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.

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Resilience of Amazonian forests : the roles of fire, flooding and climate
Monteiro Flores, B. - \ 2016
Wageningen University. Promotor(en): Marten Scheffer, co-promotor(en): Milena Holmgren Urba; Jose de Attayde. - Wageningen : Wageningen University - ISBN 9789462578876 - 128
forests - resilience of nature - fire - flooding - floods - climate - floodplains - vegetation - amazonia - bossen - veerkracht van de natuur - brand - inundatie - overstromingen - klimaat - stroomvlakten - vegetatie - amazonia

The Amazon has recently been portrayed as a resilient forest system based on quick recovery of biomass after human disturbance. Yet with climate change, the frequency of droughts and wildfires may increase, implying that parts of this massive forest may shift into a savanna state. Although the Amazon basin seems quite homogeneous, 14% is seasonally inundated. In my thesis I combine analyses of satellite data with field measurements and experiments to assess the role of floodplain ecosystems in shaping the resilience of Amazonian forests.

First, I analyse tree cover distribution for the whole Amazon to reveal that savannas are relatively more common on floodplains. This suggests that compared to uplands, floodplains spend more time in the savanna state. Also, floodplain forests seem to have a tipping point at 1500 mm of annual rainfall in which forests may shift to savanna, whereas the tipping point for upland forests seems to be at 1000 mm of rainfall. Combining satellite and field measurements, I show that the higher frequency of savannas on floodplain ecosystems may be due to a higher sensitivity to fire. After a forest fire, floodplains lose more tree cover and soil fertility, and recover more slowly than uplands (chapter 2).

In floodplains of the Negro river, I studied the recovery of blackwater forests after repeated fires, using field data on tree basal area, species richness, seed availability, and herbaceous cover. Results indicate that repeated fires may easily trap blackwater floodplains in an open-vegetation state, due the sudden loss of forest resilience after a second fire event (chapter 3).

Analyses of the soil and tree composition of burnt floodplain forests, reveal that a first fire is the onset of the loss of soil fertility that intensifies while savanna trees dominate the tree community. A tree compositional shift happens within four decades, possibly accelerated by fast nutrient leaching. The rapid savannization of floodplain forests after fire implies that certain mechanisms such as environmental filtering may favor the recruitment of savanna trees over forest trees (chapter 4).

In chapter 5, I experimentally tested in the field the roles of dispersal limitation, and environmental filtering for tree recruitment in burnt floodplain forests. I combine inventories of seed availability in burnt sites with experiments using planted seeds and seedlings of six floodplain tree species. Repeated fires strongly reduce the availability of tree seeds, yet planted trees thrive despite degraded soils and high herbaceous cover. Moreover, degraded soils on twice burnt sites seem to limit the growth of most pioneer trees, but not of savanna trees with deeper roots. Our results suggest a limitation of forest trees to disperse into open burnt sites.

The combined evidence presented in this thesis support the hypothesis that Amazonian forests on floodplains are less resilient than forests on uplands, and more likely to shift into a savanna state. The lower ability of floodplains to retain soil fertility and recover forest structure after fire, may accelerate the transition to savanna. I also present some evidence of dispersal limitation of floodplain forest trees. Broad-scale analyses of tree cover as a function of rainfall suggest that savannas are likely to expand first in floodplains if Amazonian climate becomes drier. Savanna expansion through floodplain ecosystems to the core of the Amazon may spread fragility from an unsuspected place.

Proeftuinen voor Wageningse waterkennis
Verdonschot, Ralf - \ 2016
water management - streams - knowledge - polder boards - biodiversity - floodplains
Community based fish culture in the public and private floodplains of Bangladesh
Mahfuzul Haque, A.B. - \ 2015
Wageningen University. Promotor(en): Leontine Visser, co-promotor(en): M.M. Dey. - Wageningen : Wageningen University - ISBN 9789462574533 - 166
stroomvlakten - visteelt - ontwikkelingsstudies - ontwikkelingseconomie - samenleving - huishoudens - bangladesh - zuid-azië - floodplains - fish culture - development studies - development economics - society - households - bangladesh - south asia

Seasonal floodplains are water bodies that retain water for 5-6 months during which they are suitable to grow fish and other aquatic animals. Out of 2.8 million ha of medium and deep-flooded areas, about 1.5 million ha are estimated to be suitable for Community-Based Fish Culture (CBFC). WorldFish had undertaken a five-year interdisciplinary action research project from 2005-2010 with the overall aim of enhancing the productivity of seasonally occurring floodwaters for the improved and sustained benefit of the livelihoods of the poor. My involvement in this project was as PhD Scholar from 2007-2009 for understanding the different and complex institutional arrangements and its overall impact of governing Community-Based Fish Culture in seasonal floodplains for the sustainable use and maximization of benefits to the targeted people of Bangladesh.

