TlMBERLINES 



47 



(3) Where neither beach grass nor 

 heather is available, or where the con- 

 ditions are especially severe, sand hedges 

 are used. These consist of rows of cut 

 brush or stakes or of cut reeds, which 

 are inserted in the sand in rows or quad- 

 rangles, allowing the upper end to pro- 

 ject for six inches or more. 



After the sand is temporarily fixed by 

 one of these methods young trees, usu- 

 ally conifers, are transplanted, and the 

 forest soon removes all danger of further 

 shifting. In southwestern France the 

 forest was established by sowing the 

 seed of Pinus maritima upon the sand 

 and covering with brush, but this method 

 has not been successful in northern 

 Europe. In France, and also the Ku- 



rische Nehrung, in Prussia, it has been 

 found necessary to form artificially a 

 long barrier dune between the ocean 

 and the forest which protects the lat- 

 ter. This barrier dune is fixed by 

 means of beach grass, but requires con- 

 stant oversight to keep it in order. Dur- 

 ing severe storms dangerous breaches 

 are formed, which, if neglected, would 

 soon destroy the dune and seriously in- 

 jure the forest in its lee. These breaks 

 are mended by sand fences such as 

 already described, but taller, which 

 rapidly accumulate the sand until the 

 hole is filled. 



The trees used in northern Europe 

 are chiefly Pinus montana, P. laricio, 

 P. austriaccC, and P. sylvcstris. 



TlMBERLINES 



By Israel C. Russell, of the University of Michigan 



IN the February number, 1903, of the 

 National Geographic Maga- 

 zine I proposed the terms cold tim- 

 berline, dry timberline \ and wet timberline 

 by which to designate respectively the 

 three principal boundaries of forests. 

 To this nomenclature Dr C. Hart Mer- 

 riam records a protest in the March 

 number of the same publication. 



The principal objection advanced by 

 Dr Merriam is the time-honored use of 

 the word timberline as a name for the 

 upper limit of tree growth on moun- 

 tains. To employ the word in any 

 other connection, as he states, deprives 

 it of "its fixed and definite value." 

 He also directs attention to the fact 

 that the lower limit of tree growth in 

 arid regions, or what I have termed the 

 dry timberline, is in certain instances 

 determined by temperature and not by 

 lack of humidity. 



During the past summer I made an 

 extended journey in Oregon, where 



both the upper and lower limits of the 

 forests are well defined, and was en- 

 abled to test the nomenclature referred 

 to in a typical region. On account of 

 this added experience, but fully appre- 

 ciating the value of the criticisms ad- 

 vanced by a leader in a science closely 

 related to physiography, I take this op- 

 portunity to explain, perhaps more fully 

 than in my previous communication, 

 my reasons for claiming recognition for 

 more than one timberline. 



There can be no controversy as to 

 the fact that forests on high mountains 

 frequently terminate abruptly at their 

 upper limit, or that in certain portions 

 of arid regions they have an equally 

 well defined lower limit. The question 

 is : Shall we ignore the lower boundary 

 or give it a place in geographic no- 

 menclature, and if admitted to be of 

 sufficient importance to require a name, 

 how shall it be designated ? 



Although the conditions which draw 



