Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Edifice growth and collapse of the Pliocene Mt. Kenya: Evidence of large scale debris avalanches on a high altitude glaciated volcano
    Schoorl, J.M. ; Veldkamp, A. ; Claessens, L.F.G. ; Gorp, W. van; Wijbrans, J.R. - \ 2014
    Global and Planetary Change 123 (2014)Part A. - ISSN 0921-8181 - p. 44 - 54.
    african climate-change - mount kenya - tectonic evolution - gregory rift - east-africa - deposits - geochronology - uplift - pleistocene - himalaya
    The cyclic growth and destruction of the Late Cenozoic Stratovolcano Mt. Kenya have been reconstructed for its southeastern segment. At least three major debris avalanche deposits have been reconstructed and dated. The oldest deposits indicate an edifice collapse around 4.9 Ma (40Ar/39Ar), followed by a larger event around 4.1 Ma (40Ar/39Ar). The last and best preserved debris avalanche deposit, with still some morphological expression covering the whole 1214 km2 SE sector, occurred around 2.83 Ma (40Ar/39Ar). This very large debris avalanche event must have truncated the whole top of Mt. Kenya. Of the original typical hummocky relief, only local topographical depressions are still best visible and preserved. Using known geometric empirical parameters of the 3 preserved debris-avalanche deposits, the height of the sector collapse is estimated to be in the range of 5100–6500 m above the current height of 1000 m a.s.l. near the end lobe of the VDA deposits. This demonstrates that Mt. Kenya attained impressive altitudes during its main activity in the Pliocene, being one of the highest mountains in that time and was most probably covered by an ice cap. Correcting for the known net eastward tilting post eruptive uplift of approximately 500 m of the Mt. Kenya summit, our reconstruction indicates that an at least 5.6 to 7 km a.s.l. high active Mt. Kenya existed in the Pliocene landscape between 5.1 and 2.8 Ma. This volcano must have significantly contributed to regional environmental change, by catching rain on its eastern slopes and projecting a rain shadow towards the Kenya Rift valley in the west. The last major edifice collapse event around 2.8 Ma coincides with a major change in regional vegetation. This suggests that the truncating of Mt. Kenya may have caused significant changes in the local climate surrounding Mt. Kenya with possible implications for environmental change in the central Kenya Rift valley, the cradle of hominin evolution.
    From basalts to badlands : modelling long-term landscape response to lava damming of an upland catchment in western Turkey
    Gorp, W. van - \ 2014
    Wageningen University. Promotor(en): Tom Veldkamp, co-promotor(en): Jeroen Schoorl; Arnaud Temme. - Wageningen : Wageningen University - ISBN 9789462570481 - 182
    landschap - geologie - landinrichting - evolutie - modelleren - stroomgebieden - tektoniek - vulkanische lava - pleistoceen - turkije - landscape - geology - land development - evolution - modeling - watersheds - tectonics - volcanic lava - pleistocene - turkey

    Combining field reconstruction and landscape evolution modelling can be useful to investigate the relative role of different drivers (tectonics, climate, local base level) on long term catchment evolution. In this thesis, field reconstruction and landscape evolution modelling are combined to unravel the long-term (300 ka) response to lava damming events of evolution of the Geren Catchment, a tributary of the upper Gediz river near Kula, Western Turkey. This catchment was considered suitable for such a study because its high preservationof remnant landscape surfaces and fluvial terraces which could be dated, while its base level evolution could be reconstructed by identifying and dating lava flows.

    In Chapter 2, landscape evolution modelling of an idealized catchment revealed long-term (15 ka) catchment response to natural damming. Evolution of a high erodible and low erodible landscape was simulated using landscape evolution model (LEM) LAPSUS (LandscApe procesS modelling at mUlti dimensions and Scales). The natural dam was given four different erodibilities, to mimic both the potentially more erodible landslide dams and resistant lava dams. In a low erodible landscape damming led to persistent preservation of the sediment wedge formed behind the dam, while in a high erodible landscape, damming additionally led to knickpoint persistence, hampered incision of the main river and stream rerouting. The highest erodible dam was almost removed after 15 ka, while its sediment wedge was still partly present. Comparison of results with natural dam events from literature showed that modelled response characteristics are observed in actual situations and that simulations on Quaternary timescales are useful.

