|
INDEX
(added by webmother)
|
|
|
|
|
AND
THEIR
SYLVICULTURAL CHARACTERISTICS
AND TREATMENT
BY
JOHN NISBET, D.OEc.
OF
THE INDIAN FOREST SERVICE;
TRANSLATOR
OP FÜRST'S "PROTECTION OF WOODLANDS."
London
MACMILLAN AND Co.
AND
NEW YORK
1893
The
Right of Translation and Reproduction is Reserved
Back
to Index
Our
reproduction starts from page 55 from the section:
"CHIEF SPECIES,
forming, or capable of forming, Pure Forests."
"Conifers"
and
includes all pages up to page 83
I. SCOTS OR COMMON PINE, OR SCOTS
FIR (PINUS SYLVESTRIS, L.).
Distribution.
( The details as
to distribution have generally been taken from Luerssen's Forstbotanik in
Lorey's Handbuch, & c., but such as refer to distribution throughout Great
Britain and Ireland have been mostly extracted from Loudon's Arboretum et
Fruticetum Britannicum, 1838, and Selby's History of British Forest Trees, 1842.)
Scots pine is the most widely
distributed of all the European conifers, being found over nearly the whole of
Europe and the greater part of northern Asia, from 70° N. latitude in
Scandinavia, where it even ascends to 900 ft. above sea-level, southwards to the
Sierra Nevada and the Pyrenees, where it reaches an altitude of 5,400 ft. on the
latter and 7,000 ft. on the former. No other forest tree covers such extensive
tracts as the Scots pine. It covers more than 8o per cent. of the wooded area on
the great North German plain, and forms forests of enormous extent in Russia. In
Germany it is emphatically a tree of the plain, and not of the mountain, or even
of the lower hills and uplands, as in Scotland. Towards the south the tree is
not characterised by that straight growth which distinguishes it in its northern
home.
In ancient times it was one of the
three principal forest trees (oak, beech, pine) of Britain, occuping the hilly
tracts of northern England, Scotland, and Ireland. It is the only species of the
Abietineae indigenous to Great Britain and Ireland. In the Scottish Highlands it
attains an elevation of 2,700 ft. but is then, however, merely a shrub and no
longer a forest tree.
On account of its exceedingly
moderate demands as to soil and situation, its rich seed production, the
cheapness of its cultivation, its ability to yield a fair monetary return in
less time than most other forest trees, and the possibility of planting up waste
areas with better species when once the soil has been improved by the Scots
pine, its distribution has been considerably extended by artificial means.
Back
to Index
Tree-form and Root-system are both
to a greater extent dependent on the soil and situation than in the case of
spruce or silver~ fir. On the better classes of soil it attains almost as
straight growth as these, but always unfortunately deviates more than they do
from the cylindrical form of bole, and in approaching more to the conical has
diminished value for technical purposes requiring large-sized squares. The
development of the crown is comparatively slight at all stages of its growth,
but on favourable soils the leaves or needles (formerly called spines in old
works on woodcraft) remain on for three years, whereas on the poorer localities
often only one-year-old sprays bear foliage, short in growth. (Burckhardt, Säen
und Pflanzen, 188o, p. 237, gives the following details as to defoliation
:—Whilst the larch bears foliage only in summer, breaking into leaf,
however, early in spring, the other conifers usually retain their needles for
the following periods:—
Scots
and Weymouth pines 2— 3 years
Austrian
and maritime pines 3— 4 years
Cembran
and mountain pines 4— 5 years
Spruce
; Abies balsarnea, alba and nigra 5— 7 years
Silver
fir 6— 9 years
Yew
7—12 years
Spanish
fir (Abies pinsapo) 10 - 15 years)
Scots
pine is one of the deep-rooted species of trees, and develops a strong tap-root
in good deep soil; where the latter is wanting in depth or strength the
side-roots expand in growth, and when soil-moisture also fails, surface roots
are extensively developed. On shallow lime, or coarse sand with unfavourable
subsoil, and on moors, the otherwise deep-rooted Scots pine becomes a
shallow-rooting tree like the spruce. When abnormal and excessive
root-production is induced by poverty of soil, the crown still remains
comparatively small, but ample for assimilating scanty food.
