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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Testing three approaches to estimate soil evaporation through a dry soil layer in a semi-arid area
Balugani, E. ; Lubczynski, M.W. ; Tol, C. van der; Metselaar, K. - \ 2018
Journal of Hydrology 567 (2018). - ISSN 0022-1694 - p. 405 - 419.
Arid - Dry soil layer - Semi-arid - Soil evaporation - Water vapour flow

Bare soils and grasslands in arid and semi-arid conditions constitute a large portion of the earth surface. Evaporation, which is the main component of the water balance in these conditions, often takes place through a dry soil layer (DSL). There is no scientific agreement yet on the DSL effects on evaporation rates. The implementations of three conceptual models of DSL-evaporation were tested for the simulation of evaporation rates in a semi-arid study area in Central Spain: (i) the daily-average model, based on the assumption that the daily average vapour transport in a DSL can be represented in analogy to isothermal liquid flow; (ii) the numerical model solving the Richards equation, in this case HYDRUS1D was used; and (iii) the pore-scale model, based on soil column experiments in laboratory conditions. The evaporation rates estimated by the three conceptual models for semi-arid field conditions were compared with the evaporation rates measured by an eddy covariance tower in the same area. The results indicate that the daily-average conceptual model assumption, in which the DSL has no effects on evaporation, does not hold in very dry conditions. The numerical model solving the Richards equation was not able to simulate the effects of the DSL on evaporation rates. The evaporation estimates obtained by the pore-scale conceptual model were closest to the eddy covariance measurements during the dry season, however this model was applicable only to the relatively steady evaporation conditions during afternoons and only assuming spatially constant DSL thickness.

Groei en productie van populier in Nederland
Jansen, J.J. ; Mohren, G.M.J. ; Schmidt, P. ; Goudzwaard, L. ; Oosterbaan, A. ; Ouden, J. den - \ 2018
Wageningen : Wageningen University & Research (FEM Groei en Productie rapport 2018-8) - 127
Between 1947 and 2000, growth and yield of Poplar was studied in the Netherlands. To the permanent plots measured by Becking and De Dorschkamp/IBN, the permanent sample plots from HOSP were added, resulting in 235 plots and 1808 recordings.The development of the mean height hm with age t was found to be best described by a Chapman-Richards-model, with adjustment factors for dense stand and for different parameters for forest stands, line plantings, and for aspen, using site index h25. The diameter development up to a height of 7 m was best described with a Gompertz-model in t, hm and the initial spacing (SP0).The basal area increment IG was best explained by a power function in which hm, age, h25 and the Becking-Hart spacing index S% are included. For S% > 29.2 the basal area increment dropped with a non-linear function in S%. For dense spacing and for line plantings, other models fitted best.Combining all models, a stand projection model was constructed, which described the plot develop-ment as measured reasonably well.Yield tables were made for forests with different spacing, for forests with a wide stand with and with-out systematically thinning, for forest with very dense spacing including mortality, for line plantings without thinning, and for aspen with heavy thinning from below
Genome-wide association study in 79,366 European-ancestry individuals informs the genetic architecture of 25-hydroxyvitamin D levels
