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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Plant functional diversity and nutrient availability can improve restoration of floating fens via facilitation, complementarity and selection effects
Zuidam, Jeroen P. van; Leeuwen, Casper H.A. van; Bakker, Elisabeth S. ; Verhoeven, Jos T.A. ; Ijff, Stéphanie ; Peeters, Edwin T.H.M. ; Zuidam, Bastiaan G. van; Soons, Merel B. - \ 2018
Journal of Applied Ecology (2018). - ISSN 0021-8901
assisted colonization - floating fen - functional diversity - peat formation - restoration - rhizome formation - terrestrialization - wetlands

Peat-forming wetlands, particularly floating fens that form the initial stages of these ecosystems, are declining globally due to excavation, dehydration and eutrophication. Restoration typically involves reestablishment of early-successional open-water stages, with oligotrophic conditions that are characteristic for these systems. However, restoration success is notoriously limited. A potential improvement may be to initiate succession by reintroducing of target plant species. Knowledge is therefore needed on (a) which plant functional groups should be re-introduced to stimulate fen formation; and (b) how to manage nutrient levels during restoration, considering that plant growth may be slow in oligotrophic conditions. We hypothesized that increasing functional diversity of introduced species would stimulate the formation of peat-forming target communities, their biomass accumulation and expansion onto open water. We also hypothesized that nutrient availability would mediate the relative contribution of specific functional groups to these effects. We investigated this in 36 artificial outdoor ponds by manipulating plant functional diversity (clonal dominants, clonal stress-tolerators and interstitials) on constructed rafts with fen-forming communities, and subjected these to a range of nutrient loadings over 2 years. Increasing functional diversity as well as increasing nutrient loadings had stimulating effects on plant biomass accumulation, cover formation and rhizome growth onto open water. Both complementarity (due to niche partitioning or facilitation) and selection effects were mechanisms underlying the diversity effect, with a constant relative importance over the entire range of nutrient availabilities. Different functional groups were important for biomass production at different nutrient availabilities. Rhizome formation by clonal stress-tolerators contributed disproportionately to open water colonization, identifying this functional group as key across all nutrient levels. Synthesis and applications. Restoration of floating fen communities can be stimulated during the first 2 years by introducing a high functional diversity of plant species. There include fast-growing clonal species, clonal stress-tolerators and interstitials, which facilitate each other. Restoration is dependent on the presence of clonal stress-tolerators such as Calla palustris, Comarum palustre and Menyanthes trifoliata for expansion onto the open water. Furthermore, restoration can start under a wide range of water nutrient levels, including eutrophic conditions.

Hydrological drought and wildfire in the humid tropics
Taufik, Muh - \ 2017
University. Promotor(en): Remko Uijlenhoet, co-promotor(en): Henny van Lanen. - Wageningen : Wageningen University - ISBN 9789463436359 - 99
wildfires - drought - humid tropics - wetlands - hydrology - prediction - water management - natuurbranden - droogte - humide tropen - hydrologie - voorspelling - waterbeheer

Drought is a recurrent hazard, which has happened throughout human history, and it is anticipated to become more severe in multiple regions across the world. Drought occurs in all climate regimes from humid to dry and from hot to cold. Drought is often viewed through its impact on environment and society, including wildfire, which is the topic of this study. The nature of such impacts differs remarkably from region to region. Although drought does not directly cause wildfire, it provides favorable conditions for wildfire ignition and spread. When drought coincides with strong El Niño events in the humid tropics, e.g. Southeast Asia, the impacts worsen through uncontrolled forest fires affecting the global carbon cycle. These include reduction of the carbon stock, intensifying the haze hazard, and other severe socio-economic impacts in Southeast Asia, including areas far away from the burnt area, e.g. Singapore because of fires in Sumatra.

There still remains a serious lack of scientific understanding about the fundamental role of drought in fire-generating processes. Most research, so far, suggests that climate controls wildfire occurrence in the humid tropics. However, this climate-centered approach, which is reflected in contemporary drought-fire related indices, overlooks soil and hydrological processes beneath the surface across the humid tropics. There is also uncertainty about the relative roles of climate variability and human activities in influencing the nature and distribution of drought-related wildfires. Hence, the general objective of this PhD research is to examine how characterization of hydrological drought under natural and human-modified conditions can improve understanding of wildfires in general in the humid tropics.

Chapter 2 discusses the contribution of humans to an increase of hydrological drought severity in the tropical peatland of Southeast Asia. Climate variability induces drought in the region, however, human activities (human-modified drought) may increase its severity. Analyzing long time series of simulated historical groundwater levels from selected regions in Southeast Asia, which were validated against some years with observations, revealed that human interference (through canalization and land-use change) has amplified drought severity. The drought amplification due to human interference was at least double that of climate-induced drought. The amplification is even higher when peatland is converted into acacia plantation. Further, research findings suggest that even if the Paris Agreement target is met, drought risk of peatlands remains high unless sustainable water management receives top priority in the region.

Chapter 3 deals with how an existing, well-known drought-fire related index, i.e. the Keetch-Byram Drought Index (KBDI), is modified to improve applicability in the humid climate environment of Southeast Asia. The improvement includes: (i) adjustment of the drought factor to the local climate, and (ii) addition of the water table depth as a dynamic factor to fine-tune the drought index. The results indicate that the modified Keetch-Byram Drought Index (mKBDI) performed well in predicting fire hazard. Furthermore, the research identified a critical water table depth, which represents maximum fire hazard (0.85 m for the wetland forest of South Sumatra). Below this value hazard does not increase anymore. The mKBDI could be more widely applied, if pedotransfer functions would be developed that link easily-obtainable soil properties to the parameters of the water table factor.

