SOIL ORGANISMS 



253 



mercial product. Melin and Oden were thus able to prove that the 

 humification of the high-moor peat is considerably hastened by drain- 

 age. Humification increases rapidly from the upper levels downward, 

 as the following table illustrates: 



Table 29. — Humification of a Sphagnum fuscum High Moor in Angermanland, 



Sweden, Drained about 20 Years Previously 



(Melin and Oden) 



Humification shows a different sequence in the high moor and in the 

 flat moor. The flat-moor type has a humification number of 34 to 50 

 even in the uppermost soil layers; the high-moor type, of only 6 to 17. 



To determine the degree of humification of acid forest soils, Nemec 

 (1928) made use of a method introduced by Robinson and Jones (1925) : 

 the hydrogen peroxide method. The undecayed organic materials 

 are not decomposed by H2O2, but the humified portions are separated 

 out and decomposed by appropriate treatment by hydrogen peroxide. 



One gram of air-dry humus is mixed with 60 to 100 cc. of hydrogen 

 peroxide solution (180 cc. when the proportion of humus exceeds 75 

 per cent) and boiled for 10 to 15 min. Then the combustible material 

 is determined. To determine the degree of humification the quantity 

 of material decomposed by the H2O2 is compared with that obtained by 

 the incineration method, and the result expressed as a percentage. For- 

 est soils with Calluna and Cladonia show 43 per cent humification, soils 

 with Vaccinium myrtilhis give 52 per cent, while the forests with Oxalis 

 acetosella prove most favorable for humification reaching 74 per cent. 



Pallmann (1931) has given a simple method for separating the 

 dispersed humus from the non-dispersed and for estimating the quan- 

 tity of dispersed humus. It seems necessary to make this distinction, 

 for Pallmann shows that the pH varies directly with the dispersed 

 humus content. 



