Veget Hist Archaeobot (2004) 13:23–31 DOI 10.1007/s00334-003-0030-7
ORIGINAL ARTICLE
Teija Alenius · Elisabeth Grnlund · Heikki Simola · Aleksandr Saksa
Land-use history of Riekkalansaari Island in the northern archipelago of Lake Ladoga, Karelian Republic, Russia Received: 22 April 2003 / Accepted: 15 December 2003 / Published online: 16 January 2004 Springer-Verlag 2004
Abstract Agricultural history was investigated by means of pollen and charcoal analyses from the sediment of Lake Kirjavalampi in the Riekkalansaari Island, in the northern archipelago of Lake Ladoga, NW Russia (61440 N, 30460 E). Pollen and charcoal stratigraphies, and loss-on-ignition were analysed from a 0–294-cm profile cored from the deepest part of the small lake. The pollen profile was divided into six local pollen assemblage zones Kir 1–6 and dated by three radiocarbon samples. Lake Kirjavalampi was isolated from Lake Ladoga between 1460–1300 b.c., when the River Neva was formed as a new outlet for Lake Ladoga and the water level rapidly fell. The isolation is seen as a phase of rapid sedimentation in Kir 2 (237–173 cm). Spruce (Picea) starts to decline at 113 cm ca. a.d. 70, and the earliest cereal (Secale cereale) pollen was encountered at the 97-cm level, empirically dating the onset of cultivation to ca. a.d. 600. A marked intensification in agricultural activities occurs around a.d. 1200, and the indication of an open cultivated landscape is at its strongest during the time period 1700 to 1850. Keywords Karelia · Lake Ladoga · Land use · Pollen analysis · Riekkalansaari Island
T. Alenius ()) Geological Survey of Finland, P.O. Box 96, Espoo, Finland e-mail:
[email protected] E. Grnlund · H. Simola Karelian Institute, University of Joensuu, P.O. Box 111 Joensuu, Finland A. Saksa Institute of History of Material Culture, Russian Academy of Sciences, St. Petersburg, Russia
Introduction Since the early 1990s, several pollen analytical studies, with special emphasis on the development of agricultural land use, have been carried out in the environs of Lake Ladoga, which is the largest lake in Europe (Taavitsainen et al. 1994; Saksa et al. 1996; Vuorela and Saarnisto 1997; Simola et al. 2000; Vuorela et al. 2001a; Miettinen et al. 2002). The western and northern shores of Lake Ladoga, former Finnish territory ceded to the Soviet Union in World War II, are renowned for their rich archaeological finds from the Late Iron Age and Crusade period, representing an indigenous Karelian culture (Uino 1997; Saksa 1998). Archaeological data indicate that the original cultural development in the western Ladoga region started in the Merovingian period a.d. 600–800, but this, in its early stages, was masked by traded artefacts that show predominantly external influences. Establishment of agriculture as the principal subsistence source and the consequent population growth can be seen in the archaeological material from the 11th and 12th centuries. At that period, the culture acquires a clearly local character. The aim of the paper is to provide an insight into the early stages of settlement history on Riekkalansaari Island in the northern archipelago of Lake Ladoga and to compare the results provided by the archaeological material with the present and earlier pollen analytical studies from the region. The study lake on Riekkalansaari Island was selected because it is situated close to the dwelling site of Nukuttalahti, which, according to Saksa et al. (1996), represents an example of the scanty traces of the indigenous Metal Period culture. Further finds in Riekkalansaari include a hoard and a Younger Iron Age cremation cemetery with finds dated to a.d. 950–1100 and stray finds (jewellery) dated to a.d. 1150–1250 (Uino 1997).
