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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    Integration of Algae to Improve Nitrogenous Waste Management in Recirculating Aquaculture Systems : A Review
    Ramli, Norulhuda Mohamed ; Verreth, J.A.J. ; Yusoff, Fatimah M. ; Nurulhuda, K. ; Nagao, N. ; Verdegem, Marc C.J. - \ 2020
    Frontiers in Bioengineering and Biotechnology 8 (2020). - ISSN 2296-4185
    algal cultivation - ammonia - HRT - nitrate - nitrogen - recirculating aquaculture system - removal rates

    This review investigates the performance and the feasibility of the integration of an algal reactor in recirculating aquaculture systems (RAS). The number of studies related to this topic is limited, despite the apparent benefit of algae that can assimilate part of the inorganic waste in RAS. We identified two major challenges related to algal integration in RAS: first, the practical feasibility for improving nitrogen removal performance by algae in RAS; second, the economic feasibility of integrating an algal reactor in RAS. The main factors that determine high algal nitrogen removal rates are light and hydraulic retention time (HRT). Besides these factors, nitrogen-loading rates and RAS configuration could be important to ensure algal performance in nitrogen removal. Since nitrogen removal rate by algae is determined by HRT, this will affect the size (area or volume) of the algal reactor due to the time required for nutrient uptake by algae and large surface area needed to capture enough light. Constraints related to design, space, light capture, and reactor management could incur additional cost for aquaculture production. However, the increased purification of RAS wastewater could reduce the cost of water discharge in places where this is subject to levees. We believe that an improved understanding of how to manage the algal reactor and technological advancement of culturing algae, such as improved algal reactor design and low-cost artificial light, will increase the practical and economic feasibility of algal integration in RAS, thus improving the potential of mass cultivation of algae in RAS.

    Minimising emissions to water bodies from NW European greenhouses; with focus on Dutch vegetable cultivation
    Salm, Caroline van der; Voogt, Wim ; Beerling, Ellen ; Ruijven, Jim van; Os, Erik van - \ 2020
    Agricultural Water Management 242 (2020). - ISSN 0378-3774
    drainage - DSS model - fertigation - hydroponics - irrigation - leaching - lysimeter - nitrogen - nutrients - pesticides - plant protection products - recirculation - soil grown - soil moisture sensor - substrate - water framework directive

    In large parts of the Netherlands surface water quality does not meet the chemical and ecological standards as indicated by the EU Water Framework Directive (WFD). The largest exceedances were found in areas with greenhouse horticulture, flower bulbs, fruit trees and ornamental trees. Several regulations have been implemented to improve water quality in greenhouse areas, leading finally to a target for zero emission of nutrients by 2027 in soilless cultivation and rules to minimise losses in soil bound cultivation. In addition to that an obligation exists to remove plant protection products (PPPs) from drain water by 2018 onwards. For soilless cultivation a Zero Liquid Discharge (ZLD) system gives the best options to reach these goals. For soil-bound cultivation the situation is more complicated and a combination of tools and measurements to help the farmer to tune irrigation to crop demand is most promising. These approaches will lead to a substantial decrease in losses of nutrients and PPPs to surface water. However, it is uncertain whether this will lead to the desired reduction in emissions and the water quality standards of the WFD in 2027. Obstacles might be problems with soil-bound cultivation, leakages in soilless cultivation and sodium limitations in certain crops.

    Applying a mechanistic fermentation and digestion model for dairy cows with emission and nutrient cycling inventory and accounting methodology
    Bannink, A. ; Zom, R.L.G. ; Groenestein, K.C. ; Dijkstra, J. ; Sebek, L.B.J. - \ 2020
    Animal 14 (2020)S2. - ISSN 1751-7311 - p. 406 - 416.
    digestibility - enteric methane - farm accounting - nitrogen - Tier 3

