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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.

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    Undernutrition management and the role of protein-enriched meals for older adults
    Ziylan, Canan - \ 2016
    Wageningen University. Promotor(en): Lisette de Groot; Stefanie Kremer; Annemien Haveman-Nies. - Wageningen : Wageningen University - ISBN 9789462579323 - 148
    elderly - elderly nutrition - undernutrition - enrichment - protein - eating patterns - feeding behaviour - meals - nursing homes - ouderen - ouderenvoeding - ondervoeding - verrijking - eiwit - eetpatronen - voedingsgedrag - maaltijden - verpleeghuizen

    Undernutrition is a major health problem in the growing elderly population. It is estimated that one in ten Dutch community-dwelling older adults is suffering from undernutrition, and one in three Dutch older adults who receive home care. Undernutrition may lead to many negative consequences, ranging from fatigue and falls to impaired immune function and death. This makes undernutrition an obvious target for preventive measures.

    Undernutrition can be defined as “a state of nutrition in which a deficiency or excess (or imbalance) of energy, protein, and other nutrients causes measurable adverse effects on tissue/body form (body shape, size and composition) and function, and clinical outcome”. In addition, it is often described as protein energy malnutrition. Adequate protein intake may to some extent prevent and reverse this process. However, throughout ageing, it becomes increasingly difficult to reach adequate protein intake due to higher protein needs and lower protein intakes. Finding solutions to assist older adults in reaching their optimal protein intake is necessary.

    In our overall research project, we considered 1.2g protein per kg weight per day (g/kg/d) as adequate protein intake. In Dutch community-dwelling older adults, protein intake is around 1.0 g/kg/d, implying room for improvement. However, it is possible that many of these older adults deal with physiological changes, medical conditions, and physical and mental limitations that impair their appetite and food provision. For these older adults with higher protein needs, merely recommending that they eat more would not be realistic. It would be more realistic to explore strategies that increase protein intake without having to increase food intake. This calls for the exploration of instruments that match the needs and preferences of older adults: protein-enriched regular products.

    One particular group that can be identified as a target group for such products, are older adults who receive home care. Undernutrition prevalence is high in this group, which may be explained by their health problems that led to this dependence on home care. Likewise, many of these older adults also depend on meals-on-wheels. These meals-on-wheels recipients, regardless of whether they receive home care or not, often risk undernutrition too. In both these (overlapping) care-dependent groups, difficulties in adhering to energy and protein recommendations can be discerned. For this reason, enriching the readymade meals that these older adults receive may contribute to the prevention of protein undernutrition by increasing protein intake while keeping food intake the same. Here, protein enrichment instruments can be used to prevent undernutrition, but only when implemented in a timely manner. Adequate undernutrition management systems are therefore necessary to facilitate timely intervention, ensuring that the developed protein-enriched meals are actually offered and effective. For this reason, the overall aim of our research project was to gain insight into the current state of undernutrition management in community-dwelling older adults in the Netherlands and explore the role of protein-enriched regular products as a supportive instrument in protein undernutrition management.

    In Study 1 (chapter 2) we explored the experiences of 22 Dutch nutrition and care professionals and researchers with undernutrition awareness, monitoring, and treatment among community-dwelling older adults. This qualitative study among, for example, dietitians, general practitioners, nurse practitioners, and home care nurses provided insight into the current bottlenecks within the existing undernutrition management guidelines. In these telephone interviews, these experts also discussed the current dietary behaviour problems of older adults and their impact on undernutrition risk. The experts’ experiences implied that undernutrition awareness is limited, among both older adults and care professionals. In addition, the interviewees were unclear about which professionals are responsible for monitoring and which monitoring procedures are preferred. The dietitians feel that they become involved too late, leading to decreased treatment effectiveness. In general, the interviewees desired more collaboration and a coherent and feasible allocation of responsibilities regarding undernutrition monitoring and treatment. This implied that the available guidelines on undernutrition management require more attention and facilitation.

