The studies present palaeoecological analysis of two areas in the Upper Rhine river valley. In the northern part of the Upper Rhine river valley studies concentrates on palaeomeanders of the Rhine river nearby Jockgrim, north-west of Karlsruhe. In the southern part the mire “Wasenweiler Ried” between Kaiserstuhl and Tuniberg served as a study area. The aim of the research was to reconstruct the development of the mires in the Holocene, taking into account the development of local mire- and aquatic vegetation, and reconstruction of the vegetation at the mineral locations around the mires. In addition to these two main emphasises the research also provides new cognitions about the development of the Rhine river floodplain and genesis of the landscape during the Holocene.
Pollen analysis served as main method assisted by radiocarbon dating, supplemented by litho- and stratigraphical methods as well as analyses of vegetative plant macrofossils and molluscs.
In the Northern Upper Rhine River floodplain three profiles could be analyzed. These were analyzed stratigraphic and with radiocarbon dating. Pollen analyses were done in two of them (‘Unterm Schnabel’, ‘Bruchstücke’). The analyses of the three palaeomeanders shows that their development over time varies more than one have been expecting. Firstly, initiation of deposit conditions varies considerably. Secondly, exposure to flooding after the beginning of peat accumulation showed significant differences between the three samples. The oldest meander (‘Unterm Schnabel‘) silted up during the Younger Atlanticum and peatified at the beginning of the Subboreal. Accumulation rates during this peatification phase were low. Subsequently, peat growth was interrupted during the Late Subboreal. The other meanders (‘Bruchstücke‘ and ‘Schnabelbruch‘) silted up during the Older Subatlanticum. The following peat accumulation started in both meanders at the Early Middle Ages. The relative chronological development of these three meanders is completely different from that of previous studies. Thus, a new classification of the meanders is proposed.
In the ‘Wasenweiler Ried’ in the southern study area several peat cores could be taken, three cores were analyzed stratigraphic, furthermore two of them (‘Schachen’, ‘Murr’) with pollen analysis and radiocarbon dating. The results show, that the development of the mire ‘Wasenweiler Ried’ is discontinuous in time and space. Though it is possible to distinguish two main periods of peat deposition in the mire: the first starts in the Late Glacial and lasts until the Preboreal/ Boreal. The second begins in the Older Subatlanticum. There are also peat depositions during the Mid Holocene in both areas of the mire, but not simultaneously. In the Early Atlanticum and Early Subatlanticum the peat deposition stopped in wide parts of the mire area.
One of the most interesting similarities between the analyzed mires in both study areas are the overlapping deposition gaps (hiatus). Additional we can find a common phase of peat deposits in the Youngest Subatlanticum. Due to the widespread occurrence it can be assumed that the gaps and the youngest peat deposits were not caused by local effects but by regional palaeoclimatic changes (gaps) respectively by massively anthropogenic impact into the water balance (youngest peatification).
The reconstruction of the vegetation development delivers new and sometimes even surprising results: Until the Mid/Late Subboreal anthropogenic impact on the vegetation in the Northern Rhine river floodplain was presumably only minor or absent. The site conditions during the Mid Holocene are hardly comparable to the Younger Holocene. The flood plain was seldom flooded and characterized by sandy sediments and rather dry terrestrial conditions. The accumulation of alluvial clay did not happen before the Subboreal. The present perception of a naturally classification of the flood plain forests in softwood forests of willows and poplars and hardwood forests of oak, elm and ash trees has no or hardly analogy with the last time of natural flood plain in Mid Holocene. The pollen diagrams show hardly any willow or poplar trees. In contrast the woody vegetation of the flood plain mainly consists of hazel-rich oak and elm woods with a small percentage of maple and ash trees. Probably the upper parts of the flood plain were also populated by beech trees after their re-immigration, at least till the more active flooding periode started.
Primarily the flooding and depositions of fine grain alluvial sediments during the Late Bronze Age (Late Subboreal) as well as the direct intensively human influence of the vegetation latest since the Younger Iron Ages, which is proven by pollen analysis, cause to a differentiation of sites, which influenced the current natural classification of alluvial forests. Henceforth in dependence of the microrelief, the edaphic conditions as well as the duration and intensity of flooding events willows and poplars plus oaks and elms dominate in the flood plain forests.
The few pollen of hornbeam until the Middle Ages leads to the assumption, that this tree did marginal widespread in floodplain forests and in woods of the adjacent glacial terraces. The high number of hornbeam trees today is due to direct or indirect anthropogenic influence. Similar is true for the recent great occurrences of ash trees at the Upper Rhine river.
Both pollen diagrams of the ‘Wasenweiler Ried’ are characterized by extremly high values of fir trees since the Mid Holocene. Several evidences indicate that fir trees belong to the potential natural vegetation of the nearby region. The most likely regional sites for the fir are the upper parts of the adjacent Kaiserstuhl. Since the Younger Atlanticum these levels were probably dominated by beech-fir woods.
In both researched areas pollen of pine trees nearly continuous dominates the spectrum of woody plants in all diagrams. Thus, pine tree is naturally widespread on several places at the Upper Rhine River. At northern Upper Rhine river dunes in top of the alluvial fans are one probable location. In the southern Upper Rhine river valley especially the sandy-gritty sites of the alluvial terrace in west and south-west of the ‘Wasenweiler Ried‘ are relevant for pines.