{"id":9091,"date":"2026-04-07T11:35:30","date_gmt":"2026-04-07T11:35:30","guid":{"rendered":"https:\/\/www.proefschriftmaken.nl\/portfolio\/marin-van-regteren\/"},"modified":"2026-04-23T08:23:36","modified_gmt":"2026-04-23T08:23:36","slug":"marin-van-regteren","status":"publish","type":"us_portfolio","link":"https:\/\/www.proefschriftmaken.nl\/en\/portfolio\/marin-van-regteren\/","title":{"rendered":"Marin Van Regteren"},"content":{"rendered":"","protected":false},"excerpt":{"rendered":"","protected":false},"author":8,"featured_media":13505,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"us_portfolio_category":[45],"class_list":["post-9091","us_portfolio","type-us_portfolio","status-publish","has-post-thumbnail","hentry","us_portfolio_category-new-template"],"acf":{"naam_van_het_proefschift":"Pioneering the Edges","samenvatting":"De zaadbank en het behoud van zaden na zaadval in de herfst\n\nZaden van verschillende pioniers en lage kwelder soorten waren aanwezig in de bodem van de begroeide kwelder (Hoofdstuk 2). In de transitiezone was de natuurlijke beschikbaarheid van levensvatbare zaden laag (Hoofdstuk 2, 3 en 5). Alhoewel de verspreiding van kwelderzaad voornamelijk lokaal is, waren zaden van het meerjarige Engels slijkgras bijna geheel afwezig in de transitiezone (Hoofdstuk 3 en 5). Zaden van de andere belangrijke pionier soort, zeekraal, kwamen wel voor in de zaadbank, echter zat de piek van deze zaden te diep om te zorgen voor succesvolle vestiging.\n\nHet moment van verspreiden heeft effect op het behoud van de zaden. Zaden die we voor de winter experimenteel verspreid hadden zijn weg ge\u00ebrodeerd. Zaden die na de winter verspreid zijn, waren in het voorjaar nog aanwezig en konden zich vestigen (Hoofdstuk 3). Stormachtige omstandigheden gedurende de winter, zoals hoge getijen, windsnelheden en golven, hebben het verlies van zaden tot gevolg (Hoofdstuk 3). Natuurlijke beschikbaarheid van zaden in het voorjaar is laag omdat de verspreide zaden weer weg eroderen in de winter (Fig. S2).\n\nFiguur S2. Grafische weergave van processen die beschikbaarheid van kwelder zaden be\u00efnvloeden (Hs 3).\n\nRol van bodemdieren\n\nTalrijke, kleine bodemdieren komen voor van de pionierszone tot aan het wad, merendeels bestaat dit uit oligochaeten (aquatische ringwormen), harpacticoide copepoden (benthische kreeftachtigen) en collembola (springstaarten) (Hoofdstuk 2). Deze benthische organismen woelen de bodem om en oligochaeten graven netwerken van tunnels (bioturbatie). Bioturbatie van de bodem zorgt ervoor dat zaden het sediment in getransporteerd worden, zowel in het veld (Hoofdstuk 3) als in het lab (Hoofdstuk 4). Zaden van verschillende groottes (1-20 mm) en drie verschillende soorten werden tot 3 cm diep getransporteerd binnen een periode van twee maanden (Hoofdstuk 3). Bioturbatie door oligochaeten hinderde ook de vestiging van pioniervegetatie, jonge zeekraal zaailingen werden begraven en omgewoeld (Hoofdstuk 4). Oligochaeten worden niet veel bestudeerd omdat ze klein en lastig te determineren zijn maar hebben een significante impact op de bodem door het omwoelen van het sediment. Oligochaeten veroorzaakte een tienvoudige penetratie diepte van zuurstof in vergelijking met sediment zonder deze wormen (Hoofdstuk 4). Op kwelder schaal lijkt het onwaarschijnlijk dat deze bodemdieren de vestiging van planten verhinderen. De meeste bodemdieren zijn namelijk gevonden in de pionierszone waar eenjarige pioniersvegetatie zich goed vestigt.\n\nImplicaties en conclusies\n\nDe belangrijkste conclusie van dit onderzoek is dat zelfs met een zaadbron nabij (de pionierszone), zaden een limiterende factor kunnen zijn voor vestiging van vegetatie. In het voorjaar is de beschikbaarheid van natuurlijke en levensvatbare zaden aan de kwelderrand laag (Hoofdstuk 2, 3 en 5). Het dynamische karakter van de hoogteligging van de kwelder en het wad (Intermezzo) in combinatie met winterstormen heeft verlies van zaden opgeleverd (Hoofdstuk 3). Sediment omwoelende bodemdieren, die klein maar wel talrijk zijn, be\u00efnvloeden succesvolle vestiging indirect door het begraven van zaden of het