Oaklee loves pi

 In Blog, Staff, Trees

Time for anoth­er edi­tion of Oak­lee Does Math for Pie! Actu­al­ly, it’s pi day so we’ve enlist­ed every­one’s favorite squir­rel to teach you a bit more about how to use pi to esti­mate the age of a tree.

For this exer­cise, you’ll need a tree (for­est grown trees work best — trees out in the open grow at dif­fer­ent rates depend­ing on site con­di­tions), mea­sur­ing tape, and a cal­cu­la­tor.

Step 1: Iden­ti­fy your tree and find it on the list (below).

Step 2: Mea­sure up to 54 inch­es from the ground (4 1/2 feet). This is Diam­e­ter Breast Height, or DBH.

Step 3: Mea­sure around the tree at DBH to find the cir­cum­fer­ence in inch­es.

Step 4: Divide the cir­cum­fer­ence by the math­e­mat­i­cal pi π (3.14). This will give you the tree’s diam­e­ter (we learned that last year, remem­ber?).

Step 5: Mul­ti­ply the diam­e­ter by the growth rate num­ber list­ed next to your tree species in the chart. This will give you the approx­i­mate age of your tree! For exam­ple, a white oak with a cir­cum­fer­ence of 126 inch­es would have a diam­e­ter of about 40 inch­es. Mul­ti­ply that by the white oak’s growth fac­tor of 5, and you’ll find your white oak is approx­i­mate­ly 200 years old.

C/π=d, where C is cir­cum­fer­ence and d is diam­e­ter
d*gr=age, where d is diam­e­ter and gr is growth rate num­ber

Growth Rate

Amer­i­can beech 6 Nor­way spruce 5
Amer­i­can elm 4 Pin oak 3
Amer­i­can sycamore 4 Red­bud 7
Aus­tri­an pine 4.5 Red maple 4.5
Black cher­ry 5 Red pine 5.5
Black maple 5 Riv­er birch 3.5
Black wal­nut 4.5 Scar­let oak 4
Brad­ford pear 3 Scotch pine 3.5
Com­mon horsech­est­nut 8 Shag­bark hick­o­ry 7.5
Col­orado blue spruce 4.5 Shin­gle oak 6
Cot­ton­wood 2 Shu­mard oak 3
Dou­glas fir 5 Sil­ver maple 3
Euro­pean beech 4 Sug­ar maple 5.5
Euro­pean white birch 5 Sweet gum 5.5
Green ash 4 Tulip tree 3
Iron­wood 7 White ash 5
Ken­tucky cof­fee tree 3 White fir 7.5
Lit­tle­leaf lin­den 3 White oak 5
North­ern red oak 4 White pine 5
Nor­way maple 4.5 Yel­low buck­eye 5
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