    In Chapter 3, field reconstruction resulted in a young lava flow being age constrained to the late Holocene (3.0 – 2.6 ka), by luminescence dating of fluvial sands below and on top of the flow. This lava flow dammed the Gediz river at two locations. the upstream lake was silted, while the downstream lake was not. Dams were breached catastrophically and possibly in a cascading event. The Gediz created an epigenetic gorge and its current river bed is still not at its pre-lava flow level. Results are summarized in a conceptual diagram. Furthermore, field reconstruction and 40Ar/39Ar dating revealed multiple lava dam events which have infrequently raised and lowered the base level of the Geren Catchment in the middle to late Pleistocene (311 – 175 ka). Sediment-capped palaeosurfaces in the Geren suggest change from an active fluvial system to a more lacustrine environment in the middle Pleistocene, followed by fluvial reactivation and stepped incision in the late Pleistocene.

    A second landscape evolution modelling study was conducted in Chapter 4, on a 300 ka timescale, with a larger catchment. Four scenarios have been applied on a reconstructed paleodem of the Geren Catchment. In the first scenario, the palaeodem was given constant rainfall for 300 ka. In the second scenario, three short (1 ka) damming events were added at its catchment outlet. In the third scenario, the palaeodem endured gradual base level lowering at its outlet, based on the known incision rate of its base level, the Gediz river. In the fourth scenario, base level lowering and damming events were combined. Results were interpreted by evaluating 1 ka-averaged net erosion, catchment sediment storage, longitudinal profile development and spatial differences in net erosion and sediment storage. Results showed that the net erosion signal of the catchment is complex in all cases. However, average net erosion and its variability increased due to constant base level lowering. Additionally, alternating phases of high and low variability occurred in net erosion, where high variability coincided with a strong decrease in total catchment sediment storage. Adding damming events to the gradual base level lowering scenario generated similar average net erosion as the base level lowering scenario, however its temporal pattern showed significantly different alternation of high and low variability periods. Furthermore, dampened upstream erosion was observed. Over time, this dampening migrates upstream indicating a long-term legacy of short term dam events.

    Field reconstruction and landscape evolution modelling were combined in Chapter 5, to be able to reconstruct and understand actual Geren catchment response to identified base level evolution over a 300 ka period. In all simulations, rainfall and vegetation are varied over time based on arboral pollen. Because exact significance and duration of dam events were not known, three scenarios of landscape evolution in the Geren Catchment were investigated: i) uplift driven gradual base level lowering, ii) gradual base level lowering and short damming events and iii) gradual base level lowering and long damming events. Output was evaluated for erosion-aggradation evolution in trunk gullies at two different distances from the catchment outlet. Climate influences erosion – aggradation activity in the upstream reach, although internal feedbacks influence timing and magnitude. Scenario i shows the most correlation with the climate signal, although its correlation is weak. Lava damming events leave an aggradation signal in the downstream reach, while complex and lagged response to these dams obscure correlations with climate and leave a legacy of the past in current landscape evolution. Catchment response of the long dam scenario correspond best with field reconstruction and dating. The combination of climate and base level explains a significant part of the landscape evolution history of the Geren Catchment.

    In Chapter 6, a reflection and synthesis of Chapters 2-5 is presented. Indications for response to tectonics, climate and damming events are discussed separately for both field and modelling results. It is concluded that (lava) damming events of Pleistocene age can hamper, but also enhance incision on a 300 ka timescale. Furthermore, they can still have effect on current and future catchment evolution. However, catchment response to this evolution is complex and catchment specific and model results do not exactly reproduce its catchment history. An aggregated landscape evolution model output such as stream bed elevation change can be useful for comparison with fluvial terrace sequences. Combining field reconstruction and modelling suggests that the 300 ka incision history of the Geren is best explained if the catchment endured prolonged dam events. The combination of field reconstruction, dating and landscape evolution modelling therefore can enhance our understanding of long-term evolution of a specific landscape and increases knowledge on long term impact of past events on current catchment complexities and it is suggested to embed this research approach more structurally in long-term landscape reconstructions.