    In mitigating greenhouse gas (GHG) emissions and reducing the carbon footprint of dairy milk, the use of generic estimates in inventory and accounting methodology at farm level largely ignores variation of on-farm GHG emissions. The present study aimed to implement results of an extant dynamic, mechanistic Tier 3 model for enteric methane (CH4) (applied in Dutch national GHG inventory) in order to capture variation in enteric CH4 emission, and in faecal N and organic matter (OM) digestibility, ultimately required to predict manure CH4 and ammonia emission. Tier 3 model predictions were translated into calculation rules that could easily be implemented in an annual nutrient cycling assessment tool including GHG emissions, which is currently used by Dutch dairy farmers. Calculations focussed on (1) enteric CH4 emission, (2) apparent faecal OM digestibility and (3) apparent faecal N digestibility. Enteric CH4 was expressed in CH4 yield indicated with the term emission factor (EF; g CH4/kg DM) for individual dietary components and feedstuffs. Factors investigated to cover predicted variation in EF value included the level of feed intake, the type of roughage fed (proportions of grass silage and maize silage) and the quality of roughage fed. A minimum number of three classes of roughage type (i.e. 0. 40% and 80% maize silage in roughage DM) appeared necessary to obtain correspondence between interpolated EF values from EF lists and Tier 3 model predictions. A linear decline in EF value with 1% per kg increase in DM intake is adopted based on model simulations. The quality of roughage was represented by the effect of maturity of harvested grass or of the whole plant maize at cutting, based on a survey of modelling as well as experimental work. Also, predictions were assembled for apparent faecal OM digestibility which could be used in national inventory and in farm accounting. Apparent faecal N digestibility (as a major determinant of predicted urinary N excretion) was predicted, to support current Dutch national ammonia emission inventory and to correct the level of N digestibility in farm accounting. Compared to generic values or values retrieved from the Dutch feeding tables, predicted OM and N digestibility and enteric CH4 are better rooted in physiological principles and better reflect observed variation under experimental conditions. The present results apply for conditions with fairly intensive grassland management in temperate regions.

    Data and R code: Bioconversion efficiencies, greenhouse gas and ammonia emissions during black soldier fly rearing – a mass balance approach
    Parodi, Alejandro ; Boer, Imke de; Gerrits, Walter ; Loon, Joop van; Heetkamp, Marcel ; Schelt, Jeroen van; Bolhuis, Liesbeth ; Zanten, Hannah van - \ 2020
    Wageningen University & Research
    ammonia - bioconversion - emissions - GHG - Hermetia illucens - nitrogen
    Contains data and R code for analysis and visualizations of the study Bioconversion efficiencies, greenhouse gas and ammonia emissions during black soldier fly rearing.
    Review: Impact of protein and energy supply on the fate of amino acids from absorption to milk protein in dairy cows
    Lapierre, H. ; Martineau, R. ; Hanigan, M.D. ; Lingen, H.J. Van; Kebreab, E. ; Spek, J.W. ; Ouellet, D.R. - \ 2020
    Animal 14 (2020)S1. - ISSN 1751-7311 - p. S87 - S102.
    efficiency - formulation - nitrogen - ration - requirement