    In the following mixed-methods study (chapter 3), with interviews, we qualitatively explored the dietary behaviour and undernutrition risk of 12 Dutch elderly meals-on-wheels clients, one of the largest at-risk groups. We followed up on this information by quantifying the topics that emerged from the qualitative exploration of experienced bottlenecks in performing adequate dietary behaviour. For this, we used a survey among 333 meals-on-wheels clients. The interviews with elderly meals-on-wheels clients made clear that they have fixed and habitual eating patterns, while at the same time their appetite had decreased throughout the years. This was confirmed by the survey finding that regular portion size meals were perceived as too large by the oldest group aged over 75y. In addition, as the professionals suggested earlier, the interviewed elderly clients indeed showed limited awareness of undernutrition risk. Simultaneously, the survey showed that almost one in four elderly meals-on-wheels clients was undernourished. These findings led to the conclusion that staying close to the identified dietary habits may facilitate small yet effective modifications within these habits to prevent inadequate nutritional intake. Still, the limited awareness of undernutrition risk was expected to play a limiting role in whether clients believe they need dietary modifications. Consequently, informing them about this need could facilitate their motivation to implement modifications.

    After learning about the general dietary behaviour of these older adults, we used this information for Study 3 (chapter 4). We developed two kinds of protein-enriched readymade meals that are in line with the needs and preferences of older adults: one of regular size (450g) and one of reduced size (400g). We tested these meals in a lab setting in 120 community-dwelling older adults in a single-blind randomised crossover trial. One day a week at lunchtime, for four weeks, participants had to consume and evaluate a readymade meal. Overall, regardless of portion size, the protein-enriched meals led to higher protein intakes in vital older adults in a lab setting during lunch. In this crossover study, the participants liked the protein-enriched meals and the regular meals equally. However, we did not find the expected lower ratings of satiety after the reduced-size meals, while one reduced-size enriched meal and another regular-size enriched meal led to higher ratings of subsequent satiety. This higher satiety in the enriched meals could lead to compensational behaviour on the remainder of the day.

    After establishing that the protein-enriched meals were effective and acceptable in the lab setting, we moved to the homes of older adults to test the meals in a longer-term study in Study 4 (chapter 5). In this double-blind randomised controlled trial of two weeks, we also included protein-enriched bread to assess whether both this bread and the meals could increase daily protein intake to 1.2g/kg/d in 42 community-dwelling older adults to reach optimal protein intake. We found that the enriched products again led to higher protein intakes and a high liking. The mean protein intake per day was 14.6g higher in the intervention group, which amounted to a protein intake of 1.25g/kg/d, compared with 0.99g/kg/d in the control group. In addition, the meals scored 7.7 out of 10, while the bread scored 7.8 out of 10, which both were comparable with their regular counterparts. Lastly, we found no negative effect of compensational behaviour throughout the day. These promising findings indicated that we achieved a good match between older adults’ needs and preferences regarding protein intake.

    In the general discussion of this thesis (chapter 6), we combined our learnings from the four studies to reflect on protein undernutrition management in community-dwelling older adults and the possible role of protein-enriched regular products. We have discussed a conceptual framework consisting of three wheels of protein undernutrition management. In the first wheel regarding awareness, we proposed that limited awareness of adequate nutrition and body composition forms the largest bottleneck in undernutrition management. When this awareness is generated among both older adults and professionals, it will benefit the second wheel of monitoring. Here, we argued that a policy and the actual facilitation of that policy are required for this monitoring to succeed. When the monitoring is performed adequately, in the third wheel, the appropriate treatment can be carried out. We discussed that personalisation and evaluation of this treatment are important conditions. All in all, the public health implications that we have discussed on the basis of our findings can be summarised by the three key messages that could help us ace in adequate protein undernutrition management: address awareness in both older adults and professionals, facilitate continuous collaboration between professionals, and offer protein-enriched products expediently.

