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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A clash of plants : Vegetation succession and its interaction with permafrost dynamics in the Arctic lowland tundra
Li, Bingxi - \ 2017
University. Promotor(en): Frank Berendse, co-promotor(en): Monique Heijmans. - Wageningen : Wageningen University - ISBN 9789463436168 - 100
ecological succession - ecology - plant succession - vegetation - tundra - permafrost - lowland areas - arctic regions - siberia - ecologische successie - ecologie - plantensuccessie - vegetatie - toendra - laaglandgebieden - arctische gebieden - siberië

Arctic ecosystems have been affected by severe climate change during the last decades. The increase in temperature in the Arctic has been almost double of the global rate of warming since the beginning of the 20th century. Like other ecosystems in the high latitude region, Arctic tundra appears to be extremely sensitive to the continuous warming of the past decades, which has led to dramatic vegetation changes such as rapid shrub expansion. While researchers are keen to talk about the shrubification of the Arctic tundra, there has been rather little attention for alternative vegetation shifts, such as those related to local permafrost collapse in lowland tundra. The general vegetation succession route of the ice-rich lowland tundra ecosystem is yet largely unknown. Therefore, we choose a typical Arctic lowland site (Kytalyk natural reserve) in the Northeastern Siberia to explore how vegetation is changing in this ecosystem, and how changes in the abiotic environment and vegetation succession interact.

On the basis of field observations I assumed that the plant species composition of each vegetation patch at the study site changes continuously following cycles over time. To test this assumption, two multiple-year field experiments (Chapter 2 and Chapter 3) were carried out. In addition, we applied dendrochronological techniques (Chapter 4 and Chapter 5) and molecular tools (Chapter 4). On the basis of the results of these studies, I depicted a complete vegetation succession loop in the Arctic lowland tundra, which is closely related to the dynamics of the permafrost. In this vegetation succession loop, four stages with distinctive vegetation types have been identified.

The Betula nana L. shrubs mainly dominate the well-drained elevated areas. In a field experiment, removal of B. nana shrubs resulted in abrupt permafrost degradation, rapid soil moisture increase and invasion of the grass species Arctagrostis latifolia (R. Br.) Griseb. After a short time period, when small ponds or drainages had developed, this fast-responding grass species is replaced by Eriophorum sedges. In the subsequent stage the Sphagnum mosses invade the sedge vegetation. The new Sphagnum moss carpets not only suppress the growth of Eriophorum sedges, but also create moist but unsaturated substrates that appear to be appropriate for the germination of B. nana seeds. These conditions provide new opportunities for B. nana shrubs to establish.

The reproduction mode of B. nana at the study site has been studied using molecular tools (micro- satellites), as it may explain how existing B. nana patches developed and how shrub vegetation may expand in the future (Chapter 4). The conventional point of view is that sexual reproduction of perennial plants in the Arctic tundra, like B. nana, is rare due to the pressure of the harsh environment. However, the results of our molecular study (Chapter 4) tell a different story. While vegetative reproduction of B. nana is common, sexual reproduction of B. nana is more prevalent. Seed dispersal of B. nana between different patches at the study site is not hampered by the short between-patch distances, but vegetative reproduction of B. nana appeared to be restricted to 1-2 m distances from the parent plants.

The influences of the climate on B. nana shrubs were further investigated using the dendrochronological analyses (Chapter 4 and Chapter 5). The radial growth of B. nana is positively correlated with early summer temperature, while relatively high summer precipitation during the warm years also stimulates the growth of B. nana. Moreover, sufficient summer precipitation facilitates the establishment of B. nana seedlings. Since sexual reproduction is prevalent at the site, it is suggested that the present B. nana shrubs established simultaneously, during periods with suitable climate conditions.

Along with the vegetation succession cycles, permafrost underlying the vegetation experiences clear degradation-recovery cycles. We detected a close interaction between vegetation shifts and permafrost dynamics. While abrupt permafrost degradation drove a quick vegetation shift from the B. nana dominated stage to the water-logged Eriophorum sedge dominate stage, the changes of vegetation cover affect the stability of the permafrost as well. The removal of B. nana shrub cover triggered rapid permafrost degradation (Chapter 2), while the development of Sphagnum moss carpets, which have a high isolation capacity, reduced permafrost temperature, facilitating permafrost recovery (Chapter 3).

Vegetation composition in the Arctic tundra not only influences permafrost stability, but also affects the methane emission of the site. Eriophorum sedges are able to transport methane from deep soil to the air via their aerenchyma tissues, leading to high methane fluxes. In contrast, the Sphagnum mosses significantly suppress the methane emission, since endophytic CH4-oxidizing bacteria are widespread inside the aerobic unsaturated Sphagnum carpets (Chapter 3).

To sum up, our findings provide crucial information to better understand changes in the Arctic tundra ecosystem, helping to obtain better predictions of future vegetation shifts and the associated consequences for greenhouse gas emissions, permafrost stability and the heat balance of the Earth surface.

Feiten en cijfers vergroening GLB
Doorn, Anne van; Smidt, Rob - \ 2017
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2795) - 19
landbouwbeleid - monitoring - ecologie - europa - agricultural policy - ecology - europe
The greening of the European common agricultural policy has started in 2015. This report
present facts and figures about two years of greening.
Voortgang realisatie nationaal natuurbeleid : technische achtergronden van een aantal indicatoren uit de digitale Balans van de Leefomgeving 2016
Sanders, M.E. ; Wamelink, G.W.W. ; Wegman, R.M.A. ; Clement, J. - \ 2016
Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-technical report 79) - 74
ecologische hoofdstructuur - ecologie - ecosystemen - verdroging (milieu) - verzuring - depositie - natuurbeleid - ecological network - ecology - ecosystems - groundwater depletion - acidification - deposition - nature conservation policy
The Dutch government is, together with its partners, taking measures to create a coherent network ofprotected nature areas and to improve environmental conditions. This in order to halt the decline in the areaof natural habitat and biodiversity and to improve their conservation status. The Government wants to stayinformed on the progress of this policy. The Netherlands Environmental Assessment Agency (PBL) has selectedindicators that should provide answers to the question: ‘What is the progress of the policy measures taken,especially for realising the nature network, improving the nature quality and the environmental conditions aswell?’ The selected indicators have been updated and analysed in order to assess this progress. This reportdescribes the results of the policy measures taken on the basis of the indicators, the technical setting of thedata and methods used to bring these indicators up to date and the reliability and acceptability of it
The ecology of ditches : a modeling perspective
Gerven, Luuk P.A. - \ 2016
University. Promotor(en): W.M. Mooij, co-promotor(en): Jeroen de Klein; J.H. Janse. - Wageningen : Wageningen University - ISBN 9789462579316 - 137
ditches - aquatic ecology - ecology - modeling - aquatic plants - aquatic ecosystems - water flow - sloten - aquatische ecologie - ecologie - modelleren - waterplanten - aquatische ecosystemen - waterstroming