Back
to Index
Requirements
as to Soil and Situation.—Among the forest trees there is no species whose
demands are so moderate as those of the Scots pine in regard to soil and
situation, although for the natural development of its tap-root the deep, loose,
sandy soil found on plains formerly forming the bed of the sea is that most
favourable. On hard, binding soil the growth of a normal root-system is
interfered with which often leads to fungoid disease; on stiff loam the growth
in height suffers, and on shallow rocky soil there is decided tendency towards
malformation of the bole. Between extremes, however, there are many gradations
of quality of soil to which this most useful tree readily accommodates itself.
The
mineral quality of the soil finds its expression rather in the quality of the
timber, and the duration of life of the tree, than in the cubic contents
produced. The attainment of great height is with it, as with the other trees of
the forest, one of the chief outward signs of the suitability of the situation.
Its highest development and greatest production of resin take place on loamy
sand, especially if humus be contained in it, and when the subsoil retains a
constant moderate supply of moisture.
No
other species is content with so little soil-moisture as the Scots pine, which
can be made to form forests on dry, shifting sand, or on hot, southern slopes
where even the very weeds find life difficult. In such unsuitable localities its
growth is naturally not good, but by improving the soil through the shade and
shelter of its foliage preventing insolation, and through the humus formed by
the defoliated needles, it paves the way for a better subsequent growth or for
other trees that could not be planted out in the first instance. It also, on the
other hand, is capable of being grown on peat moors and bogs, and even endures
stagnant water better than the spruce which demands soil-moisture; but under
these unfavourable circumstances its growth is not vigorous. To the attainment
of a long period of life, of large cubic contents, and of timber of first-rate
quality a constant moderate degree of freshness in the soil is essential; dry
soil yields good timber, but little of it; moist soil yields large cubic
contents, but of inferior quality as timber. It is sensitive to changes in the
quantity of soil-moisture, and when growing on a soil usually moist, suffers in
growth if either inundations take place or the soil gets dried up in unusually
hot seasons, or in consequence of neighbouring drainage, the root-system being
unable in either case to accommodate itself all at once to the altered
conditions.
In
relation to warmth, however, it possesses great power of accommodation, thriving
in localities where the summer heat and the winter cold are both very
considerable. Whilst in Germany it prefers the dry air of the North German plain
to damp hilly climates, and shows decided signs of falling off in development in
the moist atmosphere of Schleswig-Holstein, yet it thrives well in damp
localities in Scotland and northwestern Norway, producing timber of excellent
quality.
Except
at high altitudes, where the greater dampness of these exposures would cause it
naturally to seek the drier southern aspects, the northern and eastern slopes
axe best suited for the Scots pine on account of their better retention of
soil-moisture, which compensates to a certain extent for the loss of light and
warmth.
Back
to Index
Requirements
as to Light.—Decidedly a light-loving tree, the Scots pine is very sensitive
to shade, whether from above or from the side,—more so, in fact, than any
other conifer except the larch. On the poorer qualities of soil even a slight
degree of over-shadowing affects the development of the leading shoot, whilst if
the trees are cleared so as to enjoy free light and sunshine after having long
stood in shade their recuperative power seems weak, and unable to induce a
return to normal straight growth. Its ability to withstand the bad effects of
shade is greater when the soil is deep, powerful, and fresh. Even in pure
forests of Scots pine too close sowing or planting is unadvisable, especially on
the poorer soils, as the individuals influence each other disadvantageously by
side shade; on better soils, the dominating saplings assert themselves sooner
above the others, which soon become suppressed and killed off. ( Vide note at
foot of p. 57.)
Back
to Index
Attainment
of Maturity and Reproductive Capacity.—No species of forest tree grown in high
forest is subject to more different treatment as to its economic maturity as the
Scots pine, the periods of rotation varying from sixty to one hundred years and
more. Under average conditions as to soil, an eighty years’ rotation
frequently obtains, but where the larger dimensions of timber command high
prices, higher rotations are fixed if the soil is not exposed to deteriorating
influences. Good timber for ordinary building purposes is often produced by
forests of seventy years of age. On poorer soils a rotation of fifty to sixty
years is frequently more remunerative than one fixed at a later age, as increase
in contents and value of the timber on such localities is very slow.
