receiving pond effluent discharges by mass balance equations. The effect assessment is performed by combining (eco)toxicological information and food safety threshold concentrations for the studied compound. In the present study, the scientific background, strengths, and limitations of the ERA-AQUA model are presented together with a sensitivity analysis and an example showing its potential applications.
A high density recombination map of the pig reveals a correlation between sex-specific recombination and GC content
Tortereau, F.J.D. ; Servin, B. ; Frantz, L.A.F. ; Megens, H.J.W.C. ; Milan, D. ; Rohrer, G. ; Schook, L.B. ; Groenen, M.A.M. - \ 2012
BMC Genomics 13 (2012). - ISSN 1471-2164
biased gene conversion - multipoint linkage analysis - porcine genome - hot-spots - sus-scrofa - evolution - rates - humans - mice - interference
Background: The availability of a high-density SNP genotyping chip and a reference genome sequence of the pig (Sus scrofa) enabled the construction of a high-density linkage map. A high-density linkage map is an essential tool for further fine-mapping of quantitative trait loci (QTL) for a variety of traits in the pig and for a better understanding of mechanisms underlying genome evolution. Results: Four different pig pedigrees were genotyped using the Illumina PorcineSNP60 BeadChip. Recombination maps for the autosomes were computed for each individual pedigree using a common set of markers. The resulting genetic maps comprised 38,599 SNPs, including 928 SNPs not positioned on a chromosome in the current assembly of the pig genome (build 10.2). The total genetic length varied according to the pedigree, from 1797 to 2149 cM. Female maps were longer than male maps, with a notable exception for SSC1 where male maps are characterized by a higher recombination rate than females in the region between 91-250 Mb. The recombination rates varied among chromosomes and along individual chromosomes, regions with high recombination rates tending to cluster close to the chromosome ends, irrespective of the position of the centromere. Correlations between main sequence features and recombination rates were investigated and significant correlations were obtained for all the studied motifs. Regions characterized by high recombination rates were enriched for specific GC-rich sequence motifs as compared to low recombinant regions. These correlations were higher in females than in males, and females were found to be more recombinant than males at regions where the GC content was greater than 0.4. Conclusions: The analysis of the recombination rate along the pig genome highlighted that the regions exhibiting higher levels of recombination tend to cluster around the ends of the chromosomes irrespective of the location of the centromere. Major sex-differences in recombination were observed: females had a higher recombination rate within GC-rich regions and exhibited a stronger correlation between recombination rates and specific sequence features.
Diameter Growth of Juvenile Trees after Gap Formation in a Bolivian Rain Forest: Responses are Strongly Species-specific and Size-dependent.
Soliz-Gamboa, C.C. ; Sandbrink, A. ; Zuidema, P.A. - \ 2012
Biotropica 44 (2012)3. - ISSN 0006-3606 - p. 312 - 320.
tropical forest - ring analysis - canopy - increment - dynamics - patterns - release - rates - suppression - disturbance
We evaluated growth responses to gap formation for juvenile individuals of three canopy rain forest species: Peltogyne cf. heterophylla, Clarisia racemosa and Cedrelinga catenaeformis. Gaps were formed during selective logging operations 7 yr before sampling in a Bolivian rain forest. We collected wood samples for tree-ring analyses at different distances to the stump (40 m) and from trees with different diameters (5–30 cm diameter at breast height [dbh]). Tree-rings width was measured in at least two radii and converted to average diameter growth. Changes in 7-yr median diameter growth before and after selective logging were analyzed. Diameter growth rates significantly increased by 0.7–0.8 mm/yr after gap formation for P. heterophylla and C. catenaeformis, but not for C. racemosa. We applied a multiple regression analysis to explain variation in growth responses of P. heterophylla and C. catenaeformis by distance to logging gap and tree size. For P. heterophylla we found that growth increase occurring close to logging gaps was strongest for large juvenile trees (20–25 cm dbh) and almost absent in small juveniles. For C. catenaeformis, variation in growth responses was not related to tree size or distance to gaps. Our results show that growth responses to gap formation strongly differ across species and tree sizes. This finding calls for caution in the interpretation of growth releases in tree-ring series, as gap formation does not necessarily invoke growth responses and if such growth responses occur, their strength is species- and size specific.
Driving factors of forest growth: a reply to Ferry et al. (2012).