24 Fig. 1 Location of the study site, Lake Kirjavalampi, in the northern archipelago of Lake Ladoga
Site description: Lake Kirjavalampi, Riekkalansaari Island and the Sortavala region Lake Kirjavalampi (61o44’N, 30o46’E) is situated near the town of Sortavala, in the northern part of Riekkalansaari Island, which, with a land area of 75 km2,is the largest island in the North Ladoga archipelago (Fig. 1). Lake Kirjavalampi has an area of 2.4 ha with a drainage area of 94 ha, a maximum depth of 4 m and an elevation of 17 m a.s.l. At the present time there are cultivated hay fields and cattle pastures to the north and south of the lake whereas outcrops of steep bare rock occupy the western shores. The fields cover 32% and the forest 68% of the catchment area. There is a small brook flowing from the north to the lake and its outlet to Lake Ladoga is at the southern end of the lake. Forest vegetation is dominated by pine on dry soils, otherwise birch is the most common tree species. A belt of common reed (Phragmites communis) occupies the littoral zone and alder and willow thickets are found in the shore area. On the NW side of Kirjavalampi, there is lush nemoral vegetation with abundant Aconitum septentrionale, Lathyrus vernus and Melampyrum nemorosum. On the shore cliffs, Sedum telephium, Lychnis viscaria, Origanum vulgare and Dianthus deltoides, for example, are abundant. Topography in the Sortavala archipelago and on the nearby mainland is rugged and variable owing to the fractured bedrock, effects of continental glaciation and great relative height differences at the northern margin of Lake Ladoga, which is a major tectonic depression. The ancient crystalline bedrock consists mainly of schists and gneisses (Hackman 1933; Ekdahl and Philippov 1999; Koistinen and Saltykova 1999; Korsman and Glebovitsky 1999), with some limestone, skarn and volcanites. The landforms are largely due to the action of continental ice
on the fractured bedrock during the last glaciation. High and steep rock outcrops alternate with elongated valleys and the fjord-like bays and straits of Lake Ladoga. The post-glacial high-water levels of the Baltic and Lake Ladoga are clearly discernible in the landscape. The last transgressive high-water phase, reaching up to some 20 m a.s.l., ended about 1460–1300 b.c., when the River Neva was formed as a new outlet for Lake Ladoga (Saarnisto and Grnlund 1996). As a consequence, the level of Lake Ladoga rapidly sank close to the present, 5 m a.s.l., and extensive lowland areas with clay-silt soils were exposed. At this time, Lake Kirjavalampi, in our study site, became isolated from Lake Ladoga. The abundance of easily weathered minerals in the bedrock makes the soils of the area rather fertile, and the area is rightly famous for its floral richness (Linkola 1916, 1921). The vast water mass of Lake Ladoga (18,000 km2, 840 km3) affects the local climate by extending the growing season and by lowering the incidence of night frost during summer and autumn. The soils and microclimate are favourable for cultivation. Slash-and-burn has been possible even on the hill slopes, while arable cultivation has been mainly confined to the clay-silt lowland areas below the 21-m level.
Materials and methods The sediment of the lake was cored in the winter of 1992. An in-situ freezing corer (Huttunen and Merilinen 1978) was used for the upper part and a hammer-piston corer for deeper parts of the sediment (Huttunen and Merilinen 1975). The frozen sample covered 0–55 cm depth and the fresh piston-cored sample went to 40–294 cm depth of sediment. Both cores were sampled at 1 cm resolution for loss-on-ignition, pollen and charcoal particle analyses. The correlation of the two cores was based on field measurements and was later ascertained by comparing the ash percentage and the pollen stratigraphies. For loss-on-ignition
25 Table 1
14
C-data from the Lake Kirjavalampi sediment
Lab. no.
Sample depth (cm)
Hel-3876 Hel-3877 Hel-3878
74–78 114–118 169–173
14
C age b.p.
790€90 1960€100 3050€110
Calc. age (a.d./b.c.; 2s)
Explanation
a.d. 1031–1322 (1263) 1339–1393 190 b.c.–a.d. 257 (66) 295–320 1520–985 (1306) 957–942 b.c.
Opening of the landscape Oldest anthropogenic influence Isolation of Lake Kirjavalampi
of the University of Helsinki (Hel-3876–3878) (Table 1) and a time–depth curve was based on the 14C ages (Fig. 2). Calibration of the 14C-data was carried out according to Stuiver and Reimer (1993). Rarefaction analysis for pollen zones 3–6 was performed using a program by Birks and Line (1992).