From
about the fortieth to fiftieth year, and on indifferent soils much earlier, good
seed years are frequent, six being expected in every ten years, and in addition
there is generally some production of seed in the intervening years. The cones
ripen in the second October after flowering, and in the succeeding spring the
approach of warm weather causes them to open so that the seed may be wafted away
by the wind. The germinative power of the seed is good, experimental tests
generally yielding sixty to seventy per cent., although of course somewhat less
favourable results must be expected when sowing is carried out in the open. The
cones usually contain from forty to forty-five seeds, and one pound of seed
without wings represents about 75,000 seeds, which retain their germinative
power for between two to three years.
(Burckhardt,
Saen und Pflanzen, 188o, p. 418, gives the following comparative table for the
relative number of seeds contained per unit of volume:-
Scots
pine
100
Spruce
95
Larch
93
Austrian pine
56
Weymouth pine
28
Maritimepine
15
Silver fir
10)
Back
to Index
Liability
to suffer from. External Dangers is unfortunately characteristic of the Scots
pine at all stages of its growth. In its earliest years it is apt to suffer
seriously from the larvae of species of Agrotis and Gryllotalpa at time of
germinating, then of Melolontha gnawing the roots, whilst the bark is attacked
by the fully developed weevils of Hylobius and Pissodes species. The cortex and
sap-wood of young plantations suffer through the larvae of Hylurgus, and those
of poles and trees from Bostrychus, Hylurgus, Hylastes and
Polygraphus;
Gastropacha and Retinia caterpillars often decimate the buds; young shoots are
badly damaged by species of Hylurgus and Retinia; and finally the leaves form
too often a favourite grazing ground for the caterpillars of Gastropacha pini,
Liparis monacha, Trachea piniperda, Fidonia piniaria, Lophyrus pini and
Lyda pratensis.
Leaf
shedding, or the loss of foliage, a fatal disease to which Scots pine is liable,
and particularly so at the age of three to five years, is caused by drought
(according to Ebermayer), or by frost (according to Nordlinger), or (according
to R. Hartig), in many cases either by a process of drying up due to
transpiration through the leaves on sunny days in winter whilst the frost-bound
soil can yield no supplies of moisture to replace that evaporated, or else by a
fungoid disease from infection with Hysterium pinastri. ( R. Hartig’s
Lehrbuch der Baumkrankheiten, 2nd edition, 1889, pp. 103—109.)
From
fungoid diseases, too, the Scots pine has to bear somewhat more than its fair
share. The leaves of young seedlings are attacked by Hysterium pinastri and
Aecidium pini, the branches and stems of poles and trees by Trametes
pini, Aecidium pini, and Caeoma pinitorquum, and the roots and base of the stem by
Agaricus melleus and Trametes radiciperda, whilst cotyledons and leaves of
seedlings become infected by Phytophthora omnivora. Red-rot in the timber is
caused by Polyporus vaporarius and P.mollis.
( Hess, Der Forstschutz, 1890, vol. ii. p. 185, says:- "Red-rot is
occasioned by the solution of cellulose in a decomposing ferment formed in the
protoplasm of the fungus and communicated by the mycelium to the surrounding
cells; a resinous or tannic residuum is formed, which in oxidizing assumes a
reddish-brown appearance. In white-rot the ferment of the mycelium dissolves the
lignine, and leaves the bright. coloured cellulose untouched, hence the whitish
colour of the diseased wood.”
The details concerning insect enemies and fungoid diseases are mainly drawn from
Hess’s Forstschutz, 2nd Edit., 1887—1890.)
The
above-mentioned insect enemies of the Scots pine also endanger to a greater or
less extent the well being of the other species of pine—black or Austrian,
Cembran, maritime, Weymouth,—but their attacks are usually neither so frequent
nor so serious. A similar remark also obtains with reference to the fungoid
diseases.
Accumulations
of snow and ice on the branches, also heavy storms of wind and rain, often cause
much damage, as during the sapling- and pole-stages of growth the wood of the
branches is very brittle. In spite of the thin crown of foliage, on
shallow-soiled, exposed localities the danger of trees being thrown altogether
(windfall) is greater than on the sandy plains where the deep, strong tap-root
lends security to the stem.