    Making dairy farming more cost-effective and reducing nitrogen environmental pollution could be reached through a reduced input of dietary protein, provided productivity is not compromised. This could be achieved through balancing dairy rations for essential amino acids (EAA) rather than their aggregate, the metabolizable protein (MP). This review revisits the estimations of the major true protein secretions in dairy cows, milk protein yield (MPY), metabolic fecal protein (MFP), endogenous urinary loss and scurf and associated AA composition. The combined efficiency with which MP (EffMP) or EAA (EffAA) is used to support protein secretions is calculated as the sum of true protein secretions (MPY + MFP + scurf) divided by the net supply (adjusted to remove the endogenous urinary excretion: MPadj and AAadj). Using the proposed protein and AA secretions, EffMP and EffAA were predicted through meta-analyses (807 treatment means) and validated using an independent database (129 treatment means). The effects of MPadj or AAadj, plus digestible energy intake (DEI), days in milk (DIM) and parity (primiparous v. multiparous), were significant in all models. Models using (MPadj, MPadj × MPadj, DEI and DEI × DEI) or (MPadj/DEI and MPadj/DEI × MPadj/DEI) had similar corrected Akaike's information criterion, but the model using MPadj/DEI performed better in the validation database. A model that also included this ratio was, therefore, used to fitting equations to predict EffAA. These equations predicted well EffAA in the validation database except for Arg which had a strong slope bias. Predictions of MPY from predicted EffMP based on MPadj/DEI, MPadj/DEI × MPadj/DEI, DIM and parity yielded a better fit than direct predictions of MPY based on MPadj, MPadj × MPadj, DEI, DIM and parity. Predictions of MPY based on each EffAA yielded fairly similar results among AA. It is proposed to ponder the mean of MPY predictions obtained from each EffAA by the lowest prediction to retain the potential limitation from AA with the shortest supply. Overall, the revisited estimations of endogenous urinary excretion and MFP, revised AA composition of protein secretions and inclusion of a variable combined EffAA (based on AAadj/DEI, AAadj/DEI × Aadj/DEI, DIM and parity) offer the potential to improve predictions of MPY, identify which AA are potentially in short supply and, therefore, improve the AA balance of dairy rations.

    Can the presence of plantain (Plantago lanceolata L.) improve nitrogen cycling of dairy grassland systems on peat soils?
    Pijlman, Jeroen ; Berger, Stijn J. ; Lexmond, Fay ; Bloem, Jaap ; Groenigen, Jan Willem van; Visser, Eric J.W. ; Erisman, Jan Willem ; Eekeren, Nick van - \ 2020
    New Zealand Journal of Agricultural Research 63 (2020)1. - ISSN 0028-8233 - p. 102 - 122.
    grassland - nitrification - nitrogen - nitrous oxide - peat - Plantain

    Reactive nitrogen (N) losses, and in particular nitrous oxide losses, from dairy grasslands on peat soils are generally high as a result of relative high soil organic matter contents, potential N mineralisation rates and shallow groundwater levels. Effects of the inclusion of the temperate forage species plantain (Plantago lanceolata L.) (PL), which produces secondary compounds with biological nitrification inhibition capacity, on the fate of soil mineral N were studied in a combined mesocosm and field experiment. The experiments comprised four treatments differing in intentional herbage share of plantain versus perennial ryegrass (Lolium perenne L.) (100%PL, 66%PL, 33%PL and 0%PL). Potential nitrification in the mesocosm experiment was significantly lower at 100%PL versus 0%PL (p = 0.018), but soil nitrate concentrations were not. Nitrous oxide fluxes reduced by 39% (p = 0.021) in the presence of plantain in the field experiment, without an obvious link to the quantity of plantain. N use efficiency of plantain tended to increase with the quantity of plantain in the sward in the mesocosm experiment (p = 0.098), but not in the field experiment. Our results suggest that the presence of plantain can affect the fate of soil mineral N of dairy grasslands on peat soils.

    Plant communities on nitrogen-rich soil are less sensitive to soil moisture than plant communities on nitrogen-poor soil
    Shovon, Tanvir Ahmed ; Rozendaal, Danaë M.A. ; Gagnon, Daniel ; Gendron, Fidji ; Vetter, Mary ; Vanderwel, Mark C. - \ 2020
    Journal of Ecology 108 (2020)1. - ISSN 0022-0477 - p. 133 - 144.
    community assembly - environmental filtering - light - multiple resource limitation - nitrogen - plant strategies - soil moisture - trait-based ecology