Toledo, M. ; Poorter, L. ; Peña-Claros, M. ; Alarcón, A. ; Balcázar, J. ; Leaño, C. ; Licona, J.C. ; Llanque, O. ; Vroomans, V. ; Zuidema, P.A. ; Bongers, F. - \ 2012
Journal of Ecology 100 (2012). - ISSN 0022-0477 - p. 1069 - 1073.
tropical rain-forest - silvicultural treatments - tree - patterns - climate - rates - soil - amazonia - dynamics
1. In a recent paper, we analysed the effects of climate, soil and logging disturbance on tree and forest growth (Toledo et al. 2011a). We took advantage of one of the largest data sets in the Neotropics, consisting of 165 1-ha plots and over 62 000 trees distributed over an area of c. 160 000 km2, across large environmental gradients in lowland Bolivia. The main findings were that climate was the strongest driver of spatial variation in tree growth, whereas soils had only a modest effect on growth and that the effect of logging disappeared after a few years. 2. Ferry (2012) suggest that we underestimated the disturbance effects on growth because of a supposedly wrong coding of Time After Logging (TAL) for unlogged plots. Although we have good biological reasons why we coded TAL like we did, we checked Ferry et al.s suggestions for recoding and found no differences in variables that significantly explained tree and forest growth. We agree, however, that for future research, it is important to go beyond simple descriptors such as time after logging and basal area logged, to better describe the variation in logging impact found in areas under forest management. 3. Ferry et al. claim that we did not define basal area growth properly. We believe this is a semantic issue, as we clearly defined basal area growth as the net change in basal area. This net basal area change in Bolivian forests is indeed relatively high compared to other studies, which may be attributed to the higher soil fertility and biogeographic differences in species composition and their traits. 4. Synthesis. Many apparent discrepancies in the ecological literature arise because tropical forest ecologists tend to see the world from the perspective of their own forest (despite clear biogeographic differences) and try to capture the same ecological processes using different variables and measurement protocols. To advance our understanding and go beyond single-case studies, we need to assemble large databases, quantify forest dynamics and disturbances in similar ways, be aware of differences among forests and analyse environmental doseresponse curves.
Highly consistent effects of plant litter identity and functional traits on decomposition across a latitudinal gradient
Makkonen, M. ; Berg, M.P. ; Handa, I.T. ; Hättenschwiler, S. ; Ruijven, J. van; Bodegom, P.M. van; Aerts, M.A.P.A. - \ 2012
Ecology Letters 15 (2012)9. - ISSN 1461-023X - p. 1033 - 1041.
tropical rain-forest - leaf-litter - terrestrial ecosystems - central argentina - carbon-cycle - rates - dynamics - climate - quality - diversity
Plant litter decomposition is a key process in terrestrial carbon cycling, yet the relative importance of various control factors remains ambiguous at a global scale. A full reciprocal litter transplant study with 16 litter species that varied widely in traits and originated from four forest sites covering a large latitudinal gradient (subarctic to tropics) showed a consistent interspecific ranking of decomposition rates. At a global scale, variation in decomposition was driven by a small subset of litter traits (water saturation capacity and concentrations of magnesium and condensed tannins). These consistent findings, that were largely independent of the varying local decomposer communities, suggest that decomposer communities show little specialisation and high metabolic flexibility in processing plant litter, irrespective of litter origin. Our results provide strong support for using trait-based approaches in modelling the global decomposition component of biosphere-atmosphere carbon fluxes
Propagation of Uncertainties in Soil and Pesticide Properties to Pesticide Leaching
Berg, F. van den; Tiktak, A. ; Heuvelink, G.B.M. ; Burgers, S.L.G.E. ; Brus, D.J. ; Vries, F. de; Stolte, J. ; Kroes, J.G. - \ 2012
Journal of Environmental Quality 41 (2012)1. - ISSN 0047-2425 - p. 253 - 261.
