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Dunes, above and beyond : The interactions between ecological and geomorphological processes during early dune development
Puijenbroek, Marinka E.B. - \ 2017
Wageningen University. Promotor(en): F. Berendse, co-promotor(en): J. Limpens. - Wageningen : Wageningen University - ISBN 9789463432146 - 183
dunes - geomorphology - ecology - vegetation - duneland plants - beaches - duinen - geomorfologie - ecologie - vegetatie - duinplanten - stranden
Coastal dunes occur along the sandy shores of most continents where they serve as coastal defence against flooding, provide areas for recreation, store drinking water and harbour unique biodiversity. Coastal dunes and the services they provide are threatened by climate-induced sea-level rise. This threat may be mitigated by the spontaneous formation of new dunes, for example in combination with mega-nourishments aimed at increasing beach width. Coastal dunes form by the interaction between vegetation, wind and wave action. Persistent dune development begins with the establishment of vegetation on the beach: the vegetation traps the wind-blown sand, forming an embryo dune. Over time an embryo dune can develop into a bigger foredune, increasing coastal safety. The formation and development of embryo dunes into foredunes depend on the vegetation establishment on the beach, dune growth over summer and dune erosion during winter. Although vegetation succession and geomorphological processes are each well described, the interaction between ecological and geomorphological processes during embryo dune development are not well known. The thesis aimed at further exploring these interactions, using a combination of experiments and high-resolution dune monitoring to study the mechanisms underlying early dune development and their implications for mega-nourishment design.
To explore whether soil salinity, salt spray or storms determine the vegetation limit of dune building plant species on the beach, we performed a field transplantation experiment and a glasshouse experiment with two dune building grasses Ammophila arenaria and Elytrigia juncea. In the field growth of grasses transplanted into four vegetation zones from sea to dune was monitored for over a year and the response of these species to salt spray and soil salinity was tested in a glasshouse experiment. In the field, the vegetation zones were associated with differences in summer soil salinity: zones with both species present were significantly less saline than zones with only E. juncea or the zones without any vegetation. However, in our experiments the transplanted A. arenaria performed equal or better than E. juncea in all vegetation zones, suggesting soil salinity did not limit species performance at the studied site. Both species showed severe winter mortality. In the glasshouse experiment, A. arenaria biomass decreased linearly with soil salinity, presumably as a result of osmotic stress. Elytrigia juncea showed a nonlinear response to soil salinity with an optimum at 0.75% soil salinity and a decrease in biomass at higher salt concentrations. Our findings suggest that soil salinity stress either takes place in winter during storm inundation, or that development of vegetated dunes is less sensitive to soil salinity than hitherto expected.
To understand the boundary conditions for embryo dune development over a longer time period we explored the effects of beach morphology, meteorological conditions and sand nourishment on early dune development using a 30 year time series of aerial photographs and beach profile monitoring data. We concluded that 1) beach morphology is highly influential in determining the potential for new dune development, with wide beaches enabling development of larger embryo dune fields, 2) sand nourishments stimulate early dune development by increasing beach width, and 3) weather conditions and non-interrupted sequences of years without high-intensity storms determine whether progressive dune development will take place.
Dune development is the result of the interaction between vegetation development and sedimentation and erosion processes. To disentangle the effects of vegetation characteristics and that of dune size we monitored a natural dune field of 8 hectares for one year using an Unmanned Aerial Vehicle (UAV) with a camera. By constructing a digital surface model and a geometrical corrected image (an orthomosaic) for each flight campaign we calculated changes in dune volume over summer and winter and related these changes to vegetation, dune size and degree of shelter. The dune growth over summer was mainly determined by dune size, whereas dune growth over winter was determined by vegetation characteristics. Degree of shelter determined whether dune growth was limited by storm erosion (exposed dunes) or sand supply (sheltered dunes). These results suggest that vegetation characteristic may be particularly important for resisting storm erosion and speeding up recovery after erosion.
Embryo dunes have been hypothesised to facilitate development of species rich green beach vegetation in the sheltered location between the embryo dunes and the primary foredunes. To test this hypothesis we explored the relative impacts of abiotic soil conditions as affected by the geomorphological setting on the species richness and species turn-over of green beach vegetation. To this end we characterised the geomorphology and measured abiotic conditions and species composition of green beach vegetation along transects from beach to foredune. We found that the geomorphological setting influenced plant species composition indirectly by affecting soil salinity and rate of sand burial. We found that plant species richness declined less at sheltered conditions, where there was a build-up of organic matter and no sand burial. Our results further suggest a non-linear relationship between embryo dune volume and number of green beach species: embryo dunes can be a source of shelter, thus stimulating green beach development, but can also compete for space, reducing green beach development. The net effect of embryo dunes most likely depends on the sediment budget of the beach and storm intensity.
