Fennoscandia archaeologica V (1988) Reijo Solantie CLIMATIC CONDITIONS FOR THE CULTIVATION OF RYE WITH REFERENCE TO THE HISTORY OF SETTLEMENT IN FINLAND Abstract In Finland the grain cultivation economy brought about a change in the pattern of settle­ ment from even dispersal to a clustered one. The basic hypothesis of this study main­ tains that with the grain cultivation economy settlement sought its way first into areas that were climatically the most advantageous for the growing of rye and spread gradu­ ally through the various climatic regions to the less suitable areas. Regional traits of settlement in the various periods concerned can be explained in terms of present cli­ matic conditions. The ,results also suggest climatic factors possibly explaining differences in the spread of settlement in Western Finland on the one hand and in the region of Savo on the other. These take as their starting point the differences of the burn-beating rye species grown in Savo and the Scandinavian-type arable rye cultivated in Western Finland. The same explanation also applies to the areas of Norway and Sweden settled by farmers from Savo in historically documented times. It 'is also suggested that the first settlers of the north-western part of the present province of Uusimaa (Sw. Nyland) in Southern Finland came from regions to the east of the Kymijoki River. This is in agree­ ment with the climate of the Uusimaa region, the slash-and-burn farming culture, farm­ ing terminology and the properties of the burn-beating variety of rye cultivated. Reijo Soiantie, Finnish Meteorological Institute, Box 503, SF-00101 Helsinki. INTRODUCTION Accurate climatic data is available from only the 19th century onwards. For this reason it is Throughout long periods in prehistory as well as important to know how the present regional historically documented times permanent settle­ features of the risks of rye cultivation can be ap­ ment in Finland based on the cultivation of grain plied to climatic conditions in the different stages was restricted to certain regions. This pattern of this means of livelihood. In England, for differs clearly from that of settlement based on example, mean temperatures over periods of hunting and fishing. The boundaries of settle­ about a century have not varied more than ment and its spread or retreat through definite l.O°C from the present in any climatic phase of successions of regions are problems of research the past 3,000 years (Lamb 1982). However, cli­ that are unanswered to a great degree. In the matic changes of even this degree have definite present study these problems are approached effects on the risk levels of cultivated plant spe­ from the perspective of the climatic conditions cies. On the other hand, the main factors in the necessary for the cultivation of rye. Rye was a study of regional patterns of succession in the main species of grain cultivated in Finland from spread of settlement, viz. the differences of risks the beginning of grain cultivation until the end and their order of magnitude among different of the so-called natural, i.e. non-market, econ­ areas, are not subject to change even with over­ omy. Rye is considerably more demanding of cli­ all changes of climate (see DISCUSSION, be­ matic factors than barley and is thus a more re­ low). liable indicator of the mutual relationship of The development of permanent settlement in settlement and climate. Finland shows an unbroken succession from the 3 ~o Fig. 1. Migration period (ca. 400-600 A.D.) and Merovingian period (ca. 600-800 A.D.) cemeteries (Huurre 1979). o Migration period cemeteries • Merovingian period cemeteries ~o Fig. 2. Viking period cemeteries, ca. 800-1050 A.D. (Huurre 1979) • Cremation burials (!) Inhumation burials 4 Roman Iron Age to the present day. In the in­ POST-IRON AGE PHASES OF SETTLE­ itial period both barley and rye are known to MENT STUDIED have been grown (Tolonen 1978, Vuorela 1975, Nunez & Vuorela 1976). Settlement of this In the Iron Age the coastal regions of SW Fin­ period indicates clearly the regional pattern of land, protected by the surrounding archipelago, settlement that followed (Figs. 1 & 2; Huurre were permanently settled. On the other hand, 1979). the seaboard of the Gulf of Finland with less sea- , ef, I CULF Fig. 3. Geographical areas referred to in text (see also Fig. 4) Regions (hatched) Bread grain zone: SW part of the feed grain zone A \SSS'Sl = The Kyronmaa region in C 1 ~ = Southernmost tar-burning Southern Ostrobothnia. NW area of Finland in the 1850s, part of the bread grain zone high frost risk for rye culti­ B I2"ZZZI = Inland regions of Southern vation. Finland IWlll2l = Separate area of old settle­ B\> B2 ~ = Subdivisions of B with grea­ ment from Savo, climatically test wintering