Below are the volumes (per acre) by age class for the wildlife 
challenge.  We used 24 age classes.

Take the age of the stand in the time period of interest, divide 
by 5, and you will arrive at the age class.  If the resulting age 
class is above 24, use 24.

In the example below, volume[10] refers to age class 10, or
age 50.

The forest data file contains the age of each stand during period
1 (if not harvested).  To arrive at the ages during other periods,
add 5 years for each period (we used 10, 5-yr time periods).

volume[0] = 0;      
volume[1] = 0;
volume[2] = 3;
volume[3] = 5;
volume[4] = 8;
volume[5] = 12;
volume[6] = 17;
volume[7] = 23;
volume[8] = 29;
volume[9] = 36;
volume[10] = 43;
volume[11] = 49;
volume[12] = 55;
volume[13] = 60;
volume[14] = 65;
volume[15] = 69;
volume[16] = 74;
volume[17] = 78;
volume[18] = 81;
volume[19] = 84;
volume[20] = 87;
volume[21] = 89;
volume[22] = 91;
volume[23] = 91;
volume[24] = 92;