Chapter 4 shows that wetland transformation (i.e. through canalization and land-use change) not only affects hydrological drought (Chapter 2), but also influences fire behaviour. In Southeast Asia, expansion of agricultural cropland and forest plantations has changed the landscape of wetlands. The findings showed that the transformation into acacia plantation has amplified the fire hazard from 4% (under natural conditions) to 17%. An even higher amplification (40% fire hazard) is expected under poor water management, that is, uncontrolled drainage. The findings derived from this observation-based modeling experiment suggest that improved water management (controlled drainage with higher dry season surface water levels) can minimize fire susceptibility.

Chapter 5 explains the importance of hydrology for fire hazard studies. Borneo is selected to investigate the added value of including hydrological variables in fire hazard prediction approaches. More than 300 statistical models were tested, and the results showed that models that include hydrological variables better predict area burnt than those solely based on climate indicators/indices. Further, modelling evidence shows amplifying wildfires and greater area burnt in response to El Niño Southern Oscillation (ENSO) strength, when hydrology is considered. These results highlight the importance of considering hydrological drought for wildfire prediction. I recommend that hydrology should be considered in future studies of the impact of projected ENSO strength, including effects on tropical ecosystems and biodiversity conservation.

The contributions of this thesis research to science are summarized and synthesized in Chapter 6. First, the research identified that fire hazard studies would benefit from adding hydrology, which is reflected in the improved model performance when hydrological variables are integrated. Next, the research revealed that humans play a substantial role in modifying groundwater drought characteristics, hence amplifying the fire hazard in Southeast Asia. Further, the chapter identified several relevant research findings, including the model choice, which should consider the simplicity and the applicability of the model. Another finding demonstrated that controlling canal water level through canal blocking is a practical water management tool to restore degraded wetland. This restored wetland would benefit some endemic species. However, the restored wetland still faces high drought severity. Hence they remain more fire-prone until the un-impacted hydrology condition is achieved. Finally, this research suggest that currently widely-used drought indices (such as FWI) require improvements in their model structure, which means integration of hydrological variables to increase their applicability for fire hazard studies in the humid tropics.

A comprehensive assessment of agriculture in lowlands of south Brazil: characterization and comparison of current and alternative concepts
Theisen, Giovani - \ 2017
University. Promotor(en): Niels Anten, co-promotor(en): Lammert Bastiaans. - Wageningen : Wageningen University - ISBN 9789463436380 - 234
cropping systems - farming systems - crop management - lowland areas - wetlands - pampas - brazil - intensification - sustainability - productivity - indicators - soil management - rice - flooded rice - oryza sativa - maize - zea mays - glycine max - cover crops - livestock - rotation - mixed farming - seedbed preparation - farm machinery - teeltsystemen - bedrijfssystemen - gewasteelt - laaglandgebieden - pampa's - brazilië - intensivering - duurzaamheid (sustainability) - productiviteit - indicatoren - bodembeheer - rijst - natte rijst - maïs - dekgewassen - vee - rotatie - gemengde landbouw - zaaibedbereiding - landbouwwerktuigen

Agriculture in the lowlands of south Brazil is of strategic importance at the national level, since it supplies around 80% of the rice consumed by the Brazilian population. In Rio Grande do Sul, the southernmost state in Brazil, three million hectares of lowlands are ready for grain-based agriculture. Of this area, about half is fallow, partly used for cattle grazing, and irrigated rice is the predominant crop, cultivated annually on 1.1 million ha. The remaining area is used for soybean and other crops. The predominant cropping system is a combination of irrigated rice and cattle. Over the last decades, rice yields have steadily increased, but this rise in yield level has to a large extent been obtained at the expense of a continuously higher use of external inputs. The recent introduction of soybean in rotation with rice has partially improved the system, but in most areas the situation is becoming incompatible with the modern demands for sustainability. This thesis presents a long-term study (2006-2015) of five cropping systems for lowlands. Next to monocrop rice and two rice-soybean rotations conducted in either conventional or minimum tillage, the experiment contained two novel systems based on large ridges, on which soybean and maize were combined with either cover crops or crop-livestock integration in winter. In these last systems, 8-m-wide ridges were built to avoid flooding, thus allowing for diversification of cash crops and the cultivation of cover crops or pastures in winter time, as well as the use of no-tillage. All systems were evaluated at process-level, including soil preparation, seeding, plant nutrition, pest management, irrigation, harvesting, transport and cattle management, as well as regarding their performance for the different dimensions of sustainability, particularly environment, land productivity, economics, energy-use and labour. Next to system assessment, two additional experiments were conducted for the evaluation of two specific technologies for soil management in these areas. Crop livestock integration on the ridge-based system offered the best balance between food production, environmental impact and economics. This system is well suited to be used in fields that are kept fallow, thereby enlarging the agricultural productivity of the lowlands. The additional experiments revealed that a knife-roller can successfully substitute plough-and-harrow for soil preparation after rice harvest, and that germination of weed seeds can be reduced if crop seeding is conducted at a lower speed or using a no-tillage seeder equipped with an improved cutting mechanism. Overall the results show that by using alternative cropping systems that allow for diversification and new methods of field management it is possible to simultaneously attain a larger agricultural production and improved sustainability in the lowlands.

