coville: formation of leafmold 83 



an alkaline leafmold. The chief factors that contribute to the 

 acceleration of leaf decay have already been enumerated, but 

 there are other conditions of nature that obstruct and retard this 

 process. Under certain conditions the progress of decomposi- 

 tion may be permanently suspended long before the alkaline 

 stage is reached. The soils thus formed, altho high in humus like 

 a true leafmold, have an acid reaction and a wholly different 

 flora. 



Examples of such suspensions of leaf decay are found in bogs, 

 where the deposited vegetation is protected from the organisms 

 of decay by submergence in non-alkaline water, and on uplands 

 where the soil is derived from sand, sandstone, granite, or schist, 

 in which there is not enough lime or other basic material to 

 neutralize the acidity of the decaying leaves. 



There is of course a supply of lime in the leaves themselves, 

 and as a new layer of leaves is added to the soil each year it 

 might be expected that there would result an unlimited concen- 

 tration of lime in the surface soil and that all surface soils that 

 supported a growth of vegetation would ultimately become alka- 

 line. Such an indefinite accumulation of lime is prevented, how- 

 ever, by another factor which requires consideration. As soon 

 as each successive layer of leaf litter is sufficiently decayed to 

 permit the roots of plants to enter it and feed upon it, the lime 

 it contains, together with other mineral constituents, begins to 

 be absorbed. This loss of lime from the decaying leaves is suffic- 

 ient, under many situations in nature, to prevent the decaying 

 mass from reaching the alkaline stage. Decomposition is sus- 

 pended while the leaf litter is still acid. True leafmold, with an 

 alkaline reaction, is never formed under such conditions. The 

 leaf deposit remains permanently acid and such areas bear an 

 acid flora. In the vicinity of Washington one often sees hills 

 of quartz gravel, wind-swept and rain-washed, where the soil 

 contained little lime in the beginning, and none could be brought 

 by flood waters or by the dust of the atmosphere. Character- 

 istic plants of such hills are black jack oak, trailing arbutus, wild 

 pansy, azalea, and huckleberry, all plants adapted to acute con- 

 ditions of acidity. If one's front yard happens to coincide with 