The Netherlands is well-known for its extended networks of drainage ditches, with a total ditch length of about 300.000 km. Their main function is to enable agriculture by draining water. Nonetheless, ditches also have important ecological functions. They serve as ecological corridors and harbor a high biodiversity in which water plants play a crucial role. The last decades, the ecological quality of ditches is at stake. Enhanced nutrient inputs promoted the invasion by dense mats of free-floating plants like duckweed. Underneath these mats the water becomes dark and anoxic, which severely constrains aquatic life.

In this thesis I developed new concepts to better understand, predict and combat the dominance by free-floating plants in ditches. The following questions are addressed. Are floating plants a self-stabilizing state - an alternative stable state - which would make it more difficult to combat floating-plant dominance (chapter 2)? Does it make sense to fight floating-plant dominance by reducing nitrogen (N) inputs to the ditches or will it lead to an invasion of floating plants that can fix N2 from the atmosphere (chapter 3)? What about spatial aspects, does the vulnerability of a ditch to floating plants depend on the position of a ditch in a polder, like its distance to the polder outlet (chapter 4)? To answer these questions, I used ecological models that predict the abundance of free-floating plants based on the competition for nutrients and light with other plants such as submerged plants, and where possible validated these models with field data. Starting from the ecosystem model PCDitch, I developed and combined models with different complexity to see how theoretical concepts, developed in minimal models, translate to the ecosystem level. Chapter 5 deals with a method that facilitates this up- and downscaling in model complexity.

Are floating plants an alternative stable state? To answer this question I extended mechanistic resource competition theory with a framework (minimal model) describing the competition of floating and submerged plants for light and nutrients. The model predicts that the competitive advantage of floating plants - they have a primacy for light and shade submerged plants, giving rise to asymmetry in competition for light - makes that floating plants always dominate at high supply of light and nutrients. At intermediate nutrient supply, there can be alternative stable states: either the submerged plants or the floating plants dominate depending on who established first. However, based on the traits of common floating plants (duckweed; Lemna) and submerged plants (waterweed; Elodea) the model predicts, in line with field data, that floating plants are not an alternative stable state. Furthermore, from a theoretical point of view this study shows that the asymmetry in light competition ensures that common rules from standard competition theory do not apply anymore. Like the R* rule, which states that the species that can persist at the lowest resource levels always wins the competition.

Can duckweed-dominance be combatted by reducing N inputs to the ditches? Or does this promote other floating plants like water fern (Azolla) that can fix N2 from the atmosphere? Important is the question whether such N2-fixers can provide enough N to prevent N-limitation and keep the system P-limited, which would make steering on N inputs ineffective. To investigate this, I considered the competition between Lemna and Azolla for N, P and light. Both a minimal model, an ecosystem model (PCDitch) and field data reveal that N2-fixation is unlikely to lead to P-limitation. This can be explained by N2-fixers typically requiring higher P concentrations to persist, implying that they cannot keep the P concentration low enough for non-N2-fixers to become P-limited. In combination with field data that hint at constraints on N2-fixation that prevent N2-fixers from becoming abundant at low N availability, this suggests that it certainly pays off to combat floating plant-dominance by reducing N inputs.

Is every ditch in a polder equally vulnerable to floating plants? Each ditch in a polder receives water and nutrients from the adjacent land. This leads to a spatial gradient in water flow and associated nutrient loading, from low in the remote polder sites to high in the direction of the polder outlet where the water leaves the polder. I explored if this spatial gradient affects the vulnerability of a ditch to floating plants, by investigating with a simple nutrient model how this gradient affects the nutrient concentration of the ditches and by subsequently predicting the gradient's effect on the ditch ecology by applying the ecosystem model PCDitch spatially, through coupling PCDitch to the 1-D hydrodynamic model SOBEK. Surprisingly, we found that every ditch is equally vulnerable to floating plants, despite the spatial gradient in water flow and nutrient loading. It turned out that the ecological state of each ditch could already be predicted by regarding only the lateral supply of water and nutrients from the adjacent land, and not the supply from upstream ditches. However, these findings are violated when there is spatial heterogeneity in the water and nutrient supply from the adjacent land or in ditch characteristics like depth and sediment type. Then, the chance on floating-plant dominance differs throughout the network and a spatial modelling approach (PCDitch-SOBEK) is required to predict this chance.

Developing and combining models of different complexity plays an important role in this thesis. To do so, I used a Database Approach To Modelling (DATM), a recently developed method in which a model is stored in tables in a clear and clean way, which facilitates model development. In addition, with DATM a model can be automatically implemented in a modelling environment of choice. This relieves technical implementation issues and leaves room to focus on ecology rather than technology. I illustrated the use of DATM by implementing and analyzing the ecosystem model PCDitch and its twin model for shallow lakes PCLake in different modelling environments by using DATM. This showed that DATM allows one to use the environment one is familiar with and eases the switch to other environments for complementary analyses, including analysis in a spatial 1-D to 3-D setting.