Six seasonal floodplains in different areas of Bangladesh were selected under the action research project implemented by the Department of Fisheries in collaboration with the Bangladesh Agricultural Research Council and the Bangladesh Fisheries Research Institute. For the action research which is the subject of this thesis, three seasonal floodplains were selected in the Brahamaputra, the Padma and the Teesta River Basins located at Mymensingh, Rajshahi and Rangpur districts, respectively. Another three floodplains were selected as control sites in the same river basins located near to the projects sites. The control sites were included in the economic study (Chapters 4 and 5) only. All the six floodplains belong to two types of ownership categories: public floodplains surrounded by private lands.

My thesis is broadly divided into a sociological and an economic part, mainly because of methodological differences. Chapter 2 and Chapter 3 discuss the institutional arrangements and the power and decision-making process of Community-Based Fish Culture management. Chapter 4 addresses the overall economic impact of technical and institutional arrangements of fish culture at both floodplain and household levels. We here employed a random effects model to estimate the impact of participation on fish income. Finally, in Chapter 5 the economic impact of community-based fish culture on expenditure inequality was measured at household level.

In the sociological part, three project floodplains covered the different institutional arrangements for managing the floodplains and maximizing their benefits to different classes of beneficiaries. Power relations between the various key actors or stakeholders were assessed who were directly or indirectly involved in the floodplain, and decision making processes in co-management practices were also studied at different institutional levels. Sociological research methods and techniques including semi-structured interviews, Focus Group Discussions, informal discussions with key informants, and
quantitative surveys were applied to gather data from Floodplain Management Committees, villagers and institutional stakeholders to investigate the use of the floodplain as a common property resource (CPR) and the processes of the formation of local institutions and organizations.

For the economic analysis of Chapter 4 and Chapter 5, three project floodplains and three control floodplains were selected for comparing the impact of the intervention at beneficiary level and also community level. Household survey data includes a baseline survey on socioeconomic information, three months monitoring on seasonal and monthly basis at community and household levels, as well as an assessment of the floodplains’ natural resource systems. The seasonal survey covered the changes in input use for crop production, changes in quality of output from the agricultural land and the effects of the intervention on crop production. A monthly survey on the 1st and 15th day of the month was conducted to capture the household consumption pattern, especially the frequency and quantity of fish and meat consumption.

Chapter 2 improves our understanding of the complex institutional relationships governing Community-Based Fish Culture in seasonal floodplains in Bangladesh. Formal institutional linkages between DoF, WorldFish Center and the Bangladesh Agricultural Research Council (BARC) played a key role in ensuring success. DoF is a government institution with establishments at different administrative levels. Institutional embedding of DoF through the Fishers Cooperatives (FMC) as implementing institutions appeared highly instrumental. Large numbers of people, including landless poor seasonal fishers, professional landowning fishers, and non-fishing landowners benefited from the successful implementation of the CBFC activities in the floodplains. The outcomes demonstrate a significant increase in income to all classes of beneficiaries through income sharing derived from their involvement in the fisheries cooperatives and fish culture.

In case 2 and case 3 the floodplains under private ownership privately owned land is inundated during the monsoon season; these floodplains are similar in size, with comparable percentages of beneficiaries and similar numbers of communities surrounding the floodplains. However, the distribution of beneficiaries among the classes differs with more landowners than landless seasonal fishers benefitting. FMCs normally allow these non-members to access the floodplains, but only to harvest un-stocked fish using local gears, considering the importance of fishing to their livelihood. This means that the CPR character of the management by the FMCs shows a certain permissiveness or permeable boundary regarding landless non-members under strict spatial and temporal conditions. Regulation and conservation thus guarantee the availability of un-stocked small fish in the floodplains with a high catch by artisanal gears which results in higher incomes and related benefits to the poorer households. Households who own land or ditches in the floodplains do not depend on un-stocked fish as they can have ponds to trap and harvest fish obtained in the wild. Additionally, during the dry season, they may use land in lowland areas for crop production.

Case 1 of the public floodplain surrounded by private lands differs most from the private floodplain cases. Here, the public area is leased out to fishers during the monsoon, including the private land owned by the affluent and politically influential stakeholders. The floodplain is larger than in the other two cases, but both the percentages of landless fishers and of landowners are lower, making the class of the landowning professional fishers the majority among the beneficiaries.

Generally, the rules and regulations that apply to public and privately owned floodplains are written down in a Memorandum of Understanding between DoF and the individual FMC’s in a non-judicial construction. In their regular meetings the FMCs also document the everyday practices of the rules related to fish culture and management in the minutes that are distributed among its members. It appears that in the three cases, comparable rules and regulations for fish culture are applied to the public and to the private floodplains in operational rules, collective choice rule and constitutional rule.

