USE OF ANNUAL PLANTS IN CALIFORNIA FOOTHILLS 43 



of the old litter, or condition of the soil surface, is best observed during 

 the winter, when the beneficial effects of a protective soil covering are 

 most apparent (fig. 17). The layer of litter is not so readily observable 



F-460561 



Figure 17. — Appearance of foothill range in January — the time of year when condition 

 of the soil surface is best rated. 



during the spring because it is more completely masked from view by 

 vegetation. Then, too, differences in grazing during the preceding 

 months affect plant height in the spring so as to obscure the effects of 

 soil-surface condition on plant vigor. During the winter months, how- 

 ever, both the litter layer and the vigor of new plant growth can be con- 

 sidered as indicators of the productive condition of California foothill 

 ranges. 



A foothill range with unsatisfactory soil-surface condition has very 

 little decomposing herbaceous material on the soil surface, and the sparse 

 and stunted plant growth provides only a thin vegetative cover. Mineral 

 soil is readily apparent during the winter months over all of the range in 

 unsatisfactory condition. The hard, exposed soil surface inhibits the 

 establishment and growth of annual-plant seedlings. 



There are other indicators of unsatisfactory conditions. The mineral 

 soil is commonly covered with a short growth of moss, lichen, or plants 

 of similar appearance. The thin, black humic layer that ordinarily 

 covers the mineral soil may disappear after the overlying herbaceous 

 layer is lost. A miniature erosion pavement is often formed as a result of 

 loss of organic matter and possibly of some fine mineral soil. After heavy 

 rains, local movement of soil particles is evident in the tiny terraces that 

 are formed even on gently rolling slopes, and particularly on south slopes. 



Even so, accelerated erosion may not be readily apparent on foothill 

 ranges with unsatisfactory soil-surface condition. Close examination may 

 reveal slow insidious movement of the soil, as in closely grazed pasture 3 r 