Mega-nourishments are single large sand nourishments that are applied locally, and are expected to exist for about 20 years, providing opportunities for the development of embryo dunes and rare pioneer plant communities (green beach vegetation). We explored this potential by comparing growth and development of dune building species on natural beaches with the results of plant transplantation and monitoring data of two mega-nourishments: the low-elevated Hondsbossche Duinen and the high-elevated Sandmotor. Our results suggest that establishment of dune building species on high-elevated mega-nourishment proceed slower than on natural beaches due to dispersal limitation. Once vegetation has established however, embryo dune development on high-elevated mega-nourishments may proceed faster than natural beaches due to low salinity and protection against storm erosion. Development of dune-building vegetation on the low-elevated mega-nourishment Hondsbossche Duinen showed the same rate and pattern as that on a natural beach. The potential for embryo dune development on mega-nourishments is far bigger than the potential for green beach development, since green beach vegetation develops under a narrower range of abiotic conditions. Such abiotic conditions can develop behind the shelter of embryo dunes or foredunes at low beach elevations.
In conclusion this thesis shows that, 1) the potential of embryo dune development depends on a large beach width and low storm erosion which determines the vegetation limit. 2) Embryo dune growth over summer is mainly determined by existing dune volume and sand supply. 3) Heavy storms limit embryo dune development during winter, although dune erosion can be mitigated by vegetation composition. 4) On accreting beaches which continuously provide area for the development of new embryo dunes green beach vegetation can develop. 5) The design of a mega-nourishment determines the potential for the development of embryo dunes and green beach vegetation. Our findings provide insights in the interaction between ecological and geomorphological processes that determine embryo dune development. This knowledge can help to obtain better predictions of embryo dune development under the threat of sea-level rise.
Monitoring en Evaluatie Pilot Zandmotor Fase 2 - Ecotopenkaarten vooroever en getijdenstrand 2010 - 2015
Wijsman, J.W.M. ; Tangelder, M. ; Visser, Pieter ; Hoekstra, R. - \ 2016
IMARES (Rapport / IMARES C034/16) - 35 p.
getijden - stranden - zandsuppletie - natuurontwikkeling - ecologie - zuid-holland - tides - beaches - sand suppletion - nature development - ecology
Dit rapport presenteert een eerste aanzet voor de ontwikkeling van ecotopenkaarten voor de vooroever en het intergetijdenstrand van de Zandmotor over de jaren 2010 tot en met 2015. In de ecotopenclassificatie worden de abiotische parameters droogvalduur, bodemschuifspanning en getijdenstroming gecombineerd tot 11 ecotopen, waarvan 4 in de vooroever, 6 op het natte strand en 1 op het droge strand.
Beach sand dynamics : measurements, models and scales
Poortinga, A. - \ 2015
Wageningen University. Promotor(en): Coen Ritsema, co-promotor(en): Saskia Visser; Michel Riksen. - Wageningen : Wageningen University - ISBN 9789462575851 - 235
stranden - zand - modellen - meettechnieken - eolisch zand - sediment - geologische sedimentatie - beaches - sand - models - measurement techniques - aeolian sands - sediment - geological sedimentation
Monitoring en Evaluatie Pilot Zandmotor Fase 2 - Datarapport benthos bemonstering vooroever en natte strand najaar 2012
Wijsman, J.W.M. - \ 2014
Yerseke [etc.] : IMARES en Deltares (Rapport / IMARES C149/14 - 1205045-000-ZKS-100) - 49
zandsuppletie - kustbeheer - natuurontwikkeling - natuurbeheer - monitoring - benthos - stranden - oevers - zuid-holland - sand suppletion - coastal management - nature development - nature management - beaches - shores
Het doel van dit datarapport is een overzicht te geven van de verzamelde data en resultaten van de bemonstering van het sediment en benthos op het strand en de ondiepe kustzone van de Zandmotor in het najaar van 2012. Een dergelijke bemonstering is eerder uitgevoerd in 2010 (Wijsman en Verduin, 2011) en 2011 (Boon en Wijsman, 2012). De resultaten van de bemonstering zullen worden gebruikt bij de evaluatie waarbij de bovengenoemde hypothesen zullen worden getoetst.
Monitoring en Evaluatie Pilot Zandmotor Fase 2: meetrapportage monstername benthos, vis en strand najaar 2011
Boon, A.R. ; Wijsman, J.W.M. - \ 2012
Yerseke : IMARES / Deltares (Rapport / IMARES C049/12)
zandsuppletie - kustbeheer - natuurontwikkeling - natuurbeheer - benthos - vissen - stranden - oevers - monitoring - zuid-holland - sand suppletion - coastal management - nature development - nature management - fishes - beaches - shores
Dit document beschrijft de werkzaamheden die in het najaar van 2011 zijn uitgevoerd ten behoeve van de monstername van sediment, benthos, vis in de vooroever en de lagune, en van sediment en bodemgebonden fauna van het strand ter plaatse van de Zandmotor.