Benefit sharing of the fish production from the floodplains was agreed at the start of project activities by all stakeholders, but their commitment varied between the classes of beneficiaries and across the cases. A significant increase of income for different stakeholders was derived from their involvement in fish culture. In the public floodplain fishers received around 40% of net income increase and the landowners received almost 38% of net income increase, as they had to pay the lease money for the floodplain. But in private floodplain all classes of stakeholders deposited around 25% of their net income in a revolving fund. The fishers group got their income from the final harvesting of fish as they received 50% of the price of the harvest of un-stocked fish and 10-15% of the stocked fish. The landowners received 45-50% of income according to their land. The landless seasonal fishers had open access to the non-stocked fish during the monsoon. Finally, the users of the public as well as the private floodplains contributed a small portion of their income to social work, like the building of a mosque or a Hindu temple.

Chapter 3 firstly assessed the power relations between the various key actors or stakeholders who were directly or indirectly involved in floodplain fisheries in the three sites. Secondly, their shifting power relations and decision making process in co-management practices were studied in the different institutional contexts of the three research sites during WorldFish project intervention. Instead of merely listing the institutions involved, we studied the actual power practices and decisions making processes between the stakeholders in the three cases to gain insight in the different governance models used in CBFC in Bangladesh. Existing co-management arrangements are characterized by unequal power distribution among the different actors, often resulting in the marginalization of the professional fishers and the landless poor fishers. I differentiated between two types of power in the management of floodplain aquaculture and stakeholder involvement, namely a) the power to create rules and decision making procedures, and b) the power to resolve disputes and ensure compliance. The Floodplain Management Committee (FMC) reviews the rules and regulations formulated by the government to complement the vision and roles of the institution, and if there is a need, modify them. Rules and regulations governing access to the public and privately owned floodplains were developed by the Department of Fisheries (DoF) and the FMC. A similar set of rules and regulations was applied to the public and the privately owned floodplains for fish culture. Most of the rules were derived from the national fisheries law. The rules and regulations that were applied to the floodplain were written down in a Memorandum of Understanding between DoF and FMC. Examples are rules and regulations about membership, leadership, boundary and access, allocation, penalties, input, and conflict resolution that were enforced for the management of community based-fish culture.

Magistrate courts at local level in Bangladesh have the power to decide on penalties for offenders in case of violation of the Government Fisheries Act of 2010 (DoF 2013) in the management of fisheries and aquaculture including the floodplain; a range of penalties is stipulated in the Offences and Penalties paragraph of the Act. In addition, in the case of both public and private floodplains, leaders of customary organizations have the authority and power to confiscate illegal nets and penalize offenders by charging monetary fines.

Governance in the context of Community-Based Fish Culture (CBFC) management addresses the dominancy of the land-owning group, informal sets of norms and traditions, and the social network and power relationships between stakeholders. In the public floodplain governance processes resulting in the formation of a responsive, accountable leadership and representative membership appeared vital for the success of CBFC. But, the establishment of successful CBFCs in public floodplains demands continuous institutional support from agencies such as the Department of Fisheries, because an increase in production and income also increases the risk of elite capture, and the possibility of an exploitative. In the private floodplain, there was no specific governance system in place to manage access and use of the floodplains during the wet season, as opposed to the dry months when the lands of the floodplain could be used by individual households for crop production. Thanks to greater accountability of the leaders, and more equal representation of the different stakeholders including active leadership and a supporting role of DOF, leadership problems were few and easily solved. Downward accountability was well established in addition to many efforts by the project.

Chapter 4 examined the overall impact on households involved through the WorldFish project in community-based fish culture in seasonal floodplains, particularly with respect to fish production, consumption, and income generation. Qualitative as well as quantitative methods were deployed to examine the impact of Community-Based Fish Culture starting with a conceptual framework as to how positive impacts take effect. The overall fish production in the floodplains of the project appeared to have increased 274%. Due to project intervention introducing fish culture, 43% of the farmers used floodplain water to meet up irrigation needs instead of ground water and rice production increased by 18.9% for dry-season (Boro) rice and 28.9% for wet-season (Aman) rice in the project floodplain areas.

Increased income is an important economic incentive for the expansion of community-based fish culture in Bangladesh. Over that period, average income from fish production increased to USD 240 for all beneficiaries involved in the project, which is 237% higher than the income of beneficiaries in the control group. Results of the random effects model show that project-involved households significantly increased their fish income compared to the households of the control sites. Furthermore, total household income increased to about USD 175 per household for those who participated in the WorldFish project.

Fish availability increased in the project area from July to December. During these months approximately 68%-75% of the total fish consumption needs of the project beneficiaries could be fulfilled by the newly introduced fish culture in the floodplains. The consumption of nutritional food shows that per capita fish consumption of households in the project sites increased from 1.26 kg per capita per month in the baseline year to 2.31 kg per capita per month in 2009.

Apart from the direct effect on household income and food consumption, CBFC intervention also created the opportunity for employment, backward linkage, and access to market to sell harvested fish. Indirect benefits of the community based fish culture include reduced conflict; improved social capital and greater cooperation in the community.

