PROBLEMS FROM LAND OCCUPANCY 169 



not decreased infiltration capacity or increased runoff and erosion. 

 Soils, topography, rainfall intensity, and extent of vegetative re- 

 covery — all factors affecting runoff and erosion — vary so widely 

 that no single rule can be applied. We conclude that on the basis 

 of our present information burning can be neither supported nor 

 condemned for all conditions and situations in the California 

 brush and woodland-grass ranges or watersheds. 



Our available experimental data do not provide a basis for a 

 conclusion that burning of the ranges in northern California is 

 adverse to water conservation. Even where the data show increased 

 surface runoff immediately after burning, the amount of the in- 

 crease in the northern California experiments is but a small per- 

 centage of the total rainfall and of the total water supply if ap- 

 plied to a large area. The soil moisture studies in the northern 

 California experiments showed more moisture at the end of the 

 summer in the burned plots than in the covered plots, since the 

 soil moisture of all plots was raised to field capacity by the winter 

 rains and transpiration was greater on the covered plots. The 

 percentage of total precipitation represented by the surface runoff 

 from the North Fork plots in central California was greater than 

 in the northern California experiments. But whether this in- 

 creased surface runoff, if applied to a substantial portion of a 

 watershed, would reduce usable runoff is not clear. We believe 

 that a much more thorough study of the relation of brush burning 

 in northern and central California to water conservation is needed 

 before fully accepting the assumption that it is a vital factor. We 

 of course realize that some people — especially foresters and soil 

 conservationists — associate range burning in northern and central 

 California with floods, but we have not dealt with this question 

 and know of no experimental or other precise data linking range 

 burning in northern and central California with floods, from 

 which a conclusion can be drawn. We draw no conclusion as to 

 the relation of burning to water conservation and floods in south- 

 ern California, since the areas from which we have presented im- 

 portant data are not used for grazing and hence are not directly 

 involved in the range-burning problem. Extensive chaparral 

 and woodland-grass areas in Riverside and San Diego Counties 

 are used for grazing, but no definite conclusions are yet justi- 

 fied from the recently installed experiments in Riverside County, 

 nor do the observational data from the Moreno Reservoir silta- 



