GEOGKAl'Jl V AX I) \ EGK'IATIOX OF XUKTJIKUN I-I.ORIDA. 1/7 



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METHODS OF QUANTITATIVE ANALYSIS OF VEGETATION. 



Up to ten or twelve years ago nearly all descriptions of vegetation were 

 qualitative, and usually very incomplete besides. Toward the close of the 

 last century, when the importance of quantitative studies was becoming appar- 

 ent, botanists in the neighborhood of the Great Plains, where the vegetation is 

 mostly prairie, devised the scheme (commonly known as the quadrat method) 

 of counting all the plants on a measured area of ground (usually a meter 

 square in grass-land, or ten meters in forests), repeating the process at several 

 different places in the area studied, and then consolidating the returns. But 

 where plants grow in tufts or colonies, like most grasses, it is practically 

 impossible to cqunt them ; and after all it is not the number of individuals 

 that is significant so nnich as their size. (For the productivity of a forest, 

 orchard or field is not expressed in number of trees, stalks of corn or cotton, 

 or hills of potatoes, but in cords of wood, feet of lumber, gallons of turpentine, 

 boxes of oranges, bushels of corn, bales of cotton, etc.) This objection to 

 the quadrat method could of coufse be met by pulling the plants up and weigh- 

 .ng them, but even in its present form it would take an enormous amount of 

 time to apply it to a whole state or even a county. 



F"or many years foresters have been estimating timber by counting and 

 measuring all the trees on selected typical areas, of an acre or so, and repeat- 

 ing the process at intervals over the whole tract that is being investigated. 

 This method is ideal in its way, and has already been applied to small areas 

 in Florida, but it is entirely too slow for present purposes. 



be better supplied with calcium than that of some of the interior states where 

 deciduous trees are most prevalent, and limestone is particularly abundant in 

 extreme southern Florida; but in that part of the state the potassium content 

 of the soil is below the state average, and the vegetation is nearly all ever- 

 green. 



For further information on tliL- suljject of the relation of potassium to veg- 

 etation the interested reader should consult an article by Dr. H. W. Wiley 

 on "Potash and its function in agriculture'' in the Year-book of the U. S. 

 Department of Agriculture for 1896, pp. 107-1,^6. and a short note by the same 

 author in Science (II. 17:794-795) for May 15. 1903. The writer has published 

 some observations on this point in (Jeol. Surv. Ala. Alonog. 8:28-29. 1913; 

 'J'orreya 13:140-141. 1913; Bull. Torrey Bot. Chib 40:398. 1913 ; 41:218, 1914; 

 Rep. Mich. Acad. Sci. 15 :i97. 1914. 



Plants of the heath family (Ericaceae) seem to bear much the same rela- 

 tion to potassium that evergreen trees do, but may be influenced also by calcium ; 

 while the majority of leguminous plants ( Leguminosae), as well as those be- 

 longing to the large families Euphorbiaceae and Compositae, seem to prefer dry 

 soils poor in nitrogen, but well supplied with mineral plant food. Grasses evi- 

 dently prefer richer soils than sedges, but just what elements are significant in 

 these cases has not yet been determined. In all investigations of this character it 

 is essential to have quantitative data, for in the families named there are many 

 species that are exceptional in their soil preferences, so that the mere presence 

 or absence of several species belonging to one of these families might not 

 have much significance: but by consolidating the figures for each family in a 

 given area a number is derived which ought to be fairly constant for all 

 places where conditions are essentially the same. 