    Landscape Evolution Modelling of naturally dammed rivers
    Gorp, W. van; Temme, A.J.A.M. ; Baartman, J.E.M. ; Schoorl, J.M. - \ 2014
    Earth Surface Processes and Landforms 39 (2014)12. - ISSN 0197-9337 - p. 1587 - 1600.
    western grand-canyon - landslide dams - new-zealand - soil redistribution - fluvial response - outburst flood - peak discharge - dem resolution - lava dams - pleistocene
    Natural damming of upland river systems, such as landslide or lava damming, occurs worldwide. Many dams fail shortly after their creation, while other dams are long-lived and therefore have a long-term impact on fluvial and landscape evolution. This long-term impact is still poorly understood and landscape evolution modelling (LEM) can increase our understanding of different aspects of this response. Our objective was to simulate fluvial response to damming, by monitoring sediment redistribution and river profile evolution for a range of geomorphic settings.We used LEM LAPSUS, which calculates runoff erosion and deposition and can deal with non-spurious sinks, such as dam-impounded areas. Because fluvial dynamics under detachment-limited and transport-limited conditions are different, we mimicked these conditions using low and high erodibility settings, respectively. To compare the relative impact of different dam types, we evaluated five scenarios for each landscape condition: one scenario without a dam and four scenarios with dams of increasing erodibility. Results showed that dam-related sediment storage persisted at least until 15 000 years for all dam scenarios. Incision and knickpoint retreat occurred faster in the detachment-limited landscape than in the transport-limited landscape. Furthermore, in the transport-limited landscape, knickpoint persistence decreased with increasing dam erodibility. Stream capture occurred only in the transport-limited landscape due to a persisting floodplain behind the dam and headward erosion of adjacent channels. Changes in sediment yield variation due to stream captures did occur but cannot be distinguished from other changes in variation of sediment yield. Comparison of the model results with field examples indicates that the model reproduces several key phenomena of damming response in both transport-limited and detachment-limited landscapes. We conclude that a damming event which occurred 15 000 years ago can influence present-day sediment yield, profile evolution and stream patterns.
    Fluvial terraces of the northwest Iberian lower Miño River.
    Viveen, W. ; Schoorl, J.M. ; Veldkamp, A. ; Balen, R.T. van; Vidal-Romani, J.R. - \ 2013
    Journal of Maps 9 (2013)4. - ISSN 1744-5647 - p. 513 - 522.
    sea-level change - tectonic activity - portugal - uplift - climate - reconstruction - pleistocene - evolution - incision - deposits
    A new fluvial terrace map with a tectonic framework for the northwest Iberian lower Miño River is presented. It is the first integrated map to cover the entire lower, 67-km reach of the Miño River, and to cover both the Spanish and Portuguese side of the river. The map is presented at a scale of 1:200,000, although its features were mapped at a scale of 1:5000. Various map layers can be viewed, such as a digital elevation model (DEM), fluvial sediment thickness layers, a palaeoflow direction layer, a lineament and fault layer, and two terrace and tectonic basin layers, showing up to 10 fluvial terraces and a floodplain level. Interpretation of the map shows that next to regional tectonic uplift and glacioeustacy, local basin subsidence and small-scale block movement are very important for the fluvial network, localised fluvial terrace formation, and preservation.
    Mount Kenya volcanic activity and the Late Cenozoic landscape reorganisation in the upper Tana fluvial system
    Veldkamp, A. ; Schoorl, J.M. ; Wijbrans, J.R. ; Claessens, L.F.G. - \ 2012
    Geomorphology 145-146 (2012). - ISSN 0169-555X - p. 19 - 31.