    Hokverrijking om in de knaagbehoefte van konijnen te voorzien: een literatuurstudie = Environmental enrichment to fulfill gnawing requirements in rabbits: a literature study
    Rommers, J.M. ; Jong, I.C. de - \ 2010
    Lelystad : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 396) - 16
    dierenwelzijn - konijnen - verrijking - hokken - zachthout - ruwvoer (forage) - animal welfare - rabbits - enrichment - pens - softwoods - forage
    This report is a literature study to environmental enrichment in rabbits, that possibly fulfills the gnawing requirements
    Microbial enrichment of torrefied grass fibers : a novel ingredient of potting soil
    Trifonova, R.D. - \ 2008
    University of Groningen. Promotor(en): J.D. van Elsas, co-promotor(en): Joeke Postma. - [S.l.] : S.n. - ISBN 9789036736695 - 146
    groeimedia - vezels - hooi - grassen - microbiële flora - verrijking - verbeteraars - fytotoxiciteit - growing media - fibres - hay - grasses - microbial flora - enrichment - amendments - phytotoxicity
    Effecten van brand op bodem en vegetatie in dennenbossen van voedselarme zandgronden bij Kootwijk
    Kemmers, R.H. ; Dirkse, G.M. ; Hille, M.G. ; Mekkink, P. - \ 2005
    Wageningen : Alterra (Alterra-rapport 1028) - 57
    naaldbossen - bossen - verbranden - bodem - vegetatie - zandgronden - bosbranden - stikstof - verrijking - natuurgebieden - veluwe - gelderland - coniferous forests - forests - burning - soil - vegetation - sandy soils - forest fires - nitrogen - enrichment - natural areas - veluwe - gelderland
    Door atmosferische stikstofdepositie zijn veel bossen van de arme zandgronden vermest en in hun verdere successie verstoord. In een voedselarm dennenbos op zandgrond is onderzocht of door brand de overmaat aan stikstof die in de strooisellaag ligt opgeslagen kan worden teruggedrongen en de bosontwikkeling kan worden teruggezet naar een voedselarme pionierfase. Het onderzoek werd uitgevoerd bij Kootwijk waar in 1995 een bosbrand woedde. De vegetatie- en bodemkundige toestand van voor de brand, één en negen jaar na de brand werd geanalyseerd. Een belangrijke conclusie is dat brand eerder tot een verrijking van de bodem leidt dan tot een verschraling. Door brand vindt een verplaatsing van elementen van ectorganische naar endorganische horizonten plaats. Weliswaar verdwijnt er in zijn totaliteit stikstof, maar direct na de brand is de bodem sterk verrijkt met kalium, ammonium en fosfaat en in zuurgraad gedaald. Bovendien wordt het beschikbaar gekomen ammonium door micro-organismen vastgelegd in organische stof wat daardoor een rijk karakter krijgt. Dit effect is negen jaar na de brand nog steeds aanwezig. Het laten staan van de necromassa na de brand, zoals in Kootwijk plaatsvond, draagt niet bij aan het terugzetten van de vegetatiesuccessie naar een initieel schraal stadium, maar wel aan de diversiteit van bodemeigenschappen
    Personalities in pigs: Individual characteristics and coping with environmental challenges
    Bolhuis, J.E. - \ 2004
    Wageningen University. Promotor(en): V.M. Wiegant, co-promotor(en): W.G.P. Schouten; Johan Schrama. - [S.l.] : S.n. - ISBN 9789085040620 - 176
    varkens - persoonlijkheid - karakterisering - individuele kenmerken - stress - stressreactie - varkensstallen - adaptatie - diergedrag - dierenwelzijn - milieu - verrijking - immuniteitsreactie - dierfysiologie - pigs - personality - characterization - individual characteristics - stress - stress response - pig housing - adaptation - animal behaviour - animal welfare - environment - enrichment - immune response - animal physiology
    There are indications that pigs may have difficulty in adapting to the constraints of intensive housing conditions. Pigs show a wide variation in adaptive responses when exposed to the same stressful situation. Aim of this thesis was to investigate whether the behavioural coping responses of young piglets reflect and predict more general profiles of reactivity to challenges, often referred to as coping styles, under different rearing and housing conditions. For this purpose, pigs were characterized early in life as `high-resisting` (HR) or `low-resisting` (LR) on the basis of their resistance response in a so-called Backtest, in which