PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



181 



EROSION none 



INFILTRATION 



RATE o q 



(cm/hr) 



minor 



moderate 

 0.3 



severe 

 1.1 



vv 



SANDY LOAM 



: : : : : : : : : : : : : :v:vAv:-:v»«^^^»»wfw-w(y 



LOAM 



i 



CLAY 



Figure 10. — Diagrammatic representation of changing surface infiltration characteristics and texture at different 

 stages in scald formation on a red-brown earth, 32 km. W. of Condobolin, N.S.W. (Modified after Stannard 



(6-0).) 



greater wind erosion to take place. As successive 

 soil layers are exposed, the poorer infiltration 

 rates lead to greater runoff and water erosion, 

 and a more homogeneous and unfavorable habitat 

 for annual plant growth. Finally, a near uniform 

 surface of smooth, self-sealing, clay-loam soil 

 with a low infiltration rate results. Little oppor- 

 tunity exists in this microenvironment for seed 

 lodgment; maximum water penetration is about 

 15 cm. ; and a high chloride content occurs near 

 the surface. Thus, while erosion of soil is a fairly 

 obvious feature, interactions of stock with other 

 components of the microenvironment contribute 

 at all stages of degeneration. 



Maintenance Of Microenvironmental Diversity 



Maintenance of microenvironmental diversity is 

 important for the regeneration of plant commu- 

 nities and conservation of landscape stability for 

 several reasons. The role of perennials is well 

 recognized in creating diversity and thereby in- 

 fluencing community regeneration (25, 49) and 

 conserving landscape stability (40, 41, 43)- The 

 combination of contrasting environments closely 

 juxtaposed provides habitats for the growth and 

 population maintenance of the ephemeral con- 

 stituents of the community. In the absence of di- 

 versity in a uniform environment some, and occa- 

 sionally (as with scalds) all, of the component 



species of the plant community may disappear or 

 be considerably reduced in their contribution. 



Some of the contrasting factors in the peren- 

 nial-between-perennial mosaic of environments 

 have already been cited, including temperature, 

 nutrient, and water balance differences. Soil tex- 

 ture differences can also occur with mounds of lo- 

 cally accreted mineral soil and organic material 

 beneath shrubs providing more favorable seed- 

 beds than the soil of intershrub areas. With stock 

 trampling and grazing in the intershrub areas, 

 these habitats can provide refugia for the growth 

 and seeding of plants, the regeneration of which 

 would otherwise be reduced in the community 

 (6). Loss of such refugium environments can 

 consequently represent an important stage in 

 environmental degeneration. 



Ability Of Microenvironments To Recover 



Perhaps of prime importance in attempting to 

 influence management of rangelands from the 

 viewpoint of stock-microenvironment interaction 

 is the ability to recognize those situations in 

 which the soil-plant-animal complex has the ca- 

 pacity to recover from adverse stock-microenvi- 

 ronment interaction or even resist adverse inter- 

 action, and those situations where recovery is un- 

 likely. It would be particularly useful to know, 

 for any pastoral land-use situation, which stock- 