Jiang, Xia ; O'Reilly, Paul F. ; Aschard, Hugues ; Hsu, Yi Hsiang ; Richards, J.B. ; Dupuis, Josée ; Ingelsson, Erik ; Karasik, David ; Pilz, Stefan ; Berry, Diane ; Kestenbaum, Bryan ; Zheng, Jusheng ; Luan, Jianan ; Sofianopoulou, Eleni ; Streeten, Elizabeth A. ; Albanes, Demetrius ; Lutsey, Pamela L. ; Yao, Lu ; Tang, Weihong ; Econs, Michael J. ; Wallaschofski, Henri ; Völzke, Henry ; Zhou, Ang ; Power, Chris ; McCarthy, Mark I. ; Michos, Erin D. ; Boerwinkle, Eric ; Weinstein, Stephanie J. ; Freedman, Neal D. ; Huang, Wen Yi ; Schoor, Natasja M. van; Velde, Nathalie van der; Groot, Lisette C.P.G.M. de; Enneman, Anke ; Cupples, L.A. ; Booth, Sarah L. ; Vasan, Ramachandran S. ; Liu, Ching Ti ; Zhou, Yanhua ; Ripatti, Samuli ; Ohlsson, Claes ; Vandenput, Liesbeth ; Lorentzon, Mattias ; Eriksson, Johan G. ; Shea, M.K. ; Houston, Denise K. ; Kritchevsky, Stephen B. ; Liu, Yongmei ; Lohman, Kurt K. ; Ferrucci, Luigi ; Peacock, Munro ; Gieger, Christian ; Beekman, Marian ; Slagboom, Eline ; Deelen, Joris ; Deelen, Joris ; Heemst, Diana van; Kleber, Marcus E. ; März, Winfried ; Boer, Ian H. De; Wood, Alexis C. ; Rotter, Jerome I. ; Rich, Stephen S. ; Robinson-Cohen, Cassianne ; Heijer, Martin Den; Jarvelin, Marjo Riitta ; Jarvelin, Marjo Riitta ; Cavadino, Alana ; Cavadino, Alana ; Joshi, Peter K. ; Wilson, James F. ; Hayward, Caroline ; Lind, Lars ; Michaëlsson, Karl ; Trompet, Stella ; Zillikens, M.C. ; Uitterlinden, Andre G. ; Rivadeneira, Fernando - \ 2018
Nature Communications 9 (2018)1. - ISSN 2041-1723
Vitamin D is a steroid hormone precursor that is associated with a range of human traits and diseases. Previous GWAS of serum 25-hydroxyvitamin D concentrations have identified four genome-wide significant loci (GC, NADSYN1/DHCR7, CYP2R1, CYP24A1). In this study, we expand the previous SUNLIGHT Consortium GWAS discovery sample size from 16,125 to 79,366 (all European descent). This larger GWAS yields two additional loci harboring genome-wide significant variants (P = 4.7×10 -9 at rs8018720 in SEC23A, and P = 1.9×10 -14 at rs10745742 in AMDHD1). The overall estimate of heritability of 25-hydroxyvitamin D serum concentrations attributable to GWAS common SNPs is 7.5%, with statistically significant loci explaining 38% of this total. Further investigation identifies signal enrichment in immune and hematopoietic tissues, and clustering with autoimmune diseases in cell-type-specific analysis. Larger studies are required to identify additional common SNPs, and to explore the role of rare or structural variants and gene-gene interactions in the heritability of circulating 25-hydroxyvitamin D levels.
Perennial Grass Bioenergy Cropping on Wet Marginal Land : Impacts on Soil Properties, Soil Organic Carbon, and Biomass During Initial Establishment
Das, Srabani ; Teuffer, Karin ; Stoof, Cathelijne R. ; Walter, Michael F. ; Walter, M.T. ; Steenhuis, Tammo S. ; Richards, Brian K. - \ 2018
Bio Energy Research 11 (2018)2. - ISSN 1939-1234 - p. 262 - 276.
Active carbon - Marginal soil - Reed canarygrass - Soil organic carbon - Switchgrass - Wet aggregate stability
The control of soil moisture, vegetation type, and prior land use on soil health parameters of perennial grass cropping systems on marginal lands is not well known. A fallow wetness-prone marginal site in New York (USA) was converted to perennial grass bioenergy feedstock production. Quadruplicate treatments were fallow control, reed canarygrass (Phalaris arundinaceae L. Bellevue) with nitrogen (N) fertilizer (75 kg N ha−1), switchgrass (Panicum virgatum L. Shawnee), and switchgrass with N fertilizer (75 kg N ha−1). Based on periodic soil water measurements, permanent sampling locations were assigned to various wetness groups. Surface (0–15 cm) soil organic carbon (SOC), active carbon, wet aggregate stability, pH, total nitrogen (TN), root biomass, and harvested aboveground biomass were measured annually (2011–2014). Multi-year decreases in SOC, wet aggregate stability, and pH followed plowing in 2011. For all years, wettest soils had the greatest SOC and active carbon, while driest soils had the greatest wet aggregate stability and lowest pH. In 2014, wettest soils had significantly (p < 0.0001) greater SOC and TN than drier soils, and fallow soils had 14 to 20% greater SOC than soils of reed canarygrass + N, switchgrass, and switchgrass + N. Crop type and N fertilization did not result in significant differences in SOC, active carbon, or wet aggregate stability. Cumulative 3-year aboveground biomass yields of driest switchgrass + N soils (18.8 Mg ha−1) were 121% greater than the three wettest switchgrass (no N) treatments. Overall, soil moisture status must be accounted for when assessing soil dynamics during feedstock establishment.
