or 



FORESTRY 



COtLEQE Of & AGKJCUlTUffe 

 <INIVC*SITY,OF CALIFORNIA 



THE QUADRAT METHOD AS APPLIED TO INVESTI- 

 GATIONS IN FORESTRY.* 

 Arthur W. Sampson '07. 



It is the aim of phytogeographers as well as descriptive and 

 ecomonic ecologists, I believe, to determine as definitely as possi- 

 ble the relationship existing between plant associations or other 

 vegetative units and their environment. The role which the 

 quadrat method of study plays in the incidence of the environ- 

 mental factors and the corresponding adjustment of the vegeta- 

 tion, while indirectly determined, is of high significance under 

 varied field conditions. Its importance may probably best be 

 appreciated by first pointing out the complications involved in 

 the study of the direct influence of the physical factors upon 

 vegetation. 



RELATION OF HABITAT FACTORS TO VEGETATION. 



The habitat of a plant is admittedly a rather indefinite thing 

 so far as concerns the factors which have to do with the limita- 

 tions and causations of life processes. While the structural 

 ecologist has shown fairly conclusively that a given plant asso- 

 ciation has well defined geographical limits, which, in turn, are 

 represented by rather distinct complexes of environmental con- 

 ditions, he has not, as yet, determined which factor or set of 

 factors are most influential in affecting association limitations 

 or physiological functions. Before this can be done, as pointed 

 out by Livingston,** the potent factors making up a given environ- 

 ment (the controlling factors would not be the same in the case 

 of all habitats) must be recognized; and once they are known, 

 the part they play in affecting readjustment of the internal and 

 external structure of the plant, and thus in affecting distribution, 

 must be determined. 



Obviously for purposes of study, the complexes of the en- 

 vironmental factors must be reduced to their simplest form, a 

 matter which may be accomplished by maintaining constant all 



*Published by permission of the Secretary of Agriculture. 

 **Livingston, B. E. and G. J., Bot. Gaz. 56: 349-375, 1913. 