    Plant species composition and diversity are known to change across local gradients of light, moisture and nutrients, but ecologists still have a relatively limited understanding of how communities respond to multiple limiting resources. We used a trait-based approach to investigate how the functional composition and diversity of forest understorey plant communities change along gradients in light, soil moisture and nitrogen availability. We used a total of seven leaf, root and whole-plant traits for 55–78 species, and estimated the effects of the three resources on the mean and dispersion of these traits in understorey plant communities across 50 forest sites. Soil moisture and nitrogen availability (C/N ratio) both influenced plant community traits, but light availability (canopy openness) did not. Generally, increases in moisture and nitrogen both resulted in shifts towards more acquisitive resource use strategies, including greater leaf area, specific leaf area and maximum plant height, and lower leaf dry matter content, root dry matter content and rooting depth. Functional diversity of most traits also increased with increasing soil moisture and nitrogen. Although most traits varied with soil moisture on nitrogen-poor sites, moisture did not influence of the distribution of any traits on nitrogen-rich sites. Synthesis. Independent co-limitation of soil moisture and nitrogen appeared to influence the functional composition and diversity of understorey vegetation in our study area. The co-occurrence of species with resource acquisitive and conservative strategies on nitrogen-rich sites may make plant communities relatively resistant to changes to soil moisture. These results suggest that altered precipitation regimes under climate change could lead to greater changes in the composition and diversity of plant communities on nutrient-poor soils than on nutrient-rich soils.

    Data from: Plant communities on nitrogen‐rich soil are less sensitive to soil moisture than plant communities on nitrogen‐poor soil
    Shovon, Tanvir Ahmed ; Rozendaal, Danaë ; Gagnon, Daniel ; Gendron, Fidji ; Vetter, Mary ; Vanderwel, Mark C. - \ 2019
    multiple resource limitation - soil moisture - Light - nitrogen - plant strategies - trait-based ecology - Environmental filtering - community assembly
    1.Plant species composition and diversity are known to change across local gradients of light, moisture, and nutrients, but ecologists still have a relatively limited understanding of how communities respond to multiple limiting resources. 2.We used a trait‐based approach to investigate how the functional composition and diversity of forest understory plant communities change along gradients in light, soil moisture and nitrogen availability. We used a total of seven leaf, root, and whole‐plant traits for 55‐78 species, and estimated the effects of the three resources on the mean and dispersion of these traits in understory plant communities across 50 forest sites. 3.Soil moisture and nitrogen availability (C/N ratio) both influenced plant community traits, but light availability (canopy openness) did not. Generally, increases in moisture and nitrogen both resulted in shifts towards more acquisitive resource use strategies, including greater leaf area, specific leaf area and maximum plant height, and lower leaf dry matter content, root dry matter content and rooting depth. Functional diversity of most traits also increased with increasing soil moisture and nitrogen. Although most traits varied with soil moisture on nitrogen‐poor sites, moisture did not influence of the distribution of any traits on nitrogen‐rich sites. 4.Synthesis: Independent co‐limitation of soil moisture and nitrogen appeared to influence the functional composition and diversity of understory vegetation in our study area. The co‐occurrence of species with resource acquisitive and conservative strategies on nitrogen‐rich sites may make plant communities relatively resistant to changes to soil moisture. These results suggest that altered precipitation regimes under climate change could lead to greater changes in the composition and diversity of plant communities on nutrient‐poor soils than on nutrient‐rich soils.
    KringloopWijzer: voordeel voor melkveehouder en natuur
    Haan, Michael de; Oenema, Jouke ; Hilhorst, Gerjan ; Verloop, Koos - \ 2019
    circular agriculture - energy saving - nitrogen - soil management
    Het goud op de mesthoop
    Wolf, Pieter de - \ 2019
    circular agriculture - soil organic matter - nutrient management - nitrogen - residual streams - soil management
    NODULE INCEPTION Recruits the Lateral Root Developmental Program for Symbiotic Nodule Organogenesis in Medicago truncatula
    Schiessl, Katharina ; Lilley, Jodi L.S. ; Lee, Tak ; Tamvakis, Ioannis ; Kohlen, Wouter ; Bailey, Paul C. ; Thomas, Aaron ; Luptak, Jakub ; Ramakrishnan, Karunakaran ; Carpenter, Matthew D. ; Mysore, Kirankumar S. ; Wen, Jiangqi ; Ahnert, Sebastian ; Grieneisen, Veronica A. ; Oldroyd, Giles E.D. - \ 2019
    Current Biology 29 (2019)21. - ISSN 0960-9822 - p. 3657 - 3668.e5.
    auxin - CYTOKININ RESPONSE FACTOR - endosymbiosis - LATERAL ORGAN BOUNDARIES DOMAIN - lateral root/nodule organogenesis - Medicago truncatula - nitrogen - NODULE INCEPTION - rhizobia - YUCCA