Very
serious damage can be caused by forest fires in the dry months of summer,
especially when the thicket age has not yet been passed; no tree suffers so much
from this danger as the Scots pine, owing to its richness in resin. Protected by
its rough bark it is not after the twentieth year liable to be much damaged by
deer, but wounds occasioned by red-deer stripping the bark with their teeth,
both in winter and summer, and rubbing the velvet from their antlers in early
summer, heal better than those inflicted on other coniferous species,
owing to its superior recuperative capacity in this respect.
Back
to Index
Sylvicultural
Treatment of Scots Pine.—As a light-loving species, hardy in respect to
frost, Scots pine offers many contrasts to spruce and silver fir. Pure forests
of pine are usually to be found only on the poorer classes of soil, where of
course it does not attain anything like so good growth as on more favourable
soils and situations. How great are the differences in average yield between the
best and the poorest classes of pine soil may be seen from the table on page 44,
the outturn on the latter at no time even approaching the half of that on the
former, the average on soils of medium quality being, however, about 4,700 cubic
feet per acre, at sixty years of age, and 5,700 cubic feet at eighty years.
The
influences or soil and situation are apparent in every aspect of its
development. The root-system is cramped, short, and branching on loam, and quite
a contrast to the well-formed tap-root in deep, fresh, light sand, whilst
moor-pan and poor, dry situations, as well as those which are too marshy and
wet, cause the formation of long, thin strands that ramify in all directions
throughout the surface-soil. Even in the foliage the quality of the soil and
situation may at once be noted from the length of the needles and from their
persistence, for whilst on the average and better situations they still depend
from the two-year-old twigs, on the poorer sites they are mainly confined to the
one-year-old sprays,—a circumstance of no little importance with regard to the
sheltering of the soil and the retention of soil-moisture. The amount of resin
contained in the timber, its length of bole, and its general quality, are all in
like manner greatly dependent on the nature of the soil and situation, which
also to a very great extent determine, or at any rate unmistakably indicate, the
period at which the utilisation and
reproduction of the growing crop can take place most advantageously and
remuneratively.
In general the growth
of the Scots pine is most vigorous throughout the thicket, and the pole-forest,
arid until after it enters the tree-forest stage of growth, in the latter two of
which it also yields the largest returns from thinnings. But the poorer the
soil, the sooner the average increment culminates and begins to diminish, the
earlier the growth in height declines, and the rounding off of the crown begins.
Along with the latter comes increased demand for growing-space, trees die off,
and weevils, beetles, and caterpillars at once become attracted towards them as
breeding places, frequently combined with simultaneous infection with fungoid
disease, whilst the process of regular and judicious thinning out is somewhat
interfered with, as the sickly and diseased stems must be removed first of all.
Owing to the greater amount of light playing over the soil, this becomes covered
with a growth of mosses, grasses, whortleberries, or heather according to its
quality, and soon the canopy, from being at first merely interrupted, gradually
becomes completely broken, the annual increment sinks, and the question of
reproduction and clearance,—or too often merely its alternative, clearance and
reproduction, inevitably presents itself for consideration.
The
poorer classes of pine soil exhibit these changes in so short a time that low
periods of rotation are those most advantageous both in regard to outturn and
with respect to the soil, but on the better classes the quantity of the
outturn in timber, as well as its quality, points to the remunerative
advantage offered by a fall fixed at from eighty to one-hundred and twenty
years according to the circumstances of each case.
In
comparison with spruce and silver fir, Scots pine has a rapid growth in early
youth and often succeeds in forming
canopy at about the age of five to six years, if it manages to escape the
ailments peculiar to its species, which are unfortunately numerous. Should the
young seedlings or transplants, before being able to develop their tap-root,
suffer from long-continued drought, or should strong dry east winds dissipate
the soil-moisture, the stock on the ground may be sadly diminished, or even
decimated, especially when the quality of the soil is poor. A severe winter
following a dry summer finds the young plants in a weakly condition and little
able to withstand hard frosts, especially if following rapidly after heavy rain;
for although pine is hardy as regards frost, the exposure of the roots after a
sudden thaw kills the plant outright. Fungous disease (Hysterium pinastri) may
then gain an easy foothold on the foliage in its sickly condition, and even
perfectly healthy plants are liable to attacks from insects of various kinds,
the most dangerous and destructive being cockchafer grubs (Melolontha) on light
sandy soil, and various species of weevils (Curculionidae), particularly where
the stumps of the old crop of trees have not been grubbed up, as some of the
worst beetles have their breeding-places there. These youthful ailments of the
pine often necessitate extensive planting operations in the filling up of
blanks resulting from one or other of these causes, or from the browsing of
sheep, which prefer pine sprays to heather and tough wiry mountain grass, when
they can force a way through the fencing into plantations.