Advies inrichting en beheer beekdal Geeserstroom
Verdonschot, Piet F.M. ; Verdonschot, Ralf C.M. ; Jansen, Peter C. ; Massop, Harry T.L. ; Grootjans, Ab P. - \ 2017
Wageningen : Wageningen Environmental Research (Alterra) - ISBN 9789463431279 - 128
beekdalen - waterlopen - milieubeheer - natuurbeheer - waterbeheer - wetlands - drenthe - brook valleys - streams - environmental management - nature management - water management
De in 2005 uitgevoerde herinrichting van het beekdal van de Geeserstroom bestond uit de omvorming van een regulier landbouwgebied naar een door natuurlijke waterhuishoudkundige processen aangestuurd natuurgebied, met een nevenfunctie voor waterberging. Vooraf was een 19de -eeuwse beekdallandschap voorzien, met in het midden een stromende beekloop. Het beekdal blijkt zich in de periode tot 2016 echter ontwikkeld te hebben tot een zogenaamd doorstroommoeras, dat inmiddels een grote diversiteit aan moerasvegetaties en een zeer soortenrijke moerasvogelgemeenschap kent. Een doorstroommoeras is een mengvorm van moeras en beek en vormt qua watertype een overgang tussen stromend en stilstaand water. Naast de genoemde ecologische waarden zijn er lokaal echter ook enkele waterhuishoudkundige knelpunten en waterkwaliteitsproblemen ontstaan.
Large herbivores as a driving force of woodland-grassland cycles : the mutual interactions between the population dynamics of large herbivores and vegetation development in a eutrophic wetland
Cornelissen, Perry - \ 2017
University. Promotor(en): Frank Berendse; Karle Sykora, co-promotor(en): Jan Bokdam. - Wageningen : Wageningen University - ISBN 9789463430159 - 151
grasslands - woodlands - herbivores - population dynamics - vegetation - wetlands - graslanden - bosgebieden - herbivoren - populatiedynamica - vegetatie

This thesis examines the mutual interactions between the population dynamics of large herbivores and wood-pasture cycles in eutrophic wetlands. Therefore, habitat use and population dynamics of large herbivores, the effects of large herbivores on vegetation development, and the mutual interactions between vegetation development and herbivore population dynamics were studied in the eutrophic wetland the Oostvaardersplassen. At the Oostvaardersplassen cattle, horses and red deer were introduced in a fenced area with no predators, and population numbers are bottom-up controlled by food supply. The study showed that high densities of cattle, horses and red deer were able to break down woody vegetation and create grasslands. As the populations of large herbivores increased, the amount of the preferred grass available per animal decreased. This forced the large herbivores to use other food plants in other vegetation types, such as scrub, and transforming these into grasslands. In this way, the large herbivores facilitated high numbers of geese. As geese can clip the grass very short (<2 cm), they forced the large herbivores even more to forage in alternative vegetation types. Cattle, the largest herbivore in the system, were the first to experience the negative consequences of this strong competition, and their numbers declined. This raises the question whether an assemblage of bottom-up regulated populations of cattle, horses and red deer, or other large herbivores, can sustainably coexist under these circumstances. The results of our modelling study and experiences in the field suggest that resource partitioning may be a more reliable mechanism for long term coexistence than temporal variability due to climatic extremes or disease outbreaks. The best way to provide opportunities for resource partitioning in the Oostvaardersplassen is to enlarge the area and connect it to other reserves in order to increase the heterogeneity of the grazed system. Although the results of our model suggest that weather variability and presence of geese gave minor opportunities for the coexistence of large herbivores, both factors were necessary for creating windows of opportunity for the establishment of thorny shrubs. Weather variability creates strong reductions of the large herbivore populations while geese influence the maximum and minimum numbers, which are lower when geese are present. The effects of geese on the minimum numbers are small, but apparently sufficient to make the wood-pasture cycle operate. This raises another question whether a large predator, such as the wolf, could have similar effects on these ecosystems as the geese in the model. The impact of geese combined with a possible positive effect of wolves on wood-pasture cycles could perhaps increase the frequency of the windows of opportunity and increase the survival of established thorny shrubs. Until now, we have seen that a few conditions for the wood-pasture cycle are met by the herbivores. However, a few important requirements are not satisfied: (a) a temporary reduction of large herbivore numbers allowing the establishment of light demanding thorny shrubs and the development of thorny scrubland within the created grasslands; (b) the establishment of palatable trees within these thorny scrubs; (c) the formation of closed canopies which shade out the shrubs and lead to unprotected groups of trees and groves. This means that we still cannot conclude if the large herbivores are a driving force for the whole cycle in a highly productive environment. As long as we have not experienced a complete wood-pasture cycle in the Oostvaardersplassen or any other area, it remains to be seen what will happen in the future. Whatever the outcome will be, the results of our study suggest that some adjustments would benefit the Oostvaardersplassen-system such as increasing heterogeneity through connecting the area with other large nature reserves. This will not only increase opportunities for resource and space partitioning and thus increase opportunities for the coexistence of the large herbivores, but also for wood-pasture cycles and increased biodiversity.