Results Stratigraphy
Fig. 2 Depth (cm) versus three 14C dates (cal b.p.) of the sediment sequence studied from Lake Kirjavalampi (see also Table 1) analysis, the 1-cm-thick subsamples were dried at 105 C for 24 h and ignited at 550 C for 3 h (Bengtson and Enell 1986). The treatment for pollen samples followed standard procedures, with KOH, acetolysis and HF treatments (Berglund and RalskaJasiewiczowa 1986). The pollen preparations were mounted on slides in safranin-stained glycerol. Lycopodium spores (Stockmarr 1971) were added for concentration calculations of pollen and charcoal particles. About 500 arboreal pollen grains (AP) were counted from each subsample, except for five levels between 218– 252 cm, where only about 100 AP grains were recorded because of the scarcity of pollen grains in the sediment. Identification of the pollen was facilitated by the pollen and spore reference collection kept at the Dept. of Ecology of the Karelian Institute, and from literature by Erdtman et al. (1961), Faegri and Iversen (1989), Moore et al. (1991) and Reille (1992, 1995). Charcoal particles were counted from the pollen slides against 30% of the Lycopodium count achieved in the pollen analysis. The charcoal particles were measured along the longest axis and divided into two size classes: 10–50 and >50 mm. Biostratigraphical data treatment and diagrams were handled with Grimm’s (1990, 1992) TILIA and TILIA GRAPH programs. The pollen percentages of arboreal (AP) and non-arboreal pollen (NAP) were calculated from the basic sum of terrestrial pollen grains, P = AP + NAP. The aquatic pollen and spores were calculated from the sums P + AqP and P + spores. The plant nomenclature follows Hmet-Ahti et al. (1986). The pollen diagrams were divided horizontally into six local pollen zones Kir 1–6. Dating of the profile was based on three 14C determinations performed on the 5-cm-thick samples at the radiocarbon laboratory
The deepest part, 292–234 cm, of the cored sediment sequence, was homogenous clay with two mixed sandclay horizons at levels 249–246 and 243–241 cm. The grey minerogenic sediment turns to clay–gyttja above the 233-cm level up until 127 cm. There were distinct horizontal laminations at the following levels: at 215– 213 cm, 17 laminae; at 180–180.7 cm, 9 laminae; at 175– 176.9 cm, 16 laminae; at 168–164 cm, 26 laminae; and at 126–124 cm, 20 laminae. Above the 127-cm level the sediment becomes gyttja up to the 99-cm level. There is a sudden peak in mineral content between 99–94 cm followed by a steady decline to the minimum mineral content, 49% at 55 cm. The upper 0.5-m of the stratigraphy is more minerogenic, peaking at 88–97% in the topmost 7 cm. In the top 6 cm of the frozen sample, 11 clay laminations could be seen, which may represent annual spring erosional layers. Pollen The lowermost local pollen assemblage zone (Kir 1, 292– 238 cm) represents the period of maximum extent of the lake and it is characterised by high proportions of NAP and spores: at 30 and 20%, respectively (Figs. 3, 4 and 5). The most abundant NAP taxa are Artemisia, Salix, Chenopodiaceae and Poaceae, accompanied by lower values for Caryophyllaceae, Rumex, Rosaceae, Apiaceae, Rubiaceae, Asteraceae and Cichoriaceae. Shrubs and dwarf shrubs are represented by Hippopha rhamnoides with abundant Ericaceae and Calluna, while Sphagnum, Equisetum and Polypodiaceae are the most common of the spore taxa. Kir 2, 237–173 cm covers the period between the formation of the River Neva until the complete isolation of Lake Kirjavalampi ca. 1306 b.c. Typical features are a steady increase in grass pollen up to the 213-cm level (17%), followed by as steady decline to the 173-cm level. Pollen of Poaceae, Salix, Alnus and Betula appears in a successional sequence, reflecting the change from open vegetation conditions with lowering water levels to a
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Fig. 3 Sediment lithology, relative tree and shrub pollen frequencies, local pollen assemblage zones (Kir 1–6) and
Fig. 4 Sediment lithology, relative herb pollen frequencies (% P), local pollen assemblage zones (Kir 1–6) and Legend for the lithology as in Fig. 3
forested stage. Pollen of broad-leaved forest taxa (QM) occurs in relatively low (2–3%), but constant proportions. Kir 3, 172–114 cm, ca. 1306 b.c.–a.d. 66 is dominated by boreal forest taxa. The AP percentage is 92%, and the relative proportions of trees remain generally stable; Picea is increasing and QM taxa are decreasing somewhat towards the top of the zone. Kir 4, 113–40 cm, ca. a.d. 66 until the 18th century, has been divided into three subzones, indicating three phases of open landscape development as evident from the NAP proportions and the diversity of these taxa. The most characteristic feature of subzone 4a, at 113–98 cm and ca. a.d. 66–600, is an abrupt decline in Picea
14
14
C datings b.c./a.d
C datings b.c./a.d.