they were manually restrained in supine position. The major part of the thesis focused on the interaction between these individual coping characteristics of pigs and their housing environment, which was either barren or enriched with straw bedding. The experiments described in this thesis show that HR pigs are more aggressive than LR pigs and less flexible in adapting their behaviour to environmental changes. As the two types of pig differed in response to the dopamine-agonist apomorphine, some initial evidence is provided for a neurochemical background of these behavioural differences. In addition, individual coping or personality characteristics of pigs were reflected in immune reactivity and in their home pen behaviour in barren and enriched environments. HR and LR pigs adapted differently to barren housing conditions. Moreover, individual characteristics modulated the effects of rearing and housing conditions on the behavioural response to novelty, immune reactivity, prevalence of gastric lesions and behavioural development. Remarkably, for almost all of the variables that were affected by housing environment, the impact was much larger for LR than for HR pigs. Thus, individual characteristics of pigs affect their performance in different environments and should be taken into account when studying the impact of housing on their behaviour and welfare. The knowledge of individual coping or personality characteristics could be extended and used for finding the optimal match between pigs and their social and physical environment in pig husbandry.
    Prima eikwaliteit, veel pikkerij : tweede proef met verrijkte kooi Leg-Commune
    Fiks - van Niekerk, Th.G.C.M. van; Reuvekamp, B.F.J. - \ 2003
    De Pluimveehouderij 33 (2003)28. - ISSN 0166-8250 - p. 14 - 15.
    pluimveehokken - huisvesting van kippen - kooigrootte - verrijking - proeven - onderzoek - ovipositie - eierproductie - eikwaliteit - diergedrag - groepseffect - poultry housing - chicken housing - cage size - enrichment - trials - research - oviposition - egg production - egg quality - animal behaviour - group effect
    De Leg-Commune is een verrijkte kooi voor een grote groep hennen. Een voordeel is dat de dieren effectief meer ruimte hebben, een nadeel is dat in grote groepen eerder pikkerij optreedt
    Ammoniakemissie komt op gemiddeld 25,5 gram : praktijkonderzoek aan verrijkte kooien
    Emous, R.A. van; Reuvekamp, B.F.J. ; Fiks-van Niekerk, T.G.C.M. - \ 2003
    De Pluimveehouderij 33 (2003)49. - ISSN 0166-8250 - p. 10 - 11.
    pluimveehouderij - veehouderijbedrijven - kooien - verrijking - huisvesting van kippen - ammoniak - emissie - stankemissie - droge stof - pluimveemest - onderzoek - poultry farming - livestock enterprises - cages - enrichment - chicken housing - ammonia - emission - odour emission - dry matter - poultry manure - research
    Conclusies van onderzoek over de ammoniakuitstoot bij verrijkte kooien in gemiddelden over het jaar en over de grote en kleine systemen per dierplaats
    Verrijkte kooien voor leghennen in al zijn onderdelen
    Fiks, T.G.C.M. ; Reuvekamp, B.F.J. ; Emous, R.A. van - \ 2003
    Lelystad : Praktijkonderzoek Veehouderij (Praktijkboek / Animal Sciences Group 31) - 62
    hennen - pluimveehouderij - pluimveehokken - kooien - verrijking - dierenwelzijn - hens - poultry farming - poultry housing - cages - enrichment - animal welfare
    Het merendeel van de leghennen in de wereld wordt gehouden in batterijhuisvesting. Dit systeem heeft zich ontwikkeld vanuit een aantal wensen die aan de houderij van leghennen gesteld werd. Deze eisen lagen vooral op het gebied van economie, management, milieu, diergezondheid en productkwaliteit. Op deze punten scoort de legbatterij dan ook ruim voldoende. In de periode van de opkomst van de legbatterij als houderijsysteem was welzijn van dieren nog geen issue. Inmiddels wordt het welzijn van landbouwhuisdieren echter door diverse wetten en regels gewaarborgd. : :De in de EU-richtlijn van 1999 (EU, 1999a) genoemde verrijkte kooi werd ontwikkeld met het idee het goede van de batterij te behouden en de slechte kanten te verbeteren. In deze kooi zijn verschillende elementen ingebouwd, die het dier in staat stelt tot het vertonen van