Strandreservaten: voor natuur en kustveiligheid
Engelbertink, R.B.J. ; Paulissen, M.P.C.P. ; Janssen, G.M. ; Vanagt, T.J. ; Slim, P.A. - \ 2010
De Levende Natuur 111 (2010)2. - ISSN 0024-1520 - p. 108 - 112.
stranden - kustgebieden - natuurbescherming - ecosystemen - natuurreservaten - beaches - coastal areas - nature conservation - ecosystems - nature reserves
Het strand vormt een belangrijke overgangszone tussen zee en duinen met karakteristieke habitats en de daarbij behorende flora en fauna. De strandnatuur staat echter onder druk, onder andere door verstorende werking van zandsuppleties en recreatie. Een mogelijkheid tot bescherming is het instellen van strandreservaten. Kenmerkend voor strandreservaten is dat er rust wordt gecreëerd, dat natuurlijke processen hun gang mogen gaan en dat vloedmerkmaterialen niet worden opgeruimd. Aanbevelingen met betrekking tot realisatie worden gegeven
Schoon strand Texel 2005 : onderzoeksresultaten van de schoonmaakactie van het Texelse strand op 20 april 2005
Franeker, J.A. van - \ 2005
Wageningen : Alterra (Alterra speciale uitgave 2005/09) - 23
stranden - verontreiniging - verontreinigende stoffen - verontreinigingsbeheersing - vuilnis - schoonmaken - nederland - nederlandse waddeneilanden - beaches - pollution - pollutants - pollution control - refuse - cleaning - netherlands - dutch wadden islands
Effecten van eilandvarianten in de Noordzee op de ecologie van strand en duin
Sanders, M.E. ; Slim, P.A. ; Dobben, H.F. van; Wegman, R.M.A. ; Schouwenberg, E.P.A.G. - \ 2004
Wageningen : Alterra (Alterra-rapport 1092) - 100
plantensuccessie - plantenecologie - vegetatie - duinen - stranden - luchthavens - natuurbescherming - noordzee - invloeden - plant succession - plant ecology - vegetation - dunes - beaches - airports - nature conservation - north sea - influences
Door de toenemende groei in de internationale luchtvaartsector, ziet Schiphol zich genoodzaakt om uit te breiden. Gezien de ruimteclaims en de milieuwetgeving zal voor de lange termijn een verdere uitbreiding van Schiphol op de huidige locatie moeilijker worden. Een alternatief voor de locatie Schiphol is het aanleggen van een eiland in de Noordzee. Dit rapport beschrijft en waar mogelijk kwanitificeert de effecten van de aanleg van een luchthaveneiland in de Noordzee op de ecologie van strand en duin. De belangrijkste effecten van een eiland in de Noordzee op strand en duin, zijn gelegen in veranderingen in kustmorfologie en saltspray. Veranderingen in de morfologie hebben het grootste effect op het strand (en zeereep) en veranderingen in saltspray op de vegetatie in de duinen. Voor strand en zeereep geeft een aanwaskust in de luwte van het eiland mogelijkheden voor natuurontwikkeling, maar voor de duinen betekent de afname van saltspray een achteruitgang in natuurbehoudswaarde van deze internationaal beschermde gebieden.
Economische aspecten van Coastal Zone Management
Buisman, F.C. - \ 1996
Den Haag : LEI-DLO (Mededeling / Landbouw-Economisch Instituut (LEI-DLO), Afdeling Visserij 567) - ISBN 9789052423593 - 64
stranden - kusten - natuurbescherming - bescherming - samenleving - technologie - wereld - economische planning - natuur - wetenschap - oevers - beaches - coasts - nature conservation - protection - society - technology - world - economic planning - nature - science - shores
|Scenarios for european coastal areas, a promising tool for making decisions at various levels?
Klijn, J.A. - \ 1995
In: Scenario studies for the rural environment : selected and edited proceedings of the symposium scenario studies for the rural environment, Wageningen, The Netherlands, 12 - 15 September 1994 / Schoute, J.T.H., Finke, P.A., Veeneklaas, F.R., - p. 457 - 471.
stranden - kusten - ecosystemen - landgebruik - bedrijfsvoering - natuurbescherming - ruimtelijke ordening - beleid - zonering - oevers - beaches - coasts - ecosystems - land use - management - nature conservation - physical planning - policy - zoning - shores
Natural coasts, especially soft coasts, in Europe are valuable landscapes, but they are under great pressure. Trends and threats have various causes of both physico-ecological and socio-economic origin. Examples of large-scale processes are given, such as sea level rise and regional processes (reclamation, urbanization, land use changes). Regional scenarios can help to support policy making. The pros and cons of forecasting and backcasting scenarios are discussed, as well as the need of data.