    african climate-change - western turkey - sediment yield - gregory rift - debris flows - east-africa - pleistocene - evolution - river - uplift
    Volcanic–fluvial landscape interaction of the late Cenozoic Mt Kenya region in the upper Tana catchment has been reconstructed. The oldest newly dated phonolite flow is 5.78 Ma (40Ar/39Ar), placing the initiation of Mt Kenya volcanic activity within the Late Miocene, much earlier than reported before, 3–3.5 Ma (K/Ar). The main body of the stratovolcano was already in existence around 4.22–5.27 Ma (40Ar/39Ar) supplying lahars to its lower footslopes. The final recorded volcanic main vent phase in the study area produced multiple phonolitic flows and lahars around 2.8 Ma (40Ar/39Ar). There is evidence of at least two major Pliocene drainage blocking events between 3.89 and 2.81 Ma (40Ar/39Ar) causing lava dammed lakes in which volcanic tuff deposits accumulated. Around this time the river Tana did not incise much and shaped an extensive fluvial plain, whose remnants can now be found around 1150 m altitude. This fluvial plain has been incising during the last 2.8 Ma, whereby the incision rate changed in time due to changing uplift rate and volcanic events. A flood basalt eruption covering 1150 km2, estimated to be 5 km3, on the south flank of Mt Kenya of the Thiba basalts at 0.80 Ma (40Ar/39Ar) plugged the Upper Tana basin and caused significant drainage reorganisation. The Tana was diverted southwards abandoning its former valley. The terrace record in the Tana valley downstream the Thiba basalts appears to register this event as a post 0.8 Ma accelerated incision. Current Thiba valley morphology is relatively young and appears to register uplift controlled terraces with interbedded lahars for the last 300 ka only, indicating a delayed fluvial response of approximately 0.5 Ma. The landscape reconstruction demonstrates that the Tana was well able to compensate for many volcanic events such as lahars and lava flows. Only the build-up of a stratovolcano body and a large flood basalt caused prolonged impact on fluvial landscape development
    Mind the gap: modelling event-based and millennial-scale landscape dynamics
    Baartman, J.E.M. - \ 2012
    Wageningen University. Promotor(en): Tom Veldkamp; Coen Ritsema, co-promotor(en): Jeroen Schoorl. - S.l. : s.n. - ISBN 9789461732668 - 216
    geomorfologie - erosie - sedimentatie - dynamica - tijdschalen - landschapsanalyse - modelleren - rivieren - regen - menselijke invloed - landschap - ontwikkeling - spanje - pleistoceen - holoceen - geomorphology - erosion - sedimentation - dynamics - time scales - landscape analysis - modeling - rivers - rain - human impact - landscape - development - spain - pleistocene - holocene

    This research looks at landscape dynamics – erosion and deposition – from two different perspectives: long-term landscape evolution over millennial timescales on the one hand and short-term event-based erosion and deposition at the other hand. For the first, landscape evolution models (LEMs) are often used, which describe landscape forming processes by geomorphic transport laws, usually on annual temporal resolutions. LEM LAPSUS is used in this research to evaluate the landscape dynamics in a study area in south-east Spain: the Guadalentín Basin. The model is calibrated on dated river terrace levels, which show an erosion – deposition – erosion sequence that the model could reproduce. Annual precipitation in this dryland area shows large inter-annual variability and erosion is supposed to be mainly the results of low-frequency, high magnitude rainfall events. Therefore, in this research, landscape dynamics are also assessed using the event-based erosion model OpenLISEM. Eventually, the role of extreme events in long-term landscape evolution are explored by comparing the two models and by incorporating annual rainfall variability into LEM LAPSUS. Another issue that is being addressed in this study is the relative influence of humans as compared to erosion as a natural process. A conceptual model, derived on the basis of dated sediment archives, is tentatively correlated to periods of human impact on the land. Using LAPSUS, the potential influence of historical tillage erosion is simulated, showing that the relatively slow process of tillage erosion added to floodplain aggradation over thousands of years.

    Little ecological divergence associated with speciation in two African rain forest tree genera
    Couvreur, T.L.P. ; Porter-Morgan, H. ; Wieringa, J.J. ; Chatrou, L.W. - \ 2011
    BMC Evolutionary Biology 11 (2011). - ISSN 1471-2148 - 19 p.