Effects of sediment resuspension on the oxidation of acid-volatile sulfides and release of metals (iron, manganese, zinc) in Pescadero estuary (CA, USA)
Richards, Chandra M. ; Puffelen, Jasper L. van; Pallud, Céline - \ 2018
Environmental Toxicology and Chemistry 37 (2018)4. - ISSN 0730-7268 - p. 993 - 1006.
Acid-volatile sulfide - Hydrogen sulfide - Metal dissolution - Sediment chemistry - Water quality
Bar-built estuaries are unique ecosystems characterized by the presence of a sandbar barrier, which separates the estuary from the ocean for extended periods and can naturally reopen to the ocean with heavy rainfall and freshwater inflows. The physical effects associated with the transition from closed to open state, specifically water mixing and sediment resuspension, often indirectly worsen water quality conditions and are suspected to drive near-annual fish kills at the Pescadero estuary in northern California. The effects of sediment acid-volatile sulfide (AVS) oxidation, specifically oxygen depletion, acidification, and metal release, are believed to aggravate water conditions for fish but remain poorly understood. We performed slurry incubations containing sediment from 4 sites in the Pescadero estuary, representing a gradient from the Pacific Ocean to freshwater tributaries. We measured near-maximum rates of aqueous hydrogen sulfide oxidation, sediment AVS oxidation, sulfate production, and acidification, as well as near-maximum release rates of iron (Fe), manganese (Mn), and zinc (Zn) to the water column. We estimated AVS oxidation rates of 8 to 21mmolSkg-1 d-1, which were 3 orders of magnitude higher than aqueous hydrogen sulfide oxidation rates, 6 to 26μmolSkg-1 d-1. We suggest that aqueous hydrogen sulfide cannot be responsible for the observed kills because of low concentrations and minimal oxidative effects on pH and metal concentrations. However, the oxidative effects of AVS are potentially severe, decreasing pH to strongly acidic levels and releasing aqueous Fe, Mn, and Zn concentrations up to 11.2mM, 0.46mM, and 88μM, respectively, indicating a potential role in worsening water conditions for fish in the Pescadero estuary.
The rumen microbiome : An underexplored resource for novel antimicrobial discovery
Oyama, Linda B. ; Girdwood, Susan E. ; Cookson, Alan R. ; Fernandez-Fuentes, Narcis ; Privé, Florence ; Vallin, Hannah E. ; Wilkinson, Toby J. ; Golyshin, Peter N. ; Golyshina, Olga V. ; Mikut, Ralf ; Hilpert, Kai ; Richards, Jennifer ; Wootton, Mandy ; Edwards, Joan E. ; Maresca, Marc ; Perrier, Josette ; Lundy, Fionnuala T. ; Luo, Yu ; Zhou, Mei ; Hess, Matthias ; Mantovani, Hilario C. ; Creevey, Christopher J. ; Huws, Sharon A. - \ 2017
npj Biofilms and Microbiomes 3 (2017)1. - ISSN 2055-5008
Antimicrobial peptides (AMPs) are promising drug candidates to target multi-drug resistant bacteria. The rumen microbiome presents an underexplored resource for the discovery of novel microbial enzymes and metabolites, including AMPs. Using functional screening and computational approaches, we identified 181 potentially novel AMPs from a rumen bacterial metagenome. Here, we show that three of the selected AMPs (Lynronne-1, Lynronne-2 and Lynronne-3) were effective against numerous bacterial pathogens, including methicillin-resistant Staphylococcus aureus (MRSA). No decrease in MRSA susceptibility was observed after 25 days of sub-lethal exposure to these AMPs. The AMPs bound preferentially to bacterial membrane lipids and induced membrane permeability leading to cytoplasmic leakage. Topical administration of Lynronne-1 (10% w/v) to a mouse model of MRSA wound infection elicited a significant reduction in bacterial counts, which was comparable to treatment with 2% mupirocin ointment. Our findings indicate that the rumen microbiome may provide viable alternative antimicrobials for future therapeutic application.