|Kustwatersporters stellen ruimtebeleving voorop; onderzoek naar bezoekmotieven en gedrag in kustwateren
Bruin, A.H. de; Klinkers, P.M.A. ; Vries, T.A.C. de - \ 1995
Recreatie en Toerisme 5 (1995)7/8. - ISSN 0165-4179 - p. 8 - 9, 11.
openluchtrecreatie - recreatie op het platteland - recreatie - vrijetijdsactiviteiten - vrijetijdsgedrag - waterrecreatie - kusten - stranden - oevers - outdoor recreation - rural recreation - recreation - leisure activities - leisure behaviour - water recreation - coasts - beaches - shores
De kustwateren Waddenzee, Voordelta en Oosterschelde hebben de hoofdfunctie natuur; de functie waterrecreatie is hieraan ondergeschikt. De interactie tussen beide functies is onderzocht door zes typen watersporters (surfers, bootvissers, droogvallendezeilers, wadlopers, motorboot- en chartervaarders) te interviewen. De kustwateren voorzien voor alle watersporters in een basisbehoefte aan ontspannning. Centraal staan rust, ruimte, vrijheid en natuur. Het behoud van natuur- en milieuwaarden dient dus een gezamenlijk belang. Maatregelen hiertoe worden beter geaccepteerd en nageleefd als ze worden afgestemd op de doelstellingen van de watersporter. Gebruikers moeten daarom vroegtijdig bij de planvorming worden betrokken.
Ontwerpen van een methode voor tijdreeksanalyse van vegetatiegegevens ten behoeve van monitoring.
Sanders, M.E. ; Wirdum, G. van - \ 1994
Wageningen : IBN-DLO - 69
stranden - kusten - bedrijfsvoering - cartografie - monitoring - nationale parken - natuurreservaten - nederland - plantengemeenschappen - beleid - projecten - onderzoek - vegetatie - oevers - thematische cartografie - beaches - coasts - management - mapping - national parks - nature reserves - netherlands - plant communities - policy - projects - research - vegetation - shores - thematic mapping
Nematodes and decomposition in intertidal ecosystems
Alkemade, J.R.M. - \ 1993
Agricultural University. Promotor(en): A.F. van der Wal; M.A. Hemminga. - S.l. : Alkemade - ISBN 9789054851462 - 145
stranden - vegetatie - pratylenchus - heteroderidae - tylenchidae - dood - gebruiksduur - herbivoren - halofyten - beaches - vegetation - pratylenchus - heteroderidae - tylenchidae - death - longevity - herbivores - halophytes
Salt marshes in temperate regions are very productive natural vegetations. These vegetations frequently reach an above-ground production of more than 1 kg of dry weight per m 2per year. Herbivores consume only a small proportion of the annual plant production. Almost the entire amount of above ground plants dies after senescence. A small proportion may be washed away by the tides, but the major part remains at the salt marsh where it decomposes in the canopy or at the sediment surface.
Dead plant material is primarily decomposed by micro-organisms, such as fungi and bacteria. The chemical composition of the detritus to a large extent determines the rate of decomposition. A number of abiotic factors, such as temperature and humidity, also influence the decomposition process. In addition the process may be affected by fauna, present on the decomposing plant material.
In this thesis the role of nematodes in decomposition of Spartina anglica was studied. This plant species commonly occurs in salt marshes of Western Europe. In addition, one chapter is dedicated to the association between nematodes and decomposing seaweed in a completely different habitat: an Antarctic beach. In the first part of this thesis the relation between decomposition and naturally occurring nematode populations is studied. This part consists mainly of field studies. Nematodes, which are associated with the decomposition process are identified, and the population dynamics of one of these species is studied in detail. The second part of this thesis is dedicated to laboratory and model studies which were carried out to investigate the effects of nematodes on decomposition of S.anglica detritus and the possible mechanism underlying these effects.
Nematode populations on decomposing plant material
Nematodes are abundant on both S.anglica litter and on stranded Antarctic seaweed. We found that on standing dead Spartina anglica plant parts the nematode population frequently reached densities of 3000 individuals per g DW. When leaf material on the sediment surface was investigated even much higher nematode densities were found, up to 47,000 individuals per g DW. At Antarctic beaches nematode densities up to 26,000 individuals per g DW were found on seaweed wrack.