    species distribution models - phylogenetic niche conservatism - climate-change - correlated evolution - tropical africa - sample-size - diversification - annonaceae - distributions - pleistocene
    Background - The tropical rain forests (TRF) of Africa are the second largest block of this biome after the Amazon and exhibit high levels of plant endemism and diversity. Two main hypotheses have been advanced to explain speciation processes that have led to this high level of biodiversity: allopatric speciation linked to geographic isolation and ecological speciation linked to ecological gradients. Both these hypotheses rely on ecology: in the former conservation of ecological niches through time is implied, while in the latter adaptation via selection to alternative ecological niches would be a prerequisite. Here, we investigate the role of ecology in explaining present day species diversity in African TRF using a species level phylogeny and ecological niche modeling of two predominantly restricted TRF tree genera, Isolona and Monodora (Annonaceae). Both these genera, with 20 and 14 species, respectively, are widely distributed in African TRFs, with a few species occurring in slightly less humid regions such as in East Africa. Results - A total of 11 sister species pairs were identified most of them occurring in allopatry or with little geographical overlap. Our results provide a mixed answer on the role of ecology in speciation. Although no sister species have identical niches, just under half of the tests suggest that sister species do have more similar niches than expected by chance. PCA analyses also support little ecological differences between sister species. Most speciation events within both genera predate the Pleistocene, occurring during the Late Miocene and Pliocene periods. Conclusions - Ecology is almost always involved in speciation, however, it would seem to have had a little role in species generation within Isolona and Monodora at the scale analyzed here. This is consistent with the geographical speciation model for TRF diversification. These results contrast to other studies for non-TRF plant species where ecological speciation was found to be an important factor of diversification. The Pliocene period appears to be a vital time in the generation of African TRF diversity, whereas Pleistocene climatic fluctuations have had a smaller role on speciation than previously thought
    Middle Palaeolithic artefact migration due to periglacial processes; a geological investigation into near-surface occurrence of Palaeolithic artefacts (Limburg-Eastern Brabant coversand region, the Netherlands)
    Deeben, J. ; Hiddink, H. ; Huisman, D.J. ; Müller, A. ; Schokker, J. ; Wallinga, J. - \ 2010
    Netherlands journal of geosciences 89 (2010)1. - ISSN 0016-7746 - p. 35 - 50.
    Archaeological heritage management - Boxtel formation - Cryoturbation - Middle palaeolithic - Optical dating - Periglacial conditions - Pleistocene - Roer valley graben

    The original distribution pattern of Middle-Palaeolithic artefacts may be affected by tectonic movement, sedimentation and periglacial processes. This is e.g. the case in the coversand area of Limburg and Eastern Brabant (NL), where the occurrence of numerous finds in a SW-NE trending zone across the Roer Valley Graben is considered enigmatic. In order to elucidate the processes affecting the spatial distribution and the chance of recovery of such artefacts, we investigated a site in Nederweert. At this site, several Middle-Palaeolithic artefacts had been recovered earlier from unexpectedly shallow depths. A test pit profile and grain size analyses revealed that the shallow sediments at this site have been affected by intense, multi-phase cryoturbation, which has deformed the sand and loam layers and partially mixed them thoroughly. As a result, optically stimulated luminescence dating of these sediments yielded widely scattered single-aliquot equivalent dose distributions. Using a Finite Mixture Model (FMM), it was estimated that cryoturbation caused mixing of sediments deposited between 12 and 50 ka with sediment grains deposited between 60-150 ka. The latter material is probably the original context of the Middle-Paleolithic artefacts. Apparently, cryoturbation and potentially other periglacial processes have transported artefacts closer to the surface. Based on these results, we suggest that the occurrence of MiddlePalaeolithic artefacts is caused by (1) the tectonically-induced spatial distribution of layers of this age and (2) periglacial processes having caused migration of artefacts towards the surface. Although periglacial processes may facilitate finding Middle Palaeolithic artefacts, they may severely disturb the original context to such an extent that Middle Palaeolithic sites can no longer be identified. The results of this study form a basis for improving the Indicative Map of Archaeological Values that is used to predict the presence of archaeological sites. The insights gained are also relevant to other areas where Middle-Palaeolithic sites are affected by periglacial processes.

    Neogene stratigraphy of the Langenboom locality (Noord-Brabant, the Netherlands)
    Wijnker, T.G. ; Bor, T.J. ; Wesselingh, F.P. ; Munsterman, D.K. ; Brinkhuis, H. ; Burger, A.W. ; Vonhof, H.B. ; Post, K. ; Hoedemakers, K. ; Janse, A.C. ; Taverne, N. - \ 2008
    Netherlands journal of geosciences 87 (2008)2. - ISSN 0016-7746 - p. 165 - 180.
