10 



better hardwood seedlings creep in until a stand of the climax 

 or better second growth hardwood type results. If cut before 

 thirty years of age a second inferior stand of sprout origin 

 follows the first. 



COLLECTION OF DATA 



The forty-eight sample plots, containing over 18,000 trees, 

 upon which the accompanying yield tables are based were 

 carefully selected over an area of 175 square miles in northern 

 Worcester County, Massachusetts. Only fully stocked nat- 

 ural stands of even age were measured. The individual plots 

 were either one-quarter or one-half acre in area, being strips 

 one chain wide and two-and-one-half or five chains long. All 

 trees two inches and over in diameter breast high were 

 calipered and tallied in inch diameter classes by species and 

 the merchantable logs recorded by diameter and species as in 

 timber estimating. The heights of several trees in each 

 crown class were taken and a partial forest description made 

 upon the completion of the strip. Plots ranged from seven- 

 teen to seventy-five years of age, the older stands being diffi- 

 cult to find. Stands over seventy-five years of age were 

 unobtainable due to the history of the region and the fact 

 that timber is usually cut before it approaches that age. 



CONSTRUCTION OF YIELD TABLES 



Of the forty-eight sample plots gathered forty represent the 

 type designated as better second growth hardwoods and 

 eight the type designated as inferior second growth hard- 

 woods. The better second growth hardwood plots were 

 divided into site classes I and II on the basis of average 

 height of the dominant trees. Table I gives the percentages 

 of the various species in mixture on the sample plots, classi- 

 fied as to type and site class. 