percentages, persisting throughout the subsequent sediment. QM taxa decrease towards the top of the zone. Secale cereale was recorded continuously from the beginning of subzone 4b, at 97–83 cm and covering the time period ca. a.d. 600–1200. Cannabis/Humulus-type grains occur in low proportions at and above the 90-cm level. Taxa increasing at the 97 cm level include Salix, Ranunculaceae, Filipendula and Melampyrum, and spores of Polypodiaceae and Equisetum. Subzone 4c, at 82– 40 cm and ca. a.d. 1200–18th century, reflects an intensive land-use phase, with the NAP percentage at 10–20% throughout the zone. The percentages are low for Picea and Betula. Secale and Humulus/Cannabis occur in
27
14
Fig. 5 Sediment lithology, relative frequencies of spores (% P + spores), aquatics (% P+AqP), boreal/herbs, total pollen concentration (grains per cm3), loss-on-ignition percentage, local pollen
assemblage zones (Kir 1–6) and the lithology as in Fig. 3
Fig. 6 Sediment lithology, percentages of selected pollen and spore taxa, rarefaction estimate of species richness, charcoal particle concentration of two size classes (particles per cm3), local pollen
assemblage zones (Kir 3–6 only) and for the lithology as in Fig. 3
low proportions throughout the zone. Salix, Juniperus, Filipendula and Poaceae, Ranunculaceae, Asteraceae and Cichoriaceae occur in higher proportions than in the preceding subzone. Pollen of Nymphaea and Cyperaceae and spores of Pteridium and Equisetum increase considerably. New taxa in this zone are Rumex, Campanula, Plantago major/media, Fabaceae and Brassicaceae. Kir 5, at 40–19 cm and from the 18th to the 20th century, shows the strongest presence of apophyte and anthropochore pollen in the entire sequence studied. Concentrations of all the arboreal taxa decline, Betula
being the most common, whereas Picea appears only with 2.9%. The NAP percentage reaches its maximum at 35% of the total pollen sum at the 25-cm level. The abundances of Cerealia (incl. Secale), Juniperus, Rumex, Poaceae, Salix, Equisetum and Cyperaceae increase strongly. Pollen of Cannabis/Humulus-type, Pteridium, Calluna and Nymphaea are also abundant, but Pteridium disappears abruptly at the end of zone. Urtica and Spergula arvensis enter the pollen assemblage. Pollen taxa indicative of intensive land-use decline at the onset of Kir 6 at 19–0 cm. This zone represents the
C datings b.c./a.d. Legend for
14
C datings b.c./a.d. Legend
28
20th century. The NAP, Rumex, Juniperus, Salix, Cerealia (incl. Secale) and Cannabis/Humulus-type decline, the latter two taxa being absent in the topmost samples. At the beginning of the zone, Poaceae pollen first decrease and then increase again in the uppermost 5 cm. However, some cultivation-indicating types prevail at similar percentages as in the previous zone, namely Filipendula, Potentilla, Sorbus, Fabaceae, Asteraceae, Cichoriaceae and Ranunculaceae. Calluna grains are encountered only discontinuously. Picea remains at a low level, but Betula and Pinus show a tendency to recover their levels in the pre-agricultural phase. Charcoal A first increase in the larger particles, viz. the size classes >50 mm, takes place at 116–109 cm, followed by lower values between 109–96 cm. A second, more prominent increase between 96 and 56 cm is again followed by a short-term decrease, prior to an increase between 48 and 38 cm. The phases of high charcoal values correspond to the pollen zones Kir 4a, Kir 4b and Kir 4c (excluding 109–96 and 56–48 cm; Fig. 6). Rarefaction analysis The number of pollen types remains relatively low in Kir 3. In Kir 4: three clear levels of increase at 97, 82 and 49 cm can be seen. The highest values are obtained in Kir 5, and in the topmost zone the values decrease again (Fig. 6).
