812 JOURNAL OF FORESTRY 



seedling growth that came in was on soil not badly eroded in the first 

 storms. The species which were so represented and the proportion 

 they formed of the seedling growth on the plots laid out is as follows : 



Species Per cent 



Adenostoma f asciculatum 42.4 



Arctostaphyllos patula 17.1 



Ceanothus crassifolius 37.1 



Cercocarpus parvifolius 2.4 



The effect of plant cover in preventing soil erosion was well demon- 

 strated. Over a large part of the area under the chaparral cover grow 

 a number of small "moss-ferns" (Gymnogramma triangularis, Pellaea 

 andromedae folia, P. ornithopus). These plants, while absent in 

 heavy mixed stands, are nearly always present on the thin soils and 

 -under the scanty cover condition of the almost pure stands of Aden- 

 ostema at the lower elevations. On these shallow soils and unfavorable 

 sites these plants form an almost continuous carpet, protecting the 

 underlying soil from washing. The root systems are exceedingly fine 

 and decidedly fibrous and, while only going to a depth of four inches, 

 are difificult to tear apart. Such a heavy turf prevents any soil loss 

 as long as it is not broken ; but once the surface is broken, erosion takes 

 place readily by undercutting. Other plants act similarly but they 

 usually do not form so heavy a sod though there are many species. 

 Most of these plants have either a very light seed capable of being 

 blown over long distances, or a seed with a very hard and impermeable 

 seed coat which can endure heat for a short time without injury, and 

 can lie dormant for a considerable period. 



On eroded soils very few herbaceous plants of any species can be 

 found, the presence of a plant being largely due to the accidental 

 factor of catchment, as against a burned stool, stone or twig, or to 

 the accidental factor of the action of fire in passing lightly over a patch 

 of litter and not burning the compacted litter at the surface of the 

 soil. In such places the species which came up were the same as 

 given in the list following though their occurrence was conditioned by 

 chance. 



On non-eroded soil, the ground \\''as often entirely carpeted and the 

 stand of annuals complete. Other places, some species were not so 

 well represented as on others probably because of the factors of 