Abundance, Activity and Community Structure of Denitrifiers in Drainage Ditches in Relation to Sediment Characteristics, Vegetation and Land-Use
Veraart, Annelies J. ; Rocha Dimitrov, Mauricio ; Schrier-Uijl, Arina P. ; Smidt, Hauke ; Klein, Jeroen J.M. de - \ 2017
Ecosystems 20 (2017)5. - ISSN 1432-9840 - p. 928 - 943.
agroecosystem - denitrification - DGGE - ecosystem functioning - macrophytes - nitrogen - qPCR - wetlands
Drainage ditches are ubiquitous yet understudied features of the agricultural landscape. Nitrogen pollution disrupts the nutrient balance of drainage ditch ecosystems, as well as the waterbodies in which they drain. Denitrification can help ameliorate the impact of N-fertilization by converting reactive nitrogen into dinitrogen gas. However, factors affecting denitrification in drainage ditches are still poorly understood. In this study, we tested how within-ditch and regional environmental conditions affect denitrifier activity, abundance, and community structure, to understand controls on denitrification at multiple scales. To this end, we quantified in situ denitrification rates and denitrifier abundance in 13 drainage ditches characterized by different types of sediment, vegetation and land-use. We determined how denitrification rates relate to denitrifier abundance and community structure, using the presence of nirS, nirK and nosZ genes as a proxy. Denitrification rates varied widely between the ditches, ranging from 0.006 to 24 mmol N m−2 h−1. Ditches covered by duckweed, which contained high nitrate concentrations and had fine, sandy sediments, were denitrification hotspots. We found highest rates in ditches next to arable land, followed by those in grasslands; lowest rates were observed in peatlands and nature reserves. Denitrification correlated to nitrate concentrations, but not to nirK, nirS and nosZ abundance, whereas denitrifier-gene abundance correlated to organic matter content of the sediment, but not to nitrate concentrations. Our results show a mismatch in denitrification regulators at its different organizational scales. Denitrifier abundance is mostly regulated at within-ditch scales, whereas N-loads, regulated by landscape factors, are most important determinants of instantaneous denitrification rates.
Repeated fires trap Amazonian blackwater floodplains in an open vegetation state
Flores, Bernardo M. ; Fagoaga, Raquel ; Nelson, Bruce W. ; Holmgren, Milena - \ 2016
Journal of Applied Ecology 53 (2016)5. - ISSN 0021-8901 - p. 1597 - 1603.
drought - ecological transition - ecosystem shift - El Niño Southern Oscillation (ENSO) - forest succession - igapó - recovery rates - resilience - tropical forests - wetlands

Climate change may increase the occurrence of droughts and fires in the Amazon. Most of our understanding on how fire affects tropical ecosystems is based on studies of non-flooded forest–savanna ecotones. Nonetheless, tropical floodplain forests in the Amazon can burn severely during extreme droughts. The mechanisms slowing down forest regeneration in these ecosystems remain poorly understood and have never been assessed in the field. We studied the recovery of Amazonian blackwater floodplain forests after one and two fire events. We used Landsat images to map fire history and conducted field surveys to measure forest structure, tree species richness, tree seed bank and post-fire invasion of herbaceous plants. Sites burnt once had on average 0% trees, 6% tree seed abundance, 23% tree seed species richness and 8% root mat thickness compared to unburnt forests. In contrast, herbaceous cover increased from 0 to 72%. Nonetheless, forest structure and diversity recovered slowly towards pre-burn levels, except for tree seed banks that remained depleted even 15 years after fire. Sites burnt twice had on average 0% trees, 1% tree seed abundance, 3% tree seed species richness and 1% root mat thickness compared to unburnt forests. Herbaceous cover increased to 100%. Mean recovery of tree basal area was 50% slower and of root mat thickness 93% slower compared to recovery in sites burnt once. Tree seed banks did not recover at all, and herbaceous cover persisted close to 100% for more than 20 years after the second fire. Synthesis and applications. Our results indicate that after a second fire event, Amazonian blackwater floodplain forests lose their recovery capacity, and persist in a non-forested state dominated by herbaceous vegetation. Such fragility implies that preventing human ignited fires during drought episodes is a particularly important conservation strategy for these ecosystems.

Tidal river dynamics : Implications for deltas
Hoitink, A.J.F. ; Jay, D.A. - \ 2016
Reviews of Geophysics 54 (2016)1. - ISSN 8755-1209 - p. 240 - 272.
delta evolution - estuaries - river discharge - tidal analysis - tidal river - wetlands

Tidal rivers are a vital and little studied nexus between physical oceanography and hydrology. It is only in the last few decades that substantial research efforts have been focused on the interactions of river discharge with tidal waves and storm surges into regions beyond the limit of salinity intrusion, a realm that can extend inland hundreds of kilometers. One key phenomenon resulting from this interaction is the emergence of large fortnightly tides, which are forced long waves with amplitudes that may increase beyond the point where astronomical tides have become extinct. These can be larger than the linear tide itself at more landward locations, and they greatly influence tidal river water levels and wetland inundation. Exploration of the spectral redistribution and attenuation of tidal energy in rivers has led to new appreciation of a wide range of consequences for fluvial and coastal sedimentology, delta evolution, wetland conservation, and salinity intrusion under the influence of sea level rise and delta subsidence. Modern research aims at unifying traditional harmonic tidal analysis, nonparametric regression techniques, and the existing understanding of tidal hydrodynamics to better predict and model tidal river dynamics both in single-thread channels and in branching channel networks. In this context, this review summarizes results from field observations and modeling studies set in tidal river environments as diverse as the Amazon in Brazil, the Columbia, Fraser and Saint Lawrence in North America, the Yangtze and Pearl in China, and the Berau and Mahakam in Indonesia. A description of state-of-the-art methods for a comprehensive analysis of water levels, wave propagation, discharges, and inundation extent in tidal rivers is provided. Implications for lowland river deltas are also discussed in terms of sedimentary deposits, channel bifurcation, avulsion, and salinity intrusion, addressing contemporary research challenges.

