The change in the native
vegetation of the planted part of the heath was most remarkable, more than
is generally seen in passing from one quite different soil to another: not
only the proportional numbers of the heath-plants were wholly changed, but
twelve species of plants (not counting grasses and carices) flourished in
the plantations, which could not be found on the heath. The effect on the
insects must have been still greater, for six insectivorous birds were very
common in the plantations, which were not to be seen on the heath; and the
heath was frequented by two or three distinct insectivorous birds. Here we
see how potent has been the effect of the introduction of a single tree,
nothing whatever else having been done, with the exception of the land
having been enclosed, so that cattle could not enter. But how important an
element enclosure is, I plainly saw near Farnham, in Surrey. Here there
are extensive heaths, with a few clumps of old Scotch firs on the distant
hill-tops: within the last ten years large spaces have been enclosed, and
self-sown firs are now springing up in multitudes, so close together that
all cannot live. When I ascertained that these young trees had not been
sown or planted I was so much surprised at their numbers that I went to
several points of view, whence I could examine hundreds of acres of the
unenclosed heath, and literally I could not see a single Scotch fir, except
the old planted clumps.
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