    geologie - tektoniek - paleozoölogie - noord-brabant - geology - tectonics - palaeozoology - noord-brabant - north-sea basin - dinoflagellate cyst - bering strait - upper miocene - pliocene - belgium - pleistocene - age
    The locality of Langenboom (eastern Noord-Brabant, the Netherlands), also known as Mill, is famous for its Neogene molluscs, shark teeth, teleost remains, birds and marine mammals. The stratigraphic context of the fossils, which have been collected from sand suppletions, was hitherto poorly understood. Here we report on a section which has been sampled by divers in the adjacent flooded sandpit 'De Kuilen' from which the Langenboom sands have been extracted. The studied section covers part of the marine Miocene Breda Formation and Pliocene Oosterhout Formation, and is topped by fluvial Quaternary deposits of presumably the Beegden Formation. The Breda Formation (15 - 18 m below lake surface) in this section is, based on organic walled dinoflagellate cysts, of an early-middle Tortonian age. The Oosterhout Formation (7 - 15 m below lake surface) comprises two depositional sequences, the lower of which (12 - 15 m below lake surface) presumably is the source of most Langenboom fossils. Combined dinoflagellate cyst and benthic mollusc indicators point to an early Zanclean - early Piacenzian age for this lower cycle. Its basal transgressive lag and (to lesser extent) top comprise reworked Tortonian taxa as well. Dinoflagellate cysts and a single benthic mollusc point to a Piacenzian age for the upper Oosterhout Formation sequence (7 - 12 m below lake surface).
    Severnaya Zemlya, Arctic Russia: a nucleation area for Kara Sea ice sheets during the Middle to Late Quaternary
    Moller, P. ; Lubinski, D.J. ; Ingolfsson, O. ; Forman, S.L. ; Seidenkrantz, M.S. ; Bolshiyanov, D.Y. ; Lokrantz, H. ; Antonov, O. ; Pavlov, M. ; Ljung, K. ; Zeeberg, J.J. ; Andreev, A. - \ 2006
    Quaternary Science Reviews 25 (2006)21-22. - ISSN 0277-3791 - p. 2894 - 2936.
    western yamal peninsula - last glacial maximum - taymyr peninsula - northern eurasia - marginal zone - luminescence - pleistocene - siberia - sediments - history
    Quaternary glacial stratigraphy and relative sea-level changes reveal at least four expansions of the Kara Sea ice sheet over the Severnaya Zemlya Archipelago at 79°N in the Russian Arctic, as indicated from tills interbedded with marine sediments, exposed in stratigraphic superposition, and from raised-beach sequences that occur at altitudes up to 140 m a.s.l. Chronologic control is provided by AMS 14C, electron-spin resonance, green-stimulated luminescence, and aspartic-acid geochronology. Major glaciations followed by deglaciation and marine inundation occurred during MIS 10-9, MIS 8-7, MIS 6-5e and MIS 5d-3. The MIS 6-5e event, associated with the high marine limit, implies ice-sheet thickness of >2000 m only 200 km from the deep Arctic Ocean, consistent with published evidence of ice grounding at 1000 m water depth in the central Arctic Ocean. Till fabrics and glacial tectonics record repeated expansions of local ice caps exclusively, suggesting wet-based ice cap advance followed by cold-based regional ice-sheet expansion. Local ice caps over highland sites along the perimeter of the shallow Kara Sea, including the Byrranga Mountains, appear to have repeatedly fostered initiation of a large Kara Sea ice sheet, with exception of the Last Glacial Maximum (MIS 2), when Kara Sea ice did not impact Severnaya Zemlya and barely graced northernmost Taymyr Peninsula.