Although numerous, not all of these nematodes present on plant detritus are expected to influence the decomposition process. In chapter I an attempt was made to distinguish the nematode species which play a role in decomposition of S. anglica detritus from nematodes which do not have such a role. As decomposition is largely a microbial process, higher decomposition rates presumably coincide with a higher microbial production and, consequently, a higher availability of food for microbivorous nematodes. Amongst the microbivorous nematodes, those species were considered of possible importance to the decomposition process when their numbers increased with increasing decomposition rate. In the experiments, mesh containers, filled with Spartina anglica leaves, were placed on the sediment surface. Different decomposition rates were induced by using decaying leaf material of different ages and by repeating the experiments during four subsequent seasons. Mesh containers with inert material (plastic drinking straws) served as controls. Sixty nematode species were found in the mesh containers. Using a multivariate analysis (redundancy analysis) different nematode communities were found on plant material with different decomposition rates. These differences were caused by the changing abundance of only a few species. The majority of the species were found in equal numbers in treatments with decomposing Spartina leaves and in the control treatment. The numbers of individuals of those species which appeared closely correlated with the decomposition rate of Spartina anglica leaf-detritus were all bacterivorous nematodes. Numerically the most dominant were species of the family Monhysteridae ( Diplolaimelloides bruciei, Diplolaimella dievengatensis, Monhystera parva ). The highest numbers of these nematodes were found in treatments with the highest decomposition rates i.e. on decaying fresh leaves, during the warmer seasons. In the winter, when decomposition is slower, their numbers were lower.
The species diversity on standing dead plant parts of Spartina anglica is much lower than the species diversity on the sediment surface in mesh containers filled with S.anglica leaves. The dominant species on standing dead plants are the bacterivorous nematodes Diplolaimelloides bruciei, Monhystera disjuncta and Pellioditis marina. In chapter 11 a study is presented on the population dynamics of D. bruciei. This species was commonly found on above ground plant parts of Spartina. In a field study, population densities of this species were estimated on four classes of S.anglica plant material, representing the whole range of decomposition stages found in the canopy. D. bruciei was found throughout the year on all types of plant material, including living green plant parts. The population densities were highest on the older plant material, where densities of 1000-2000 individuals per g DW were reached. The highest densities were recorded in late summer and autumn.
S. anglica vegetations are regularly flooded at high tide, which potentially reduces the nematode population density on the plant material, as nematodes may be flushed from the plants. Since in situ measurements of the flooding effect are not possible, the population dynamics of D. bruciei was studied in the laboratory under a controlled flooding regime. The population densities of D.bruciei indeed seemed to be highly influenced by flooding. A considerable part of the population disappeared during flooding, but on younger, yellow, decomposing leaves the rate of removal by flushing was much lower than on older, brown, leaves. This is probably caused by the change of the leaf structure during decomposition. Nematodes may become less well attached to the leaf surface when the groove structure of the leaves disappears with progressive decay; consequently, a higher proportion is flushed away. The growth rate of the population, however, was equal on both leaf types. The growth rate of the nematode population, as estimated in the laboratory, was used to calculate the total production of nematodes in the field. It was shown that the total biomass production of D. bruciei equalled 114 mg C per m 2per year. If 30% of the detritus was decomposed by bacteria and a trophic efficiency of 10 % is assumed, the total amount of bacteria] carbon ingested by D.bruciei accounted for 7.5 % of the total bacterial biomass produced. It was estimated that the dominant bacterivorous nematodes together may consume over 20% of the total bacterial biomass production.
In chapter III a study of nematodes found in stranded seaweed at an Antarctic beach is presented. Large amounts of seaweed are deposited along the coast of Admiralty Bay, King George Island, Antarctica. The stranded seaweed partly decomposes on the beach and supports populations of various meiofauna species, mostly nematodes. The factors determining the number of nematodes found in the seaweed packages were studied. The densities of nematodes appeared to be correlated primarily with salinity, height and C:N ratio of the detritus. Salinity and height were most likely related to the flooding regime in conjunction with the off-stream of melt water. Decomposition rate appeared mainly determined by the water content and the sediment composition. Melt water run-off or the impact of the surf probably increased seaweed weight losses in these situations.
The effect of nematodes on decomposition of S.anglica
Experiments with D. bruciei, a species numerously present on standing dead S.anglica plants (see chapter II), were set up to study the effect of this nematode on decomposition (chapter IV). Green and yellow leaves were placed on agar in petri dishes and inoculated with D. bruciei. CO 2 production was determined regularly after inoculation. Weight, carbon and nitrogen losses were determined at the end of the experiment, 30 days after inoculation. In the presence of nematodes, CO 2 -production on green, decaying leaves increased by 20 - 25 %. Losses of dry weight, carbon and nitrogen during decomposition increased with at least 30 %. On yellow, more senescent leaves no effect on CO 2 -production was found, but losses of dry weight, carbon and nitrogen tended to be higher in the presence of nematodes. The results of this study show that D.bruciei may enhance the decomposition rate of S.anglica -leaves; the extent of the stimulatory effect, however, depends on leaf condition and the population density of the nematode. The minimal nematode population density for a measurable stimulatory effect was estimated to be 4000 individuals per g DW of S.anglica leaves. As described in chapter II, field population densities are often of the same order of magnitude.
