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MISCELLANEOUS PUBLICATION 1271, U.S. DEPARTMENT OF AGRICULTURE 



one interaction occurs separately. Interrelation- 

 ships exist between practically all the interac- 

 tions and certainly between all of them and the 

 plant component of the rangeland ecosystem. 

 At this stage of our poor knowledge of the inter- 

 actions themselves, commentary on interrelation- 

 ships would appear unjustified. Certainly, the 

 more subtle interrelationships as they first affect 

 the regeneration of the plant communities re- 

 main obscure. However, consideration of scald 

 formation and the reduction of habitat diversity 

 can serve to illustrate the complexity of actual 

 stock-microenvironment interactions. Also, just 

 as semipermanent degradation of the microen- 

 A'ironment can result from effects of stock so, also, 

 can examples be found of resilience in micro- 

 environments where, given apparently the same 

 treatment by stock, the microenvironment has the 

 capacity to recover. This forms the third topic 

 of discussion. 



Scalds — A Case Study Of Interacting Micro- 

 environmental Responses To Stock 



The term "scald" has been applied to practi- 

 cally level areas of ground which are denuded of 



vegetation (9) (fig. 9) and the natural regenra- 

 tion of which is slow (10, 32). A number of dif- 

 ferent types have been recognized by Beadle 

 (10) and some controversy surrounds the precise 

 stages of their formation (9, 10, 66). It is not 

 the intention here to be concerned with the dif- 

 ferent types of scald or details of their formation 

 but rather to present scalds as an end point in 

 microenvironment degradation following interac- 

 tion with stock. 



Scald susceptible country usually has texture 

 contrast soils in which layers of heavier texture 

 underlie the top, light-textured layer, and are 

 progressively poorer in their infiltration rates 

 with depth (fig. 10). Scald initiation then in- 

 volves interrelationships between stock grazing 

 and trampling, the water balance and soil sta- 

 bility components, and, perhaps, the radiation 

 mici'oclimate component of the microenviron- 

 ment. As a result, the grazed perennial species die. 

 The water infiltrating into the soil is probably 

 reduced at this stage by trampling and greater 

 exposure to raindrop action, and some soil ero- 

 sion b} T wind and by water is likely. Exposure 

 of large areas unprotected by vegetation allows 



Figure 9.— A scald 37 km. N.N.W. of Hay, N.S.W. 