soortspecifiek gedrag. Hoewel de kostprijs van een ei uit de verrijkte kooi hoger is dan uit de batterij, biedt het systeem goede perspectieven met betrekking tot milieu, management, diergezondheid en productveiligheid. Voor het welzijn van het dier is het systeem een compromis tussen wat het dier verlangt en wat de pluimveehouder nodig heeft. In deze uitgave belichten we alle aspecten van verrijkte kooien, zowel vanuit de dierkant als vanuit de pluimveehouder. Het doel van deze uitgave is meerledig: : :1) Het geven van een samenvatting over al het verrichte onderzoek heen. : :2) Het op een toegankelijke wijze presenteren van alle aspecten, die van belang zijn bij verrijkte kooien. : :3) Het geven van tips waarop men moet letten bij de aanschaf en voor het management van verrijkte kooien.
    Verrijkte kooien
    Emous, R.A. van; Fiks, T.G.C.M. ; Reuvekamp, B.F.J. - \ 2003
    Lelystad : Praktijkonderzoek Veehouderij (PraktijkRapport / Animal Sciences Group, Praktijkonderzoek : Pluimvee ) - 77
    hennen - pluimveehokken - kooien - verrijking - snavelkappen - zitstokken (vogels) - legresultaten - verenpikken - kannibalisme - belichting - dierenwelzijn - hens - poultry housing - cages - enrichment - debeaking - perches - laying performance - feather pecking - cannibalism - illumination - animal welfare
    Ruim 75 % van de leghennen in Nederland wordt in batterijkooien gehouden. Deze kooi werd vele jaren gezien als het ideale houderijsysteem voor leghennen. Vanuit ethologisch gezichtspunt is het houden van legkippen in batterijsystemen echter een flinke beperking voor de dieren. Om deze reden is de batterij in een kwaad daglicht komen te staan en is vanuit de maatschappij de roep om welzijnsvriendelijkere huisvestingssystemen steeds sterker geworden. Men houdt steeds meer leghennen in alternatieve systemen als scharrel en volière, waar de dieren de beschikking hebben over een ruime hoeveelheid strooisel. Verder zijn er legnesten en zitstokken in de systemen ingebouwd. Volière en scharrel zijn voor de kleinere bedrijven goede alternatieven. Voor grote bedrijven zijn ze minder aantrekkelijk, omdat ze minder voorspelbaar in arbeid zijn, storingsgevoeliger in productie, hogere milieubelasting (NH3 en stof) hebben en een hogere kostprijs van de eieren. Tot eind jaren 90 verliep de omschakeling naar dit soort systemen erg langzaam, maar nadat de EU-richtlijn voor het houden van leghennen in 1999 van kracht werd, is in Nederland veel geïnvesteerd in alternatieve systemen. De ontwikkelingen naar welzijnsvriendelijke houderij van leghennen is geen Nederlandse aangelegenheid. Dit bleek uit de wijziging in de Europese regelgeving, die in 1999 is doorgevoerd. Deze legt de huisvesting van leghennen in kooien aan banden en verbiedt het huidige batterijsysteem per 1 januari 2012. Vanaf die datum is alleen de huisvesting in alternatieven (scharrel/volière) of in verrijkte kooisystemen toegestaan. Het Nederlandse bedrijfsleven heeft de roep naar welzijnsvriendelijkere huisvestingssystemen voor leghennen onder anderen vertaald naar een opdracht voor het Praktijkonderzoek om de verrijkte kooisystemen te onderzoeken en te ontwikkelen. Als uitgangspunt voor de systemen gold dat ze gebaseerd moesten zijn op het kooiprincipe en minimaal moesten voldoen aan de eisen zoals die in de EU-richtlijn van juli 1999 zijn geformuleerd. Dit onderzoek heeft vorm gekregen in het Project Verrijkte kooien voor leghennen, ook wel kortweg bekend onder de naam Project 1030 (het aanvankelijke interne projectnummer). Gezien de korte termijn waarop bedrijfsleven en politiek informatie moesten hebben over verrijkte kooisystemen, is gekozen voor een proefopzet, waarbij veel verschillende systemen zijn getest. Het Ingrepenbesluit bepaalt dat in nieuwe houderijsystemen die men na 1 september 2001 in gebruik neemt geen dieren mogen worden opgezet die een snavelbehandeling hebben ondergaan. Voor alternatieve houderijsystemen is echter een uitstel van 5 jaar verleend. Dit geldt niet voor kooisystemen (dus ook verrijkte kooien), omdat de kleinere groepsgrootte verenpikkerij en kannibalisme daar beter beheersbaar maakt. Hoewel de groepen dieren in kooien kleiner zijn dan in alternatieve houderijsystemen moet men echter wel rekening houden