    To overcome nitrogen deficiencies in the soil, legumes enter symbioses with rhizobial bacteria that convert atmospheric nitrogen into ammonium. Rhizobia are accommodated as endosymbionts within lateral root organs called nodules that initiate from the inner layers of Medicago truncatula roots in response to rhizobial perception. In contrast, lateral roots emerge from predefined founder cells as an adaptive response to environmental stimuli, including water and nutrient availability. CYTOKININ RESPONSE 1 (CRE1)-mediated signaling in the pericycle and in the cortex is necessary and sufficient for nodulation, whereas cytokinin is antagonistic to lateral root development, with cre1 showing increased lateral root emergence and decreased nodulation. To better understand the relatedness between nodule and lateral root development, we undertook a comparative analysis of these two root developmental programs. Here, we demonstrate that despite differential induction, lateral roots and nodules share overlapping developmental programs, with mutants in LOB-DOMAIN PROTEIN 16 (LBD16) showing equivalent defects in nodule and lateral root initiation. The cytokinin-inducible transcription factor NODULE INCEPTION (NIN) allows induction of this program during nodulation through activation of LBD16 that promotes auxin biosynthesis via transcriptional induction of STYLISH (STY) and YUCCAs (YUC). We conclude that cytokinin facilitates local auxin accumulation through NIN promotion of LBD16, which activates a nodule developmental program overlapping with that induced during lateral root initiation.

    Impacts of intensifying or expanding cereal cropping in sub-Saharan Africa on greenhouse gas emissions and food security
    Loon, Marloes P. van; Hijbeek, Renske ; Berge, Hein F.M. ten; Sy, Veronique De; Broeke, Guus A. ten; Solomon, Dawit ; Ittersum, Martin K. van - \ 2019
    Global Change Biology 25 (2019)11. - ISSN 1354-1013 - p. 3720 - 3730.
    fertilizer - food self-sufficiency - intensification - land use conversion - nitrogen - nutrient use efficiency - yield gaps

    Cropping is responsible for substantial emissions of greenhouse gasses (GHGs) worldwide through the use of fertilizers and through expansion of agricultural land and associated carbon losses. Especially in sub-Saharan Africa (SSA), GHG emissions from these processes might increase steeply in coming decades, due to tripling demand for food until 2050 to match the steep population growth. This study assesses the impact of achieving cereal self-sufficiency by the year 2050 for 10 SSA countries on GHG emissions related to different scenarios of increasing cereal production, ranging from intensifying production to agricultural area expansion. We also assessed different nutrient management variants in the intensification. Our analysis revealed that irrespective of intensification or extensification, GHG emissions of the 10 countries jointly are at least 50% higher in 2050 than in 2015. Intensification will come, depending on the nutrient use efficiency achieved, with large increases in nutrient inputs and associated GHG emissions. However, matching food demand through conversion of forest and grasslands to cereal area likely results in much higher GHG emissions. Moreover, many countries lack enough suitable land for cereal expansion to match food demand. In addition, we analysed the uncertainty in our GHG estimates and found that it is caused primarily by uncertainty in the IPCC Tier 1 coefficient for direct N2O emissions, and by the agronomic nitrogen use efficiency (N-AE). In conclusion, intensification scenarios are clearly superior to expansion scenarios in terms of climate change mitigation, but only if current N-AE is increased to levels commonly achieved in, for example, the United States, and which have been demonstrated to be feasible in some locations in SSA. As such, intensifying cereal production with good agronomy and nutrient management is essential to moderate inevitable increases in GHG emissions. Sustainably increasing crop production in SSA is therefore a daunting challenge in the coming decades.