Expenditure is a better measurement of welfare than income where most of the people are poor and struggle for food. In this study I therefore used data on expenditure instead of income. The results in Chapter 5 show that the CBFC project had a positive and significant impact on food expenditure, as well as on non-food (other basic needs) and overall total expenditure. The impact of CBFC on household expenditure and expenditure inequality was measured by using Propensity Score Matching (PSM) method and Gini decomposition. Results revealed that the overall average food expenditure per year per household (for panel estimation) increased due to participation in the CBFC project from USD 93 to USD 141. Project participants were able to spend significantly more on food compared to non-participants. In addition, expenditure on food was increasing year by year. Moreover, participant households were capable to spend more compared to non-participants on non-food items like cloth, health, education, housing, transport etc. (from USD 45 to USD 74 per year). This non-food expenditure also gradually increased per year. Finally, total household expenditure of CBFC project participants was between USD 134 and USD 215 per year higher than the total expenditure of control households, which implies a better livelihood of the households involved in the project.

Gini index of total expenditure was found to be 0.34 and 0.40 for the CBFC project and control households respectively, which indicate that expenditure was equally distributed among households, but that it is more equally distributed among the CBFC households as compared to the control households. The expenditure inequality difference between the CBFC project and the control sites was 0.06, which implies that the CBFC management system helped to distribute total expenditure more equally among the surrounding communities.

Policy advice

For better management of the floodplain beels, the government may apply a similar policy for better utilization of the resources and for the economic benefits of the beneficiaries. Accountability, sustainable management of the floodplains, proper marketing of fish and equity in the distribution of benefits of the floodplains have proven to increase the productivity and ensure the accessibility of the poor and landless farmers, as long as elite capture is controlled.

Taking all CBFC project lessons into consideration, the Bangladesh government could indeed make some changes to their floodplain /wetland policy in order to accommodate the poor fishers and the landless poor. Policy (re)formulation may be needed for the dissemination of the CBO-based fish culture approach to scale-up its impact. In order to establish the rights of the CBOs (under the leadership of fishers) there is a need for modification of the policy of leasing of public floodplains. The major issues to be included are to bring private and public floodplains under CBO management; to secure government support for the registration of the CBOs and the strengthening of the institution; to guarantee that CBOs obtain long term (10-15 years or more) lease of the public areas of the floodplains as priority; to support small infrastructure constructions in the outlet and inlets of the floodplains; and to develop a functional model for the scaling-up (influencing policy) and scaling-out of the CBO fish culture approach in Bangladesh.

Future research

To assess the effectiveness of the scaling-up of the innovation in Community-Based Fish Culture in public and private floodplains, using a CBO to CBO approach will have to be developed with the support and facilitation from formal institutions. This will be considered as the subject of future research.

Interactions between land use and flood management in the Chi River Basin
Kuntiyawichai, K. - \ 2012
Wageningen University. Promotor(en): E. Schultz; S. Uhlenbrook. - [S.l. : S.n. - ISBN 9789461732491 - 213
hoogwaterbeheersing - overstromingen - waterbeheer - landgebruik - rivieren - stroomvlakten - watervoorraden - wiskundige modellen - thailand - flood control - floods - water management - land use - rivers - floodplains - water resources - mathematical models - thailand
Leren van de Wolga; vloedvlaktes blijken belangrijk voor vis
Nagelkerke, L.A.J. - \ 2011
Visionair : het vakblad van sportvisserij Nederland 20 (2011). - ISSN 1569-7533 - p. 16 - 19.
stroomvlakten - vissen - habitats - rusland - floodplains - fishes - russia
Eind 2007 verscheen in Visionair een artikel over een uniek onderzoek naar de relatie tussen vloedvlaktes en vis in de Russchische Wolga. Inmiddels is de eerste fase succesvol afgesloten. De onderzoeksresultaten bieden een schat aan informatie over de biologie en het beheer van riviervissen.
Floods and fish : recruitment and distribution of fish in the Volga River floodplain
Górski, K. - \ 2010
Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Leo Nagelkerke; Erwin Winter. - [S.l. : S.n. - ISBN 9789085858157 - 223
rivieren - stroomvlakten - overstromingen - vissen - populatie-aanwas - distributie - populatiedynamica - visbestand - rusland - visserijbiologie - hydrogeologie - aquatische ecosystemen - rivers - floodplains - floods - fishes - recruitment - distribution - population dynamics - fishery resources - russia - fishery biology - hydrogeology - aquatic ecosystems
Natural river floodplains are among the most diverse and productive ecosystems on Earth and provide key habitats for foraging, spawning and as a nursery for many riverine fish species. Periodic flooding plays a principal role in the ecological processes in floodplain systems resulting in high productivity and diversity, as formulated in the Flood Pulse concept (FPC, a major conceptual framework for understanding the hydro–ecological processes operating in river-floodplain systems). However, little progress has been made in exploring the FPC over larger spatial scales due to lack of empirical data. The Volga-Akhtuba floodplain (Russian Federation) is still relatively undisturbed, while in Europe and North-America about 90% of floodplains have effectively been lost. This thesis provides a quantitative assessment of the FPC by (1) analyzing flood pulse dynamics in response to changes in river flow regime on various spatial and temporal scales and (2) relating these to recruitment success of riverine fish species that use the floodplain; and (3) identifying the hydro-geomorphic variables that are most involved shaping fish abundance and distribution in the floodplain. The results obtained demonstrate that the flood pulse magnitude in the lower Volga has noticeably decreased due to damming of the Volga upstream from the Volga-Akhtuba floodplain. Still, in spite of this hydrological control, considerable year-to-year variation in flood magnitude and timing has remained. Therefore fish populations in the floodplain still depend on variations in the year-to-year flow regime. Moreover, spring temperature and its match with flooding control the recruitment of young fish at the end of the growing season. However, the main sources of spawning stocks in the large-scale Volga-Akhtuba floodplain originate from local floodplain populations and not from the main river channels. Spatial heterogeneity of hydro-geomorphic attributes of the floodplain water bodies is highly significant for structuring fish abundance and distribution in the floodplain. Therefore, even under changing environmental and social circumstances, it is essential to preserve flood dynamics, which is fundamental not only for fish recruitment success but also governs fish distribution and diversity in the floodplain.