met dit potentiële pikkerijprobleem. Dit gegeven was aanleiding om extra aandacht te besteden aan het houden van ongekapte hennen en het voorkómen van verenpikkerij en kannibalisme. Het toepassen van verschillende verlichtingssystemen is daarom onderwerp van onderzoek geweest. Het eerste en belangrijkste doel van het onderzoek aan verrijkte kooisystemen was het testen ervan en het opdoen van ervaringen met verschillende ontwerpen. Ook binnen elk kooisysteem zijn diverse varianten getest om te zien welke het beste functioneert. Daarbij is ervaring opgedaan die breder gaat dan alleen dat bewuste systeem, zodat ook algemenere conclusies mogelijk zijn. De hoofdvraag van het onderzoek was telkens: hoe functioneert een systeem. De punten waarnaar we keken zijn: Wat zijn de productieresultaten? Hoe is de eikwaliteit? Wat is de uitval en in het bijzonder de uitval door pikkerij? Hoe functioneren het legnest, de strooiselruimte, de zitstokken en het nagelgarnituur? Hoe gedragen de dieren zich: gebruiken ze het strooisel, het legnest en d
    Effect van verrijking omgeving en beperking weidegang op wroetschade door zeugen
    Mheen, H. van der; Spoolder, H.A.M. - \ 2003
    Lelystad : Praktijkonderzoek Veehouderij (PraktijkRapport / Praktijkonderzoek Veehouderij : Varkens ) - 21
    zeugen - varkenshouderij - rantsoenbeweiding - weiden - schade - verrijking - mineralen - stikstof - diergedrag - biologische landbouw - sows - pig farming - controlled grazing - pastures - damage - enrichment - minerals - nitrogen - animal behaviour - organic farming
    Veel biologische varkenshouders weiden hun drachtige en guste zeugen. Het in stand houden van de graszode is door het wroeten van varkens echter niet vanzelfsprekend, maar wel gewenst. Zonder gras valt er weinig meer te grazen en valt het voordeel vanextra voeropname weg. Daarnaast is de uitspoeling van mineralen op kale grond veel groter dan op grasland.
    Huisvesting en verzorging van vleeskuikenouderdieren zonder ingrepen
    Haar, J.W. van der; Voorst, A. van; Middelkoop, J.H. van; Lourens, A. - \ 2002
    Lelystad : Praktijkonderzoek Veehouderij (PraktijkRapport. Pluimvee 3) - 23
    vleeskuikens - pluimveehokken - dierenwelzijn - milieu - verrijking - vleeskuikenouderdieren - broilers - poultry housing - animal welfare - environment - enrichment - broiler breeders
    Door het Ingrepenbesluit zijn ingrepen bij vleeskuikenouderdieren op termijn verboden. Praktijkonderzoek Veehouderij (voorheen Praktijkonderzoek Pluimveehouderij) onderzoekt daarom sinds 1998 het effect van het achterwege laten van ingrepen bij vleeskuikenouderdieren in relatie tot huisvesting en verzorging. Dit rapport beschrijft de resultaten van de laatste (derde) proef. Al eerder verschenen de bevindingen over de effecten van weglaten van ingrepen bij vleeskuikenouderdieren op gedrag, veer- en huidbeschadigingen, uitval en technische resultaten.
    Strooiselverstrekking in verrijkte kooien
    Fiks-van Niekerk, Th. ; Reuvekamp, B. ; Emous, R. van - \ 2001
    Praktijkonderzoek. Pluimvee 15 (2001)1. - ISSN 1570-2537 - p. 7 - 9.
    hennen - vrouwelijke dieren - huisvesting, dieren - strooisel - organisch bodemmateriaal - kooien - verrijking - eu regelingen - richtlijnen (guidelines) - stof - bedrijfshygiëne - hens - female animals - animal housing - litter (plant) - soil organic matter - cages - enrichment - eu regulations - guidelines - dust - industrial hygiene
    De nieuwe EU-richtlijn voor het houden van leghennen stelt strooisel in verrijkte kooien op termijn verplicht. Hoewel er voldoende technieken zijn om dit te kunnen realiseren, blijkt de keuze van de juiste technieken en materialen van groot belang. Indit artikel de laatste stand van zaken.
    Restoration of species-rich grasslands on reconstructed river dikes
    Liebrand, C.I.J.M. - \ 1999
    Agricultural University. Promotor(en): K.V. Sýkora. - S.l. : Liebrand - ISBN 9789058080318 - 217
    graslanden - vegetatiebeheer - botanische samenstelling - soortendiversiteit - plantensuccessie - rivieren - herstel - verrijking - dijken - nederland - grasslands - vegetation management - botanical composition - species diversity - plant succession - rivers - rehabilitation - enrichment - dykes - netherlands