    Quickscan: belemmeringen in de mestwetgeving die de omslag naar kringlooplandbouw afremmen : Notitie opgesteld op verzoek van de vaste commissie voor LNV
    Zijlstra, J. ; Haan, M.H.A. de; Ehlert, P.A.I. ; Dijk, W. van; Ham, Kees van; Verloop, Koos - \ 2019
    Wageningen : Wageningen Livestock Research - 15 p.
    nitrogen - circular agriculture
    Invited review: Nitrogen in ruminant nutrition: A review of measurement techniques
    Hristov, A.N. ; Bannink, A. ; Crompton, L.A. ; Huhtanen, P. ; Kreuzer, M. ; McGee, M. ; Nozière, P. ; Reynolds, C.K. ; Bayat, A.R. ; Yáñez-Ruiz, D.R. ; Dijkstra, J. ; Kebreab, E. ; Schwarm, A. ; Shingfield, K.J. ; Yu, Z. - \ 2019
    Journal of Dairy Science 102 (2019)7. - ISSN 0022-0302 - p. 5811 - 5852.
    environment - manure - metabolism - nitrogen - ruminant animal - technique

    Nitrogen is a component of essential nutrients critical for the productivity of ruminants. If excreted in excess, N is also an important environmental pollutant contributing to acid deposition, eutrophication, human respiratory problems, and climate change. The complex microbial metabolic activity in the rumen and the effect on subsequent processes in the intestines and body tissues make the study of N metabolism in ruminants challenging compared with nonruminants. Therefore, using accurate and precise measurement techniques is imperative for obtaining reliable experimental results on N utilization by ruminants and evaluating the environmental impacts of N emission mitigation techniques. Changeover design experiments are as suitable as continuous ones for studying protein metabolism in ruminant animals, except when changes in body weight or carryover effects due to treatment are expected. Adaptation following a dietary change should be allowed for at least 2 (preferably 3) wk, and extended adaptation periods may be required if body pools can temporarily supply the nutrients studied. Dietary protein degradability in the rumen and intestines are feed characteristics determining the primary AA available to the host animal. They can be estimated using in situ, in vitro, or in vivo techniques with each having inherent advantages and disadvantages. Accurate, precise, and inexpensive laboratory assays for feed protein availability are still needed. Techniques used for direct determination of rumen microbial protein synthesis are laborious and expensive, and data variability can be unacceptably large; indirect approaches have not shown the level of accuracy required for widespread adoption. Techniques for studying postruminal digestion and absorption of nitrogenous compounds, urea recycling, and mammary AA metabolism are also laborious, expensive (especially the methods that use isotopes), and results can be variable, especially the methods based on measurements of digesta or blood flow. Volatile loss of N from feces and particularly urine can be substantial during collection, processing, and analysis of excreta, compromising the accuracy of measurements of total-tract N digestion and body N balance. In studying ruminant N metabolism, nutritionists should consider the longer term fate of manure N as well. Various techniques used to determine the effects of animal nutrition on total N, ammonia- or nitrous oxide-emitting potentials, as well as plant fertilizer value, of manure are available. Overall, methods to study ruminant N metabolism have been developed over 150 yr of animal nutrition research, but many of them are laborious and impractical for application on a large number of animals. The increasing environmental concerns associated with livestock production systems necessitate more accurate and reliable methods to determine manure N emissions in the context of feed composition and ruminant N metabolism.

    Recycling nutrients contained in human excreta to agriculture: Pathways, processes, and products
    Harder, Robin ; Wielemaker, Rosanne ; Larsen, Tove A. ; Zeeman, Grietje ; Öberg, Gunilla - \ 2019
    Critical Reviews in Environmental Science and Technology 49 (2019)8. - ISSN 1064-3389 - p. 695 - 743.
    blackwater - carbon - feces - fertilizer - nitrogen - organic matter - Phosphorus - potassium - recovery - resource-oriented sanitation - sewage - soil amendment - source-separation - urine - wastewater