Discussion In the bottom-most deposits of the Kirjavalampi sediments (Kir 1), representing the phase when Lake Kirjavalampi was part of the Lake Ladoga basin water body, herb pollen reaches 10% of the total pollen. The pollen assemblage appears to contain a fair number of redeposited pollen grains from the preceding vegetational phases, brought in by wave action and by reworking of the old water-deposited sediments of Lake Ladoga. In particular, the abundance of Artemisia, Chenopodiaceae and Ericaceae point to the Late Glacial Artemisia zone (Hyvrinen 1972; Tolonen and Ruuhijrvi 1976), whereas the abundances of Alnus and Picea point to younger vegetational phases. When the River Neva was formed, the water level of Lake Ladoga dropped several metres and the basin was isolated. The isolation phase at the 237cm level is reflected by the increasing organic content of the sediment and increasing pollen concentrations. The expansion of the dry land area is reflected by an increase in herb pollen taxa. Most abundant are grasses belonging to the pioneer flora of the alluvial land, which was exposed when the water level of Lake Ladoga sank to its present level. According to radiocarbon dating, the
isolation phase ended at the 169–173-cm level ca. 1306 b.c. This is in agreement with Saarnisto and Grnlund (1996), who dated the formation of River Neva to ca. 1460–1300 b.c. No indications of human activity were found in the pollen data in the sequence Kir 3, which corresponds in age to the Finnish archaeological periods of the Bronze Age (1500–500 b.c.) and the Pre-Roman Iron Age (500 b.c.–0). Pollen diversity remains low and the pollen data mainly indicate arboreal taxa. The first indications of apparent human land-use activities date to a.d. 66 (Hel-3877) to the Early Roman Iron Age (0–a.d. 200). Small-scale land clearance is implied by the clear decrease in spruce pollen frequencies. At the same level, mineral content of the sediment starts to increase, indicating increased soil erosion in the vicinity of the pond. The absolute Cerealia limit (Cº), i.e. the earliest rye pollen, was recorded at a depth of 97 cm placing the onset of cultivation to ca. a.d. 600 i.e. to the beginning of the Merovingian period. This result correlates with archaeological evidence from Riekkalansaari, where the oldest archaeological find is a cairn-type grave dated to ca. a.d. 500 (Kivikoski 1961; Saksa 1998). At the same level, an increase in large charcoal particles can be seen. On the basis of the pollen spectra it seems reasonable to infer that these high concentrations of charcoal particles were produced by slash-and-burn cultivation. A sharp peak in the mineral content at 99–92 cm and the high values of small charcoal particles at the 98-cm level may also be connected to increased fire frequency, which caused soil erosion and re-deposition of the old fragmented charcoal particles from the area surrounding the pond. Forest clearance appears to have been of minor extent, as the proportion of trees still amounts to some 90% of total pollen. Disturbance, however, has increased structural diversity in the landscape, which can be seen in a slight increase in the number of pollen types that coincide with the onset of cultivation. Earlier pollen analytical studies from the western and northern coastal Lake Ladoga area indicate somewhat similar results for the onset of cultivation. To the south of Riekkalansaari, on Valamo Island, the earliest rye pollen was dated in E. Igumeeninlampi to a.d. 650, and in Luostarinlahti Bay to a.d. 800 (Vuorela and Saarnisto 1997; Vuorela et al. 2001a). On the eastern coast of Lake Ladoga, close to the monastery of Svir, field cultivation of rye, which was practised in ca. a.d. 1300, has been recorded (Simola et al. 2000; Grnlund et al. 2001). On the western shore of the lake on Kilpolansaari Island in Hiitola, the introduction of slash-and-burn cultivation dates back to the Late Roman Iron Age at a.d. 200–400 and, in nearby Kuuppala (Kurkijoki), the earliest indications of human activity can be seen from the Late Iron Age, from about a.d. 400–800 onwards (Taavitsainen et al. 1994; Miettinen et al. 2002). Further south, in the central Karelian Isthmus, early signs of forest clearance around Lake Ohalampi (Valkjrvi) appear at around at a.d. 600–800 (Saksa et al. 1996). On the northern shore of