spatial variability - water-flow - groundwater - model - degradation - vulnerability - framework - rates
In the new Dutch decision tree for the evaluation of pesticide leaching to groundwater, spatially distributed soil data are used by the GeoPEARL model to calculate the 90th percentile of the spatial cumulative distribution function of the leaching concentration in the area of potential usage (SP90). Until now it was not known to what extent uncertainties in soil and pesticide properties propagate to spatially aggregated parameters like the SP90. A study was performed to quantify the uncertainties in soil and pesticide properties and to analyze their contribution to the uncertainty in SP90. First, uncertainties in the soil and pesticide properties were quantified. Next, a regular grid sample of points covering the whole of the agricultural area in the Netherlands was randomly selected. At the grid nodes, realizations from the probability distributions of the uncertain inputs were generated and used as input to a Monte Carlo uncertainty propagation analysis. The analysis showed that the uncertainty concerning the SP90 is 10 times smaller than the uncertainty about the leaching concentration at individual point locations. The parameters that contribute most to the uncertainty about the SP90 are, however, the same as the parameters that contribute most to uncertainty about the leaching concentration at individual point locations (e.g., the transformation half-life in soil and the coefficient of sorption on organic matter). Taking uncertainties in soil and pesticide properties into account further leads to a systematic increase of the predicted SP90. The important implication for pesticide regulation is that the leaching concentration is systematically underestimated when these uncertainties are ignored.
Evaluation of the NH3 removal efficiency of an acid packed bed scrubber using two methods: a case study in a pig facillity
Estellés, F. ; Melse, R.W. ; Ogink, N.W.M. ; Calvet, S. - \ 2011
Transactions of the ASABE / American Society of Agricultural and Biological Engineers 54 (2011)5. - ISSN 2151-0032 - p. 1905 - 1912.
livestock buildings - northern europe - ammonia - emissions - operations - rates
The use of air cleaning systems to reduce ammonia emissions from animal houses is increasing. These systems are normally used in order to comply with local or national regulations of ammonia emission. Therefore, accurate determination of the proportion of ammonia being removed by these systems is crucial. There are two main methods available to measure ammonia removal efficiency of scrubbers: air balance (based on the measurement of ammonia concentrations in air) and combined water-air balance (in which it is also necessary to determine the amount of nitrogen recovered in the liquid phase). The first method is simpler to establish, while the second method might provide deeper information about the processes occurring. The main aim of this work was to assess, in terms of the variability of the results, the use of these two methods to evaluate the efficiency of an acid packed bed scrubber on a pig farm. An acid packed bed scrubber (70% NH3 removal) was monitored during ten complete 24 h cycles for ammonia concentrations, airflow rates, and nitrogen accumulation in the acid solution basin. The average efficiency calculated using the air balance method was 71% (±4%), close to the design value of 70%, while the average efficiency when using the combined water-air balance method was 255% (±53%). The accumulation and precipitation of ammonium salts in the packing material seem to be the main cause of the high variability and inaccuracy of the combined water-air balance method observed for this type of scrubber. According to these results, it is recommended to use the air balance method when determining the ammonia removal efficiency for acid packed bed scrubbers similar to the one studied here. According to the variability of the results observed in this work, at least 24 measurement days are needed in order to keep the relative error below 5% when using the air balance method to determine the ammonia removal efficiency of an acid packed bed scrubber
Environmental significance of mineral weathering and pedogenesis of loess on the southernmost Loess Plateau, China
Huang, C. ; Zhao, W. ; Liu, F. ; Tan, W.F. ; Koopal, L.K. - \ 2011
Geoderma 163 (2011)3-4. - ISSN 0016-7061 - p. 219 - 226.
clay-minerals - soils - climate - kaolinite - dynamics - taiwan - forest - quartz - rates - alps
Soils derived from the Loess Plateau of China are regionally important and expression of the soil properties along the soil profile may be directly related to climate changes. The objective of this research was to analyze the clay mineral transformation of loess from the southernmost Loess Plateau, in relation to the pedogenesis and the regional climate changes. The mineralogy of the soil profile at the site was studied by using X-ray diffraction. The results showed that 2:1 layer type minerals dominated with the illite in the majority throughout the profile. The changes of the soil minerals were consistent with the soil genetic horizons and with the variable CaCO3 content, particle size distribution, and variations of magnetic susceptibility. A relatively high vermiculite content and the presence of hydroxyl-interlayered mineral (HIM) occurred in the most weathered horizon (50–150 cm) corresponding to the buried palaeosol (S0) formed during the ‘optimum’ Holocene (8400–3100 B.P. yr) which indicated the acidic conditions with low organic matter in this period. During the formation of palaeosol, the expected transformation of illite and chlorite into vermiculite through the formation of mixed layers has occurred. The distribution of kaolinite was uniform with depth in the palaeosol suggesting inheritance from the original eolian deposition materials. Generally, the depotassication of illite and the degradation of chlorite were the major mineral transformation processes that occurred with soil-formation. Calculation of the total amount of carbonate leaching of the palaeosol suggested that the annual precipitation during the ‘optimum’ Holocene was probably approximately to 880 mm. The regional climate during the ‘optimum’ Holocene on the southernmost Loess Plateau was analogous with the modern climate conditions in the northern subtropical zone (the southern slope of Qingling Mountains) for the formation of Udic Luvisols (Brown Soil). However, as a result of its specific pedogenic pattern, the pedogenic strength of the palaeosol did not reached the level of Udic Luvisols (Brown Soil). The hydroxyl-interlayered mineral presence in the 50–150 cm horizon only, also illuminated that the palaeosol was buried rapidly by post depositional loess during the abrupt cold-dry climate in the late Holocene. The contradiction between the type clay minerals present and the measured alkaline soil pH values in the palaeosol could be understood by the recalcification caused by the post-pedogenic leaching from the overlying loess.