When
once the young pine woods, however, have fairly established themselves, and have
with close planting in about five to seven years attained the canopy usual in
the thicket stage, their growth in height soon becomes vigorous. From heights
varying at ten years of age from 3’8” to 7’4”, according to the quality
of the soil, it quickly shoots up to from ten to twenty-four feet at twenty
years of age, and twenty-five to
fifty-two feet at forty years of age, during which time of greatest energy of
growth in height the pine surpasses most other trees of the forest, annual
shoots of two feet m length throughout all the dominating poles being common
enough on good situations. The energy of the Weymouth pine is even greater in
this direction than that of the Scots pine, whilst that of the black or Austrian
and maritime pines is somewhat less. At this stage of growth, unless the density
of canopy be interfered with by accidents due to climate, such as breakage
owing to accumulations of snow on the branches, or the foliage be eaten up by
swarms of caterpillars, or the bark and sap-wood be destroyed by the larvae of
Bostrichini, the soil being well protected becomes greatly improved by the rich
fall of needles annually, which on decomposition form good humus, and stimulate
the soil to increased timber production. The impetus thus given to the general
energy in growth favours, on the better classes of soil, the self-assertion of
the dominating and predominating poles throughout the whole crop; but on soils
of the poorer class the improvement thus brought about is apt to be frittered
away and dissipated in prolonging the struggle between the dominating and the
dominated classes, so that what on one situation may be gained by close planting
in forcing up the poles and favouring the early development of a distinctly
dominating class, may lead to exactly the opposite. result on a poorer
situation. Poles that have once stood in shade seldom develop into good normal
stems.
The age at which a
natural interruption of the canopy begins, and the rate at and extent to which
it continues, are matters varying in general according to the quality of the
soil, and the suitability of the situation for the pine. On shallow soils, or
those which, like lime or poor sand, are easily heated, it begins to take place
about the fortieth to the fiftieth
year, whilst on deeper, fresher, more humose sands and loams, and milder soils
generally, the tendency does not make itself so apparent until about the
sixtieth to eightieth year. It is only under such circumstances as in the latter
case that the pine gets fair play as a forest tree, and has the opportunity of
developing normally into the fine and profitable timber tree that it
unquestionably is. The characteristic reddening of the pine stems along the
upper portion of the bole and near the crown takes place at the time when
forests begin to thin themselves strongly.
With continued
interruption of the canopy two points of interest press themselves on the
attention of the owner; first, that in consequence of the diminution of the
number of stems the total annual increment begins to fall below the average
maximum that the soil can and should yield, and secondly, that insolation of the
soil and its exposure to the wasting influence of dry winds must lead to
deterioration and impoverishment. Both of these circumstances indicate the
proper and prudent time for reproduction, which can then be most advantageously
undertaken either before or after the crop on the ground has been utilised.
As
already remarked, with no other species of high forest does the period of
rotation or fall of the timber range between more varying limits than in the
case of the Scots pine. Sometimes the indications above referred to recommend
the utilisation of the crop at fifty to sixty years on the poorer situations,
when the total average annual yield is often much greater than at a higher age,
and where advancing years do not necessarily bring with them a finer development
of large timber; on soils of such quality, however, the outturn yielded is more
generally suitable for petty requirements than for building purposes, or works
requiring large squares. Many pine forests give good useful building timber at
seventy years of age, yielding at the same time fair returns for the
capital represented by soil and growing-stock. For medium circumstances a
rotation of seventy to eighty years is what is naturally indicated as the most
remunerative, although, where large timber is well paid for and in good demand,
the fall may often profitably be delayed till the hundredth, or even the hundred
and twentieth year; for such long periods of rotation, however, favourable soils
and situations are a sine quâ non, both from the sylvicultural and the monetary
points of view.
