THE CONTINENTAL FLORA OF SOUTH SWEDEN 263 



climate, is especially connected with the precipitation. (To express this more accur- 

 ately, the connection is to be looked for in the relation between precipitation and 

 evaporation, and as the latter is primarily determined by the temperature, also 

 in a relation between tlie quantity of precipitations and the temperature). Accor- 



9 



ding to Tamm (1920, p. 227), the podsolization is very weak in the neighbour- 

 hood of Kalniar, but very strong in the south-west of Sweden. The thrown 

 soily>, a less humid soil-type characterized by the facts that soluble salts are car- 

 ried away, while the colloidal compounds are only in a minor degree carried aw^ay 

 from the upper layers, and which are characteristic of the deciduous forest region 

 in Central Europe, has also a great distribution in South Sweden (Hesselman, 

 1907 a, p. 399; Tamm, 1921). This type of soil is formed under the influence 

 of a humid, but more temperate climate. 



Of greater importance from the present point of view, however, are the edafic 

 soil-types. \x\ a climate such as that of South Sweden, which does not run to great 

 extremity the percentage of lime contained in the weathering material and the 

 water in the soil, and also topography, will in a high degree determine the forma- 

 tion of the soil. 



It has already been pointed out how the supply of lime influences the nature 

 of the soil. In South Sweden, the percentage of lime being sufficiently great, we 

 find mould soils. 



Topography is of a very great importance to the nature of the soil in clima- 

 tic transition-districts. The chemical and physical changes in the soil are greatly 

 dependent on the soil temperature. It is natural, therefore, that a southerl)- 

 exposed hillside should have a soil-type different from a level area or a northerly 

 exposed hillside, especially if it is not shaded. Kraus's well known investigations 

 in Central Germany (Kraus 191 1), have shown how, in such cases, the tempera- 

 ture of the soil may reach a very considerable number of degrees, and how the 

 nature of the soil assumes a completely continental stamp. Hesselman (1910) 

 has pointed out that the close contact of the upper layers with oxygeneos ground- 

 water promotes on the slopes the creation of forest types that produce a humus 

 cover of such a character as can counteract the process of podsolization. Tamm 

 (1920), who has made extensive examinations of soil-types in North Sweden, 

 repeatedly points out the contrasts between the nature of the soil of hillsides 

 and plateaus. In marked slopes there is often no podsolization (p. 131); and 

 again a quite normal podsolization can only be expected on level terraces, or 

 plateaus, or gently sloping hillsides (p. 133). 



In judging the nature of the soil, w-e must thus to a great extent take into 

 consideration the lime-percentage in the weathering constituents of the soil and 

 the topography. 



Soils rich in lime may consist of »soil produced in silu-» b\- weathering on calca- 