risks for rye. favourable for the burn-beat­ Last burn-beating areas of B. ing variety of rye Bodies of water 1 Lake Lohjanjarvi 7 Lake region of Lappajarvi 2 Large lakes of Central Harne 8 Lake region of Kainuu 3 Lake Paijanne 9 Northern large lakes feeding 4 Lake Saimaa the Kymijoki River 5 Lake Ladoga Western boundary of Savo 6 Kymijoki River dialects 5 ward protection was still without permanent THE CULTIVATION OF RYE IN PRESENT settlement by the end of the Iron Age (Figs. 1 & CLIMATIC CONDITIONS 2). This lack of settlement on the southern coast has been explained as a result of restless con­ The northern boundary of the so-called feed ditions. The inland regions of Southern Finland, grain zone can also be regarded as the northern both in the south and south-west, were also with­ limit of rye cultivation (Rantanen & Solantie out settlement (Fig. 3, Area B). The wilderness 1987) (Fig. 4). At this boundary, the growing areas extended to the settlements of the season in even slightly less favourable years is so Kokemaenjoki River, the lake region of Harne short and cool that rye cannot mature before the and the Paijanne - Saimaa lakes region in the period is over. east. On the other hand, ~f there had been a po­ Even with a growing season of sufficient du­ tential threat to settlemen't from the sea, would ration, rye is also threatened by servere summer not the uninhabited inland of SW Finland have frosts and the damages of wintering. In summer been more secure than the coast despite the pro­ rye is sensitive to night frosts until its grains tection afforded by its outlying archipelago? The harden in late July - early August. All of the Swedish settlers of early medieval times kept to varieties of rye grown in Finland are resistant to the coast to an even greater degree than the SW the effects of too small amounts of snow in Finns. Orrman (1987) has suggested that the winter (ice-scorching and severe frosts). On the Swedes were capable of CUltivating the gyttja other hand, in winters with a thick snow cover clay soils of these areas, but not the heavier forming before the ground freezes properly and clayey soils of the inland (Eronen 1974, Kurki consequently remaining unfrozen for most of the 1982). The area of heavier clays borders on the winter, snow mould destroys the sprouts Litorina clay zone of the coast only in the eas­ (Mukula & Rantanen 1987). In Southern Fin­ tern part of the province of Uusimaa. In the in­ land this can happen in mild winters even if the land of western Uusimaa the soils are especially snow cover is not very thick. In the feed grain easy to cultivate with fine sandy till predominat­ zone the risks of frosts and wintering either ing in the fields (Kurki 1982). In these regions jointly or separately are usually considerable and there are also areas of lake mud soils which were in the poorest years the growing season is too also occupied and utilized by the earliest settlers short. Thus, in this zone rye cultivation is viable (Jussila 1977). only in the most advantageous locations and The coast, the shores of large rivers and the using the best possible varieties. On the other regions of the large lakes were all especially suit­ hand, in the so-called bread grain zone of South­ able for settlement not only because of their op­ ern Finland (Fig. 4) the growing season is suf­ portunities for fishing but also because of the ficient for rye with only rare exceptions. How­ fact that the bodies of water facilitated com­ ever, the joint damages caused by night frosts munications and transport within the areas con­ and wintering make rye cultivation considerably cerned. The regional distribution of Iron Age risk-prone in certain parts of even this latter re­ cemeteries shows that for some reason settle­ gion. ment was more dense in the coastal regions of SW Finland, along the Kokemaenjoki River and in the vicinity of the large lakes of Central Harne than in the valleys of Lakes Saimaa and METHOD Nasijarvi. A further problem is the origin of a separate pocket of settlement in Ostrobothnia in The growth conditions of rye in the present cli­ the Early Iron Age and its disappearance at the mate were first studied. Following this, the re­ end of the Viking period (Fig. 3). A central gional differences of the risks of rye cultivation problem, hitherto unanswered, is the expansion were applied to explaining the spread of perma­ of settlement in Savo in comparison to that of nent settlement in Finland. The starting point in the Harne regions. Related issues are also the this connection was that at first areas with little routes of the spread of settlement in Savo and or no risk were settled after which settlement the subsequent formation of the border between spread to areas of progressively greater risk .