Potential macro-detritivore range expansion into the subarctic stimulates litter decomposition: a new positive feedback mechanism to climate change?
Geffen, K.G. van; Berg, M.P. ; Aerts, R. - \ 2011
Oecologia 167 (2011)4. - ISSN 0029-8549 - p. 1163 - 1175.
leaf-litter - atmospheric co2 - elevated co2 - cold biomes - earthworms - quality - biodiversity - millipedes - rates - complementarity
As a result of low decomposition rates, high-latitude ecosystems store large amounts of carbon. Litter decomposition in these ecosystems is constrained by harsh abiotic conditions, but also by the absence of macro-detritivores. We have studied the potential effects of their climate change-driven northward range expansion on the decomposition of two contrasting subarctic litter types. Litter of Alnus incana and Betula pubescens was incubated in microcosms together with monocultures and all possible combinations of three functionally different macro-detritivores (the earthworm Lumbricus rubellus, isopod Oniscus asellus, and millipede Julus scandinavius). Our results show that these macro-detritivores stimulated decomposition, especially of the high-quality A. incana litter and that the macro-detritivores tested differed in their decomposition-stimulating effects, with earthworms having the largest influence. Decomposition processes increased with increasing number of macro-detritivore species, and positive net diveristy effects occurred in several macro-detritivore treatments. However, after correction for macro-detritivore biomass, all interspecific differences in macro-detritivore effects, as well as the positive effects of species number on subarctic litter decomposition disappeared. The net diversity effects also appeared to be driven by variation in biomass, with a possible exception of net diversity effects in mass loss. Based on these results, we conclude that the expected climate change-induced range expansion of macro-detritivores into subarctic regions is likely to result in accelerated decomposition rates. Our results also indicate that the magnitude of macro-detritivore effects on subarctic decomposition will mainly depend on macro-detritivore biomass, rather than on macro-detritivore species number or identity.
Modification of light utilization for skeletal growth by water flow in the scleractinian coral Galaxea fascicularis
Schutter, M. ; Kranenbarg, S. ; Wijffels, R.H. ; Verreth, J.A.J. ; Osinga, R. - \ 2011
Marine Biology 158 (2011)4. - ISSN 0025-3162 - p. 769 - 777.
reef coral - madracis-mirabilis - photosynthesis - calcification - oxygen - respiration - rates - temperatures - mechanisms - organisms
In this study, we tested the hypothesis that the importance of water flow for skeletal growth (rate) becomes higher with increasing irradiance levels (i.e. a synergistic effect) and that such effect is mediated by a water flow modulated effect on net photosynthesis. Four series of nine nubbins of G. fascicularis were grown at either high (600 µE m-2 s-1) or intermediate (300 µE m-2 s-1) irradiance in combination with either high (15–25 cm s-1) or low (5–10 cm s-1) flow. Growth was measured as buoyant weight and surface area. Photosynthetic rates were measured at each coral’s specific experimental irradiance and flow speed. Additionally, the instantaneous effect of water flow on net photosynthetic rate was determined in short-term incubations in a respirometric flowcell. A significant interaction was found between irradiance and water flow for the increase in buoyant weight, the increase in surface area, and specific skeletal growth rate, indicating that flow velocity becomes more important for coral growth with increasing irradiance levels. Enhancement of coral growth with increasing water flow can be explained by increased net photosynthetic rates. Additionally, the need for costly photo-protective mechanisms at low flow regimes could explain the differences in growth with flow.
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