Low-Frequency Synonymous Coding Variation in CYP2R1 Has Large Effects on Vitamin D Levels and Risk of Multiple Sclerosis
Manousaki, Despoina ; Dudding, Tom ; Haworth, Simon ; Hsu, Yi Hsiang ; Liu, Ching Ti ; Medina-Gómez, Carolina ; Voortman, Trudy ; Velde, Nathalie Van Der; Melhus, Håkan ; Vandenput, Liesbeth ; Noordam, Raymond ; Forgetta, Vincenzo ; Greenwood, Celia M.T. ; Biggs, Mary L. ; Psaty, Bruce M. ; Rotter, Jerome I. ; Zemel, Babette S. ; Mitchell, Jonathan A. ; Taylor, Bruce ; Lorentzon, Mattias ; Karlsson, Magnus ; Jaddoe, Vincent W.V. ; Tiemeier, Henning ; Campos-Obando, Natalia ; Franco, Oscar H. ; Utterlinden, Andre G. ; Broer, Linda ; Schoor, Natasja M. van; Ham, Annelies C. ; Ikram, Arfan M.A. ; Karasik, David ; Mutsert, Renée De; Rosendaal, Frits R. ; Heijer, Martin den; Wang, Thomas J. ; Lind, Lars ; Orwoll, Eric S. ; Mook-Kanamori, Dennis O. ; Michaëlsson, Karl ; Kestenbaum, Bryan ; Ohlsson, Claes ; Mellström, Dan ; Groot, Lisette C.P.G.M. de; Grant, Struan F.A. ; Kiel, Douglas P. ; Zillikens, M.C. ; Rivadeneira, Fernando ; Sawcer, Stephen ; Timpson, Nicholas J. ; Richards, J.B. - \ 2017
American Journal of Human Genetics 101 (2017)2. - ISSN 0002-9297 - p. 227 - 238.
GWAS - Low-frequency genetic variants - Multiple sclerosis - Vitamin D
Vitamin D insufficiency is common, correctable, and influenced by genetic factors, and it has been associated with risk of several diseases. We sought to identify low-frequency genetic variants that strongly increase the risk of vitamin D insufficiency and tested their effect on risk of multiple sclerosis, a disease influenced by low vitamin D concentrations. We used whole-genome sequencing data from 2,619 individuals through the UK10K program and deep-imputation data from 39,655 individuals genotyped genome-wide. Meta-analysis of the summary statistics from 19 cohorts identified in CYP2R1 the low-frequency (minor allele frequency = 2.5%) synonymous coding variant g.14900931G>A (p.Asp120Asp) (rs117913124[A]), which conferred a large effect on 25-hydroxyvitamin D (25OHD) levels (-0.43 SD of standardized natural log-transformed 25OHD per A allele; p value = 1.5 × 10-88). The effect on 25OHD was four times larger and independent of the effect of a previously described common variant near CYP2R1. By analyzing 8,711 individuals, we showed that heterozygote carriers of this low-frequency variant have an increased risk of vitamin D insufficiency (odds ratio [OR] = 2.2, 95% confidence interval [CI] = 1.78-2.78, p = 1.26 × 10-12). Individuals carrying one copy of this variant also had increased odds of multiple sclerosis (OR = 1.4, 95% CI = 1.19-1.64, p = 2.63 × 10-5) in a sample of 5,927 case and 5,599 control subjects. In conclusion, we describe a low-frequency CYP2R1 coding variant that exerts the largest effect upon 25OHD levels identified to date in the general European population and implicates vitamin D in the etiology of multiple sclerosis.
Hotspots of nitrous oxide emission in fertilized and unfertilized perennial grasses
Mason, Cedric W. ; Stoof, Cathelijne R. ; Richards, Brian K. ; Das, Srabani ; Goodale, Christine L. ; Steenhuis, Tammo S. - \ 2017
Soil Science Society of America Journal 81 (2017)3. - ISSN 0361-5995 - p. 450 - 458.
Hotspots of nitrous oxide (N2O) emission are thought to contribute substantially to annual emissions from agricultural soils. We observed N2O fluxes from fertilized and unfertilized C3 and C4 perennial grasses on a wet silt loam soil in New York, United States during the growing season in 2013, 2014, and 2015 using static chambers. Analysis of N2O hotspots within the research plots revealed that hotspots contributed between 34.3 and 39.1% of the total emissions, and constituted between 0.8% and 5.0% of all flux observations. Hotspots were more frequent and of greater magnitude in the fertilized treatments, and occurred when soil temperature was greater than 9.1°C and soil moisture was between about 40% and 80% water filled pore space (WFPS). A single chamber location in the fertilized switchgrass treatment was consistently a hotspot for N2O emission, suggesting that hotspots maintain a stable spatial pattern over extended periods. The maximum magnitude of N2O hotspot emission exhibited a relationship to soil temperature that is similar to that of the microbial growth rate constant.
