$8 THE MANAGEMENT OF WOODLANDS. 



II. Estimating the Age of Logs, Trees, and Timber Crops. 



1. Logs. The age of logs can be estimated by counting the 

 annual rings at the butt-end of the lowest log or on the stump, 

 and allowing three or four years for growth up to that height. 

 And similarly the diameter or girth at any particular age, as 

 also the rate of growth from time to time, can be ascertained 

 by counting the annual rings and measuring the results for 

 comparison. 



2. The Age of Standing Trees can be told with fair accuracy 

 in the case of Conifers forming regular branch-whorlssuch as 

 Pines, on which the whorls can often be counted back for 30 

 to 40 years. Otherwise one can only estimate the apparent age 

 from the height and the girth, and taking into account the 

 quality of the soil, unless there are records as to date of 

 planting or regenerating. By felling an average tree, however, 

 the age can easily be determined by counting the annual rings 

 at the stump. 



3. For Whole Crops of Wood the mean age can also be easily 

 ascertained in fairly even-aged woods by felling a stem here and 

 there, counting the annual rings on each stump, and taking the 

 average of these. But when patches of wood of different ages 

 are comprised within a compartment, the average age for the 

 whole compartment can be ascertained by taking the mean 

 arithmetical average, stems being felled to fix the age of each 

 patch, if necessary. 



For example, suppose that, in a compartment of 12 acres, there are 5 

 acres of 50 years old, 4 acres 60 years old, and 3 acres 70 years old, then 

 the true average age for the whole compartment would be =[ (5 x 50) + 

 (4x60) + (3x70)]-rl2 = 58 years. 



III. Measurement of the Increment or Rate of Growth on 

 Logs, Trees, and Timber Crops must be made in order to have 

 the necessary data for making a working-plan. 



The Annual Increment in any timber -crop consists iri 

 growth in height and growth in girth. 



