REVIEWS 293 



"The question of whether it is financially better to continue to grow hard- 

 woods or to transform the present hardwood stands to conifers is still an open 

 one. That the transformation can be accomplished is proved by the results in 

 comp. 2, sub-comps. 3 and 16. By setting the conifers farther apart, using only 

 one hundred to two hundred plants per acre, the cost would be greatly reduced, 

 and virtually a pure stand of conifers eventually obtained. 



"Old-ficid type. — Wherever the stands are only partially stocked conifers are 

 planted ; otherwise the old fields are allowed to revert gradually to the hardwood 

 type. 



"Coniferous plantations. — Establishment is as yet the principal problem. The 

 young plantations must receive cleanings as needed. On hardwood land two to 

 three are required ; on pastures and meadows rarely more than one, and some- 

 times not any. A liberation cutting is often required to remove large trees 

 interfering with the conifers. 



"It is believed that thinning can be made in the coniferous stands by the 

 twenty-fifth to the thirtieth year. Pruning of selected trees will probably be a 

 profitable operation. 



"This is naturally a hardwood region and it will not be possible, in most in- 

 stances, to reproduce the planted conifers by natural means. Probably clear cut- 

 ting and replanting will be the system of management adopted." 



T. S. W., Jr. 



Gila River Flood Control. By Frank H. Olmsted. Senate Docu- 

 ment 43G, 1919. 



While not engineers, foresters may find this work of interest as it 

 considers forestry and grazing in relation to floods in the Gila River 

 drainage of the Southwest. The erosion of this stream is tremendous, 

 single storms moving the channel of the stream many hundred feet 

 and destroying a considerable acreage of fertile agricultural land. 

 Could we shorten the geological history of this stream to the length 

 of a single reel of film, the result would resemble the contortions of a 

 bunch of tortured angleworms and go through gyrations that no self- 

 respecting worm would think of doing. 



The first step in the improvement of watershed conditions "will auto- 

 matically be accomplished to a considerable extent by the control of 

 grazing" as much serious erosion has been started by overgrazing and 

 improper methods of handling both sheep and cattle. The second step 

 is the use of check dams or small retarding works located in the 

 stream channel from the headwaters of the river to below its dangerous 

 marks to lessen the velocity, control the silt carried, and to flatten out 

 the flood peak of the stream. To protect the banks from under-cutting, 

 a system of floating gates is described. Much of the construction 