Prospects of fen restoration in relation to changing land use—An example from central Poland
Klimkowska, A. ; Dzierza, P. ; Grootjans, A.P. ; Kotowski, W. ; Diggelen, R. - \ 2010
Landscape and Urban Planning 97 (2010)4. - ISSN 0169-2046 - p. 249 - 257.
groundwater regime - temperate zone - vegetation - netherlands - management - mire - wet - floodplains - hydrology - nitrogen
We carried out an eco-hydrological analysis to evaluate the most important effects of land use changes on the hydrological functioning of a fen system in Poland. We measured water levels (hydraulic heads) and water flow along a transect through the study area and also analysed land use changes using historical maps. Major hydrological changes occurred after c. 1950 when a dense drainage network was constructed and in the last decade when large fishponds were built. Nowadays, water levels in most of the fens and fen meadows are too low and the fluctuations too large for a long-term preservation of fen ecosystems. The mean water tables range from 0.3 to 0.8 m below soil surface with fluctuations from 0.7 up to 1.5 m. A second important cause of the hydrological changes of the system was the afforestation of the adjacent infiltration areas leading to increased evapotranspiration and a decreased groundwater flow to the wetlands. Finally, a recent increase in groundwater abstraction for agricultural purposes has probably lowered the groundwater even further. We conclude that a full restoration of the fen is not possible under the present conditions. An alternative restoration goal could be conservation and restoration of species-rich fen meadows, but also then improving the hydrological conditions will be necessary. While the focus is often on the local factors influencing the restoration prospects of a fen system, the regional processes are at least equally important. In this paper we discuss an importance of both local and regional factors.
Upgrading system-oriented ecotoxicological research
Eijsackers, H.J.P. ; Groot, M. ; Breure, A.M. - \ 2008
Science of the Total Environment 406 (2008)3. - ISSN 0048-9697 - p. 373 - 384.
sediment quality triad - river rhine - soil - netherlands - populations - floodplains - ecosystems - pollution - recovery - metals
In the 1990s the Dutch government expressed the need to investigate the impacts of diffuse pollution at (sub)-ecosystem levels. The resulting Netherlands Stimulation Programme on System-oriented Ecotoxicological Research (SSEO programme) ran from 1998 to 2006. Its primary objective was to assess the impacts of low- to medium-level, diffuse, multiple contaminations on ecosystems. The research results were intended as underpinning for policies on environmental, conservation and nature issues. Research was carried out at three sites that were selected because of their importance for nature management and the presence of diffuse contamination. These sites were: a river meadow/floodplain area (Afferdensche en Deestsche Waarden), an estuarine reed-land area (Biesbosch) and an area of lowland peat soils that had been contaminated with urban waste in past centuries (De Ronde Venen).
Profieldocument Habitattype 1160 Grote, ondiepe kreken en baaien
Imares, - \ 2008
floodplains - wetlands - habitats
Nematode-based risk assessment of mixture toxicity in a moderately polluted river floodplain in The Netherlands
Vliet, P.C.J. van; Goede, R.G.M. de - \ 2008
Science of the Total Environment 406 (2008)3. - ISSN 0048-9697 - p. 449 - 454.
stroomvlakten - zware metalen - nematoda - rivieren - indicatoren - graslanden - verontreiniging - toxiciteit - gelderland - land van maas en waal - waal - floodplains - heavy metals - rivers - indicators - grasslands - pollution - toxicity - river waal - soil - sensitivity - communities - cadmium - metals - forest
Heavy metal polluted soils usually contain mixtures of different metals, whereas legislation is derived from concentrations of individual metals. The mixture toxicity of the Dutch floodplain Afferdensche and Deestsche Waarden was estimated to be high (msPAF ranged from 67¿94%). Analyses of nematode community based bioindicators (Maturity Index, taxonomic diversity, trophic groups, multivariate analysis, DoFT-sentinels) were used to determine the ecological effects of the mixture toxicity in the floodplain soil. None of the indices indicated direct effects of heavy metals on the nematode community. This can be explained by the high adsorption of heavy metals on organic matter and clay particles resulting in a low bioavailability, and questions the estimation of the toxicity based on total concentrations of heavy metals in such environments. The nematode fauna showed great seasonal variation, which most probably was related to the temporal inundation of the floodplain.
Aeolian and fluviolacustrine landforms and prehistoric human occupation on a tectonically influenced floodplain margin, the Méma, central Mali
Makaske, B. ; Vries, E. de; Tainter, J.A. ; McIntosh, R.J. - \ 2007
Netherlands journal of geosciences 86 (2007)3. - ISSN 0016-7746 - p. 241 - 256.
