Heikki Simola

Cultivation History Beyond the Periphery: Early Agriculture in the North European Boreal Forest

We have investigated the environmental history of human occupation and the development of agriculture in the eastern interior Lake District of Finland. The material consists of archaeological data, which is reviewed in topographical and agrogeological context, and pollen analytical evidence of agricultural indices from eight precisely dated (varved) lake sediment sequences. Before the Viking Age, archaeological evidence, consisting of stray finds, dwelling sites, and graves, is very scarce. Iron Age finds are clearly confined to the lowland environs with silty and clayey soils. During the Viking Age, the number of stray finds multiplies and the first cemeteries are established. Comparison between Viking and Crusade Period finds reveals a topographic shift toward higher locations and morainic soils. Most of the cup-stones are located on upland sites—that is, not in connection with known Iron Age sites. These are interpreted as medieval indicators of slash-and-burn farming of the fertile but stony supraaquatic morainic soils. There is pollen analytical evidence of sporadic cultivation in the area from the Bronze Age onward. Afterca. AD 700, the occurrence of cereal pollen grains becomes regular but remains discontinuous at each site until after the turn of the millennium. There is then an exponential rise in the cereal pollen rain, indicating a fully agricultural population.

Harmonization is more important than experience—results of the first Nordic–Baltic diatom intercalibration exercise 2007 (stream monitoring)

The goal of this study was a harmonization of diatom identification and counting among diatomists from the Scandinavian and Baltic countries to improve the comparison of diatom studies in this geographical area. An analysis of the results of 25 diatomists following the European standard EN 14407 during an intercalibration exercise showed that a high similarity was achieved by harmonization and not because of a long experience with diatoms. Sources of error were wrong calibration scales, overlooking of small taxa, especially small Navicula s.l., misidentifications (Eunotia rhomboidea was mistaken for Eunotia incisa) and unclear separation between certain taxa in the identification literature. The latter was discussed during a workshop with focus on the Achnanthes minutissima group, the separation of Fragilaria capucina var. gracilis from F. capucina var. rumpens, and Nitzschia palea var. palea from N. palea var. debilis. The exercise showed also that the Swedish standard diatom method tested here worked fine with acceptable error for the indices IPS (Indice de Polluo-sensibilité Spécifique) and ACID (ACidity Index for Diatoms) when diatomists with a low similarity (Bray–Curtis <60%) with the auditor in at least one of the samples are excluded.

Limnological effects of peatland drainage and fertilization as reflected in the varved sediment of a deep lake

Stratigraphy of diatoms and chemistry in the surface sediment deposited at 35 m depth in Lake Polvijärvi was studied. The existence of annual laminations or varves in the sediment allowed a precise dating of the profile. Diatoms were analysed in 0.5 cm sequences; from 0 to 16.0 cm continuously and then intermittently every fourth 0.5 cm down to 44.0 cm. Sediment chemistry (loss-on-ignition, C, N, Fe, Mn, Mg, P, chlorophyll and carotenoids) was analysed from sediment surface down to 10.5 cm of altogether 33 subsamples, each containing 1–3 varves, and spanning the period 1921–1980.From 4.5 cm depth upwards the diatom concentration strongly increases, and the plankton diatom succession from Tabellaria flocculosa through Asterionella formosa to Melosira ambigua and Fragilaria crotonensis reflects a marked eutrophication of the lake. This algal succession occurs in pace with an increase in sediment accumulation rate and changes in sediment chemistry, which indicate increased allochthonous inputs and enhanced algal production in the lake. The change of the lake ecosystem is contemporaneous with extensive peatland draining and fertilizing that was carried out on its watershed during the past two decades. Existing chemical data from a number of lakes situated within the drainage area prove that at present the treated peatlands are the main source of nutrient loading of Lake Polvijärvi.A former period with indications of slightly increased productivity of the lake was dated by varve counting to AD 1690–1910 (35–12 cm). This period (characterised by Asterionella formosa) may coincide with that of the slash-and-burn cultivation in the area.

Palaeolimnological analyses as information source for large lake biomonitoring

A routinely applicable palaeolimnological sampling and analysis programme for large lake monitoring was developed as part of the Lake Saimaa Biomonitoring Project (1990–1993). The scope of palaeolimnological analyses is to gain background information of the recent past (ca. 0–200 yr) of the lake ecosystem that is being monitored. We analyzed short sediment cores from three contrasting basins of the complex lake Saimaa in eastern Finland (nutrient-poor clearwater Lake Puruvesi; oligotrophic mesohumic Lake Paasivesi, and eutrophied and polluted mesohumic Lake Haukivesi). Each basin shows a unique developmental history under the various forms of human influence on the ecosystem. The following research approaches are evaluated in the study: echosounding, dating (210Pb, varves, soot stratigraphy), element stratigraphies, biological remains (diatoms, cladocera, chironomids, sedimentary pigments).