Electricity from wetlands : technology assessment of the tubular Plant Microbial Fuel Cell with an integrated biocathode
Wetser, K. - \ 2016
University. Promotor(en): Cees Buisman, co-promotor(en): David Strik. - Wageningen : Wageningen University - ISBN 9789462576964 - 153 p.
electricity generation - wetlands - fuel cells - bioenergy - salt marshes - spartina anglica - phragmites australis - electrodes - opwekking van elektriciteit - brandstofcellen - bio-energie - zoutmoerassen - elektrodes

Sustainable electricity generation by the plant microbial fuel cell

Fossil fuels are currently the main source of electricity production. Combustion of fossil fuels causes air pollution severely affecting human health and nature. This results in an increasing demand for renewable electricity sources. One of the emerging renewable electricity technologies is the plant microbial fuel cell (PMFC) as explained in chapter 1. PMFC generates electricity from the rhizodeposits of living plants. Naturally occurring electrochemically active microorganisms oxidize the rhizodeposits producing electrons at the anode of the PMFC. The electrons flow from the anode, via an external circuit where the electricity is harvested, to the cathode. At the cathode, the electrons reduce oxygen to water. PMFC is based on naturally occurring sustainable and renewable processes without net emissions and competition for arable land or nature. Large scale application of the PMFC is preferred in wetlands because a large waterlogged area is required.

Prior to application, the cathode limitations of the PMFC have to be solved. Oxygen reduction at the cathode is slow, limiting the current and power output of the PMFC. An unsustainable chemical cathode is often used in PMFC research to overcome the cathode limitations. The sustainable oxygen reducing cathode has to be catalyzed when integrated in the PMFC. Most chemical catalyst are expensive and prohibit the commercial use in the PMFC. Oxygen reduction can also be biologically catalyzed by cheap and self-replenishing microorganisms. Next to the biocathode, also a suitable design of the PMFC has to be developed before application in wetlands. A tubular design was previously developed which can be invisibly integrated in wetlands. However, this design still used a chemical cathode and energy intensive pumping. The oxygen reducing biocathode should be integrated in the tubular design and oxygen should be passively supplied in the cathode.

The objective of this thesis is to apply PMFC in wetlands with a sustainable biocathode. First, the biocathode is integrated in a lab scale PMFC. Afterwards, the PMFC is installed in wetlands using an improved tubular design with an integrated biocathode and passive oxygen supply.

Lab scale experiments: integration of the biocathode and electricity localization in the bioanode of the PMFC

In chapter 2, the oxygen reducing biocathode is integrated in a flat plate lab scale PMFC replacing the chemical ferricyanide cathode. The PMFC operated as a completely biocatalyzed system for 151 days. The sustainable PMFC with a biocathode was able to generate more power than the PMFC with a chemical cathode. The long term power generation of the lab scale PMFC improved from 155 mW m-2 plant growth area (PGA) to a record of 240 mW m-2 PGA. This record was reached due to the higher redox potential of oxygen reduction compared to ferricyanide reduction. Oxygen reduction was effectively catalyzed by microorganisms lowering the voltage losses at the cathode. As a result, the PMFC with a biocathode operated at a 127 mV higher cathode potential than a similar PMFC with a chemical ferricyanide cathode. The long term current generation of both PMFCs was 0.4 A m-2 PGA. The current generation was likely limited by the substrate availability in the anode of the PMFC.

In chapter 3, the biocathode is further investigated. This chapter shows that the oxygen reducing biocathode can also catalyze the reversible reaction, water oxidation. Water is the most abundant electron donor available for electrochemical fuel production like the reduction of protons to hydrogen and the reduction of carbon dioxide to hydrocarbons. However, the water oxidation reaction is currently hampering the development of large scale water oxidation technologies. A bioanode containing electrochemically active microorganisms was able to reach a current density of 0.93 A m-2 at 0.7 V overpotential with a 22 % Coulombic efficiency linked to water oxidation. An optimized system could be used to produce fuels on a large scale.

The flat plate PMFC of chapter 2 was also used to localize the electricity generation in the PMFC (chapter 4). In this experiment, the anode was partitioned in 30 separate small anodes at different width and depths. The current generation of each anode was analyzed over time and linked to the plant roots. The results show that after a start-up period of 70 days, significantly higher current was generated at anodes close to the plant roots due to rhizodeposition. Besides rhizodeposition (i.e. electron donors), the plant roots also excrete oxygen which is an electron acceptor lowering the current generation of the PFMC. Also oxygen was measured at the anodes close to the plant roots. This likely resulted in internal currents in the PMFC. Current was likely generated both from living and death roots. The electrons in the PMFC were probably transferred via mediators to locations without roots as mediators were present also at locations without plant roots. These mediators were likely excreted by plants and/or microorganisms in the anode. Electrons were likely not transferred over centimeter distance through conductive microorganism on the plant roots in the PMFC.

Installation of the tubular PMFC with an integrated biocathode in wetlands

After the successful integration of the biocathode in the PMFC, the focus of the research changed to application in wetlands. Two wetlands with an abundant occurrence in the Netherlands were investigated in this research. The first wetland was a Phragmites australis dominated fen peat soil, a large perennial grass. The peat soil in this research was collected in national park Alde Feanen in the north of the Netherlands. The second investigated wetland was a Spartina anglica dominated salt marsh. Spartina anglica is a perennial grass found in coastlines spread over the world. The salt marsh was collected in the Oosterschelde tidal basin in the southwest of the Netherlands.

The first experiment in the wetlands was conducted to investigate the spatial and temporal differences in current and power generation in and between wetlands (chapter 5). PMFCs in the salt marsh were able to generate more than 10 times more power than the same PMFCs in the peat soil (18 vs 1.3 mW m-2 PGA on a long term). The higher power generation is mainly explained by the high ionic conductivity of the salt marsh and the presence of sulfide which is also oxidized next to the rhizodeposits at the anode of the PMFC. The top layer of the salt marsh generated most power due to the presence of the plants and tidal advection. In the peat soil, there was no significant difference in power generation over depth. Even though, in the top layer more living roots were present. Also the dead roots and organics in peat can be oxidized by the PMFC. In chapter 5, also the maximum current and power output of the wetlands was predicted based on rhizodeposition of the investigated plants and microbial processes in these wetlands. The calculations showed that the potential current generation of PMFC in the salt marsh is 0.21-0.48 A m-2 PGA and in peat soil 0.15-0.86 A m-2. In the peat soil, the PMFC is potentially able to generate a power density up to 0.52 W m-2 PGA.