eolische afzettingen - geomorfologie - geologische sedimentatie - rivieren - landschap - stroomvlakten - mali - aeolian deposits - geomorphology - geological sedimentation - rivers - landscape - floodplains - niger - holocene - africa
The Méma is a semi-arid region in central Mali with a rich archaeological heritage indicating the former existence of large urban settlements. The archaeological data suggest millennia of occupation history of the Méma preceding relatively sudden abandonment by the 14th or 15th century AD. Population numbers have remained low since then and today's human presence in the area is sparse and largely mobile. Geomorphologically, the Méma can be characterized as a graben hosting various generations of aeolian landforms and (presently mostly dry) interdunal channels and lakes, linked to the neighbouring Inland Niger Delta floodplain. Given this setting, and the variability of the Sahelian climate, climatic contributions to the region's sudden abandonment are likely. A geomorphological survey of the region, and interpretation of the observed geomorphological record in terms of climatic history, aimed at providing a basis for understanding the intensive occupation and subsequent abandonment of the Méma. The results of this study underscore dramatic Holocene climatic variability, leading to the region's present geomorphological diversity, but also suggest that neotectonic movements constitute an important additional cause of regional desiccation. Both may have encouraged prehistoric people to abandon the Méma after a long period of occupation.
Bioaccumulation of persistent organic pollutants from floodplain lake sediments: linking models to measurement
Moermond, C.T.A. - \ 2007
Wageningen University. Promotor(en): Bart Koelmans, co-promotor(en): J.J.G. Zwolsman. - [S.l.] : S.n. - ISBN 9789085047056 - 192
sedimentmaterialen - stroomvlakten - ecotoxicologie - aquatische ecosystemen - bioaccumulatie - persistente organische verontreinigende stoffen - sedimentary materials - floodplains - ecotoxicology - aquatic ecosystems - bioaccumulation - persistent organic pollutants
The main research questions of this research were (1) what is the extent and nature of bioavailability of sediment-bound polychlorobiphenyls (PCBs) and polyaromatic hydrocarbons (PAHs) and (2) what are the effects of lake ecosystem structure on fate and bioaccumulation of PCBs and PAHs. Fast-desorbing fractions in the sediment of floodplain lakes were estimated by the 6-h Tenax-extractable fractions with a correction factor. These fractions varied between 1 and 40% and did not show a clear trend with log KOW. This means that contaminants in these sediments were available, but to a smaller extent than total concentrations would suggest. The 6-h Tenax extractable concentration often correlated better with bioaccumulation than the total extractable concentration in sediment. Despite the reduced availability, benthivorous fish and invertebrates in floodplain lakes still rapidly accumulated substantial amounts of PCBs. PAHs were accumulated relatively less because PAHs were relatively less available than PCBs due to their stronger sorption to carbonaceous materials, also referred to as soot or black carbon. For fish, metabolic transformation caused even lower PAH concentrations. Contaminants that have been present in the sediment for longer periods of time (years to decades), were less available for Tenax extractions as well as for uptake by biota in different parts of the food web than contaminants that were recently added. Thus, aging may translate directly into reduced uptake at higher trophic levels. Nutrient additions in enclosures with benthivorous fish had a positive effect on PCB accumulation by these fish. Measured bioaccumulated concentrations of PCBs and PAHs in invertebrates in flood plain lakes were not influenced greatly by seasonal effects or ecological structure. Although effects were statistically significant, their magnitude in terms of accumulation factors was small, which may have been caused by the similar sediment composition and bioavailability of contaminants in our systems. Differences between compounds were much larger than differences due to ecosystem structure, seasons, or species composition. As for total masses of PCBs and PAHs in certain compartments however, lake ecosystem structure appeared to have a large influence on the biomass of biota and therefore also on the mass distribution of PCBs and PAHs in biotic compartments. Thus, changes in ecosystem structure strongly influenced PCB and PAH dynamics, although concentrations within the biotic compartments were not significantly influenced by biotic biomass. As for bioaccumulation modelling, when aquatic exposure concentrations were quantified accounting for sorption to carbonaceous materials, model results improved substantially. Including metabolic transformation and sediment uptake in the model accounted for a further improvement of the model fit. Implications are discussed for food chain bioaccumulation modeling, bioavailability assessment, sediment policy making and floodplain lake management.