    Up until 30 years ago an extensive, flower-rich grassland vegetation containing many species rare in the Netherlands used to be common on Dutch river dikes. However, the deterioration of the flora on dikes was already being reported at the end of the 1960s. At that time too, ecologists warned that the planned reinforcement of the dikes along the Rhine, Waal, Lek and IJssel would adversely affect the flora. Their gloomy forecasts have proved to be correct. Between 1968 and 1992 as much as 89% of the locations with a dry floodplain grassland vegetation in the Netherlands disappeared.

    In 1992 the vegetation of over 90% of the river dikes consisted of species-poor grassland on which sheep graze, and rough vegetation mown for hay. Only about 7% of the surface area of the river dikes was covered by relatively species-rich grasslands belonging to the phyto-sociological syntaxa Arrhena-theretum elatioris and Lolio-Cynosuretum , both belonging to the Arrhenatherion elatioris . Only 1% was covered by the typical species-rich dry grassland Medicagini-Avenetum . The last remnants of these grasslands are in imminent danger of disappearing.

    The deterioration in the semi-natural vegetation has mainly been caused by the fact that the slopes of the dikes are increasingly being used agriculturally (fertilization, overgrazing, use of herbi-cides) but also because ecological features were insufficiently taken into account while reinforcing the dikes. In 1984 a research project was started to ascertain the optimum structure and growing con-ditions for the grass cover on river dikes (Sýkora & Liebrand, 1987; van der Zee, 1992). The next step was to test the feasibility of the ecological engineering measures proposed in the above mentioned projects empirically.