Paleolimnological reflections of fiber-plant retting in the sediment of a small clear-water lake

Likolampi is a small groundwater kettle-hole lake in Ilomantsi, Eastern Finland. At 11 m water depth the uppermost 51 cm of sediment contains about 390 varves. A thin layer of chrysophyte statospores is the main structural unit in these; in some varves it is followed by a layer of cf. Drepanocladus fluitans moss spores. Below the laminated sequence, two layers of moss detritus (110–87 cm, 81–51 cm) alternate with greyish brown fine detritus. Pollen analysis reveals that the start of the deposition of varved sediment coincides with the beginning of intensive fiber plant retting with large quantities of Cannabis/Humulus -type pollen and even regular occurrence of the insect-pollinated Linum usitatissimum. The cf. Drepanocladus spores are almost absent during the retting period (c. 1590–1900 by the varves), but very common before and after it. Drepanocladus fluitans is capable of assimilating dissolved CO2 in water, so it thrives at low pH and is typical for oligotrophic clear-water lakes. We conclude that the stratigraphy of Drepanocladus fragments and spores is a true negative indicator of cultural influence in Likolampi.

Palaeolimnology of Lake Piene-Kuuppalanlampi (Kurkijoki, Karelian Republic, Russia): isolation history, lake ecosystem development and long-term agricultural impact

The post-glacial history of Lake Pieni-Kuuppalanlampi, western Lake Ladoga region, was studied by means of stratigraphic pollen and diatom analyses. Diatoms were analysed to track the isolation history of the basin and the limnological effects of the early land-use phases indicated by pollen analysis. Chrysophycean stomatocysts and Isoëtes spores were also employed in the limnological reconstructions. Sediment dating was provided by six conventional radiocarbon dates.The lower part of the 370-cm long sediment sequence represents early Holocene, large lake conditions: the (freshwater) Yoldia and Ancylus stages of the Baltic basin, with a short-term lagoonal or isolation phase at the end of Yoldia. The basin was isolated due to Ancylus lake regression at 9785 cal B.P. For the small-lake sequence (0–250 cm) we used diatom inferences (WA-method) for hindcasting water chemistry. The post-isolation limnology of Pieni-Kuuppalanlampi reflects the development of vegetation on its small hill-top catchment. In its early development, the lake was mesotrophic, but became more acidic (pH about 6) and oligotrophic after the decline of temperate hardwood trees and the spread of spruce to the area after around 5000 B.P. The lake ecosystem appears to have reacted sensitively to agricultural land-use in the catchment from AD 400–800 onwards: inferred total phosphorus levels and pH both rise during these periods.

Palaeolimnological study of an environmental monitoring area, or, Are there pristine lakes in Finland?

A palaeolimnological study of Lake Iso-Hietajärvi in Patvinsuo National Park, Lieksa, East Finland was conducted. The drainage area of the lake is one of four Integrated Monitoring areas established in Finland. Lead-210 dating reveals a period of increased sedimentation in the lake from 1920 to 1950. Increased atmospheric burden of several heavy metals in the order Pb > Cu> Zn > Ti = Al > Cr = Ni = V is recorded. The first to expand during the 19th century is Pb, whilst V increases after 1950. Sedimentary chlorophyll derivatives expand in the early part of the 20th century. Assemblages of diatoms and Cladocera were also changed somewhat during this time, but water quality seems not to have varied much: e.g. the diatom-inferred pH has remained in the range 6.4–6.8 (with a slight decrease) throughout the period of study.

Drainage ditch erosion history as recorded in the varved sediment of a small lake in East Finland

Short core stratigraphy of total N, P, Zn, Hg and diatoms were investigated in the varved sediment of Lake Heinälampi, a small 8 m deep pond in East Finland. The sediment has recently changed from organic mud to minerogenic silt. The presence of varved sediment offers independent control for 210Pb and 137Cs dates and these are in good agreement: the sediment quality initially changed around the year 1930 due to increaed field erosion, and the inflow of mineral matter was further increased by ditching of paludified forests in 1980.Diatom analysis reveals that eutrophication has occurred before and concurrent with the sedimentary change. The causes of eutrophication and the increased levels of Zn and Hg are discussed.

Changes in diatom assemblages in the profundal sediments of two large oligohumic lakes in eastern Finland

Sedimentary diatom assemblages in two large oligotrophic clear-water lakes were analysed, to assess their present ecological state and possible eutrophication due to diffuse nutrient loading. The lakes Pyhajarvi and Puruvesi (Finnish lake district) are proportionally large for their catchment areas which accounts for their long retention times (ca 7 and 11 yr) and oligohumic character. Pyhajarvi was studied by pairwise comparison of surface sediment diatom assemblages collected in 1985 and 1990 at 12 sites from different parts of the lake. In Puruvesi, the stratigraphy of diatoms was analysed in two short cores from 8 m and 32 m depths.

The First International Lake Ladoga Symposium

Lake Ladoga (the largest lake in Europe) was characterized by good water quality some decades ago. Now as a result of human impact, the saprobity and toxicity of water have changed, phytoplankton biomass has increased, and populations of many sensitive species have declined. Morphological deformities of invertebrates are observed in heavily polluted areas and toxic effects are commonly encountered in fishes. The ecological crisis of Lake Ladoga is caused by human activities in its drainage area. This area is characterized by a relatively high degree of industrialization and economic development. The adverse environmental effects appear to be spatially irregular, occurring mostly in isolated bays and near-shore areas, especially when thermal bars are present, but there is also evidence of general increase of nutrient concentrations in the entire lake. Urgent measures should be taken for restoration of Lake Ladoga ecosystem.