veranderen van de chemische samenstelling van de bodem (Hoofdstuk 2 en 4). Wanneer men het voorkomen van gezonde en veerkrachtige kwelders tracht te stimuleren, zijn de juiste randvoorwaarden betreft beschikbaarheid van zaden en sediment dynamiek essentieel (Fig. S1). Beheerders van kustsystemen zullen rekening moeten houden met de mogelijkheid dat beschikbaarheid van zaden verder daalt doordat, in verband met klimaatverandering, waarschijnlijk meer stormen en hoge getijen zullen voorkomen. Dit in combinatie met zeespiegelstijging zal impact hebben op hydrodynamische dynamiek en kan de groei van kwelders belemmeren of zelfs voor kwelder erosie zorgen.","summary":"Importance of salt marshes\n\nPositive effects of salt marshes on biodiversity, nature-based coastal protection and other ecosystem services are unequivocal. The future of salt marshes is threatened by climate change and sea level rise, which could result in salt marsh degradation and erosion. In addition, the presence of dykes constrains the retreat of salt marshes inland. Salt marshes can keep pace with sea level rise through vertical accretion if sufficient sediment is available and vegetation establishment at the salt marsh edge is an essential requirement to keep marshes vital and resilient. The aim of this thesis was to better understand the ecological and physical processes that determine successful initial establishment of pioneer vegetation beyond the marsh edge.\n\nInitial pioneer vegetation establishment\n\nThe focus of this thesis lies at the interface of the salt marsh and the intertidal flats. This transition zone has the highest potential for lateral marsh expansion. Expansion requires successful vegetation establishment, which is influenced by many factors including soil conditions, environmental variables, such as inundation regime and sediment dynamics, bioturbation and seed availability. In this thesis, these factors were studied using a combination of descriptive research, laboratory and field experiments.\n\nBased on vegetation cover we found a gradual change from densely vegetated salt marsh to bare intertidal flat (Figure S1). However, we found a distinct border between the pioneer zone and the sparsely vegetated transition zone, based on distinct benthic communities and environmental characteristics (Ch. 2). A strong increase in soil oxygenation and a much higher abundance of seeds characterised the border between the transition zone and the pioneer (Ch. 2). Although the transition zone has the appropriate elevation for vegetation establishment, it much more resembled the bare intertidal flat than the salt marsh pioneer zone.\n\nIf seeds are available in an appropriate area the following spring, a window of opportunity is crucial for seed germination and successful establishment (Ch. 3 and 5). Successful germination of the annual pioneer Salicornia procumbens was mainly driven by increased temperature and precipitation with a low sedimentation rate (Ch. 5). Experimental seed-additions in the transition zone demonstrated that boundary conditions for successful pioneer vegetation establishment were met for S. procumbens and Spartina anglica but not for Aster tripolium (Ch. 3 and 5). Sudden sedimentation events were detrimental as they buried small S. procumbens seedlings entirely (Ch. 5).\n\nThe seed bank and seed retention\n\nSeeds of multiple pioneer and low marsh plant species were present in the soil of the vegetated marsh (Ch. 2). In the transition zone, the availability of natural viable seeds was low (Ch. 2, 3, and 5). Although seed dispersal of marsh vegetation is mostly local, seeds of the perennial pioneer S. anglica were practically absent from the transition zone (Ch. 3 and 5). Seeds of the other main pioneer, the annual S. procumbens, were present in the seed bank but the peak abundance of seeds occurred too deep for successful germination.\n\nDispersal timing affected seed retention. Seeds manually dispersed before winter eroded away but seeds dispersed after winter were retained in the transition zone (Ch. 3). Storm conditions during winter, high tides, wind speed and waves, caused the loss of seeds (Ch. 3). Natural seed availability in spring may also be low because freshly dispersed seeds suffer from secondary dispersal during winter (Fig. S2).