A part of the senescent S.anglica leaves and stems decompose at the sediment surface, where the material is covered with sediment. In chapter I a clear correlation was found between the number of the bacterivorous nematode Diplolaimella dievengatensis and the decomposition rate of S.anglica detritus present on the sediment surface. The effect of the D.dievengatensis on the carbon mineralization of S.anglica detritus was examined in a laboratory experiment (chapter V). Detritus mixed with sediment appeared to decompose at higher rates in the presence of the nematodes. CO 2 production per hour was 74 % higher in the presence of the nematode than in its absence; O 2 consumption per hour increased to a similar extent. Diffusion coefficients were calculated from measurements of both O 2 consumption, using gas chromatography, and O 2 micro-gradients, using micro-electrodes. The apparent diffusion coefficient of O 2 in the sediment in the presence of nematodes was 40% to 70 % higher than the bulk sediment diffusion coefficient. Since the increase of the CO 2 production and of the diffusion of oxygen in the presence of nematodes was of the same magnitude, we concluded that the enhanced turnover time of Spartina detritus presumably was largely caused by the bioturbation activity of the nematodes.
A simulation model was constructed to quantify the relations between decomposing S.anglica detritus, bacteria and their grazers (chapter VI). The model takes the various stages of above ground litter decomposition into account. The heterogeneity of the decomposing litter was described by a number of successive quality classes. Decomposition was considered to be primarily a microbial process. The microbial population was assumed to consist of a number of successional species each possessing a unique preference for the different quality classes. Grazers were all considered as a single species grazing upon all microbial species. Three mechanisms by which grazers may stimulate decomposition were evaluated using the data from the laboratory study presented in chapter IV. In the first place: if the microbial population grows to a certain maximal density than removing microbial biomass by grazers may stimulate decomposition since space is created for growth of new microbes at the expense of organic substrate. In the second place: the excretion of highly nutritive mucus by grazers may stimulate bacterial growth. In the third place: reworking of the sediment-detritus-microbial mixture in the grooves of the leaves (see also chapter II), or in the upper layer of the sediment may increase the oxygen availability and may, by mechanical force, enlarge the surface of the substrate on which the microbes attack. The model calculations suggested that removing of microbial biomass by grazers has some stimulatory effect on the decomposition rate of detritus, but not enough to account for the total effect. Recycling of organic matter by excretion of mucus seemed to have no effect at all.
According to the model, bioturbation or reworking contributed most to the stimulation of the decomposition rate.
The model was validated with field data. The model could describe field data obtained from a variety of locations. The biomass of bacteria and grazers estimated by the model were in the same order of magnitude as those found in the field. The model is useful to evaluate decomposition data from different studies and calculate an approximate amount of microbes and primary grazers available for higher trophic levels.
When the model calculations were performed over a period of about a year the stimulating effect of grazers gradually seemed to vanish. This is in agreement with the experiments described in chapter IV, which show that the effect of nematodes on decomposing yellow leaves were less pronounced than on green leaves. Thus, any stimulatory effect of nematodes on decomposition of Spartina anglica in the salt marsh may be restricted to the first stages of the decomposition process.
Remote sensing voor classificatie en kwantificatie van de vegetatie op ganzenpleisterplaatsen in het Waddengebied = Remote sensing of vegetation in spring staging areas of brent geese
Bijlsma, R.J. - \ 1989
Arnhem : Rijksinstituut voor Natuurbeheer (RIN-rapport 89/5) - 62
anser - toepassingen - stranden - ganzen - plantengemeenschappen - remote sensing - onderzoek - vegetatie - waddenzee - applications - beaches - geese - plant communities - research - vegetation - wadden sea
Establishment, growth and degeneration of Ammophila arenaria in coastal sand dunes
Putten, W.H. van der - \ 1989
Agricultural University. Promotor(en): L. 't Mannetje; C. van Dijk. - S.l. : Van der Putten - 152
grassen - poaceae - duinen - duinplanten - vegetatie - plantengemeenschappen - vastleggen van duinen - kusten - bescherming - beschermende structuren - versterking - fixatie - stranden - eolisch zand - groei - plantenontwikkeling - nederland - plantenecologie - grasses - poaceae - dunes - duneland plants - vegetation - plant communities - sand dune stabilization - coasts - protection - protective structures - reinforcement - fixation - beaches - aeolian sands - growth - plant development - netherlands - plant ecology
This study deals with the establishment, growth, and degeneration of Ammophila arenaria (marram grass), a grass species that dominates the vegetation in coastal foredunes. Following natural establishment from rhizomes on high parts of the beach A.arenaria reduces wind velocity, which results in the accretion of windblown sand and the formation of dunes. A. arenaria grows vigorously in mobile dunes where fresh sand is deposited by wind, but it disappears from the vegetation when these dunes become stabilized.