Back
to Index
Pure Forests of Scots
Pine.—It cannot be denied that under certain circumstances pure forests of
pine offer distinct advantages. They make little demand on the soil, are easily
formed, tended, and worked, and yield both in the thinnings, and at the final
harvesting of the crop, good useful kinds of timber generally saleable, and
capable of supplying requirements of the most various descriptions. Where,
however, accumulations of snow and ice are likely to occur in exposed
localities, the formation of pure forests of Scots pine is not to be
recommended; the interest of the owner will most probably be better served by
the formation of mixed forests. But the greatest drawback of pure forests of
equal age, which the usual system of total clearance with artificial
reproduction entails, lies in the defective and only partial protection which
the older woods are able to afford the soil; this is more especially the case on
poor dry soils unsuited for the growth of other species along with the pine, and
where it is not possible to regenerate the pinewoods naturally under parent
standards.
For the production of
large and valuable stems of Scots pine, prolongation of the fall of the whole
crop would be a costly and unremunerative measure; but a choice always remains
between retaining well-grown groups on good patches of soil, or the selection of
healthy, well-developed trees as standards here and there over the area being
reproduced. In general the latter
practice has most to recommend it, but the number of standards selected must be
small, not exceeding ten to fifteen per acre, and for some time previous to
the clearance of the crop they should gradually be accustomed to greater light
and air, and prepared for standing isolated by being cut free from neighbouring
trees. Even with such preliminary precautions, however, the standards often
become windfall, and that too in localities not unduly exposed to heavy and
violent storms, besides being liable to the attacks of insects and of fungous
disease in the crown (Peridermium pini), whilst the young growth around such
standards is always more or less interfered with. But where the standards
maintain themselves healthy till the close of the second period of rotation,
they yield a good return. The retention of standards is only advisable on the
better classes of soil, where there is least danger of the younger generation of
trees being too much retarded in growth by the light shadow cast around by the
former. Without doubt the same object can perhaps be better attained by growing
the pine in admixture with spruce or silver fir, and on the whole pure pine
forests are only to be recommended on soils unsuited for the formation of mixed
forests in which the shade-bearing conifers form the ruling species or matrix.
Back
to Index
M
ixed Forests with Scots Pine as the ruling Species.— Spruce is the tree most
frequently grown in admixture with Scots pine, and even where it is not able to
develop as well as the latter, it still performs good service as a subordinate
species protecting the soil. In some localities it grows as quickly as the pine;
in others it is at first slower in growth, but ultimately succeeds in forming
canopy along with the pine. When this begins to slacken in growth in height and
gets overtaken at about thirty to fifty years of age, the spruce often threatens
to crush out the pine unless the axe is freely used. On
the poorer qualities of soil spruce never really ranks much higher than
underwood, but is even then of great advantage to the pine in maintaining and
stimulating the productive power of the soil, and in hindering the formation of
a rank growth of whortleberry or heather.
When older forests of
Scots pine have an admixture of spruce forming canopy along with them, they are
usually characterised by a good cylindrical form of bole and large production of
cubic contents per acre. They also suffer far less than pure forests from
various dangers, and when the foliage of the pine has been stripped by the
caterpillars of swarms of moths, the spruce can often take its place in the
blanks formed, except when the ‘Nun’ moth (Liparis monacha) has been the
cause, for then spruce is usually much more injured than pine. In such mixed
forests breakage from snow is much less frequent than in woods of pure Scots
pine. Although in general advantageous, there are however two cases in which
an admixture of spruce is not advisable; namely, in the first instance, on the
better class of pine soils, where the pine is of decidedly quicker growth
than the spruce, and where the interests of the proprietor are best served by
growing the pine pure and then later on under-planting with spruce, and in the
second instance, on the poorer classes of pine soil where the spruce is unable
to thrive. But on dry, impoverished mountain soil a mixture is often
preferable, as in pure forests the pine soon thins itself and does not protect
the soil sufficiently, whilst the spruce has only a sickly growth without any
nurse. In such cases it depends on circumstances whether the treatment to be
accorded will result in the mixed forest being pine with spruce, or spruce with
pine. Many of the present middle-aged mixed crops of Scots pine and spruce in
Germany arose from the malpractices of seedsmen
formerly in mixing the cheaper spruce seed with that of the pine at a time when
communications were not so good as they are now, and the errors could not
conveniently be rectified immediately.