The second experiment in the wetland was the installation of a tubular PMFC with an in situ started oxygen reducing biocathode and passive oxygen supply into the cathode (chapter 6). The anode was the outside of the tube and placed directly between the plant roots. The oxygen reducing biocathode was located inside the tube. A silicone gas diffusion tube was placed in the cathode compartment to passively supply the required oxygen. The tubular PMFC with biocathode was successfully installed and started in the peat soil reaching a maximum daily average power generation of 22 mW m-2 PGA. In the salt marsh, the tubular biocathode PMFC only started while supplying pure oxygen in the gas diffusion tube. Air diffusion did not result in the start-up of the biocathode, likely because the oxygen was directly reduced via internal currents and therefore more oxygen was required. Once started with pure oxygen, the tubular PMFC was able to generate 82 mW m-2 PGA which was again higher than the peat soil. Completely biocatalyzed tubular PMFC were installed in both wetlands with natural occurring microorganisms in the anode and cathode. The power generation can be further increased by improving the PMFC design limiting crossover of oxygen and substrate.

Future outlook: application of the PMFC in wetlands

In chapter 5, the potential power generation of the two investigated wetlands was calculated. In chapter 7, these calculations were extended to a worldwide scale. PMFC applied in all wetlands could generate 0.67 to 1.35 TW and could cover 30 to 60 % of the global electricity consumption. 70 % of all the potential power could be generated in the tropics. Worldwide, 1.1 billion people have insufficient access to electricity from which 88 % lives in the tropics (i.e. Sub-Saharan Africa and South Asia). PMFC could be used to reach universal access of electricity in these locations and decrease the amount of premature deaths due to air pollution.

PMFC can be applied with passive or active oxygen supply from the outside air into the silicone tube. The used tubular PMFC with passive oxygen supply can have a maximum length of less than one meter. Active supply of oxygen reduces the net power output of the PMFC, but allowing installation of long tubular PMFC. However, in both cases the material costs should be significantly reduced for economically feasible application at large scale. The costs of the material should be decreased to less than 1 % of the current PMFC costs to have a payback time of 50 years in the Dutch electricity market for only the tubular PMFC. Further cost reduction is required when also the current collectors, electricity transmission, production and installation costs are included. Application of PMFC in remote locations increases the economic feasibility of the PMFC as the PMFC could be applied independent from the grid reducing the transmission costs and avoiding the regular electricity network charges.

Application of the PMFC in the total area of Spartina anglica salt marsh in the Oosterschelde, the location were the plants were collected, could produce a total of 11.6 GWh yr-1. The Oosterschelde could produce the electricity consumption of 8,360 persons and as such produce the electricity need of an average village directly located at the tidal basin. The Phragmites australis peat soil in the Alde Feanen national park could produce 2.5 GWh yr-1. The electricity could be directly used for ecotourism purposes, for example for the use of electric boats and a holiday park.