The insights provided by this thesis can help us to improve the ecological quality of ditches. A challenging task, given the fast human-driven environmental changes at both local and global level. To predict and to anticipate the effect of these changes on the ecology, it is essential to understand how the ditch ecosystem functions. The developed and applied methods described in this thesis may be helpful in that. For example, using models of different complexity makes it possible to translate fundamental theory to the ecosystem scale, which is essential to better grasp the behavior of an ecosystem. Furthermore, the in this thesis established coupling between PCDitch and SOBEK breaks new grounds for spatial ecosystem modelling. In combination with the growing amount of remote sensing data from satellites and drones, which allow for the continuous and potentially real-time validation and calibration of spatial ecosystem models, such a spatial approach has the potential to greatly increase our ecological understanding of ditches. These advances facilitate the development of successful management strategies that make our ditch ecosystems future-proof.

Making eco logic and models work : an integrative approach to lake ecosystem modelling
Kuiper, Jan Jurjen - \ 2016
University. Promotor(en): W.M. Mooij, co-promotor(en): J.H. Janse; Jeroen de Klein. - Wageningen : Wageningen University - ISBN 9789462579446 - 192
ecology - models - ecosystems - modeling - aquatic ecology - water management - water quality - databases - ecologie - modellen - ecosystemen - modelleren - aquatische ecologie - waterbeheer - waterkwaliteit - databanken

Dynamical ecosystem models are important tools that can help ecologists understand complex systems, and turn understanding into predictions of how these systems respond to external changes. This thesis revolves around PCLake, an integrated ecosystem model of shallow lakes that is used by both scientists and water quality managers to understand and predict eutrophication effects in shallow lake ecosystems. Shallow lakes provide some of the clearest examples of alternative stable states in natural systems. PCLake can be used to calculate the critical nutrient loading, that is, the nutrient loading where an abrupt regime shift occurs from a clear aquatic plant dominated state to a turbid phytoplankton dominated state, or vice versa. Four different aspects of modelling with PCLake are addressed in this thesis: (1) making the model better accessible for the modelling community, (2) improving the model, (3) developing scientific theory, and (4) exploring new applications for water quality management.

Following a general introduction to the thesis in chapter 1, the Database Approach To Modelling (DATM) is introduced in chapter 2. DATM is invented to make dynamic models more accessible. The idea of DATM is that the mathematical equations of a model are stored in a database independently of program language and software specific information. From the database, the information can be automatically translated, augmented and compiled into working model code of various different modelling frameworks (software programs).

In chapter 3 the weak link between ecosystem models and real ecosystems is discussed in relation to model calibration and improvement. In a previous stage PCLake has been calibrated using data of more than 40 lakes to obtain a best overall fit, which has greatly increased the scope of the model by making it suitable for more generalized studies on temperate shallow lakes. However, because of this calibration, adding missing functional components to the model at a later stage does not automatically increase the validity of the model, as it may bring the model ‘out of balance’. This is exemplified by adding filter feeding zoobenthos to PCLake, which were previously ignored.

In chapter 4, the relation between food-web theory and alternative stable states theory is scrutinized. Both theoretical paradigms are highly influential in modern ecology as they help scientists understand how stability emerges in complex natural ecosystems. Unfortunately, they developed independently and it is largely unclear how the resilience of a food web relates to the stability of the complete ecosystem. For this study PCLake was used as a virtual reality from which ‘empirical’ information is sampled to parameterize a food web model, following traditional food web methods. This allowed calculating the stability of the food web along a gradient of environmental change, knowing that the complete ecosystem shows a regime shift once the critical nutrient loading is exceeded.

In chapter 5 the question is asked to what extent models of a different form can be used to describe the same natural phenomenon, and hence, how these models can be used for a better understanding of such natural phenomena. Using three classical extensions of the famous Lotka-Volterra equations, which unlike PCLake can be fully mathematically understood, we analyze the consequence of changing a system with a sophisticated functional response term (e.g. Holling type II or III) into a system with a simpler functional response term while maintaining equilibrium densities and material fluxes. These results give new insight into when empirical data can be linked to mathematical models to estimate the stability properties of real ecosystems.

Although PCLake is predominantly applied in the context of ecosystem restoration of turbid phytoplankton dominated lakes, chapter 6 focusses on the clear water state after the reestablishment of aquatic plant dominance as occured. Dense stands of aquatic plants easily cause nuisance, and hence the removal of aquatic plants is an emerging management issue. Yet, because aquatic plants play an important role in stabilizing the clear water state, the removal of plant biomass can potentially trigger a critical transition back to the turbid water state. Currently there is only limited empirical and theoretical understanding of how harvesting of aquatic plants affects ecosystem functioning, which frustrates effective and efficient ecosystem management. With PCLake the impact of harvesting is evaluated, in terms of reducing nuisance and ecosystem stability, for a wide range of external nutrient loadings, mowing intensities and timings. Additionally, the model is used to estimate how much phosphorus is removed from the system during harvesting.

In chapter 7 I discuss the added value of taking an integrative approach to modelling, and discuss the integrated nature of the studies presented in this thesis. It’s also important to note that these studies were part of a larger research project with the overall aim of increasing the usefulness and the validity of PCLake and its twin model PCDitch, and to enhance the confidence in the models among water quality managers. A synopsis of the overarching collaborative research project on PCLake and PCDitch is presented in chapter 8.

