Tree surveying

To find out the number of trees in a small wood, and if trees are
in rows, you can count every one or (say) every fifth one and work
out  the  total.  If  rows  are  not  obvious  sample  your  wood  by
randomly locating square plots of 10 x
10 m. Mark the corners and count the trees inside the plot. For a 2 ha (5 acre) wood lay out 10
plots, for a 5 ha (12 acre) wood 15 plots should do unless the wood
is  very  variable.  Now  calculate  the  average  number  of  trees  per
plot, multiply by 100 to discover the number of trees per hectare,
and then multiply by your wood’s total area for the total number
of trees.