(a) For eligible timberlands held by the taxpayer for at least a 10-year period__beginning on or after January 1, 2005 but less than an 11-year period beginning on or after January 1, 2005, 10% of the gain recognized on the sale of the eligible timberlands;

(b) For eligible timberlands held by the taxpayer for at least an 11-year period__beginning on or after January 1, 2005 but less than a 12-year period beginning on or after January 1, 2005, 20% of the gain recognized on the sale of the eligible timberlands;

(c)__For eligible timberlands held by the taxpayer for at least a 12-year period__beginning on or after January 1, 2005 but less than a 13-year period beginning on or after January 1, 2005, 30% of the gain recognized on the sale of the eligible timberlands;

(d)__For eligible timberlands held by the taxpayer for at least a 13-year period__beginning on or after January 1, 2005 but less than a 14-year period beginning on or after January 1, 2005, 40% of the gain recognized on the sale of the eligible timberlands;

(e)__For eligible timberlands held by the taxpayer for at least a 14-year period__beginning on or after January 1, 2005 but less than a 15-year period beginning on or after January 1, 2005, 50% of the gain recognized on the sale of the eligible timberlands;

(f)__For eligible timberlands held by the taxpayer for at least a 15-year period__beginning on or after January 1, 2005 but less than a 16-year period beginning on or after January 1, 2005, 60% of the gain recognized on the sale of the eligible timberlands;

(g)__For eligible timberlands held by the taxpayer for at least a 16-year period__beginning on or after January 1, 2005 but less than a 17-year period beginning on or after January 1, 2005, 70%