Managing resources through stakeholder networks : collaborative water governance for Lake Naivasha basin, Kenya
Ogada, Job Ochieng ; Krhoda, George Okoye ; Veen, Anne Van Der; Marani, Martin ; Oel, Pieter Richards van - \ 2017
Water International 42 (2017)3. - ISSN 0250-8060 - p. 271 - 290.
Collaborative water governance - Kenya - Lake Naivasha basin - social networks - stakeholder analysis
Stakeholder analysis and social network analysis were used to analyze stakeholders’ social and structural characteristics based on their interests, influence and interactions in Lake Naivasha basin, Kenya. Even though the Kenyan government and its agencies seem to command higher influence and interest in water resource management, the presence of influential and central stakeholders from non-government sectors plays a key role in strengthening partnership in a governance environment with multiple sectors, complex issues and competing interests. Interactions in the basin are guided by stakeholders’ interest and sphere of influence, which have both promoted participation in implementing a collaborative water governance framework.
A framework for determining unsaturated zone water quality time lags at catchment scale
Vero, Sara E. ; Healy, Mark G. ; Henry, Tiernan ; Creamer, Rachel E. ; Ibrahim, Tristan G. ; Richards, Karl G. ; Mellander, Per Erik ; McDonald, Noeleen T. ; Fenton, Owen - \ 2017
Agriculture, Ecosystems and Environment 236 (2017). - ISSN 0167-8809 - p. 234 - 242.
Nitrate - Soil - Time lag - Unsaturated - Water framework directive
The responses of waterbodies to agricultural programmes of measures are frequently delayed by hydrological time lags through the unsaturated zone and groundwater. Time lag may therefore, impede the achievement of remediation deadlines such as those described in the EU Water Framework Directive (WFD). Omitting time lag from catchment characterisation renders evaluation of management practices impossible. Time lag aside, regulators at national scale can only manage the expectations of policy-makers at larger scales (e.g. European Union) by demonstrating positive nutrient trajectories in catchments failing to achieve at least ‘good’ status. Presently, a flexible tool for developing spatial and temporal estimates of trends in water quality/nutrient transport and time lags is not available. The objectives of the present study were first to develop such a flexible, parsimonious framework incorporating existing soil maps, meteorological data and a structured modelling approach, and to secondly, to demonstrate its use in a grassland and an arable catchment (∼10 km2) in Ireland, assuming full implementation of measures in 2012. Data pertaining to solute transport (meteorology, soil hydraulics, depth of profile and boundary conditions) were collected for both catchments. Low complexity textural data alone gave comparable estimates of nutrient trajectories and time lags but with no spatial or soil series information. Taking a high complexity approach, coupling high resolution soil mapping (1:10,000) with national scale (1:25,000) representative profile datasets to <5 m depth, indicated trends in nutrient transport of 10–12 months and 13–17 months throughout the grassland and arable catchments, respectively. For the same conditions, regulators relying on data from groundwater sampling to test the efficacy of the present measures would be delayed by 61–76 months and 46–79 months, respectively. Variation in meteorological datasets enabled temporal analysis of the trends in nutrient transport and time lag estimates. Such a tool could help catchment scientists to better characterise and manage catchments, determine locations for monitoring or mitigation, assess the efficacy of current measures, and ultimately, advise policy makers and regulators.
Methods for environment: Productivity trade-off analysis in agricultural systems
Wijk, M.T. van; Klapwijk, C.J. ; Rosenstock, T.S. ; Asten, P.J.A. van; Thornton, P.K. ; Giller, K.E. - \ 2016
In: Methods for Measuring Greenhouse Gas Balances and Evaluating Mitigation Options in Smallholder Agriculture / , T.S. Rosenstock, Rufino, M.C., Butterbach-Bahl, K., Wollenberg, E., Richards, M., Cham : Springer International Publishing - ISBN 9783319297927 - p. 189 - 198.
Trade-off analysis has become an increasingly important approach for evaluating system level outcomes of agricultural production and for prioritising and targeting management interventions in multi-functional agricultural landscapes. We review the strengths and weakness of different techniques available for performing trade-off analysis. These techniques, including mathematical programming and participatory approaches, have developed substantially in recent years aided by mathematical advancement, increased computing power, and emerging insights into systems behaviour. The strengths and weaknesses of the different approaches are identified and discussed, and we make suggestions for a tiered approach for situations with different data availability.