Het voorkomen van loopkevers binnen een vegetatiegradiënt in de Millingerwaard (Coleoptera, Carabidae)
Verdonschot, R.C.M. ; Noordijk, J. ; Sykora, K.V. ; Schaffers, A.P. - \ 2007
Entomologische Berichten 67 (2007)3. - ISSN 0013-8827 - p. 82 - 91.
habitatselectie - multivariate analyse - stroomvlakten - vegetatie - coleoptera - insecten - gelderse poort - habitat selection - multivariate analysis - floodplains - vegetation - insects
Op basis van een vangpotonderzoek wordt de relatie tussen het voorkomen van loopkeversoorten, abiotische factoren en de vegetatie beschreven. Het onderzoek werd uitgevoerd in 2004 in de Millingerwaard. Er kan geconcludeerd worden dat bepaalde loopkeversoorten alleen bij een bepaald type vegetatie voorkomt
Identifying the appropriate scales to model nitrogen flows from land to water
Dumont, E.L. - \ 2007
Wageningen University. Promotor(en): Rik Leemans; A. Stein, co-promotor(en): Carolien Kroeze; Lex Bouwman; Evert Jan Bakker. - [S.l.] : S.n. - ISBN 9789085046516 - 142
stikstof - stroming - modellen - land - water - stroomvlakten - rivieren - kustwateren - nitrogen - flow - models - land - water - floodplains - rivers - coastal water
Avoidance of polycyclic aromatic hydrocarbon-contaminated sediments by the freshwater invertebrates Gammarus pulex and Asellus aquaticus
Lange, H.J. de; Sperber, V. ; Peeters, E.T.H.M. - \ 2006
Environmental Toxicology and Chemistry 25 (2006)2. - ISSN 0730-7268 - p. 452 - 457.
waterverontreiniging - sediment - stroomvlakten - besmetters - toxicologie - polycyclische koolwaterstoffen - waterinvertebraten - waterdieren - gammarus pulex - asellus aquaticus - waterbodems - ecotoxicologie - water pollution - floodplains - contaminants - toxicology - polycyclic hydrocarbons - aquatic invertebrates - aquatic animals - water bottoms - ecotoxicology - oligochaete lumbriculus-variegatus - induced community tolerance - rhine-meuse delta - pollution - toxicity - amphipod - metals - food - earthworm - responses
Contamination of sediments is a serious problem in most industrialized areas. Sediments are often contaminated with trace metals and organic contaminants like polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Bioassays are often used to determine the effect of contaminants on biota. However, survival or growth may not be the most sensitive endpoints. Behavioral changes often occur at much lower concentrations. Our study aimed to assess the effect of PAHs on habitat choice of two common freshwater invertebrates, the amphipod Gammarus pulex and the isopod Asellus aquaticus. We spiked clean field sediment with a mixture of four PAHs, fluoranthene, pyrene, chrysene, and benzo[k]fluoranthene, to a total concentration of 30 mg PAH/kg dry weight. Both species were offered a choice between PAH-spiked sediments and clean sediments in laboratory experiments. Results show that both species avoid PAH-spiked sediment. Origin of the population, either from a clean reference site or from a polluted site, did not affect habitat choice of either species
Trace metals in floodplain lake sediments : SEM/AVS as indicator of bioavailability and ecological effects
Griethuysen, C. van - \ 2006
Wageningen University. Promotor(en): Bart Koelmans. - [S.l. ] : S.n. - ISBN 9085043654 - 223
sporenelementen - metalen - stroomvlakten - meren - sediment - verontreinigende stoffen - waterverontreiniging - methodologie - ecologie - risicoschatting - waterkwaliteit - nederland - land van maas en waal - trace elements - metals - floodplains - lakes - sediment - pollutants - water pollution - methodology - ecology - risk assessment - water quality - netherlands - land van maas en waal
This thesis addresses the geochemical aspects of AVS (Acid Volatile Sulfide) and SEM (Simultaneously Extracted Metals) in floodplain lake sediment, its spatial distribution in floodplain lakes and dynamics over time, the link with effects on single species (bioassays), as well as the impact of excess SEM on the in situ benthic community, in one consistent methodological approach. Using this approach the SEM-AVS concept is thus evaluated on various levels from geochemical through ecotoxicology towards ecology. Furthermore, the aspect of spatial and temporal variability is addressed. For the case studies in the field, several floodplain lakes located in the floodplain area Afferdensche and Deestsche Waarden along the Waal branche of the Rhine were selected. Occasionally, this selection was extended towards other floodplain lakes along the Rhine branches. The main goal of this research is a) to explore the actual risks of trace metals to benthic communities in floodplain systems and b) to evaluate the SEM-AVS concept as a tool to assess bioavailable concentrations of trace metals in dynamic floodplain sediment
Dynamiek versluiert; veldeffecten van metalen in dynamische ecosystemen
Klok, C. - \ 2006
Bodem 16 (2006)3. - ISSN 0925-1650 - p. 120 - 121.
