It's a different scale. Human blood is well under 0.08% iron, this tree has 25% nickel. So over 300x as concentrated.

PS: 4 grams of iron in a persons body, ~5kg of blood.

The fluids also contain various electrolytes, i.e. metal cations. But still nowhere close to those trees.

The hemoglobin molecule itself only has something like one iron atom per 1000 non-iron atoms.

Yea it's: C2952 H4664 O832 N812 S8 Fe4 so 2315:1.