128 E. R. C.REYNOLDS AND L.LEYTON 



Table i 



Throughfall distribution patterns under young Spruce, 1959 

 y= throughfall in inches, x— distance from tree stem in inches 



* Significant at o-i% level, t at 1% level and % at 5% level. (Gauges not moved 

 between 10-6 and 30-7.) 



the canopy (see Fig. i). However, perhaps the most marked discontinuity 

 in the pattern of throughfall occurs near the stem where water trickhng 

 down the trunk is concentrated over a small but iU-defmed area around 

 the base. Stem flow has been measured on twenty trees selected at random 

 within the stand. If we express this part of the throughfall arbitrarily in 

 terms of the projected area of the trunk at \\ ft, i.e. 'breast height' 

 (B.H.), the mean stem flow (Table 2) varied between four and twenty 

 times the incident rainfall. 



IMPLICATIONS OF THROUGHFALL DISTRIBUTION 



During certain periods, the uneven distribution of throughfall below a 

 forest stand wiU lead to an uneven distribution of soil moisture and this may 

 have some important consequences ; however, surprisingly few systematic 

 investigations have been made into this phenomenon. Voigt (i960) 

 investigated the effect under considerably larger trees of the species Tsuga 

 canadensis and Vinus resinosa, using fibre-glass resistance units at four depths 

 down to two feet, at each of five points along a radius of the tree crown. 

 With Tsuga, stem flow increased soil moisture near the trunk, but only at 

 shallow depths; with Finns, although stem flow itself had no measurable 

 effect, increasing throughfall with increasing distance from the tree was 

 reflected in increasing soil moisture even down to a depth of two feet. 