Reducing emissions from agriculture to meet the 2 °C target
Wollenberg, Eva ; Richards, Meryl ; Smith, Pete ; Havlík, Petr ; Obersteiner, Michael ; Tubiello, Francesco N. ; Herold, Martin ; Gerber, Pierre ; Carter, Sarah ; Reisinger, Andrew ; Vuuren, Detlef P. van; Dickie, Amy ; Neufeldt, Henry ; Sander, Björn O. ; Wassmann, Reiner ; Sommer, Rolf ; Amonette, James E. ; Falcucci, Alessandra ; Herrero, Mario ; Opio, Carolyn ; Roman-cuesta, Rosa Maria ; Stehfest, Elke ; Westhoek, Henk ; Ortiz-Monasterio, Ivan ; Sapkota, Tek ; Rufino, Mariana C. ; Thornton, Philip K. ; Verchot, Louis V. ; West, Paul C. ; Soussana, Jean-François ; Baedeker, Tobias ; Sadler, Marc ; Vermeulen, Sonja ; Campbell, Bruce M. - \ 2016
Global Change Biology 22 (2016)12. - ISSN 1354-1013 - p. 3859 - 3864.
More than 100 countries pledged to reduce agricultural greenhouse gas (GHG) emissions in the 2015 Paris Agreement of the United Nations Framework Convention on Climate Change. Yet technical information about how much mitigation is needed in the sector vs. how much is feasible remains poor. We identify a preliminary global target for reducing emissions from agriculture of ~1 GtCO2e yr−1 by 2030 to limit warming in 2100 to 2 °C above pre-industrial levels. Yet plausible agricultural development pathways with mitigation cobenefits deliver only 21–40% of needed mitigation. The target indicates that more transformative technical and policy options will be needed, such as methane inhibitors and finance for new practices. A more comprehensive target for the 2 °C limit should be developed to include soil carbon and agriculture-related mitigation options. Excluding agricultural emissions from mitigation targets and plans will increase the cost of mitigation in other sectors or reduce the feasibility of meeting the 2 °C limit.
A methodological framework to determine optimum durations for the construction of soil water characteristic curves using centrifugation
Vero, Sara E. ; Healy, Mark G. ; Henry, Tiernan ; Creamer, Rachel E. ; Ibrahim, Tristan G. ; Forrestal, Patrick J. ; Richards, Karl G. ; Fenton, Owen - \ 2016
Irish Journal of Agricultural and Food Research 55 (2016)2. - ISSN 0791-6833 - p. 91 - 99.
Centrifuge - Equilibrium - Soil water characteristic curve

During laboratory assessment of the soil water characteristic curve (SWCC), determining equilibrium at various pressures is challenging. This study establishes a methodological framework to identify appropriate experimental duration at each pressure step for the construction of SWCCs via centrifugation. Three common temporal approaches to equilibrium – 24-, 48- and 72-h – are examined, for a grassland and arable soil. The framework highlights the differences in equilibrium duration between the two soils. For both soils, the 24-h treatment significantly overestimated saturation. For the arable site, no significant difference was observed between the 48- and 72-h treatments. Hence, a 48-h treatment was sufficient to determine ‘effective equilibrium’. For the grassland site, the 48- and 72-h treatments differed significantly. This highlights that a more prolonged duration is necessary for some soils to conclusively determine that effective equilibrium has been reached. This framework can be applied to other soils to determine the optimum centrifuge durations for SWCC construction.

Nitrous Oxide and Methane Fluxes from Smallholder Farms: A Scoping Study in the Anjeni Watershed.
Bayabil, Haimanote K. ; Stoof, C.R. ; Mason, C. ; Richards, B.K. ; Steenhuis, T.S. - \ 2016
Climate 4 (2016)4. - ISSN 2225-1154
While agricultural practices are widely reported to contribute to anthropogenic greenhouse gas (GHG) emissions, there are only limited measurements available for emission rates in the monsoon climate of the African continent. We conducted a scoping study to measure nitrous oxide (N2O-N) and methane (CH4) emission rates from 24 plots constructed on smallholder agricultural farms along the slope catena of three transects in the sub-humid Anjeni watershed in the Ethiopian highlands. Greenhouse gas flux samples were collected in 2013, before, towards the end, and after the rainy monsoon phase. At each location, three plots were installed in groups: two plots grown with barley (one enriched with charcoal and the other without soil amendment) and lupine was grown on the third plot without any soil amendment. Preliminary study results showed that nitrous oxide emission rates varied from −275 to 522 μg·m−2·h−1 and methane emissions ranged from −206 to 264 μg·m−2·h−1 with overall means of 51 and 5 μg·m−2·h−1 for N2O-N and CH4, respectively. Compared with the control, charcoal and lupine plots had elevated nitrous oxide emissions. Plots amended with charcoal showed on average greater methane uptake than was emitted. While this study provides insights regarding nitrous oxide and methane emission levels from smallholder farms, studies of longer durations are needed to verify the results
Improved ruminant genetics: Implementation guidance for policymakers and investors
Haas, Y. de; Davis, S. ; Reisinger, A. ; Richards, M. ; Difford, Gareth ; Lassen, Jan - \ 2016
Genetics makes use of natural variation among animals. Selecting preferred animals as parents can yield permanent and cumulative improvements in the population. More efficient animals can greatly reduce greenhouse gas emissions and feed costs. Breeding, including cross-breeding between indigenous and imported species, can also improve resilience to diseases and heat stress and increase reproductive performance.
