THE WOODLOT 31 



woodlot, may cause the soil to deteriorate or may endanger 

 the future of the woodlot. No attempt should be made to 

 make a woodlot park-like. Forest trees grow best under wild 

 and natural conditions. 



The Forest Floor. — The forest floor consists of the ground 

 cover of weeds and grass and the underlying mulch of more 

 or less decomposed leaves called the humus. Where the ground 

 cover is not thick, the weeds and grass being scattered here 

 and there, it does but little damage and may even have a 

 beneficial effect in helping to protect the soil and prevent 

 evaporation when the canopy is thin. But where this growth 

 is very thick, as is usually the case where there are but few 

 trees in the woodlot and the canopy is broken, it will absorb 

 moisture and nutriment from the upper layers of the soil 

 and so lessen the growth of the trees. It will also tend to 

 prevent new trees from starting or if any start will suppress 

 them by their shade. 



Beneath the ground cover and above the soil is an accu- 

 mulation of leaves and twigs called the humus. This is usually 

 in several layers. The upper layer is composed of leaves of 

 the last year pressed down by the snow and flattened by rain. 

 Underneath this is a matted layer of leaves partly decomposed. 

 These layers together are usually called the litter. Just above 

 the mineral soil is found a black, powdery substance, the result 

 of the rotting of the leaves and twigs. This black powder 

 or humus mixes with the soil and where present in consider- 

 able amounts darkens it, often making it black like muck. 

 Humus acts as a fertilizer to the trees. It improves the soil 

 both chemically and physically. The decay of the leaves 

 and twigs sets free many salts which are immediately avail- 

 able as food for the tree. Being a vegetable substance, 

 the humus will absorb and hold water like a sponge, giving 

 it out gradually as needed by the trees. 



The humus, or duff as it is often called, will vary in thick- 

 ness according to the conditions under which it accumulates. 



