DISADVANTAGES FROM UNFAVOURABLE SOIL, &C. 45 



CHAPTER Y. 



DISADVANTAGES ARISING FROM UNFAVOURABLE SOIL AND 

 SITUATION. 



A. EXCESS OF MOISTURE ; WETNESS. 



28. Causes of Surplus Moisture in the Soil ; Disadvantages 

 due to the Same. 



Wetness, or excessive moisture in the soil, a condition that 

 is not infrequently to be met with in woodlands, may be due to 

 one or other of various causes. It may be caused either in con- 

 sequence of springs without any proper off-flow channel ; or it may 

 be due to plastic, clayey, impermeable subsoil hindering and 

 rendering impossible the percolation towards deeper layers of 

 the atmospheric precipitations and of the water formed by the 

 melting of snow on the ground ; or finally it may be the result of 

 temporary inundations, after the subsidence of which there has 

 been no suitable means of a portion of the water draining off 

 again. Stagnation of water in the soil may also be caused by the 

 undue increase of soil-moisture percolating horizontally from 

 neighbouring water-channels, or lakes, or ponds in the immediate 

 vicinity. When there is a high degree of wetness, the soil be- 

 comes a marsh, log, or swamp. 



The vegetation forming the soil- covering offers a ready practical 

 means of estimating off-hand the amount of superfluous moisture 

 contained in the soil, and the ruling degree of moisture generally. 

 The occurrence of Bulrushes (Scirpus) and Eushes (Juncus) already 

 indicates stagnating moisture, as also the common Wire Bent 

 or mat grass (Nardus), and the Hair-moss (Polytrichum) ; Sedges 

 (Carex), Cotton-grass (Eriophorum), and Knot-grass (Polygonum) 

 show a still higher degree of wetness ; whilst Bog-moss (Sphagnum), 

 in association with Cranberry and Bog Bilberry (Vaccinium 