Predicting bee community responses to land-use changes : Effects of geographic and taxonomic biases
Palma, Adriana De; Abrahamczyk, Stefan ; Aizen, Marcelo A. ; Albrecht, Matthias ; Basset, Yves ; Bates, Adam ; Blake, Robin J. ; Boutin, Céline ; Bugter, Rob ; Connop, Stuart ; Cruz-López, Leopoldo ; Cunningham, Saul A. ; Darvill, Ben ; Diekötter, Tim ; Dorn, Silvia ; Downing, Nicola ; Entling, Martin H. ; Farwig, Nina ; Felicioli, Antonio ; Fonte, Steven J. ; Fowler, Robert ; Franzén, Markus ; Goulson, Dave ; Grass, Ingo ; Hanley, Mick E. ; Hendrix, Stephen D. ; Herrmann, Farina ; Herzog, Felix ; Holzschuh, Andrea ; Jauker, Birgit ; Kessler, Michael ; Knight, M.E. ; Kruess, Andreas ; Lavelle, Patrick ; Féon, Violette Le; Lentini, Pia ; Malone, Louise A. ; Marshall, Jon ; Pachón, Eliana Martínez ; McFrederick, Quinn S. ; Morales, Carolina L. ; Mudri-Stojnic, Sonja ; Nates-Parra, Guiomar ; Nilsson, Sven G. ; Öckinger, Erik ; Osgathorpe, Lynne ; Parra-H, Alejandro ; Peres, Carlos A. ; Persson, Anna S. ; Petanidou, Theodora ; Poveda, Katja ; Power, Eileen F. ; Quaranta, Marino ; Quintero, Carolina ; Rader, Romina ; Richards, Miriam H. ; Roulston, Tai ; Rousseau, Laurent ; Sadler, Jonathan P. ; Samnegård, Ulrika ; Schellhorn, Nancy A. ; Schüepp, Christof ; Schweiger, Oliver ; Smith-Pardo, Allan H. ; Steffan-Dewenter, Ingolf ; Stout, Jane C. ; Tonietto, Rebecca K. ; Tscharntke, Teja ; Tylianakis, Jason M. ; Verboven, Hans A.F. ; Vergara, Carlos H. ; Verhulst, Jort ; Westphal, Catrin ; Yoon, Hyung Joo ; Purvis, Andy - \ 2016
Scientific Reports 6 (2016). - ISSN 2045-2322 - 14 p.

Land-use change and intensification threaten bee populations worldwide, imperilling pollination services. Global models are needed to better characterise, project, and mitigate bees' responses to these human impacts. The available data are, however, geographically and taxonomically unrepresentative; most data are from North America and Western Europe, overrepresenting bumblebees and raising concerns that model results may not be generalizable to other regions and taxa. To assess whether the geographic and taxonomic biases of data could undermine effectiveness of models for conservation policy, we have collated from the published literature a global dataset of bee diversity at sites facing land-use change and intensification, and assess whether bee responses to these pressures vary across 11 regions (Western, Northern, Eastern and Southern Europe; North, Central and South America; Australia and New Zealand; South East Asia; Middle and Southern Africa) and between bumblebees and other bees. Our analyses highlight strong regionally-based responses of total abundance, species richness and Simpson's diversity to land use, caused by variation in the sensitivity of species and potentially in the nature of threats. These results suggest that global extrapolation of models based on geographically and taxonomically restricted data may underestimate the true uncertainty, increasing the risk of ecological surprises.