    The African rain forest during the Last Glacial Maximum an archipelago of forests in a sea of grass
    Leal, M.E. - \ 2004
    Wageningen University. Promotor(en): Jos van der Maesen; A.M. Cleef. - Wageningen : S.n. - ISBN 9789085040378 - 96
    caesalpinioideae - regenbossen - soorten - soortendiversiteit - plantengeografie - droogteresistentie - klimaatverandering - uitsterven - gabon - afrika - glaciale perioden - pleistoceen - holoceen - caesalpinioideae - rain forests - species - species diversity - phytogeography - drought resistance - climatic change - extinction - gabon - africa - glacial periods - pleistocene - holocene
    In centralGabon(Africa) the distribution ecology of the Caesalpinioideae tree species (Leguminosae) were studied in two separate low rainfall areas which straddled the same geological transition from upland to lowland. The principle environmental force arranging their distribution was regional drought stress during the two dry seasons. These drought sensitive tree species were able to survive in the two forest-savannah mosaics because local compensation was provided by the permanent presence of water along some of the streams and by reduced exposure (shade) in narrow valleys. According to the Pleistocene forest refuge theory the Caesalpinioideae in the two study areas arrived during the last 10,000 years (Holocene) from the closest forest refugium- the Chaillu Massif (80 km further south). This part ofGabondid not become deforested during the Last Glacial Maximum when climate was much drier because cloud forest conditions in this elevated area compensated for the shortage of rainfall. Arrival of the Caesalpinioideae trees by migration from this refuge area by their normal dispersal mechanism of explosively opening pods is excluded as their advance over the Holocene was only 36 km. Also arrival through occasional long-distance dispersal events by water along watercourses is not viable, because species composition along streams does not show a decreasing gradient with distance from the refuge area. Long-distance dispersal events in the past now obscured by an equilibrium situation of species distributions with present-day habitat is also not possible as the similar hills and lowland in the two study sites are inhabited by very different species. The only conclusion is that the Caesalpinioideae survived the Last Glacial Maximum in the study areas themselves. The present-day general presence of these Caesalpinioideae in the African rain forest between the former forest refugia shows that small pockets of forest persisted in the then savannah.
    Bodemfysische schematisatie van het Fochteloerveen en omliggende landbouwgronden
    Stolte, J. ; Rosing, H. ; Veldhuizen, A. - \ 1995
    Wageningen : DLO-Staring Centrum (Rapport / DLO-Staring Centrum 382) - 55
    veengronden - bodemwater - nederland - holoceen - postglaciale perioden - pleistoceen - friesland - peat soils - soil water - netherlands - holocene - postglacial periods - pleistocene - friesland
    Voor het natuurgebied Fochteloërveen en omliggende landbouwgronden is een bodemfysische schematisering gemaakt om bodemfysische gegevens beschikbaar te krijgen voor modelinvoer. Voor de omliggende landbouwgronden zijn bestaande bodemkaarten op verschillende schalen gebruikt. Voor het natuurgebied is een detailkartering uitgevoerd. Voor de onderscheiden horizonten zijn Staringreeks-bouwstenen geselecteerd. Voor de horizonten waarvoor dit niet mogelijk was, zijn nieuwe bouwstenen samengesteld op basis van metingen uit vergelijkbare gebieden. Door bestaande gegevenssets te gebruik kan een fysische schematisering worden uitgevoerd. Een gevoeligheidsanalyse zal aantonen of de basisgegevens nauwkeurig genoeg zijn en of de gekozen schaal volstaat.
    De geologische en geohydrologische opbouw van Noord-Holland benoorden het Noordzeekanaal
    Pomper, A.B. - \ 1979
    Wageningen : I.C.W. (Nota / Instituut voor Cultuurtechniek en Waterhuishouding 1135) - 74
    geologie - grondwater - hydrologie - watervoerende lagen - geohydrologie - noord-holland - pleistoceen - geology - groundwater - hydrology - aquifers - geohydrology - noord-holland - pleistocene
    Beschreven worden de bestaande geologische lagen binnen het Pleistoceen (zoals Formatie van Maassluis, Harderwijk, Peelo etc.).
    Notes on the tertiary and pleistocene geology of East Gelderland, The Netherlands
    Rees Vellinga, E. van; Ridder, N.A. de - \ 1973
    Wageningen : I.L.W.M.R. (Technical bulletin / Institute for land and water management research no. 85) - 19
    watervoerende lagen - nederland - gelderland - achterhoek - hydrogeologie - tertiair - pleistoceen - aquifers - netherlands - gelderland - achterhoek - hydrogeology - tertiary - pleistocene
    Sedimentpetrologische onderzoekingen: Sediment-petrologische onderzoekingen in Midden-Nederland, in het bijzonder van het Jong-Pleistoceen
    Crommelin, R.D. - \ 1938
    Wageningen : Veenman (Mededeelingen van de Landbouwhoogeschool te Wageningen dl. 42, verhandeling 2)
    geologie - geologische sedimentatie - pleistoceen - utrecht - zuid-holland - gelderland - geology - geological sedimentation - pleistocene - utrecht - zuid-holland - gelderland
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