Historical Biogeography In Central Europe

Norway spruce migrated into the geographic region of present-day Poland from both a primary Carpathian refugium as well as from a northwestern source. SRODON (1967b) describes the proliferation of spruce in Poland in subsequent periods of the Late Glacial and Holocene (Fig. 1.1). Lang (1994) in his monograph on the history of vegetation in Quaternary Europe also depicts the incursion of spruce into present-day Poland. In the Late Glacial the migration and expansion of spruce occurred from several refugia. Lang (1994) identifies three glacial refugia. A major refugium was located in northeastern Europe and included regions of contemporary north-central Russia, a second was located in the Carpathians and another in the northeastern Alps.

The northern portion of the contemporary range of spruce was likely formed through a northern migration route, which quite early divided into two pathways. One path traversed northern Scandinavia where range expansion occurred somewhat more slowly. This is evidenced by the relatively late proliferation of spruce in the southern part of Norway, at about 500 BC. About 1100 years later (600 A.D.) the range limit of spruce had extended to only approximately one third of its contemporary area (HAFSTEN 1985). In contrast, the wave of spruce migration emanating from the southern migration route arrived in northeastern Poland much earlier than in Scandinavia. The migration of spruce from its Carpathian refugium was apparently much faster, resulting in the presence of Norway spruce, in some places in considerable abundance, in the forests of southern Poland as early as the first half of the Holocene (Fig. 1.1, see also Chapter 5).

Contrasting pathways and rates of migration of spruce that shaped both the northern European and the central-southeastern portions of the species range are illustrated in LANG'S (1994) monograph. In the northern portion, 5000 years ago spruce occupied 51% of its present-day range, and 10,000 years ago, only 22%. The central-southeastern European range of Norway spruce was already 80% occupied 5000 years ago, whereas 10,000 years ago, it occupied 26% of the present day geographic range. Thus, the expansion in geographic range of the central-southeastern portion occurred quite differently from the pattern observed in the north.

Historically Norway spruce expanded into present-day Poland from the Carpathian and northeastern refugia at different times. Spruce initially migrated into Poland from the south. There it occupied numerous sites as early as the late Glacial and during the transition to the Holocene, including the areas of the present-day Carpathian disjunction in the range of spruce (SRODON 1990). The migration of spruce from the northeast resulted in the earliest appearance of spruce in Poland near the present-day Suwalki region. There it remained throughout the latter part of the Boreal period of vegetation history. The meeting of the two expanding ranges occurred probably near the end of the Atlantic period.

Without settling either the time or the place where the northern (lowland) range met the southern (mountain) range, the currently accepted view is that there was a continuous expansion of the range of spruce throughout Poland. Range expansion also occurred in the northern Carpathians, where in the Lower Beskid region, an earlier Carpathian disjunction was identified (compare SRODON 1967a, b, 1990). The dominance of spruce during the interglacial phases when the climate was cold and humid suggests that the present-day range of spruce, so markedly different from its geographic range during the interglacials, reflects a continuing process of migration. This supposition is reasonable when one considers that the Holocene is also an interglacial period. The climatic conditions are likely close to those prevalent during the past waning Eemian Interglacial and qualitatively support the notion of an expanding range of spruce. In the glacial-interglacial cycle, spruce belongs to the terminocratic group. In the Eemian cycle, spruce attained its dominance during the telocratic phase (BIRKS 1986). However, the last contemporary glacial-interglacial cycle has been marked from as early as the Neolithic by the increasing influence of human activities (TOBOLSKI1976). Presently, our ability to track migrations is hampered by historical and contemporary changes brought about by human activities that affect the composition and structure of forests and land-use change.

On the basis of the paleorecord of spruce, its presence in the Late Carpathian Glacial is certain. However, spruce occupied the Sudety Mts much later. According to RYBNicKOVA and RYBNicEK (1988) spruce appeared there at relative frequencies of 10 to 25% only 7000 years ago. However, forested areas between the two large areas of the species' contemporary geo-

Andrzej SrodoƱ , Kazimierz Tobolski

Figure 1.1. Distribution of spruce in the Late Glacial and Holocene periods. Locations numbers are shown on the first panel (Srodon, 1967b)

Average values of the proportion of spruce pollen shown by the symbols on the first panel: 1 = 0.01-0.5%, 2=0.6-1.0%, 3=1.1-3.0%, 4 = 3.1-5.0%, 5=5.1-10.0%, 6=10.1-20.0%, 7=20.1-30.0%, 8=30.1-60.0%

graphic distribution show a relatively small proportion of spruce during the Holocene. At the same time, it is likely that the low frequency of occurrence of spruce on the central Poland lowlands was the result of non-favorable edaphic conditions in addition to the effects of humans. This migration occurred at a time when conditions were likely suboptimal for the proliferation of spruce. The postglacial expansion of spruce onto the lowlands of central Europe, the formation migration routes in areas subjected to human disturbances, beginning with the waning Mesolithic, remain exciting research challenges in the historical biogeography of Norway spruce.

Andrzej Srodon, Polish Academy of Sciences, Institute of Botany, Krakow. Kazimierz Tobolski, Adam Mickiewicz Uniwersity, Poznan.

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