Implications and application of the Raats superclass of soils equations
Heinen, Marius ; Bakker, Gerben - \ 2016
Vadose Zone Journal 15 (2016)8. - ISSN 1539-1663 - 12 p.

According to the Richards equation, the capacity of a soil to hold and conduct water is determined by the water retention and hydraulic conductivity characteristics. Many mathematical relationships have been proposed in the literature to describe these characteristics. Raats introduced a general functional relationship with only four parameters that included as special cases four pre-1990 models found in the literature, including the well-known relationships by Mualem-van Genuchten and Brooks and Corey. The aims of this study were (i) to discuss this general functional relationship and its four special cases, (ii) to present expressions for the differential moisture capacity, water diffusivity, and matric flux potential corresponding to the general functional relationship and its special cases, (iii) to discuss methods for determining the parameter elasticity and sensitivity, and (iv) to apply the Raats model to experimental data. Soil water retention and hydraulic conductivity data for 11 soils were used to optimize the values of the four major parameters in the Raats model. In none of the cases did the optimized coefficients indicate that the Raats model approached one of the four submodels that it includes.

Genetic and epigenetic differences associated with environmental gradients in replicate populations of two salt marsh perennials
Foust, C.M. ; Preite, V. ; Schrey, A.W. ; Alvarez, M. ; Robertson, M.H. ; Verhoeven, K.J.F. ; Richards, Christina L. - \ 2016
Molecular Ecology 25 (2016)8. - ISSN 0962-1083 - p. 1639 - 1652.
While traits and trait plasticity are partly genetically based, investigating epigenetic mechanisms may provide more nuanced understanding of the mechanisms underlying response to environment. Using AFLP and methylation-sensitive AFLP, we tested the hypothesis that differentiation to habitats along natural salt marsh environmental gradients occurs at epigenetic, but not genetic loci in two salt marsh perennials. We detected significant genetic and epigenetic structure among populations and among subpopulations, but we found multilocus patterns of differentiation to habitat type only in epigenetic variation for both species. In addition, more epigenetic than genetic loci were correlated with habitat in both species. When we analysed genetic and epigenetic variation simultaneously with partial Mantel, we found no correlation between genetic variation and habitat and a significant correlation between epigenetic variation and habitat in Spartina alterniflora. In Borrichia frutescens, we found significant correlations between epigenetic and/or genetic variation and habitat in four of five populations when populations were analysed individually, but there was no significant correlation between genetic or epigenetic variation and habitat when analysed jointly across the five populations. These analyses suggest that epigenetic mechanisms are involved in the response to salt marsh habitats, but also that the relationships among genetic and epigenetic variation and habitat vary by species. Site-specific conditions may also cloud our ability to detect response in replicate populations with similar environmental gradients. Future studies analysing sequence data and the correlation between genetic variation and DNA methylation will be powerful to identify the contributions of genetic and epigenetic response to environmental gradients.
Get Local’: ICT, Tourism and Community Place Making in Auckland, New Zealand
Milne, S. ; Deuchar, Carolyn ; Peters, K.B.M. - \ 2016
In: Reinventing the Local in Tourism / Russo, A.P., Richards, G., Channel View Publications - ISBN 9781845415686 - p. 101 - 116.
Modeling of horizontal water redistribution in an unsaturated soil
Zhuang, Luwen ; Hassanizadeh, S.M. ; Genuchten, Martinus Th. van; Leijnse, Toon ; Raoof, Amir ; Qin, Chaozhong - \ 2016
Vadose Zone Journal 15 (2016)3. - ISSN 1539-1663 - 11 p.

When two soil samples with the same hydraulic properties but different initial water saturations are brought into contact, water will redistribute horizontally between the samples until some equilibrium is reached. The part with a higher initial saturation undergoes drainage while imbibition occurs including scanning curves). This approach assumes continuity in the water pressure and flux across the contact surface between the two sides. In the second approach, we used an extended two-phase flow formulation based on rational thermodynamics principles and involving the air–water specific interfacial area. For this approach, we used continuity in the Gibbs free energy for air–water interfaces and the interfacial area flux as additional conditions at the contact surface. We employed two different initial conditions: uniform initial saturation for each side and slightly nonuniform initial saturation distributions consistent with the measured water contents. We compared results of both models with measurements. The Richards equation with full hysteresis could not reproduce the measured saturation distribution unless an unrealistic value of the imbibition retention curve was assigned. The interfacial area model compared well with the experimental data after optimization of some of the model parameters.

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