Waar is het bosbeleid gebleven? : (en wie zit er eigenlijk op te wachten?)
Arts, Bas ; Nabuurs, Gert-Jan - \ 2016
forest policy - nature conservation policy - netherlands - felling - ecology - timber production
Welk lid van de Tweede Kamer weet nog iets van bos? Hoeveel bosbouwers werken er nog bij het ministerie van Economische zaken? Waarom hebben we geen Boswet, bosvisie of Bosbeleidsplan meer? Allemaal vragen die bosbouwers onder elkaar zich regelmatig afvragen. Vindt de samenleving het bos niet meer de moeite waard? Of is er iets anders aan de hand?
Improving communication and validation of ecological models : a case study on the dispersal of aquatic macroinvertebrates
Augusiak, Jacqueline A. - \ 2016
University. Promotor(en): Paul van den Brink, co-promotor(en): V. Grimm. - Wageningen : Wageningen University - ISBN 9789462579378 - 192
macroinvertebrates - aquatic invertebrates - ecological modeling - ecology - models - dispersal - environmental policy - macroinvertebraten - waterinvertebraten - ecologische modellering - ecologie - modellen - verspreiding - milieubeleid

In recent years, ecological effect models have been put forward as tools for supporting environmental decision-making. Often they are the only way to take the relevant spatial and temporal scales and the multitude of processes characteristic to ecological systems into account. Particularly for environmental risk assessments of pesticides the potential benefits of including modelling studies were recognized and a dialogue between different stakeholder groups was opened. Representatives from academia, pesticide-producing industries, and regulators are nowadays discussing their needs, possibilities, and ways of implementation for improving the use and usefulness of such models. However, it quickly became evident that not all involved parties possess the same background knowledge in regards to modelling terminology and model quality understanding. Proper communication of a given model's structure, robustness, and soundness is crucial to render a model of real use to the decision-making. Doubts about a model's quality and mode of operation may lead to an immediate rejection of the conclusions drawn from its estimations.

In this thesis, we addressed this point of concern, and performed a literature review focusing on aspects surrounding quality assessments, validation, and communication of models. "Validation" was identified as a catch-all term, which is thus useless for any practical purpose. Based on the review, we developed a framework that splits the seemingly blurry process into associated components and introduce the term ‘evaludation’, a fusion of ‘evaluation’ and ‘validation’, to describe the entire process of assessing a model's quality and reliability. Considering the iterative nature of model development, the modelling cycle, we identified six essential elements of evaludation: (i) ‘data evaluation’ for scrutinising the quality of numerical and qualitative data used for model development and testing; (ii) ‘conceptual model evaluation’ for examining the simplifying assumptions underlying a model's design; (iii) ‘implementation verification’ for testing the model's implementation in equations and as a computer programme; (iv) ‘model output verification’ for comparing model output to data and patterns that guided model design and were possibly used for calibration; (v) ‘model analysis’ for exploring the model's sensitivity to changes in parameters and process formulations to make sure that the mechanistic basis of main behaviours of the model has been well understood; and (vi) ‘model output corroboration’ for comparing model output to new data and patterns that were not used for model development and parameterisation.

In a subsequent step, we used the evaludation framework to re-evaluate and adjust the documentation framework TRACE (TRAnsparent and Comprehensive Eco- logical modelling; Schmolke et al. 2010), a general framework for documenting a model's rationale, design, and testing. TRACE documents should provide convincing evidence that a model was thoughtfully designed, correctly implemented, thoroughly tested, well understood, and appropriately used for its intended purpose. TRACE documents link the science underlying a model to its application, thereby also linking modellers and model users, for example stakeholders, decision makers, and developers of policies. TRACE thus becomes a tool for planning, documenting, and assessing model evaludation, which includes understanding the rationale behind a model and its envisaged use.

To provide an example of the measures that can be taken to increase general trust in a model's design and output, we chose MASTEP (Metapopulation model for Assessing Spatial and Temporal Effects of Pesticides) for a case study. MASTEP is an individual-based model used to describe the effects on and recovery of the water louse Asellus aquaticus after exposure to an insecticide in pond, ditch, and stream scenarios. The model includes processes of mortality of A. aquaticus, life history, random walk between cells and density dependence of population regulation. One of the submodels receiving particular criticism was the random walk procedure and the uncertainty attached to the parameters used. The parameters were estimated based on experimental studies performed under very limiting conditions.

We designed and performed experiments to derive more precise parameters and to better understand the movement behaviour of this freshwater isopod. The experimental procedure that we developed employed video tracking of marked individuals that were introduced alone or as part of a group of unmarked individuals into arenas of approximately 1m2 in size. We recorded the paths of the marked individuals under a set of different conditions, i.e. presence or absence of food or shelter, population density, and after sublethal exposure to chlorpyrifos and imidacloprid. Based on the experimental findings, we refined the movement modelling procedure used in MASTEP to derive more realistic dispersal estimates, with which we revisited a modelling study performed previously by Galic et al. (2012). In this study, the effects of pesticide application timing on population dynamics and recovery times were tested and compared to outcomes from previous versions. It was furthermore possible to integrate an increased level of environmental complexity that could not be addressed before due to a lack of data. Compared to former versions of the population model, recovery times did not change significantly when the same movement parameters were applied to all simulated individuals. This indicates that the previous assumptions already yielded robust estimations. Accounting for life stage dependent movement restraints, though, delayed recovery when exposure occurred shortly before a reproduction cycle. Based on these findings, it was concluded that an increase of ever more realism and environmental complexity in modelling studies needs to be done carefully on a case-by-case basis. Increased realism in models can introduce an unwarranted increase in model complexity and uncertainty, which is not always supporting an improved credibility level of a model.

Despite the need for basic ecological research for more comprehensive ecological models, we further argue that a modelling study in general can benefit greatly from an improved plan that considers communication needs from the start. Considering such needs early on can help develop a time- and cost-saving strategy for model testing and data collection, while providing a thorough understanding of a model's underlying mechanisms across several layers of stakeholder groups.