    The need for better nutrient management has spurred efforts towards more comprehensive recycling of nutrients contained in human excreta to agriculture. Research in this direction has intensified throughout the past years, continuously unfolding new knowledge and technologies. The present review aspires to provide a systematic synthesis of the field by providing an accessible overview of terminology, recovery pathways and treatment options, and products rendered by treatment. Our synthesis suggests that, rather than focusing on a specific recovery pathway or product and on a limited set of nutrients, there is scope for exploring how to maximize nutrient recovery by combining individual pathways and products and including a broader range of nutrients. To this end, finding ways to more effectively share and consolidate knowledge and information on recovery pathways and products would be beneficial. The present review aims to provide a template that aims to facilitate designing human excreta management for maximum nutrient recovery, and that can serve as foundation for organizing and categorizing information for more effective sharing and consolidation.

    Phenotypic plasticity as a clue for invasion success of the submerged aquatic plant Elodea nuttallii
    Szabó, S. ; Peeters, E.T.H.M. ; Várbíró, G. ; Borics, G. ; Lukács, B.A. - \ 2019
    Plant Biology 21 (2019)1. - ISSN 1435-8603 - p. 54 - 63.
    Alien - aquatic plant - competition - light - macrophyte - nitrogen

    Two closely related alien submerged aquatic plants were introduced into Europe. The new invader (Elodea nuttallii) gradually displaced E. canadensis even at sites where the latter was well established. The aim of the study was to evaluate the combined effects of environmental factors on several phenotypic characteristics of the two Elodea species, and to relate these phenotypic characteristics to the invasion success of E. nuttallii over E. canadensis. In a factorial design, Elodea plants were grown in aquaria containing five different nitrogen concentrations and incubated at five different light intensities. We used six functional traits (apical shoot RGR), total shoot RGR, relative elongation, root length, lateral spread, branching degree) to measure the environmental response of the species. We calculated plasticity indices to express the phenotypic differences between species. Light and nitrogen jointly triggered the development of phenotypic characteristics that make E. nuttallii a more successful invader in eutrophic waters than E. canadensis. The stronger invader showed a wider range of phenotypic plasticity. The apical elongation was the main difference between the two species, with E. nuttallii being more than two times longer than E. canadensis. E. canadensis formed dense side shoots even under high shade and low nitrogen levels, whereas E. nuttallii required higher light and nitrogen levels. We found that under more eutrophic conditions, E. nuttallii reach the water surface sooner than E. canadensis and through intensive branching outcompetes all other plants including E. canadensis. Our findings support the theory that more successful invaders have wider phenotypic plasticity.

