No More Learning

In this neighborhood, where oaks and pines are about equally
dispersed, if you look through the thickest pine wood, even the
seemingly unmixed pitch pine ones, you will commonly detect many
little oaks, birches, and other hard woods, sprung from seeds carried
into the thicket by squirrels and other animals, and also blown
thither, but which are overshadowed and choked by the pines. The
denser the evergreen wood, the more likely it is to be well planted
with these seeds, because the planters incline to resort with their
forage to the closest covert. They also carry it into birch and other
woods. This planting is carried on annually, and the oldest seedlings
annually die; but when the pines are cleared off, the oaks, having got
just the start they want, and now secured favorable conditions,
immediately spring up to trees.

The shade of a dense pine wood is more unfavorable to the springing up
of pines of the same species than of oaks within it, though the former
may come up abundantly when the pines are cut, if there chance to be
sound seed in the ground.

But when you cut off a lot of hard wood, very often the little pines
mixed with it have a similar start, for the squirrels have carried off
the nuts to the pines, and not to the more open wood, and they
commonly make pretty clean work of it; and moreover, if the wood was
old, the sprouts will be feeble or entirely fail; to say nothing about
the soil being, in a measure, exhausted for this kind of crop.

If a pine wood is surrounded by a white oak one chiefly, white oaks
may be expected to succeed when the pines are cut. If it is surrounded
instead by an edging of shrub oaks, then you will probably have a
dense shrub oak thicket.

I have no time to go into details, but will say, in a word, that while
the wind is conveying the seeds of pines into hard woods and open
lands, the squirrels and other animals are conveying the seeds of oaks
and walnuts into the pine woods, and thus a rotation of crops is kept
up.

I affirmed this confidently many years ago, and an occasional
examination of dense pine woods confirmed me in my opinion. It has
long been known to observers that squirrels bury nuts in the ground,
but I am not aware that any one has thus accounted for the regular
succession of forests.

On the 24th of September, in 1857, as I was paddling down the Assabet,
in this town, I saw a red squirrel run along the bank under some
herbage, with something large in its mouth. It stopped near the foot
of a hemlock, within a couple of rods of me, and, hastily pawing a
hole with its fore feet, dropped its booty into it, covered it up, and
retreated part way up the trunk of the tree. As I approached the shore
to examine the deposit, the squirrel, descending part way, betrayed no
little anxiety about its treasure, and made two or three motions to
recover it before it finally retreated. Digging there, I found two
green pignuts joined together, with the thick husks on, buried about
an inch and a half under the reddish soil of decayed hemlock
leaves,--just the right depth to plant it.
In short, this squirrel was
then engaged in accomplishing two objects, to wit, laying up a store
of winter food for itself, and planting a hickory wood for all
creation. If the squirrel was killed, or neglected its deposit, a
hickory would spring up. The nearest hickory tree was twenty rods
distant. These nuts were there still just fourteen days later, but
were gone when I looked again, November 21st, or six weeks later
still.

I have since examined more carefully several dense woods, which are
said to be, and are apparently, exclusively pine, and always with the
same result. For instance, I walked the same day to a small but very
dense and handsome white pine grove, about fifteen rods square, in the
east part of this town. The trees are large for Concord, being from
ten to twenty inches in diameter, and as exclusively pine as any wood
that I know. Indeed, I selected this wood because I thought it the
least likely to contain anything else. It stands on an open plain or
pasture, except that it adjoins another small pine wood, which has a
few little oaks in it, on the southeast side. On every other side, it
was at least thirty rods from the nearest woods. Standing on the edge
of this grove and looking through it, for it is quite level and free
from underwood, for the most part bare, red-carpeted ground, you would
have said that there was not a hardwood tree in it, young or old. But
on looking carefully along over its floor I discovered, though it was
not till my eye had got used to the search, that, alternating with
thin ferns, and small blueberry bushes, there was, not merely here and
there, but as often as every five feet and with a degree of
regularity, a little oak, from three to twelve inches high, and in one
place I found a green acorn dropped by the base of a pine.

I confess I was surprised to find my theory so perfectly proved in
this case. One of the principal agents in this planting, the red
squirrels, were all the while curiously inspecting me, while I was
inspecting their plantation. Some of the little oaks had been browsed
by cows, which resorted to this wood for shade.

After seven or eight years, the hard woods evidently find such a
locality unfavorable to their growth, the pines being allowed to
stand.