APEIL 17, 1903.] 



SCIENCE. 



605 



APPLIED ECOLOGY. 



Ecology as a special branch of botanical 

 study has been segregated from the broad- 

 er field only in recent times, the name hav- 

 ing been first suggested by Hackel some 

 twenty-five years ago. But like many 

 phases of human knowledge, practically 

 the study of ecology, that is, of the adapt- 

 ation of plants to their surroundings, has 

 occupied man these hundreds of years. 

 Long before the study of ecology assumed 

 the dignity of a science did practitioners 

 not only study but apply their knowledge 

 for practical purposes in the production 

 of plants. Agriculture and, still more so, 

 silviculture are based upon the recognition 

 of the ecological relations of plants. 



The agriculturist goes so far as to create 

 the oiy.o<s, the environment, and hence 

 needs less knowledge of adaptation. He 

 can create an environment desirable to any 

 plant. But the silviculturist has not the 

 opportunity to the same extent to fit the 

 environment to his crop ; he must study the 

 fitting of his crop to the environment, and 

 as his crop is required to persist for a 

 century or so, adapted to both the stable 

 and variable conditions of the environ- 

 ment, the adaptations must be studied with 

 great care, so that the changes in environ- 

 ment may not prove detrimental to his crop. 

 There are many botanists, even those de- 

 voted to ecological studies, who have not 

 given thought to all the factors of impor- 

 tance in the environment which need con- 

 sideration with a plant of such long dura- 

 tion as a tree. That trees are plants, 

 unique in character and differently situ- 

 ated, as regards ecological factors, from 

 the low vegetation, has hardly been 

 realized. 



It is in the hope of stimulating develop- 

 ment in this direction and to enlist botan- 

 ists to aid the practitioners that I venture 

 to point out the directions in which more 

 light is desired by the silviculti^rist. 



Besides the general laws of ecology, which 

 establish principles of adaptation, and 

 which have been so satisfactorily elucidated 

 by Schimper, Warming and others, the 

 practitioner is especially interested in defi- 

 nite knowledge regarding particular species 

 in their adaptations to particular condi- 

 tions; he needs knowledge of the 'silvicul- 

 tural requirements' of species, which is and 

 has been for a hundred years his term for 

 ecology. 



There are stable or practically unchange- 

 able factors, and unstable or variable fac- 

 tors of environment, with which the sil- 

 viculturist has to deal. 



To the stable factors he must find the 

 crop adapted; the variable factors he can 

 to a certain extent control and shape so 

 as to secure satisfactory results. 



The stable factors of environment are 

 soil and general or local climate; the un- 

 stable are seasonal variations and certain 

 climatic conditions, plant and animal asso- 

 ciates, and light. 



As regards soil, it is first of all to be 

 considered that chemical constitution plays 

 probably only a small part or practically 

 none; the reliance of tree growth on min- 

 eral constituents being relatively small. 



For European species a long series of 

 analyses has shown a great variability of 

 ash contents according to the soil on which 

 the tree has grown, proving that a large 

 part of these contents may be simply 

 fortuitous and not essential to the growth. 

 Moreover, the total amount of mineral con- 

 stituents in a tree is not only very small, 

 but by far the largest portion is found 

 in the leaves and young parts, suggesting 

 again their merely fortuitous presence as 

 a residue of the transpiration current, and 

 mostly not required. For our own species, 

 I am not aware that any extended investi- 

 gation has been made in this respect. 



The physical conditions of the soil, es- 

 pecially with reference to water conduc- 