29
Lake Onega at Pegrema Bay, the start of land clearance for permanent cultivation was dated to the late 13th century and the beginning of more intensive field cultivation to a.d. 1450 (Vuorela et al. 2001b). Overall, timing and emergence for the onset and development of agriculture in the eastern Finnish Lake District was rather slow and gradual in the cultivated landscape throughout this large area up until about a.d. 1200 (Grnlund 1995, Taavitsainen et al. 1998). At Riekkalansaari, a marked intensification in agricultural activities is recorded from 82 cm onwards. In the pollen data, development of the landscape is reflected by increasing frequencies of herb and shrub pollen, and in decreasing frequencies of AP. This stage also represents the empirical Cerealia limit (C+). According to radiocarbon dating from 74–78 cm (a.d. 1263, Hel-3876), this change dates back to the Crusade period (a.d. 1025– 1300). Results from Riekkalansaari correspond well with the archaeological material, where the establishment of agriculture as the principal subsistence source and consequent population growth can be seen during the 11th and 12th centuries. Saksa (1998) relates this to an economy based on cereal crop cultivation, animal husbandry and the fur trade. According to pollen analytical studies from Valamo, Kurkijoki and Kilpolansaari Island, the Middle Ages, a.d. 1000–1250, seem also to have been a period of growth and of developing settlements. In the eastern interior Lake District of Finland there is a steady rise in the cereal pollen rain after the turn of the millennium (Grnlund 1995, Taavitsainen et al. 1998). From the Crusade period onwards pollen and charcoal evidence clearly indicates slash-and-burn cultivation. Herb pollen that can be clearly associated with increased fires includes Melampyrum and Rumex, as well as spores of Pteridium aquilinum. Rumex is particularly typical of the weed flora that indicates slash-and-burn cultivation (Heikinheimo 1915; Oinonen 1967; Behre 1981; Vuorela 1986; Grnlund 1995). At the same level, an increase in species richness and the numbers of large charcoal particles is clearly demonstrated. Slash-and-burn cultivation was the traditional Finnish means of clearing land for cultivation, and it remained as the major method of cereal-crop cultivation in eastern Finland until the late 19th century (Heikinheimo 1915; Soininen 1974). Slashand-burn cultivation was based on rotation cycles where land was cleared by fire for cultivation. Usually one to three cereal crops were grown on the site, after which the plots where either left to grow back to forest or were used as pasture for cattle. At the early stages of slash-and-burn cultivation, the rotation periods remained long and the forests had time to reach a mature, conifer-dominated stage prior to the next felling. As a consequence of progressive population growth and, hence, an increased need for crop production, the rotation cycles gradually had to be shortened. During the most intensive slash-andburn period of a.d. 1750–1850 the mean fire interval in eastern Finland dropped to about 36 years from more than
60 years during the preceding 17th century (Lehtonen and Huttunen 1997). Slash-and-burn had a great effect on the structure of the forests. Besides increasing openness of the landscape, repeated burning changed the forest structure to one dominated by deciduous trees. In the pollen data from Riekkalansaari, the decreasing pollen concentration of Betula and Alnus, evident from a.d. 1200 onwards, clearly indicates the utilisation of deciduous tree-dominated secondary forests for cultivation. Even though the pollen and charcoal evidence from the Crusade period onwards clearly indicates slash-and-burn cultivation, there is also an increase in apophyte taxa, which points to intensive local occupation and the presence of livestock. Cultural pollen indicators associated with ruderal communities include Plantago, Brassicaceae and Fabaceae. Juniperus is considered to be the best indicator of grazing in Finland; other pollen types indicative of grazing