Monitoring en Evaluatie Pilot Zandmotor Fase 2 - Ecotopenkaarten vooroever en getijdenstrand 2010 - 2015
Wijsman, J.W.M. ; Tangelder, M. ; Visser, Pieter ; Hoekstra, R. - \ 2016
IMARES (Rapport / IMARES C034/16) - 35 p.
getijden - stranden - zandsuppletie - natuurontwikkeling - ecologie - zuid-holland - tides - beaches - sand suppletion - nature development - ecology
Dit rapport presenteert een eerste aanzet voor de ontwikkeling van ecotopenkaarten voor de vooroever en het intergetijdenstrand van de Zandmotor over de jaren 2010 tot en met 2015. In de ecotopenclassificatie worden de abiotische parameters droogvalduur, bodemschuifspanning en getijdenstroming gecombineerd tot 11 ecotopen, waarvan 4 in de vooroever, 6 op het natte strand en 1 op het droge strand.
Evaluatie van de ecologische effectiviteit van de houtconstructies in de Snelle loop
Verdonschot, R.C.M. ; Brugmans, Bart ; Moeleker, Mieke ; Verdonschot, P.F.M. - \ 2016
H2O online (2016)27 juli.
ecologie - waterlopen - noord-brabant - hydrologie - macrofauna - monitoring - bemonsteren - hout - aquatische ecosystemen - dood hout - ecology - streams - hydrology - sampling - wood - aquatic ecosystems - dead wood
In de Snelle Loop zijn in 2012 verschillende typen houtconstructies aangebracht. Waterschap Aa en Maas en studenten van de HAS Hogeschool in Den Bosch verrichten sindsdien jaarlijks fysisch-chemische, hydromorfologische en biologische metingen. In deze studie zijn de tot nu toe verzamelde gegevens over de effecten op de levensgemeenschap na drie jaar geëvalueerd. Het hout bleek effect te hebben op de levensgemeenschap, maar grote jaarlijkse verschillen lieten zien dat met name effecten op een groter schaalniveau een sturende rol spelen. Er worden aanbevelingen gedaan voor de opzet van monitoring om onderscheid te kunnen maken tussen effecten op verschillende schaalniveaus
Data-architectuur natuur
Bulens, J.D. ; Boss, M. - \ 2016
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2737) - 35 p.
milieumonitoring - ecologie - monitoring - informatiemanagement - milieuwetgeving - natuur - environmental monitoring - ecology - information management - environmental legislation - nature
Het Rijk en de provincies werken samen aan één samenhangend systeem voor de ecologische
monitoring en natuurinformatie. Er wordt gezamenlijk gewerkt aan een samenhangend systeem van
onder andere landelijke en gebiedsgerichte ecologische monitoring om efficiënt gegevens in te winnen
en doelmatig met middelen om te gaan. Vaak is nu nog onbekend welke data nu precies beschikbaar
zijn, waar en in welke vorm. Juist omdat geput wordt uit diverse databronnen, is het belangrijk deze
inzichtelijk en vergelijkbaar voor betrokkenen beschikbaar te stellen. Het samenbrengen en
harmoniseren van data heeft een grote toegevoegde waarde om transparant en eenduidig deze data
te kunnen gebruiken. De beschreven data-architectuur als basis voor een informatievoorziening is
daarvoor een onmisbaar uitgangsprincipe.
In dit rapport is beschreven wat de basis is om tot een informatievoorziening te komen. Dit omvat het
ontwikkelen van domeinstandaarden (informatiemodellen), de inrichting van een infrastructuur en het
vormgeven van samenhangende processen of systemen om onder andere tot natuurrapportages te
komen. Dit laatste is in 2015 is in een aantal inventarisaties vastgelegd met aangegeven wat de
huidige situatie (IST) en de toekomstige, gewenste situatie (SOLL) van het natuurnetwerk in
Nederland is. Samen met deze inventarisaties maakt dit het beeld compleet. Dit vormt een kader om
komende, nieuwe ontwikkelingen aan te toetsen.
Voor de data-architectuur voor de informatievoorziening Natuur wordt in dit rapport als basis een
grondplaat geschetst en gevisualiseerd, waarin de basisobjecten voor de informatievoorziening zijn
benoemd. De Nederlandse referentie-architecturen, NORA en PETRA, zijn goed bruikbaar met de
aanvulling dat, uitstijgend boven de eigen organisatie, goede afspraken gemaakt moeten worden met
partners in de natuurinformatieketen. In het rapport Monitoring en Informatievoorziening
Natuurrapportages [Batenburg 2015] is dit aspect benoemd en uitgewerkt. Voor het samenbrengen en
harmoniseren is het belangrijk het principe van het scheiden van data en processen voor informatie
verwerkende systemen te hanteren. Voor een beschrijving in de vorm van objecten met
eigenschappen is het cruciaal dat er eenduidige definities worden gebruikt. Hiervoor moeten
bestaande definities afkomstig uit verschillenden bronnen goed op elkaar afgestemd zijn. Het verdient
aanbeveling definities in een gegevenscatalogus bij elkaar te brengen en centraal via een register te
ontsluiten.
Dit betekent ook dat de data los van de gebruikte systemen opgeslagen moeten worden. Deze komen
zo ook beschikbaar voor andere processen. Hergebruik vergroot dan in sterke mate de waarde van de
gegenereerde data. Scheiding van data enerzijds en processen en regels anderzijds zijn daarmee
cruciaal en kunnen veel meerwaarde creëren. Ruwe (maar wel gevalideerde) data zijn de basis voor
afgeleide data en informatie. Het is daarom van belang te investeren in kwalitatief goede basisdata.
Houd de data (informatie) bij de bron. Daar is de kennis voor het onderhoud en beheer van de
inhoudelijk component het best belegd. Maar realiseer wel slechts één toegang tot alle informatie voor
Natuur. Dit kan in de vorm van een landelijke voorziening, informatiehuis of soortgelijk. In dit licht zijn
relevante ontwikkelingen als het Digitale Stelsel Omgevingswet (voorheen de Laan van de
Leefomgeving) en INSPIRE lopende ontwikkelingen waarop aansluiting moet worden gezocht.
Woningbouw Abbekerk : effect op weidevogelgrasland in open landschap
Schotman, A.G.M. - \ 2016
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2732) - 23 p.
weidevogels - woningbouw - woningbouwbeleid - graslanden - ecologie - ruimtelijke ordening - landschapsecologie - noord-holland - grassland birds - house building - housing policy - grasslands - ecology - physical planning - landscape ecology
De gemeente Medemblik wil in Abbekerk woningbouw realiseren. Hiervoor zijn drie scenario’s met twee bouwfasen. Deze woningbouw is strijdig met de provinciale ruimtelijke verordening, artikel 25. Het te bebouwen gebied is op kaart gezet als ‘weidevogelleefgebied’. Een bestemmingsplan mag daar alleen woningbouw toelaten als er van ‘netto geen verstoord’ weidevogelgebied sprake is. Uit het onderzoek blijkt dat in de eerste bouwfase van de drie scenario’s het netto verstoorde oppervlak varieert van 2,9 tot 9,4 ha en het aantal verstoorde gruttoterritoria (2014) daarin van 0 tot 4. Formeel is er dus netto-verstoring. In een inbreidingslocatie is dit niet het geval. Er worden argumenten aangevoerd dat er in ecologische zin geen sprake is van verstoring van het door het beleid beoogde weidevogelkerngebied, o.a. omdat de gebieden op de kaart in 2014 al niet voldeden aan de criteria en in 2016 ook niet.
The facilitative role of trees in tree-grass interactions in savannas
Priyadarshini, K.V.R. - \ 2016
University. Promotor(en): Herbert Prins; Steven Bie, co-promotor(en): Ignas Heitkonig. - Wageningen : Wageningen University - ISBN 9789462577008 - 134 p.
plant interaction - trees - grasses - savannas - ecosystems - ecology - planteninteractie - bomen - grassen - savannen - ecosystemen - ecologie

