594 JOURNAL OF FORESTRY 



On the basis of such data it is possible to state authoritatively whether 

 or not a change should be made in a given system of management. 



llie Quadrat 



Regardless of the experience the ecologist has had in successional 

 and revegetational studies, he cannot determine with precision the 

 successional trend of vegetation subject to more or less close grazing 

 season after season. Accordingly the quadrat method of study has 

 been developed to furnish authentic records of the vegetative changes. 

 Three methods of mapping or quadrating are usually employed: (1) 

 the chart quadrat in which the exact location of each plant specimen 

 is shown as it occurs naturally on the plot, (2) the list quadrat in 

 which the abundance and composition of the vegetative cover are 

 merely listed regardless of exact location, and (3) the denuded or 

 depopulated quadrat in which the vegetation is completely removed 

 and the subsequent invasion and succession recorded. These differ- 

 ent kinds of quadrats have particular merits in revegetational studies 

 and are applicable to special conditions. 



Analysis of the Data 



To obtain reliable data by means of the quadrat is one thing, and 

 to analyze and crystallize the data into tangible and usable form is 

 quite another. In range revegetational work it has been found help- 

 ful to divide the data obtained from the various quadrats in three 

 groups: (1) those showing progressive or positive succession, (2) 

 those upon which the succession is retrogressive or negative, and (3) 

 those upon which the succession is problematic or indifferent. Pro- 

 gressive or positive succession pertains to the invasion and establish- 

 ment of species having a forward march towards the climax type. 

 Retrogressive or negative succession has to do with vegetative inva- 

 sions that go back or away from, rather than towards, the ultimate 

 type — in other words, invasions characterized by the establishment 

 of transitory and possibly more primitive species, such as character- 

 istically occupy newly formed and depleted soils. Problematic or in- 

 different successions pertains to vegetation whose successional trend 

 cannot be declared either as positive or negative, but merely marking 

 time as it were. 



From revegetation studies conducted by various investigators it 

 is now well known that certain species inhabit newly formed, depleted, 

 and sterile soils while quite different species predominate on the older 

 and richer soil types. During the past season several cultivated and 