include pollen from the families Cichoriaceae and Ranunculaceae, all of which show a marked increase from ca. a.d. 1200 onwards (Behre 1981; Vuorela 1986). An increase in Nymphaea and the steadily increasing organic content of the sediment of Lake Kirjavalampi can be interpreted as signs of eutrophication. An increase in Equisetum, Cyperaceae and Menyanthes corresponds to the expansion of wet meadows in the areas surrounding the pond. The highest abundance of rye, beginning at the rational cerealia limit (C++), together with the highest values of Rumex, Juniperus and Poaceae, are recorded in Kir 5. According to Heikinheimo (1915), the area of slash-andburn cultivation amounted to over 75% in the northern and north-western areas of Lake Ladoga during the period a.d. 1700–1850, and the landscape of eastern Finland was generally open and largely devoid of mature coniferous forests. In the pollen data, dominance of rye can be associated with cultivation in slash-and-burn plots. However, a decline in small sized charcoal particles suggests diminishing use of fire. It is historically known that crop cultivation in Sortavala parish was already predominantly based on permanent fields by the year 1637 (Saloheimo 1977). This is probably due to the extent of the finegrained water-deposited soils that are well suited for field cultivation on the shore of this lake. This plausibly explains the low values of charcoal particles at Kir 5. The concomitant increase of minerogenic matter in the sediment can be interpreted as indicating increased soil erosion due to modernisation in field agriculture (Simola 2000). The appearance of barley as a new cultivated species also suggests cereal cultivation on permanent fields (Soininen 1974). Furthermore, increasing weed seed, such as that from Brassicaceae, Chenopodium, Centaurea and Spergula, can be associated with permanent field cultivation because weeds were poorly represented on slash-and-burn plots (Heikinheimo 1915). Diverse land-use practices involving a variety of methods, such as slash-and-burn cultivation, cultivation in permanent fields and grazing, yielded the highest values in
30
species richness, a phenomenon that is clearly seen in the pollen data in Kir 5. According to Heikinheimo (1915), the area of slashand-burn cultivation was already reduced by a.d. 1910 to 0.1–14.9%. In the uppermost zone, representing the 20th century, a clear decline in species richness, as well as pollen types indicative of intensive land-use, can be seen.
Conclusions The local settlement history of Riekkalansaari Island was investigated from the sediment of Lake Kirjavalampi. The interpretation of human impact was based on 166 stratigraphic samples and three 14C determinations. Final isolation of the small lake from the large Lake Ladoga in ca. 1300 b.c. can be seen in the loss-on-ignition curve as a clear change from minerogenic clay to organic gyttja. The oldest pre-agricultural phase, indicated by a decrease in Picea and an increase in mineral content, was recorded in Riekkalansaari ca. a.d. 70, i.e. the Early Roman Iron Age. Direct evidence of the beginning of cereal crop cultivation in the Riekkalansaari Island stems from the Merovingian period, at about a.d. 600. Marked intensification of agricultural activities is recorded from the Crusade period from around a.d. 1200 onwards. The most intensive period of land use is recorded in Kir 5. This stage can be interpreted to indicate a combination of slash-and-burn and permanent field cultivation representing the time period a.d. 1700–1850. A clear decline of agricultural activities can be seen in the uppermost zone representing the 20th century. Today, the landscape is characterised by open meadows, and in the pollen data slight signs of forest recovery can be seen. Acknowledgements The present study was financed by the Academy of Finland (projects nos. 8577 and 40922). We sincerely thank Terttu Lempiinen (University of Turku) for the identification of various plant species growing around Lake Kirjavalampi. The wintertime fieldwork was facilitated by Kari Ratilainen and Ilkka Kinnunen, who are technical staff of the Karelian Institute.
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