Monitoring van het voor vogels oogstbare voedselaanbod in de kombergingen van het Pinkegat en Zoutkamperlaag
Ens, B.J. ; Krol, J. ; Meer, J. van der; Piening, H. ; Wijsman, J.W.M. ; Schekkerman, H. ; Rappoldt, C. - \ 2015
Nijmegen : Sovon (Sovon-rapport 2015.15) - 54
aardgas - nadelige gevolgen - natura 2000 - kustgebieden - vogels - waddenzee - foerageren - wetlands - groningen - friesland - natural gas - adverse effects - coastal areas - birds - wadden sea - foraging
De gaswinning vanaf de locaties Moddergat, Lauwersoog en Vierhuizen kan effecten hebben op het Natura 2000 gebied Waddenzee. Uit voorzorg vindt de winning plaats volgens het ‘Hand aan de kraan’ principe. In dat kader vindt een uitgebreide monitoring plaats van biotische en abiotische parameters, om te controleren of gaswinning vanaf de bovengenoemde locaties geen meetbaar nadelig effect heeft op de instandhoudingsdoelstellingen van de speciale beschermingzone Waddenzee, waaronder een groot aantal vogelsoorten waarvoor het gebied is aangewezen.
Passende Beoordeling Natuurbeschermingswet 1998 voor project Kwelderontwikkeling Koehoal door een slibmotor
Baptist, M.J. - \ 2015
Den Burg : IMARES (Rapport / IMARES Wageningen UR C081/15) - 44
havens - sediment - wetlands - bagger - geologische sedimentatie - natura 2000 - natuurbescherming - waddenzee - friesland - harbours - dredgings - geological sedimentation - nature conservation - wadden sea
Pilotproject om het gebaggerd slib uit de haven van Harlingen te verspreiden over de wadden. In het natura 2000 gebied. Door middel van een experimentele ‘slibmotor’ wordt het sedimentaanbod langs de kust ten noordoosten van Harlingen vergroot met als uiteindelijk doel het areaal kwelders te vergroten.
Investigating the suitability of constructed wetlands for the treatment of water for fish farms
Heijden, P.G.M. van der; Dien, F. van; El-Beshbishi, D.A. - \ 2015
Wageningen : Centre for Development Innovation, Wageningen UR (Report / CDI 15-079) - 27
wetlands - artificial wetlands - fish farms - heavy metals - farming - pesticides - waste water - tilapia - development projects - egypt - north africa - africa - helofytenfilters - viskwekerijen - zware metalen - landbouw bedrijven - pesticiden - afvalwater - ontwikkelingsprojecten - egypte - noord-afrika - afrika
Many fish farms in Egypt rely on water of drainage canals to fill the fish ponds. There is a risk that this water is contaminated with pesticides and heavy metals. This report describes the results of a collaborative project that took place in 2012-2014 and that aimed to test the suitability of a constructed (engineered) wetland as treatment device for the removal of such pollutants from drainage canal water on a private fish farm in Egypt
Schorherstel in de Ooster- en Westerschelde met gebruik van schorrenmatten
Tangelder, M. ; Dalen, J. van; Ijzerloo, L. van; Ysebaert, T. - \ 2015
Yerseke : IMARES (Rapport / IMARES Wageningen UR C024/15) - 54
wetlands - kweldergronden - herstel - dijken - bekledingen - habitat vernietiging - natuurtechniek - oosterschelde - westerschelde - salt marsh soils - rehabilitation - dykes - linings - habitat destruction - ecological engineering - eastern scheldt - western scheldt
Projectbureau Zeeweringen verbetert de dijkbekledingen langs de Oosterschelde en Westerschelde. Daarbij kan helaas niet voorkomen worden dat kwetsbare schorren en slikken verstoord en deels vernietigd worden tijdens de dijkverbeteringswerkzaamheden. Het doel van deze studie was om na te gaan onder welke omstandigheden herstel en groei van schorvegetatie in dijkwerkstroken en pionierzones mogelijk is door het aanplanten van Engels Slijkgras (Spartina anglica) in zogenaamde kokosmatten. Het basiskokosmateriaal fungeert als substraat en bescherming tegen erosie voor de jonge planten gedurende de eerste groeiperiode totdat ze goed geworteld zijn in de bodem.
Onderzoekprogramma ecologisch herstel Eems-Dollard
Brinkman, A.G. ; Baptist, M.J. - \ 2015
Den Burg : IMARES (Rapport / IMARES Wageningen UR C008/15) - 40
estuaria - aquatische ecosystemen - ecologisch herstel - wetlands - eems-dollard - onderzoeksprojecten - estuaries - aquatic ecosystems - ecological restoration - research projects
Al vele jaren spelen er discussies over de ecologische kwaliteit van het Nederlandse Waddengebied. Vijftig jaar geleden speelde de mogelijke inpoldering. Contaminanten als dieldrin en PCB’s waren een belangrijk thema in de jaren erna en vanaf de jaren ’90 tot (deels) nu toe is schelpdiervisserij onderwerp van studie waarbij ook gesteld wordt dat er een verzanding van het systeem optreedt. Streefdoelen voor de waterkwaliteit zijn in de Kaderrichtlijn Water vastgelegd, het gehele Waddengebied (inclusief dus de Eems-Dollard) is aangewezen als Vogel- en Habitatrichtlijngebied, en is daarmee Natura2000-gebied. Hiermee zijn vele kwaliteitsdoelen geformuleerd, waarmee de beheerder verplicht wordt maatregelen te treffen opdat daar aan voldaan wordt.
Restoration of acidified and eutrophied rich fens: Long-term effects of traditional management and experimental liming
Diggelen, J. van; Bense, I.H.M. ; Brouwer, E. ; Limpens, J. ; Schie, J.M. van; Smolders, A.J.P. ; Lamers, L.P.M. - \ 2015
Ecological Engineering 75 (2015). - ISSN 0925-8574 - p. 208 - 216.
laagveengebieden - eutrofiëring - verzuring - ecologisch herstel - bekalking - fens - eutrophication - acidification - ecological restoration - liming - vegetation development - nutrient availability - nitrogen deposition - surface-water - groundwater - phosphorus - level - limitation - wetlands
Rich fens are known for their high botanical diversity encompassing many endangered species. For decades, several management measures, including mowing and burning, have been applied to maintain a high biodiversity by means of slowing down the natural succession from calcareous rich fens to acidic poor fens or woodland. In this study, we assessed the long-term effects of these traditional management measures, and explored the effectiveness of liming as a measure to restore rich fen vegetation. Effects of summer mowing, and of burning after winter mowing, were assessed by comparing current (2013) and historical (1967) vegetation data. Effects of experimental liming, using different levels of lime addition (0, 1000, 2000, and 4000 kg Dolokal/ha), were monitored in the field during 7.5 years. Summer mowing led to more acidic and nutrient-poor conditions as indicated by a shift from rich to poor fen vegetation, including a well-developed bryophyte cover dominated by Sphagnum with some threatened species. Burning (after winter mowing) counteracted acidification but increased nutrient availability, as indicated by dominance of vascular species characteristic of productive tall-herb grasslands and a sparse bryophyte cover with common species. We conclude that the traditional measures were unable to maintain rich fen composition in the long term. Given the fact that the restoration of hydrological conditions, favouring rich fens, is not always feasible, liming could be an alternative to counteract acidification and improve rich fen conditions in the short term. This measure, however, appeared to be unsustainable as the re-establishment and dominance of Sphagnum spp. seriously complicated the development of rich fen vegetation in the longer term.