\n\nFigure S1. Processes that affect successful initial vegetation establishment and thus lateral salt marsh expansion onto the intertidal flat. Underlined are the most crucial mechanisms in dynamic transition zones.\n\nThe role of benthos\n\nNumerous, small bioturbators occurred from the pioneer zone to the intertidal flat, mostly oligochaetes, harpacticoid copepods and collembolans (springtails) (Ch. 2). Benthic bioturbators were capable of transporting seeds downwards into the soil, i.e. seed burial, in the field (Ch. 3) and in the lab (Ch. 4). Seeds from different sizes (1-20 mm) and species, S. procumbens, Spartina anglica and A. tripolium, were buried up to 3 cm in a two-month period (Ch. 3). Bioturbation of oligochaetes also hindered pioneer vegetation establishment, toppling and burying small S. procumbens seedlings (Ch. 4).\n\nOligochaetes are generally understudied due to their size, although they can have a significant impact on the soil by reworking the sediment. Our studies revealed that oligochaetes can cause a ten-fold increase in soil oxygenation depth (Ch. 4). It is improbable that meiobenthic bioturbation will inhibit vegetation establishment on a marsh scale, because benthic bioturbators, mainly oligochaetes, were most abundant in the pioneer zone, the area with ample establishment of annual pioneer vegetation.\n\nImplications and conclusions\n\nThe main conclusion of this thesis is that, even with a seed source in proximity (the pioneer zone), seed availability can still form a threshold for initial pioneer vegetation establishment in the transition zone. In spring, the natural availability of viable seeds was low beyond the marsh edge (Ch. 2, 3, and 5). The dynamic nature of the bed level (Intermezzo) in combination with winter storms induced a loss of seeds (Ch. 3). Bioturbating benthos, small but numerous, may indirectly influence vegetation establishment success, either through seed retention by burial or intermediated by altering soil conditions (Ch. 2 and 4). When aiming to promote resilient and healthy salt marshes, the appropriate boundary conditions regarding seed availability and sediment dynamics must be ensured (Figure S1). To account for imminent climate change, coastal management should implement the possibility that seed availability may be further reduced, caused by soil erosion due to storms. This is particularly important since increased storm frequencies are expected. Together with sea level rise, these effects will alter hydrodynamic regimes and can thus constrain lateral expansion or even cause salt marshes erosion.","auteur":"Marin Van Regteren","auteur_slug":"marin-van-regteren","publicatiedatum":"9 oktober 2020","taal":"EN","url_flipbook":"https:\/\/ebook.proefschriftmaken.nl\/ebook\/marinvanregteren?iframe=true","url_download_pdf":"","url_epub":"","ordernummer":"FTP-202604071132","isbn":"978-94-635-282-8","doi_nummer":"","naam_universiteit":"Wageningen University","afbeeldingen":13505,"naam_student:":"","binnenwerk":"","universiteit":"Wageningen University","cover":"","afwerking":"","cover_afwerking":"","design":""},"_links":{"self":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/9091","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio"}],"about":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/types\/us_portfolio"}],"author":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/comments?post=9091"}],"version-history":[{"count":1,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/9091\/revisions"}],"predecessor-version":[{"id":9094,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/9091\/revisions\/9094"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media\/13505"}],"wp:attachment":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media?parent=9091"}],"wp:term":[{"taxonomy":"us_portfolio_category","embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio_category?post=9091"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}