    In the research project described in this thesis the core questions were therefore whether the valuable, species-rich vegetation on the dikes can return after reinforcement works, and, if so, what are the pre-conditions for this during and after the reinforcement. The research was carried out on the basis of data of 209 permanent quadrats divided over 125 trial fields. Each permanent quadrat has its own specific method of reconstruction, sowing and management.

    Ninety-eight percent of the plant species found before reconstruction, reappeared after recon-struction. Most species reappeared on the replaced former top layer. Only a few (rare) species did not reappear but were still present in the unmodified zone. Most relatively rare species occur only in low numbers and consequently they are still at risk of disappearing, especially if no proper management is applied. Because of this, a spared zone seems to be the best guarantee for the conservation of the plant species after the reconstruction.

    In the period 1987-1994 9 plant communities were distinguished within the vegetation of the experimental river dike. They can be classified as follows on the basis of method of reconstruction, management and successional stage: the Arrhenatheretum with Peucedanum carvifolia and Rumex thyrsiflorus (I) is typical for the spared zone, the species-poor Arrhenatheretum with Urtica dioica and Valeriana officinalis (II) is a rough vegetation resulting from bad management, the Arrhenatheretum with Leucanthemum vulgare and Lysimachia nummularia (III) is a species-rich grassland occurring under good and moderate management practices on replaced sods and replaced topsoil, the Arrhenatheretum with dominance of Alopecurus pratensis (V) is an intermediate vegetation which will develop further, either into a hayfield vegetation or into a pasture vegetation, depending on the management applied, the Lolio-Cynosuretum with Crepis capillaris and Ranunculus repens (VI) is a grassland vegetation strongly influenced by grazing and the Arrhenatheretum with Leucanthemum vulgare and Trifolium pratense (IV), the association fragment of the Arrhenatheretum with Phleum pratense and Ranunculus repens (VII), the fragmentary community with Matricaria maritima and Plantago major [ Arrhenatherion/Chenopodion ] (VIII) and the fragmentary community with Capsella bursa-pastoris and Poa annua [ Eu-Polygono-Chenopodion ] (IX) are pioneer stages, which had wholly or almost disappeared in 1994.

    The best way to assure maintenance of species-rich grassland vegetation on reconstructed river dikes is to spare a strip or zone of this vegetation during the reconstruction. Species disperse from here to other parts of the dike and the redevelopment of the vegetation is stimulated. To ensure opti-mal results, the soil composition of those new parts should resemble the soil composition of the spared zone as much as possible. If it is not possible to save part of the original vegetation, the upper soil layer can be set aside in the form of turves or as topsoil and can be replaced as the new topsoil after the reconstruction. Replacing the original topsoil after the reinforcement provides a topsoil of similar composition to that before the reinforcement. Besides, the redevelopment of species-rich grasslands is promoted by previously occurring species re-establishing from the propagules present in the replaced topsoil. The application of the under layer as the new top layer and the use of imported clay as the new top layer both prevent a quick restoration of botanically valuable, semi-natural, species-rich grasslands. Propagules are very rare or even absent.

    The seed mixtures applied influence the development of succession. Application of seed mixtures gathered locally accelerates succession. Seed mixtures containing a considerable proportion of Lolium perenne seeds are unsuitable, as the redevelopment is retarded, especially when applied in the high densities (such as 70 kg.ha -1) which used to be common. Sowing an annual grass species like Lolium multiflorum or the standard seed mixture D1 in a low density of 20 to 25 kg.ha -1seemed not to retard the development of a species-rich vegetation.

    In the first years after reconstruction the influence of the methods of reconstruction and the seed mixtures applied appears to be preponderant. In the first years the structure of the vegetation is quite open and the competition between species is low. When the vegetation closes, competition increases. Subsequently, management of the vegetation can be used as an important means to regulate competition and, consequently, species composition. A species-rich vegetation only develops when managed properly.

    On the basis of erosion resistance features like openness of the sward, ground cover, root density and shear resistance, the best management practices appear to be grazing in June in combination with hay-making in September, hay-making in June in combination with grazing in September and hay-making twice a year. In this respect, grazing twice a year, grazing during the whole season, hay-making in September and hay-making in June in combination with mulching in September are moderately effective. Hay-making in June, mulching twice a year, hay-making once every two year, burning and no management are bad management practices.

    On the basis of ecological features such as species-richness and number and proportion of rare species, the best management is hay-making twice a year. In this respect, hay-making in June in combination with mulching in September, hay-making in June, hay-making in September and hay-making in June in combination with grazing in September are moderately effective. The other grazing practices, mulching twice a year, hay-making once every two year, burning and no management are bad management practices.

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