CHAPTER XIV 



The Non-Protozoan Fauna of the Soil 



Animal ecology as a whole and classification of soil forms. In addi- 

 tion to protozoa, other groups of invertebrate animals inhabit the 

 soil, namely, the rotifers, nematodes, annelid-worms, insects and others. 

 Such animals which live in the soil can be generally divided into three 

 groups : 



1. Those that spend all their life in the soil, coming to the surface only oc- 

 casionally or not at all. These include various worms and rotifers. 



2. Those that spend only a part of their life cycle in the soil or on its surface, 

 as in the case of various insects. 



3. Those that find only their habitat in the soil, while they may spend a large 

 part of their time on the surface of the soil. These include ants, termites and 

 many insects. 



These organisms influence directly or indirectly various soil processes 

 and plant growth: 



1. They cause a change in the physical condition of the soil, by modifying 

 the mechanical structure of the soil, through their continued motion or by pass- 

 ing the soil through their bodies as in the case of earth worms. 



2. They cause various chemical changes in the soil, either directly, in their 

 digestive processes, or indirectly, by influencing the activities of the soil fungi 

 and bacteria. 



3. They bring about a more uniform distribution of various soil bacteria 

 and other organisms. 



4. They may devour other members of the soil flora and fauna, like algae, fungi 

 and protozoa. In this way, the higher fauna also contributes to the complex 

 system of numerous activities going on in the soil. 



5. Damage may be done to crops by certain representatives of these groups, 

 particularly by some of the nematodes, earthworms, insects, etc. 



The soil or terrestrial fauna, outside of the protozoa, includes mem- 

 bers from the following systematic groups: 



I. Plathelminthes or Flatworms, represented in the soil, in moist environ- 

 ments, by the (1) Turbellaria or flatworms and (2) Trematoda or flukes. 

 II. Nemathelminthes or Roundworms, represented in the soil by the Nema- 

 toda or true roundworms. 



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