Terrestrial ecosystems support a high plant diversity where different plant types coexist. However, the mechanisms that support plant coexistence are not entirely clear. Savanna ecosystems that are nutrient and water limited are characterized by a unique ecological feature: the coexistence of trees and grasses. Tree-grass interactions in savannas are typically viewed as being competitive and are based on the Gaussian principle of niche or habitat differentiation. Trees and grasses are reported to suppress the growth of each other and the interactions are viewed as competition. However, tree-grass mixtures persist in a range of rainfall conditions in savannas. This study examined tree-grass interactions to understand the ecological processes that may sustain tree-grass coexistence in dry savannas (< 800 mm of rainfall) of southern Africa. Water and nitrogen resource-use patterns of trees and grasses were investigated and the effects of competition between trees and grasses on resource storage in perennial grasses were examined. An ecological perspective of the role of trees in two human land-use types in African drylands is provided and the functionality of trees in these land-use types was reviewed.

Seasonality of plant available water imposes intense water limitation to plants in savannas. Yet, trees and grasses coexist. The water relations between trees and grasses are poorly understood. In Chapter 2, the principal water-sources for trees and grasses in different seasons were identified using the natural variation in H and O stable isotope composition of source waters. Seasonal differences in the stable isotope composition of water in trees and grasses indicated that there was water-source use partitioning as well as overlap. Trees and grasses used water from the topsoil after rainfall indicating overlap of water-sources. Trees shifted to groundwater or subsoil water when there was no water in the topsoil, indicating partitioning of water-use. Grasses always used water from the topsoil. By labelling deep-soil (2.5 m depth) with a deuterium tracer, hydraulic-redistribution in all the studied tree species and water transfer to grasses via the topsoil was confirmed. However, this occurred only in the dry-season. Results indicated possible shifts in tree-grass interactions during different periods of the year. Furthermore, dry-season hydraulic-redistribution indicated potential facilitation affects by trees to their understory grasses.

A key question in savanna ecology is how trees and grasses coexist under nitrogen limitation. In Chapter 3, the sources of nitrogen for trees and grasses in a semi-arid savanna were investigated using natural abundance of foliar δ15N and nitrogen content. 15N tracer additions were used additionally to investigate the redistribution of subsoil nitrogen by trees to grasses. Foliar δ15N values were consistent with trees and grasses using mycorrhiza-supplied nitrogen in all seasons and a switch to microbially-fixed nitrogen during the wet season. Based on seasonal variation in mineralization rates in the Kruger Park region, the use of mineralized soil nitrogen by trees and grasses seemed highly unlikely. The foliar δ15N values were similar for all the studied tree species differing in the potential for nitrogen-fixation consistent with the absence of nodules indicating the lack of rhizobially fixed nitrogen. The tracer experiment showed that nitrogen was redistributed by trees to understory grasses in all seasons. Redistribution of nitrogen by trees and subsequent uptake of this tree redistributed nitrogen by grasses from the topsoil was independent of water redistribution. Although there was overlap of nitrogen sources between trees and grasses, dependence on biological sources of nitrogen coupled with redistribution of sub-soil nitrogen by trees could be contributing to the co-existence of trees and grasses in semi-arid savannas.

An important plant response to competition and resource limitation is an increase in root reserves. In Chapter 4, the root characteristics of perennial grasses in the presence and absence of trees as a proxy of competition in South African savannas in three sites that differed in rainfall were investigated. The hypothesis on which this investigation was based was that competition from trees and water limitation will result in increased storage in roots of grasses under trees. However, no significant effect of variation in rainfall of the different study locations on root characteristics of grasses were found. Furthermore, most root characteristics were not significantly influenced by tree presence with the exception of nitrogen-content. The root nitrogen content showed an increase with rainfall and tree presence through potentially higher mineralization rates and nitrogen availability in the under-tree canopy environment. The study sites occurred in the drier rainfall range in South Africa. Therefore, it is likely that trees and grasses in these dry savannas might have a positive relationship conforming to the stress-gradient hypothesis. Alternatively, grasses and trees might be using complementary water and nutritional resources.

The mix of trees and grasses is critical for the functioning of the savanna biome, which supports a large fraction of the human population and sustains the highest densities and diversities of herbivores in the world. Both, increases and decreases in tree densities have been reported from savannas globally, which are attributed to human activities and climate change. Changes in tree densities could drastically impact ecosystem functioning and lead to land degradation and large economic losses. Consequently, the sustainable and heterogeneous nature of various savanna land-use types is compromised. In Chapter 5, the significant role of trees in dry savannas (< 800mm rainfall) based on nutrient and water-redistribution capabilities of savanna trees is illustrated. An ecological perspective of the role of trees in two human land-use types in African drylands: agroforests and rangelands which include silvo-pastoral systems and mixed-game-livestock farming systems, is provided. The causes for the loss of trees in these land-use types is evaluated and the role of trees for better land and sustainable natural resource management is highlighted.

