152 E.B.OKSBJERG 



place, not even in the uppermost layers, did it approximate to wilting 

 capacity. In the summer of 1957 no substantial fluctuations occurred in 

 the water content except for a sHght and nearly uniform decrease in the 

 uppermost 50 cm. The field capacity of the profile to a depth of 85 cm is 

 about 215 mm and the wilting capacity ca. 100 mm. 



CONCLUSION 



The investigations of soil moisture show that Norway spruce during severe 

 drought does not exhaust the accessible soil water to the depth of the 

 deepest roots, except in one example, in a former field soil. In older 

 plantations, especially on podsoHsed soils the spruce roots become more 

 and more superficially situated or concentrated in some 'rootfriendly* 

 horizons. 



But also young plantations show-e.g. in comparison with oak- a very 

 ineffective water uptake which sometimes can be an advantage. As an 

 example I shall mention two young stands, one of spruce and one of oak 

 [Qnercus rohur (L.)), growing side by side in Silkeborg Forest district in 

 Central Jutland. In the summer of 1955 some of the spruce plants died 

 about 20 July, and by 28 July 8% had died. After that none of the spruces 

 died even though drought and heat continued. Until 28 July not a single 

 oak had died- on the contrary they seemed to appreciate the heat-but 

 in the first week of August the whole plantation of oak died. No examina- 

 tions of soil humidity were undertaken in a quantitative sense but the soil 

 under the oaks was considered to be completely desiccated whereas it was 

 evident that some humidity was left in small pockets under the spruces. One 

 got the impression that the spruces were already thirsting by the middle 

 of July whereas the oaks had grown well until the last days of their hfe. 



REFERENCES 



Oksbjerg, E.B. (1956) Sommervejrct 1955 pa en midtjydsk lokalitet og torkens 

 virkning pa parceller med tidligt og sentudspringende rodgraner. (English 

 summary-The weather of the summer 1955 and the effect of the drought upon 

 plots with early and late flushing Norway spruce.) Datisk Skovforcnitigs Tids- 

 skr. 41, 273-302. 



Oksbjerg, E.B. (1958) Udspring og torketalsomhed. (Enghsh summary -Flushing 

 time and drought resistance.) Dansk Skovforenings Tidsskr. 43, 292-307. 



Oksbjerg, E.B. (1961) Transpiration of growing shoots in Norway spruce {Picea 

 abies) with some notes on drought phenomena. St'ensk Bot. Tidsskr. 55, 397- 

 415. 



Penman, H.L. (1956) Estimating evaporation. Trans. Arner. Geophys. Utiion, 37, 43-5°. 



Walter, H. (193 i) Die Hydratur der PJianze.Jen^. 



