El debate de los imaginistas y las posturas dualistas

The environment of past ecosystems can be analysed by grouping the environmental preferences of all species present in a startigraphic unit. In order tan o get accurate reflec- tion of the past environment, it is important to have as little time-averaged assemblages per unit as possible, as these time-averaged samples can yield faunal and floral data from contrasting environments.

The habitat preferences of the faunal species in Schö 13 II show gradual change in the four succeeding levels. There is a clear shift in the amount of woodland species and spe- cies that thrive in a water rich environment. The forest and woodland habitats appear to decline with the climatic change, whereas the number of species related to water rich environments increases. Also the amount of species not related to a specific habitat in- creases over time. This could lead to the interpretation that these species tend to avoid forested environments.

Figure 38 Change in environmental preferences per level. a = Schö 13 II-1, b = Schö 13 II-2, c = Schö 13 II-3, d = Schö 13 II-4.

Even though the amount of woodland and grassland species generally decreases over the course of time, the number of steppe adapted species does not increase. This change in composition suggests an advance of the lake level, or increase in marshland, towards 13 II-4 and a deterioration of the climate, where the openness of the environment has in- creased. An increase in steppe environments, however, is not supported in terms of a sig- nificant increase of steppe adapted species, but rather by the decrease in forest and wood- land adapted species.

The proxies for the aquatic environment indicate that there is little change in the composi- tion of water dependent species (fish, amphibians, pond turtle, water birds). The freshwa- ter species remain dominant in the succeeding levels, as well as the amount of species that are also associated with brackish or saline water conditions (tab. 29). The species that can occur in brackish or saline environments are not restricted to these environments, but can also cope with freshwater environments. Thus, this analysis shows that the water body was dominantly a freshwater body with little water movement (tab. 30). The salinity conditions have not changed significantly over time, as there are no species found that are characteristically limited to brackish or saline environments, without a tolerance for freshwater environments. Because of the continental position of Schöningen, it is unlikely that the brackish and saline conditions are of Pleistocene marine origin. The brackish or saline soil conditions at this site could be caused by chemical influences of the nearby saltdome.

13 II-1 13 II-2 13 II-3 13 II-4 freshwater 2 13 11 13

B+F 2 4 3 3

F+B+S 0 1 0 1

F+S 0 0 0 1

Table 29 Species preference for salinity (B+F = brackish and freshwater, F+B+S = freshwater, brackish and saline, F+S = freshwater and saline)

Species Vegetation Bottom type Water body

Triturus vulgaris abundant vegetation no preference still, shallow waters

Pelobates fuscus abundant marginal vegetation no preference still

Emys orbicularis abundant vegetation soft bottoms ponds

Anas acuta abundant marginal vegetation no preference various

Anas crecca abundant vegetation no preference shallow, permanent waters, marshes, freshwater lakes

Anas platyrhynchos dense vegetation no preference shallow water

Cygnus olor abundant vegetation no preference freshwater lakes, ponds

Aythya fuligula abundant marginal vegetation no preference eutrophic waters, 3-5m deep

Bucephala clangula abundant vegetation no preference freshwater lakes, rivers, ponds deep marshes

Tadorna tadorna little vegetation no preference brackish inland lakes

Rallus aquaticus dense vegetation mud bottom fresh and saline swamps, fens, marshes, lakes

Esox lucius abundant vegetation no preference Lake, pond, slow-moving rivers

Perca fluviatilis little vegetation no preference estuaries, streams

Rutilus rutilus dense vegetation sand or gravel bottom lake, lowland streams, brackish coastal lagoons

Alburnus alburnus little vegetation no preference open water lakes, rivers

Gobio gobio little vegetation sand or gravel bottom fast-flowing rivers, still waters

Tinca tinca little vegetation mud bottom warm lakes and pools

Scardinius erythrophthalmus abundant vegetation soft bottoms lakes, rivers, marshland, ponds

connected to rivers

Carassius carassius dense vegetation mud bottom well-vegetated lakes, oxbows, backwaters

Lota lota little vegetation sand or gravel bottom lakes and rivers

Misgurnus fossilis dense vegetation mud bottom backwaters of lowland streams, rivers and lakes

Pungitius pungitius dense vegetation soft bottoms freshwater streams and ponds, brackish water

Cottus gobio abundant vegetation gravel bottom river systems, lowland rivers, lakes

Gasterosteus aculeatus abundant vegetation no preference Freshwater lakes, coastal and marine waters

Table 30 Preferences of (semi-)aquatic species that occur in the record of Schö 13 II for vegetation, bot- tom and water type.

The preferences of species living in and living from an aquatic habitat are shown in tab. 30. The dependence on vegetation is variable, but the majority of the species prefers an aquatic habitat with abundant to dense vegetation. The species are indicative for soft bot- toms of mud or sand. The preferred type of water bodies varies per species, but all species are indicative for either ponds, lakes or marshlands.