Because of its ability to stabilize the sand, A. arenaria is often used in dunes to control erosion. It is planted according to a long practicised manual technique, using culms that are collected from stands at the foredune. When foredunes are reconstructed, however, (e.g. after storms) the establishment of A. arenaria is often unsuccessful, which means that erosion control can become very costly.
This study was carried out to develop new methods of establishing A. arenaria and to investigate the cause of the replant failures on reconstructed dunes. In addition, experiments were carried out to eludicate the relationship between the colonization of windblown sand and the vigour of A. arenaria .
Two alternative methods were developed: (1) the sowing of seeds, which is rarely practiced and (2) the disk-harrowing of rhizomes, which has not previously been applied.
Experiments showed that seeds hardly germinate at constant temperatures. A high rate of germination can be achieved with fluctuating high temperatures, but at low temperatures the seeds required stratification in order to germinate. In the field the seeds germinated well if they had been sown during the winter, which was probably because of natural stratification. Seeds can be sown mechanically while afterwards the sand surface needs to be stabilized. For this purpose straw proved to be more effective for seedbed stabilization than spraid compost.
Rhizomes (i.e. vertical underground stems) were collected from the foredune by mechanical sieving of the sand. Experiments proved that the disk-harrowing of rhizomes was a useful method of establishing A. arenaria provided that the sand surface was temporarily stabilized with straw or planted bundles of reed (chapter 2).
Field experiments showed that higher sowing rates and higher planting densities of rhizomes resulted in higher numbers of seedlings and primary shoots. However, after one growing season production of biomass and numbers of tillers appeared to be independent of the initial density. Application of slow-release NPK fertilizer (Osmocote, 12 to 14 months active at 21 °C) increased dry matter yield and numbers of tillers (chapter 2).
In a large-scale field experiment, rhizomes and a combination of planted culms and rhizomes produced more biomass and percentage cover than a sown stand during the first growing season. The lowest dry matter yield and percentage cover were obtained with traditionally planted culms. All plantings had been supplied with the same amount of slow- release NPK fertilizer. In the second year, however, the highest production was recorded for planted culms and for seeds in combination with compost. During these two years less than 5 per cent of the total area had to be replanted. All methods, therefore, were satisfactory in terms of sand stabilization.
The influence of uncontrolled factors was demonstrated by a 100 per cent higher production from a one-year-old stand in 1986 compared to 1987. The origin of the culms and rhizomes also influenced growth. Culms or rhizomes that had been collected from a stable dune with degenerated A.arenaria produced less dry matter and percentage cover than when the plant material was obtained from a mobile dune which was covered by vigorous plants (chapter 3).
Growth of seedlings of A.arenaria was strongly reduced in sand from the root zone of a foredune, when compared to growth in fresh (sea) sand. However, no differences occurred when both sand samples were sterilized prior to planting of the seedlings. In sea sand, growth was equal to that in sterilized sand. It was concluded, therefore, that the rhizosphere of A. arenaria contained harmful soil organisms (chapter 4).
In order to trace the nature of these organisms, biocides (bactericides, a nematicide, and fungicides) were applied to rhizosphere sand, which was planted with seedlings of A.arenaria. Bacteria were not supposed to be involved in the degeneration of A. arenaria , as bactericides did not affect plant growth. The nematicides effectively eliminated endoparasitic
The harmful soil organisms from a certain location reduced growth of local, as well as of foreign populations of A. arenaria. The growth of Calammophila baltica (purple, or hybrid marram grass, a sterile bastard of A. arenaria x Calamagrostis epigejos ) was also reduced by harmful soil organisms, but less than A. arenaria (chapters 4 and 6).
In three Dutch coastal dune systems harmful soil organisms were detected in the root zones of stable, as well as of mobile foredunes (degenerating and vigorous A. arenaria , respectively), but not in beach sand. The relation between sand deposition by wind and vigorous growth of A. arenaria was explained by supposing that windblown sand, originating from the beach, enables A. arenaria to escape harmful soil organisms (chapter 6). However, within one year after plants had produced new roots in fresh windblown sand, the root system became colonized by harmful soil organisms (chapter 7).
If harmful organisms were present in the sand prior to root growth, root hair formation was reduced severely and the branching of the roots was stimulated (chapter 7). This deformation of the root system by harmful soil organisms is assumed to be related to the degeneration of A. arenaria. A reduced uptake function and a shallow placement of the root system due to attack by harmful soil organisms in stable dunes increases the susceptibility of the plants to stress of drought, high soil temperatures, and shortage of nutrients. It is concluded that the degeneration of A. arenaria in stable dunes is caused by a combination of harmful biotic factors and abiotic stress.
