ON THE DISTRIBUTION OF THE PRECIPITATION 



IN A SPRUCE STAND 



AN ATTEMPTED ANALYSIS 



M. G. Stalfelt 

 University of Stockholm, Sweden 



An attempt was made to analyse the water economy of a natural plant 

 community. This was done by measuring the water supply to the root 

 zone and the water uptake through overground organs, as well as by 

 measuring the distribution of the precipitation by transpiration, interception 

 and surface run-oft'. 



For this purpose, I chose a plant community of simple composition, 

 namely, a spruce wood, in which the tree layer consisted only of spruce 

 {Picea excclsa Link.) and the remainder of the higher vegetation was chiefly 

 in the form of mosses. The stand was about 40 years old, and was not 

 completely closed. The trees covered about half the ground surface. The 

 other half-that is, the gaps between the trees-was covered mainly by 

 Hybcomium species. Mosses grew near the periphery of the surface under 

 the tree canopy; otherwise, there was only a htter of needles, pieces of bark, 

 twigs, remains of cones, etc. 



The site was in southern Sweden (Scania). It is a low-hiHed moraine, 

 .e., an imstratified, unsorted glacial deposit, of which about half consists 

 of fens and bogs. The other half-the low hills-is covered by woods. 



Transpiration was measured in 11 spruces; these are denoted in the 

 following as the experimental trees. Three of them grew on the edge of a 

 fen, with the water table about 0-2 m below the base of the tree stems. The 

 remaining trees grew on the moraine hills, and had a distance to the water 

 table ranging from 2 to 7 m. 



Precipitation was measured on the open ground, as well as below the 

 crowns of the trees, and in the gaps between the trees. Triangular troughs, 

 with a length equal to half the diameter of the crown, were placed under 

 the crowns. Their opening measured 53-66 dm^. The apex of the triangle 

 lay close to the stem of the tree, and the base in the periphery of the crown. 

 The triangular shape was chosen in view of the fact that the quantity of 

 water penetrating the crown of a spruce differs in the peripheral and central 

 parts of the ground covered by it. The quantity increases from the centre 

 outwards, and is relatively great under the tips of the branches. 



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