Sustainable hydraulic engineering through building with nature
Vriend, H.J. de; Koningsveld, M. van; Aarninkhof, S.G.J. ; Vries, M.B. de; Baptist, M.J. - \ 2015
Journal of Hydro-environment Research 9 (2015)2. - ISSN 1570-6443 - p. 159 - 171.
sea-level rise - intertidal habitats - river - protection - wetlands - coastal
Hydraulic engineering infrastructures are of concern to many people and are likely to interfere with the environment. Moreover, they are supposed to keep on functioning for many years. In times of rapid societal and environmental change this implies that sustainability and adaptability are important attributes. These are central to Building with Nature (BwN), an innovative approach to hydraulic engineering infrastructure development and operation. Starting from the natural system and making use of nature's ecosystem services, BwN attempts to meet society's needs for infrastructural functionality, and to create room for nature development at the same time. By including natural components in infrastructure designs, flexibility, adaptability to changing environmental conditions and extra functionalities and ecosystem services can be achieved, often at lower costs on a life-cycle basis than ‘traditional’ engineering solutions. The paper shows by a number of examples that this requires a different way of thinking, acting and interacting.
Vegetatie en opslibbing in de Peazemerlannen en het referentiegebied west-Groningen: Jaarrapport 2013
Duin, W.E. van; Leeuwen, P.W. van; Sonneveld, C. - \ 2014
Den Burg : IMARES (Rapport / IMARES Wageningen UR C026/14) - 56
wetlands - kustgebieden - vegetatiemonitoring - kweldergronden - geologische sedimentatie - monitoring - friesland - coastal areas - vegetation monitoring - salt marsh soils - geological sedimentation
Deze rapportage beschrijft de monitoring in het kader van de bodemdaling onder de kwelder de Peazemerlannen, gelegen aan de Friese noordoostkust. Er wordt een overzicht gegeven van de activiteiten en meetresultaten in de kwelder en zomerpolder van de Peazemerlannen en het referentiegebied in de kwelderwerken in west-Groningen gedurende de jaren 2007 t/m 2013. De meeste gegevens worden weergegeven vanaf 2007, het startjaar van deze gaswinning.
Rapportage werkbezoek Zuid-Korea
Baptist, M.J. - \ 2014
Den Burg : IMARES (Rapport / IMARES ) - 22
mariene gebieden - republiek korea - wadden - wetlands - informatieverspreiding - internationale samenwerking - nederland - marine areas - korea republic - tidal flats - diffusion of information - international cooperation - netherlands
Sinds 2009 bestaat er een samenwerkingsovereenkomst tussen de trilaterale waddenzeestaten en Korea. In de afgelopen vijf jaar is er veel bereikt, vooral op het gebied van educatie en voorlichting, en zijn diverse MoU bijeenkomsten gehouden. Voor de komende jaren is de doelstelling om meer aan wetenschap, management en monitoring te doen. In dat kader is een nadere samenwerking op de vakgebieden van monitoring en onderzoek naar benthische ecologie en morfologie gevraagd.
A quantitative model for understanding and exploring land use decisions by smallholder agrowetland households in rural areas of East Africa
Sakane, N.S. ; Wijk, M.T. van; Langensiepen, M. ; Becker, M. - \ 2014
Agriculture, Ecosystems and Environment 197 (2014). - ISSN 0167-8809 - p. 159 - 173.
west-africa - management - systems - wetlands - farmers - rice - sustainability - determinants - productivity - typology
Land use change in rural areas often result from the decision-making of individual farming households. It is a complex process that operates at different temporal and spatial scales through the interactions between diverse drivers. Main drivers of wetland conversion for agricultural production in Sub-Saharan Africa (SSA) and those influencing its land use change have been explored in the past. But often the factors have not been explicitly considered in these studies. Tools and concepts that consider the decision-making processes of farmers have become common approaches used in studies to understand and explore changes in land use. This paper describes an empirical model framework to analyse land development and use processes as a result of individual farmer’s decision-making in small wetlands in SSA. The model framework uses information on the drivers of land use change, landscape classification, and household typologies. Processes of land conversion, as well as of probabilistic and heuristic decision-making were integrated in the framework. The model framework was applied to a case study on a sub-humid lowland floodplain in Tanzania, where land conversion, fallow, and use change processes are shaping the structure of the wetland. The scenario of increasing land scarcity on upland was simulated to explore how defined processes will respond to the rising pressure exerted on the wetland. Land conversion increased by 10 percent, fallow practices decreased by one-third to half. Wetland fields were defragmented due to increasing demand for crop production in the wetland. Shifts in relative distributions of farm types were simulated within and between wetland cluster groups, where all upland dependent crop-based farmers disappeared. The application revealed the potential of including individual decision-making in understanding the heterogeneity and functioning of such systems. The application possibilities and limitations of the model as well as challenges to model complex interactions in land use systems are discussed. The study raised the need to improve the means by which socio-environmental systems are anticipated and managed in the face of likely or projected changes in demography, economics, and resources at different scales.
Van frustratie naar integratie: Handelingsperspectieven om kennis en beleid over de Waddenzee beter op elkaar aan te laten sluiten
Molen, F. van der; Floor, J.R. ; Enst, W. van; Seijer, C. ; Giebels, D. ; Tatenhove, J. van - \ 2014
Utrecht : Deltares - 36
landgebruik - wetlands - aquatische ecosystemen - natuurbeleid - kennismanagement - waddenzee - land use - aquatic ecosystems - nature conservation policy - knowledge management - wadden sea
Deze handelingsperspectieven zijn het resultaat van samenwerking tussen onderzoekers van Rijksuniversiteit Groningen, Erasmus Universiteit Rotterdam, Universiteit Utrecht, Wageningen Universiteit, Universiteit Twente en Deltares. In 2013 ontstond het idee een discussie aan te gaan met mensen die professioneel actief zijn in het waddengebied, met de inzichten die zijn opgedaan in ons onderzoek. In het najaar van 2013 is hiervoor een bijeenkomst op Texel georganiseerd. Daarna is in verschillende schrijf- en feedbackrondes aan deze tekst gewerkt.
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