REPORT OF THE FORESTER. 181 



Many of the National Forests include watersheds which supply 

 large irrigation projects with water. Closely bound up with the pro- 

 tection of such watersheds is the erosion problem. Many streams 

 carry such enormous quantities of silt that the storage capacity of 

 reservoirs is impaired seriously within a relatively short time, while 

 an expense is involved in keeping the diversion works free from an 

 excess of this material. Closely connected with excessive erosion 

 is rapid run-off. A study to determine in what way the adminis- 

 tration of the National Forests can keep the destructive processes 

 of erosion on these watersheds at a minimum showed the balance 

 between stability and rapid erosion of slopes often to be so delicate 

 that slight abuse may result in complete loss of the fertile top soil 

 and permanent changes in the character of the vegetation. Pre- 

 ventive measures, such as the regulation of grazing, conservative 

 cutting of timber, and prevention of cultivation of nonagricutural 

 soils, were shown to be much more effective and less costly than 

 remedial measures. 



In the more strictly technical studies dealing with the reforestation 

 problems on the National Forests and elsewhere, further progress 

 has been made. The study of artificial methods of extracting the 

 seed of lodgepole pine from its cones has been completed, and valu- 

 able data obtained on the effect of different temperatures on the 

 opening of the cones and on the quality of the seed. Probably the 

 most important single point established is that lodgepole pine seed is 

 usually not affected by drying temperatures up to 150° F., and may, 

 in fact, germinate better after such treatment than seed obtained by 

 air-drying, provided the kiln is properly constructed to insure free 

 ventilation. 



The study to find a relation between germination of seed in the 

 greenhouse and in the field has been practically brought to com- 

 pletion. The analysis of hundreds of greenhouse tests seems to show 

 that in the greenhouse the rate and vigor of germination is affected 

 mainly by the quality of the seed and not by its source, while in the 

 field just the opposite is true. 



Tests to show the effect of the source of seed on form and growth 

 of trees indicate very clearly that with all species the seed grown in 

 the locality where the trees are planted give, as a rule, better re- 

 sults than seed imported from another region. 



Important advance was made in the studies of nursery practice. 

 Experiments are establishing the optimum spacing for the develop- 

 ment of the best and cheapest plant ing stock. Experiments in 

 grading seedlings at the time of transplanting brought out the need 

 of a radical revision of our grading standards. Present standards 

 do not eliminate the seedlings most likely to succumb in the trans- 

 plant beds. 



Experiments were made to determine the amount of seed to sow 

 in nursery beds and the depth to which the seed of sugar pine, west- 

 ern yellow pine, Jeffrey pine, Douglas fir, white fir, incense cedar, and 

 bigtree could be most advantageously covered. 



Studies of the comparative value of burlap and pine-needle mulch- 

 ing in the growing of western yellow pine, sugar pine, Jeffrey pine, 

 Douglas fir, white fir, and incense cedar showed that burlap as a 

 mulch for spring-sown seed beds is in most cases superior to pine 