The impact of sea level rise on the Dutch coastal ecosystems
Brouns, J.J.W.M. - \ 1988
Texel : NIOZ [etc.] (NIOZ-rapport 1988-8) - 102
stranden - biocenose - kusten - ecosystemen - opwarming van de aarde - broeikaseffect - hydrobiologie - nederland - regressie - transgressie - aquatische ecosystemen - zeeniveau - zeespiegelschommelingen - oevers - beaches - biocoenosis - coasts - ecosystems - global warming - greenhouse effect - hydrobiology - netherlands - regression - transgression - aquatic ecosystems - sea level - sea level fluctuations - shores
The impact of elevated carbon dioxide levels on marine and coastal ecosystems
Brouns, J.J.W.M. - \ 1988
Texel : NIOZ [etc.] (NIOZ-rapport 1988-7) - 101
atlantische oceaan - atmosfeer - stranden - biocenose - kooldioxide - kusten - samenstelling - opwarming van de aarde - broeikaseffect - halofyten - hydrobiologie - mariene gebieden - zout water - aquatische ecosystemen - oevers - atlantic ocean - atmosphere - beaches - biocoenosis - carbon dioxide - coasts - composition - global warming - greenhouse effect - halophytes - hydrobiology - marine areas - saline water - aquatic ecosystems - shores
Processes of formation and degradation of marshes along the Louisiana Gulf Coast
DeLaune, R.D. - \ 1988
Agricultural University. Promotor(en): N. van Breemen. - S.l. : DeLaune - 171
stranden - klimaat - overstromingen - landschap - louisiana - mariene sedimenten - morfologie - zoutmoerassen - bodemvorming - verwering - beaches - climate - floods - landscape - louisiana - marine sediments - morphology - salt marshes - soil formation - weathering
Processes governing the stability of Louisiana's rapidly deteriorating Gulf coast marsh were investigated. Vertical marsh accretion determined from 137 Cs dating were compared to water level increase obtained from tide gauge data. In subsiding coastal environments the continued existence of marsh habitat is dependent on the ability of marsh to maintain elevation through vertical marsh accretion (mineral sediment and organic matter accumulation). Coast-wide average vertical accretion was 0.60 to 0.80 as compared to water level increase of over 1 cm year. Rapid water level increase, attributed primarily to subsidence, was 3 to 5 times greater than eustatic sea level changes reported to be 0.23 cm yr-1
The measured accretionary deficits (difference between water level increase and vertical marsh accretion) parallels reported marsh disappearance of over 100 km2 yr -1Organic matter accumulation was identified as an important component of marsh aggradation in response to changes in water level. A appreciable amount of organic production of marsh macrophytes remains on the marsh as peat or is decomposed to carbon dioxide or methane. Organic matter on a dry weight basis constituted an increasing fraction of soil solids as its marine influence diminishes inland from the coast. Organic matter is of greatest structural significance in low density, fresh, and brackish marsh environments. However, on a unit volume basis, the organic matter occupies the same volumes in fresh, brackish, and salt marshes.
Louisiana Gulf coast marsh will likely continue disappearing at a rapid rate unless means are implemented for distributing Mississippi River sediment to the marshes. The combined effect of rapid subsidence, eustatic sea level rise and accompanying salt water intrusion will likely destroy much of these marshes. Results presented may represent future conditions for many coastal regions of the world, which may experience a rapid rise in water level as a result of the predicted "greenhouse" warming and resultant accelerated worldwide sea level rise.
|Lowland development in Indonesia = Pengembangan daerah rawa pasang surut di Indonesia, Jakarta, Indonesia, 24-31 August 1986: Supporting papers
International Institute for Land Recalamation and Improvement, - \ 1987
Wageningen : International Institute for Land Reclamation and Improvement - ISBN 9789070754044 - 594
ontginning - zwampen - hoogveengebieden - landbouwsituatie - economische situatie - plattelandsplanning - plattelandsontwikkeling - sociale economie - indonesië - moerassen - wetlands - polders - kusten - stranden - economische planning - oevers - reclamation - swamps - moorlands - agricultural situation - economic situation - rural planning - rural development - socioeconomics - indonesia - marshes - coasts - beaches - economic planning - shores
De ontwikkeling van de hoogte en van de omvang van de kwelders in de landaanwinningswerken in Friesland en Groningen
Bouwsema, P. ; Bossinade, J.H. ; Dijkema, K.S. - \ 1986
Texel etc. : R.I.N. (RIN-rapport no. 86/3) - 58
stranden - kusten - nederland - polders - ontgonnen land - ontginning - sediment - wetlands - friesland - groningen - beaches - coasts - netherlands - reclaimed land - reclamation