    The Potential for Upscaling Kelp (Saccharina latissima) Cultivation in Salmon-Driven Integrated Multi-Trophic Aquaculture (IMTA)
    Fossberg, Julia ; Forbord, Silje ; Broch, Ole Jacob ; Malzahn, Arne M. ; Jansen, Henrice ; Handå, Aleksander ; Førde, Henny ; Bergvik, Maria ; Fleddum, Anne Lise ; Skjermo, Jorunn ; Olsen, Yngvar - \ 2018
    Frontiers in Marine Science 5 (2018). - ISSN 2296-7745
    nitrogen - bioremediation - stable isotope - numerical modeling - Norway
    Integrated multi-trophic aquaculture (IMTA) has the potential of reducing open-cage fish farming impacts on the environment while also introducing new value chains. The aim of this study was to investigate the growth and composition of the kelp Saccharina latissima in salmon-driven IMTA, and to assess the spatial extent of the influence of salmon derived nitrogen in order to evaluate the upscaling potential for IMTA. S. latissima was cultivated 100, 200, and 1,000 m east and 1,000 m west of a 5,000 tons salmon farm in Western Norway from February to September 2013. The proportion of salmon derived nitrogen available for the kelp showed a clear decline with distance from the farm. Accordingly, the kelp cultivated near the salmon cages grew faster during the spring season, and growth rate decreased with increasing distance from the farm. A spatially explicit numerical model system (SINMOD), including compartments for dissolved nutrients and kelp growth, was tuned to the field data and used to investigate the potential for upscaling IMTA production. The model was used to introduce a new metric—the impacted area IA—for the areal effects of IMTA in terms of the increase in production by IMTA. The model showed that a 25 hectare kelp farm in the vicinity of the studied salmon farm could take up 1.6 of the 13.5 tons of dissolved inorganic nitrogen released during kelp cultivation, amounting to almost 12% of the ammonia released during the cultivation period from February to June. The 25 hectare kelp farm would have a production yield of 1,125 tons fresh weight (FW), being 60% more than that of a non-IMTA kelp farm, while a 20% increase of kelp FW could be obtained over a 110 hectar area in salmon-driven IMTA. To achieve an even mass balance, an area of approximately 220 ha−1 would be needed to cultivate enough kelp to fix an equivalent of the nitrogen released by the fish
    Data from: Relationships between leaf mass per area and nutrient concentrations in 98 Mediterranean woody species are determined by phylogeny, habitat and leaf habit
    Riva, Enrique G. de la; Villar, Rafael ; Pérez-Ramos, Ignacio M. ; Quero, José Luis ; Matías, Luis ; Poorter, L. ; Marañón, Teodoro - \ 2018
    Wageningen University & Research
    functional traits - leaf economics spectrum - nitrogen - phosphorus - phylogenetic independent contrast (PIC) - stoichiometry
    Leaf structural and nutrient traits are key attributes of plant ecological strategies, as these traits are related to resource-use strategies and plant growth. However, leaf structure and nutrient composition can vary among different habitats, leaf habits or phylogenetic groups. In this study, we measured 13 leaf traits (one structural—leaf mass per area, LMA—and 12 nutrient traits) in 98 Mediterranean woody species growing over a wide range of environmental conditions, with the final aim of discerning the main causes of leaf trait variability. The variance decomposition results show that phylogeny, leaf habit and habitat type affected in several ways the structural and nutrient traits studied. Leaf nutrient concentrations are strongly positively correlated amongst themselves, and negatively correlated with LMA, in accordance with the “leaf economics spectrum”. We found that leaf habit and phylogeny were important causes of variation in LMA and in a broad number of leaf nutrients (i.e., C, N, Mg, S, K), while other micronutrients seemed to be more dependent on the environment (i.e., Cu and Mn). In summary, our study reinforces the existence of the leaf economics spectrum in a broad pool of Mediterranean woody species, and demonstrates the strong influence of phylogeny, leaf habit and environmental context as the main drivers of variability in some leaf structural and nutrient traits.
    Bepaling samenstelling van vaste mest met NIRS
    Rietra, R.P.J.J. ; Oenema, O. - \ 2017
    Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2837) - 27
    dierlijke meststoffen - stikstof - fosfor - nabij infrarood spectroscopie - referentienormen - analyse - betrouwbaarheid - analytische methoden - animal manures - nitrogen - phosphorus - near infrared spectroscopy - reference standards - analysis - reliability - analytical methods
    Hemp (Cannabis sativa L.) leaf photosynthesis in relation to nitrogen content and temperature : implications for hemp as a bio-economically sustainable crop
    Tang, Kailei ; Struik, Paul C. ; Amaducci, Stefano ; Stomph, Tjeerd Jan ; Yin, Xinyou - \ 2017
    Global change biology Bioenergy 9 (2017)10. - ISSN 1757-1693 - p. 1573 - 1587.
    Hemp (Cannabis sativa L.) - model - nitrogen - photosynthesis - sustainable crop - temperature

    Hemp (Cannabis sativa L.) may be a suitable crop for the bio-economy as it requires low inputs while producing a high and valuable biomass yield. With the aim of understanding the physiological basis of hemp's high resource-use efficiency and yield potential, photosynthesis was analysed on leaves exposed to a range of nitrogen and temperature levels. Light-saturated net photosynthesis rate (Amax) increased with an increase in leaf nitrogen up to 31.2 ± 1.9 μmol m−2 s−1 at 25 °C. The Amax initially increased with an increase in leaf temperature (TL), levelled off at 25–35

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