Chapter 6 synthesises the conclusions of all the preceding chapters highlighting the importance of facilitative interactions in tree-grass coexistence in savannas that are mostly overlooked. A simple Gaussian model of niche or habitat differentiation may not be a holistic and functional explanation of plant coexistence but rather the role of biotic interactions that include symbionts, parasites, or predators that will influence not only the competitive ability of plants but also facilitation, may be more pragmatic. Plant-plant interactions are complex and a multitrophic approach may be necessary to understand the functioning of these interactions and their roles in ecosystems.

Searching for balance : stability and equilibria of food webs
Altena, C. van - \ 2016
University. Promotor(en): Peter de Ruiter; J.A.P. Heesterbeek; Wolf Mooij, co-promotor(en): Lia Hemerik. - Wageningen : Wageningen University - ISBN 9789462576827 - 130 p.
food webs - models - interactions - ecology - biocoenosis - ecological balance - voedselwebben - modellen - interacties - ecologie - biocenose - ecologisch evenwicht

Abstract

How complexity of food webs relates to stability has been a subject of many studies. Often,

unweighted connectance is used to express complexity. Unweighted connectance is

measured as the proportion of realized links in the network. Weighted connectance, on the

other hand, takes link weights (fluxes or feeding rates) into account and captures the shape

of the flux distribution. Here, we used weighted connectance to revisit the relation between

complexity and stability. We used 15 real soil food webs and determined the feeding rates

and the interaction strength matrices. We calculated both versions of connectance, and

related these structural properties to food web stability. We also determined the skewness

of both flux and interaction strength distributions with the Gini coefficient. We found no

relation between unweighted connectance and food web stability, but weighted connectance

was positively correlated with stability. This finding challenges the notion that complexity

may constrain stability, and supports the ‘complexity begets stability’ notion. The positive

correlation between weighted connectance and stability implies that the more evenly flux

rates were distributed over links, the more stable the webs were. This was confirmed by the

Gini coefficients of both fluxes and interaction strengths. However, the most even

distributions of this dataset still were strongly skewed towards small fluxes or weak

interaction strengths. Thus, incorporating these distribution with many weak links via

weighted instead of unweighted food web measures can shed new light on classical

theories

Inventarisatie van modellen van Alterra voor beheervragen Rijkswaterstaat : waterkwaliteit en ecologie
Veldhuizen, A.A. ; Assinck, F.B.T. - \ 2016
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2698) - 29 p.
waterbeheer - waterkwaliteit - modellen - ecologie - water management - water quality - models - ecology
Rijkswaterstaat wil modellen en modeltoepassingen, die de komende jaren voor het beheer van rijkswateren op het gebied van waterkwaliteit en ecologie nodig geacht worden, onder beheer en onderhoud brengen. Alterra heeft modellen voor waterkwaliteit en ecologie die voor beheervragen van Rijkswaterstaat gebruikt kunnen worden. Dit rapport geeft daar een overzicht van. Het rapport is opgesteld in het kader van het door Deltares in opdracht van Rijkswaterstaat uitgevoerde B&O Waterkwaliteitsmodelschematisaties. De modellen zijn onderverdeeld in modeltypen: Nutriënten procesmodellen, Nutriënten effectmodellen, Procesmodellen bestrijdingsmiddelen, Procesmodellen natuur, Effectmodellen natuur, Graadmeters natuur, Planningstools en Procesmodellen Water. Per modeltype is een factsheet opgesteld waarin globaal wordt aangegeven waarvoor de modellen bedoeld zijn, hoe ze werken, welke vragen ermee beantwoord kunnen worden, wat de belangrijkste output is en wat de mogelijkheden en beperkingen zijn. Tevens is er een lijst met modeltoepassingen opgesteld, waarvoor vragen zijn beantwoord.
The mountain vegetation of South Peru : syntaxonomy, ecology, phytogeography and conservation
Montesinos-Tubée, D.B. - \ 2016
University. Promotor(en): Karle Sykora; Frank Berendse, co-promotor(en): Antoine Cleef. - Wageningen : Wageningen University - ISBN 9789462576797 - 334 p.
vegetation - mountains - phytogeography - ecology - taxonomy - nature conservation - andes - peru - vegetatie - gebergten - plantengeografie - ecologie - taxonomie - natuurbescherming

THE MOUNTAIN VEGETATION OF SOUTH PERU: SYNTAXONOMY, ECOLOGY, PHYTOGEOGRAPHY AND CONSERVATION

This thesis presents an overview and revision of plant communities from xerophytic and mountain landscapes in the dry Andes of South Peru. The revision is based on comparison of the collected vegetation data with other regional and interregional studies. This phytosociologic overview comprises the arid and semi-arid montane vegetation of the province of Arequipa and besides the plant communities of Moquegua from the prepuna between 3470 and 3700 m, the puna between 3750 and 4500 m and the superpuna between 4450 and 4800 m. The Braun-Blanquet approach and multivariate ordination and classification methods have been applied to classify the different plant communities and to study the relation between plant communities and environmental variables, such as altitude, slope degree and exposition, rock and stone cover percentage, manure cover and grazing. Furthermore the results are presented of a phytogeographical analysis of the Andean puna flora (at vascular genus level) and its relation to other tropicalpine regions in South America. Finally, the descriptions of six recently published new species are included in this thesis. The results provide an important database for nature conservation issues, stressing the significance of protecting the fragile and diverse ecosystems of the Moqueguan Andes. The results of this vegetation survey can be used to prioritize the selection and assignment of nature reserves.

