Een palynologisch onderzoek van in dekzand ontwikkelde bodemprofielen

The relation was studied between vegetational development and soil formation in the Pleistocene cover sands in the Netherlands, particularly whether forests, rather than heaths, were early involved in the formation of podsolic soils. The pollen content of profiles of various podsols and some gleys were examined, all lying below layers of drift sand and peat of various ages. Beyerinck's palynological method had to be extended with a study of the significance of sand diagrams. In an undisturbed podsol pollen decreased in concentration roughly geometrically from the sand surface downward.A relation could be observed between the length of the vertical distribution of pollen (pollen profile) and the depth above, in which the original stratification of the Eolian cover sand had entirely disappeared.It was concluded that most of the pollen permeated before podsolisation, during the biologically very active stage of the homogeneous forest profile. The lowest part of the pollen profile, already fixed, constantly 'grew' on the top through addition of continually younger spectra; in later degradation stages illuviation of pollen could also become significant. A paucity of tree pollen in the whole spectrum could occur after various types of vegetation and after certain conditions of soil moisture.During the Boreal, Atlantic and Fagus-Carpinus period both homogeneous forest profiles and podsolic profiles occurred under diverse vegetation. During each of these periods homogeneous forest profiles were degraded to new podsolic profiles.</p

Palynological evidence for environmental and climatic change in the lower Guadiana valley, Portugal, during the last 13 000 years

Pollen analysis of a 48 m AMS radiocarbon-dated sediment sequence from the Guadiana estuary provides the first record of Lateglacial and Holocene vegetation history in the Algarve province of Portugal. This paper focuses on the record of terrestrial pollen taxa, which document a series of forest expansions and declines during the period 13 000 cal. BP to 1600 cal. BP and provide insights into climate evolution in southwestern Iberia. The main vegetation phases identified in the Guadiana valley are (1) Lateglacial interstadial (Allerød) forest with Quercus and Pinus under a temperate, moist, continental climate; (2) a Younger Dryas forest decline (Quercus) and expansion of pinewoods, xeric scrub and open ground habitats (with Juniperus, Artemisia, Ephedra distachya type, Centaurea scabiosa type) under arid and cold conditions; (3) an early Holocene forest/scrub/open-ground vegetation mosaic developing under a warm, dry and continental climate; (4) a maximum of Quercus forest and thermomediterranean evergreen taxa (Olea, Phillyrea, Pistacia) reflecting a warm, moist oceanic climate between c. 9000 cal. BP and c. 5000 cal. BP; and (5) the expansion of shrublands with Cistaceae and Ericaceae under a drier climatic regime and increasing anthropogenic activity since c. 5000 cal. BP. Holocene episodes of maximum climatic aridity are identified in the record of xerophytic taxa (Juniperus, Artemisia, Ephedra distachya type) centred around 10 200 cal. BP, 7800 cal. BP, 4800 cal. BP, 3100 cal. BP and 1700 cal. BP. Regional comparisons suggest a correlation of arid phases across southern Iberia and northwest Africa, which can be related to abrupt North Atlantic coolings (Bond events).Research Council studentship for WJF (NERC/S/A/2001/06109), with the support of Trinity College and the Department of Geography, University of Cambridg

Een palynologisch onderzoek van in dekzand ontwikkelde bodemprofielen

The relation was studied between vegetational development and soil formation in the Pleistocene cover sands in the Netherlands, particularly whether forests, rather than heaths, were early involved in the formation of podsolic soils. The pollen content of profiles of various podsols and some gleys were examined, all lying below layers of drift sand and peat of various ages. Beyerinck's palynological method had to be extended with a study of the significance of sand diagrams. In an undisturbed podsol pollen decreased in concentration roughly geometrically from the sand surface downward.A relation could be observed between the length of the vertical distribution of pollen (pollen profile) and the depth above, in which the original stratification of the Eolian cover sand had entirely disappeared.It was concluded that most of the pollen permeated before podsolisation, during the biologically very active stage of the homogeneous forest profile. The lowest part of the pollen profile, already fixed, constantly 'grew' on the top through addition of continually younger spectra; in later degradation stages illuviation of pollen could also become significant. A paucity of tree pollen in the whole spectrum could occur after various types of vegetation and after certain conditions of soil moisture.During the Boreal, Atlantic and Fagus-Carpinus period both homogeneous forest profiles and podsolic profiles occurred under diverse vegetation. During each of these periods homogeneous forest profiles were degraded to new podsolic profiles