ecosystemen - toxicologie - aardwormen - bodemfauna - overstromingen - stroomvlakten - zware metalen - ecotoxicologie - ecosystems - toxicology - earthworms - soil fauna - floods - floodplains - heavy metals - ecotoxicology
Deze bijdrage richt zich op de invloed van overstroming op de kans dat effecten van vervuiling zichtbaar worden op regenwormpopulaties
Effects of flooding on germination, establishment and survival of woody species; a field and modeling study on the floodplains of the river Rhine
Kramer, K. ; Nijhof, B.S.J. ; Vreugdenhil, S.J. ; Werf, D.C. van der; Wyngaert, I.J.J. van den; Armbruster, J. ; Späth, V. ; Siepmann-Schinker, D. - \ 2006
Wageningen : Alterra (Alterra-rapport 1345) - 72
inundatie - kieming - vestiging - overleving - oeverbossen - stroomvlakten - wateropslag - hoogwaterbeheersing - houtachtige planten - nederland - duitsland - bomen - rijn - flooding - germination - establishment - survival - riparian forests - floodplains - water storage - flood control - woody plants - netherlands - germany - trees - river rhine
Climate change results in higher water levels and therefore more frequent flooding and longer inundation of the floodplains of the river Rhine. Retention basins are installed in Germany and anticipated in the Netherlands to reduce peak flows and to prevent loss of property. In Germany, many of the retention basins are covered with forests that have experienced few floodings and that may be severely damaged by an extensive flood. In the Netherlands, the allocation of retention basins provides opportunities for new forest development. In both cases, knowledge is required on the effects of flooding on germination, establishment and survival of woody species to support the selection of retention basins. We analyzed the effects of flooding regimes on germination, establishment and survival of both saplings and adult trees, using analyzing available data; by collecting observational data; by performing field experiments; and by integrating this knowledge in a simulation model. We found clear differences between species in their response to flooding characteristics. The model is available for future studies on selection of retention basins
Ecoflood guidelines : how to use floodplains for flood risk reduction
Blackwell, M.S.A. ; Maltby, E. ; Gerritsen, A.L. ; Haasnoot, M. ; Hoffmann, C.C. ; Kotowski, W. ; Leenen, E.J.T.M. ; Okruszko, T. ; Penning, W.E. ; Piorkowski, H. ; Platteeuw, M. ; Querner, E.P. ; Siedlecki, T. ; Swart, E.O.A.M. de - \ 2005
[S.l.] : Ecoflood Project - 144
stroomvlakten - hoogwaterbeheersing - overstromingen - risicovermindering - richtlijnen (guidelines) - rivieren - europa - risicobeheersing - floodplains - flood control - floods - risk reduction - guidelines - rivers - europe - risk management
The main objective of these guidelines is to promote the use of floodplains as natural flood defence measures, while at the same time optimising other compatible functions and values through conservation and restoration. It is intended that these guidelines will be used as a tool primarily by policy-makers and decision-makers who are aware of the potential advantages of floodplain restoration and management in the role of flood control, but may benefit from comprehensive guidance on assessing, initiating, funding and carrying-out such schemes as well as information on the other functions floodplains can perform. It is also intended that they will be an accessible source of information for a wide range of stakeholders with an interest in floodplain management. Case studies are provided to illustrate the wide range of schemes that can be carried out and the degrees of success that have been achieved. Case studies from the Netherlands are: 1. Meinerswijk, Rhine; 2. Zandmaas and Grensmaas, Meuse; 3. Gamerensche Waard, Lower Rhine; 4. Afferdensche en Deestsche Waarden, Lower Rhine
Rehabilitating large regulated rivers; lowland river rehabilitation conference; Wageningen, 29 september - 3 oktober 2003
Buijse, A.D. ; Klijn, F. ; Leuven, R.S.E.W. ; Middelkoop, H. ; Schiemer, F. ; Thorp, J.H. ; Wolfert, H.P. - \ 2005
Stuttgart (Germany) : Schweizerbart (Archiv für Hydrobiologie Suppl. vol. 155, no. 1-4) - 738
stroomvlakten - herstel - rivierregulering - rivieren - hydrobiologie - floodplains - rehabilitation - river regulation - rivers - hydrobiology
Regulating rivers has reduced the natural dynamic processes, altered the landscape and its biodiversity. Along large rivers that serve manifold functions, rehabilitation attempts have recovered stretches or certain features, but complete restoration probably will be a utopia. Key questions of the conference were e.g. how sustainable or effective are we so far; how well did we assess our achievements; what are the costs and benefits, opportunities and constraints, the end-points? More than 50 oral contributions and over 40 posters were presented at the conference, 45 of which, from 14 different countries, are published as peer-reviewed papers in this issue
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