The ecological effects of deep sand extraction on the Dutch continental shelf : Implications for future sand extraction
Jong, M.F. de - \ 2016
University. Promotor(en): Han Lindeboom; P. Hoekstra, co-promotor(en): Martin Baptist. - Wageningen : Wageningen University - ISBN 9789462576834 - 164 p.
sand - coastal areas - ecology - marine environment - marine ecology - aquatic ecosystems - netherlands - zand - kustgebieden - ecologie - marien milieu - mariene ecologie - aquatische ecosystemen - nederland
Kennissysteem agrarisch natuurbeheer : ondersteuning voor lerend beheer in het agrarisch natuurbeheer
Melman, T.C.P. ; Buij, R. ; Schotman, A.G.M. ; Vos, C.C. ; Verdonschot, R.C.M. ; Sierdsema, H. ; Vanmeulebrouk, B. - \ 2016
Alterra, Wageningen-UR (Alterra-rapport 2702) - 109 p.
agrarisch natuurbeheer - kennissystemen - weidevogels - vogels - ecologie - biodiversiteit - agri-environment schemes - knowledge systems - grassland birds - birds - ecology - biodiversity
In het nieuwe stelsel agrarisch natuurbeheer (ANLb-2016) heeft het collectief dat een beheeraanvraag indient een verantwoordelijkheid voor het realiseren van de natuurresultaten. Kennis over vóórkomen en ecologische vereisten van de soorten krijgen daarin een steeds belangrijker plek. Kennisontsluiting is daarvoor nodig. Voor alle 67 soorten waarvoor ANLb-2016 doelstellingen heeft, zijn al eerder opgestelde fiches aangevuld, met name wat betreft dispersieafstanden en minimumareaal. Er is een format ontwikkeld om deze informatie op handzame wijze te ontsluiten en op een aantrekkelijke manier te presenteren: het kennissysteem ANB. Om er met het beheer gemakkelijker grip op te krijgen, is per leefgebiedtype een poging gedaan de soorten in enkele clusters te groeperen. Het kennissysteem ANB is een topografisch gestuurde, web-based ontsluiting van deze kennis. Voorkomen, ecologische randvoorwaarden en beheer worden daarin opgenomen en zijn interactief benaderbaar. Voor weidevogels is het in voorgaande jaren opgebouwde systeem verder ontwikkeld en kan nu in de praktijk worden beproefd. Voor akkervogels, droge dooradering en natte dooradering is voor enkele voorbeeldsoorten het concept van kennisontsluiting ontwikkeld. Voor elk leefgebiedtype is een Prezipresentatie gemaakt die de gebruiker inleidt in het concept van het kennissysteem. Deze is bedoeld om gebruikers te ondersteunen bij verdere wensen ten aanzien van de ontwikkeling van het kennissysteem.
Kan het natuurbeleid tegen een stootje? : enkele botsproeven van de herijkte Ecologische Hoofdstructuur
Os, J. van; Schrijver, R.A.M. ; Broekmeyer, M.E.A. - \ 2015
Wettelijke Onderzoekstaken Natuur & Milieu (WOt-technical report 49) - 76 p.
ecologische hoofdstructuur - ecologie - natuurbeleid - natuurwaarde - milieuwetgeving - nederland - ecological network - ecology - nature conservation policy - natural value - environmental legislation - netherlands
Met de herijking van de Ecologische Hoofdstructuur (EHS) heeft de Nederlandse overheid een keerpunt in het
natuurbeleid gemaakt. De EHS is verkleind, de uitvoering is bij provincies neergelegd en de financiering van
het natuurbeheer is veranderd. Eigendom en beheer van natuurgebieden wordt niet meer automatisch gegund
aan Staatsbosbeheer, Natuurmonumenten of provinciale landschappen. Ook de naam is vernieuwd: Natuurnetwerk
Nederland (NNN). Deze rapportage beschrijft vier botsproeven, waarin mogelijke veranderingen na
herijking van de EHS aan bod komen. Het natuurbeleid rust op vier pijlers: wettelijke bescherming door de
Flora- en faunawet, de Natuurbeschermingswet, de Boswet en de Natuurschoonwet; ruimtelijke bescherming
via provinciale verordeningen en bestemmingsplannen van gemeenten; het eigendom van terreinbeherende
organisaties; en de overheidssubsidies voor verwerving, inrichting en beheer van natuurgebieden. Het blijkt
dat de gewenste natuurbeheertypen alleen in het subsidiekader zijn vastgelegd. Als één van deze pijlers
wegvalt of verandert, heeft dat in eerste instantie vaak geen grote gevolgen voor de continuïteit van het
natuurbeheer. In veel gevallen worden bestaande natuurwaarden beschermd door algemene wetgeving en
lokale bestemmingsplannen. Om bepaalde gewenste natuurontwikkelingen of het behoud van bepaalde
natuurtypen te realiseren, zijn beheersubsidies echter vaak onmisbaar
"De revolutie hangt niet van een persoon af" : Tittonell levert belangrijke bijdrage aan ontwikkeling van agro-ecologie
Tittonell, P.A. ; Veluw, C. van - \ 2015
Ekoland (2015)7/8. - ISSN 0926-9142 - p. 11 - 11.
agro-ecologie - landbouw - voedselproductie - ecologie - kennisoverdracht - universitair onderzoek - biologische landbouw - agroecology - agriculture - food production - ecology - knowledge transfer - university research - organic farming
Argentijnse ‘bioprof’ Pablo Tittonell verlaat Wageningen Universiteit. Hij inspireerde drie jaar lang studenten, medewerkers en boeren.
Omgaan met bodemverontreiniging in het landelijk gebied
Waarde, J.J. van der; Boels, D. ; Hopman, M. - \ 2015
De Levende Natuur 105 (2015)3. - ISSN 0024-1520 - p. 110 - 114.
bodemverontreiniging - bodembiologie - herstel - natuurbescherming - ecologie - risicoschatting - bodemkwaliteit - soil pollution - soil biology - rehabilitation - nature conservation - ecology - risk assessment - soil quality
Bodemverontreiniging kan leiden tot ecologische effecten en risico's voor plant en dier. Soms moeten er daarom maatregelen worden getroffen. In de praktijk van natuurbeheer en natuurontwikkeling is er nog veel onduidelijkheid over hoe deze effecten bepaald moeten worden. Daartoe is door VROM, LNV, RIZA, RIVM en Bioclear (mede gefinancierd door SKB) PERISCOOP opgezet (Platform Ecologische Risicobeoordeling)
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