1884.1 FOBESTAL NOTES. 359 



FOBESTAL NOTES. 



The Draining Power of Conifers; Effects of Grasses 

 AND Weeds. 



m. THINK ' An Enquirer ' may safely feel reassured with regard to 

 ffl the draining effect of coniferte in general, and of the Scotch Pine 

 ^ in particular. It is entirely beneficial, and would be better 

 described by the expressive French term for drainage, 'assainisse- 

 menty literally, the rendering sound, or sweetening of the soil, 

 than by the English word ' drying,' which might be understood in an 

 unfavourable sense as well as in a good one. 



The hygrometric function of trees is the regulation and equable 

 distribution of moisture in the air and the earth, not by any means 

 its extinction. Their leaves intercept a portion of the rain-water as 

 it falls ; the roots absorb more of what sinks into the ground, and 

 store it up provisionally in the tissues of the tree, until it also is sent 

 up into the leaves ; all to be aerated, and in due time evaporated 

 through the sfcomata. The soil is thus saved, by the continued action 

 of these organs, from excess of moisture on the one hand, from excess 

 of evaporation, due to the direct influence of burning sun and sweeping 

 winds, on the other. The number of ' Forestry ' for September, 

 1883, contained an extract from the interesting report by Mr. 

 Franklin Hough, on a number of meteorological observations taken 

 in the United States, and according to which, if I recollect rightly, 

 direct evaporation from woodland soil, covered with fallen leaves, 

 was reduced to one-fifth of what it amounted to on open ground ! 



I believe that the difference in this distributive action between 

 broad-leaved and coniferous trees is one not of kind, but simply of 

 degree ; and is, as I formerly observed, due to the fact that in winter, 

 when such aid to evaporation is most required, the vital functions of 

 the former class of trees are almost . entirely suspended, while the 

 coniferae keep up a constant circulation of moisture through their 

 tissues. 



In a young wood of Scotch Pines (at a later age the trees are less 

 numerous and their cover thinner), under the thick deposit of leaves 

 which forms a natural mulching, the ground wiU never be found 

 very wet, but always, except under very extreme circumstances, 

 sufficiently moist to ensure the well-being of the plantation. I do 

 not say there would be enough for anything else one might choose to 

 plant along with or under the Scotch Pine, for the latter takes for 

 itself all the nourishment it can get in the soil, and is, in the struggle 

 for life, ' exclusive and intolerant.' 



2 B 