In what proportion
the admixture of the spruce should take place is mainly dependent on the nature
of the soil and situation. If the pine is towards the maturity of the crop to be
unmistakably the chief or ruling species, then the spruce should not be
introduced in greater quantity than from one-sixth to one-fourth. Where past
experience, however, has shown that the pine can easily be protected from
being overgrown and suppressed by the spruce about its fiftieth year, the latter
can be planted in equal quantity in alternating squares or rows, in which case
the spruce will at first require most attention, whilst later on measures will
have to be taken to protect the pine against the other. Where spruce forms only
a small proportion of the stock it is better to introduce it as individuals or
in small patches than to plant it out in rows.
In mixed forests of
pine and silver fir the latter is almost always the ruling species, so that this
mixture will be considered later on (vide page
125).
In the Scottish
highlands a mixture of birch with the pine seems a most natural one. They are
both species with a considerable power of accommodation, and whose natural
habitat ranges from moors to sandy soils; as the light winged seed is easily
wafted into the pine woods, birch is very often found growing there. But in
general the introduction of birch into pine forests has not much to recommend
it, as it leads to interruption of the canopy and insolation of the soil. Even
on poor soils birch is the more rapid in growth up till about the fifteenth to
twentieth year, when it is outstripped in height by the pine; but until this has
taken place the leading shoots of the latter are liable to be damaged by the whip-like
twigs of the former. Under certain circumstances, however, the birch is a
welcome guest in pine woods, only its stay must not be too prolonged. On soils
of somewhat inferior quality, which suffice for the birch but are hardly good
enough to ensure the thriving of other species, an admixture of birch protects
the pine against insects, snow, and fire. Where, again, the pine is likely to
find difficulty in establishing itself, an admixture of birch as a nurse often
yields good results, as on very dry, almost shifting, sandy soils and on moors
and marshes, on which experience shows that such mixed forests thrive better
during the younger stages of growth. But in these cases the birch should be
removed early in the way of thinning, especially on the more sandy varieties of
soil.
The admixture of
larch with Scots pine was formerly not at all infrequent, but has now pretty
generally fallen into disrepute in most countries except Scotland, as might from
the very first have been expected from the natural characteristics of the two
species. Even on soils below the average in quality, the larch is the quicker in
growth till. between the tenth to the twentieth year, when it is caught up by
the pine, and the one condition of its growth—absolute freedom of crown—can
no longer be satisfied unless at the sacrifice of the surrounding pines; at
such a stage of growth the almost inevitable measure to be adopted is the
removal of the larch poles before they fall a prey to canker (Peziza Willkommii).
But in any case the poorer classes of pine soil are no suitable situation for
the larch, which requires a deep, fresh, and strong soil, such as will seldom be
best utilised by being planted up with Scots pine. Where, however, the larch is
desired in pine woods, it can better be reared and tended if planted in patches
or groups than individually or in rows.
On peat-moors or sour
boggy soils Scots pine has often aspen and alder mixed with
it, but on the whole the appearance of crops of this kind is seldom
satisfactory.
Scots pine woods are
often the matrix throughout which other varieties of pine, in particular
Weymouth and also black or Austrian pine, are grown with satisfactory results.
The former often assists materially in maintaining the canopy, and both are less
impatient of shade than our indigenous species. The Weymouth pine is,
however, apt to overtop and crowd out the Scots pine, so that it should be
introduced in clumps for more easy tending in favour of the latter. The black
pine is notably backward in growth during its tenth to fifteenth year, but can
bear a light shade well, and improves the soil considerably through its heavy
fall of needles and its thicker foliage.
Back
to Index
Formation and Reproduction
of Pine Forests.—The methods of reproduction of pure pine forests are various.
Natural regeneration under parent standard trees was long the rule, and is even
now, in extensive pine tracts where low local timber rates, or a limited demand
for timber, did and do not seem to call for or justify the outlay of large sums
on artificial reproduction, although it cannot be denied that the latter leads
to more regular and complete results. But wherever the whole crop can be
profitably disposed of, natural reproduction of this species—and, indeed, of
every species of forest tree except the beech and the silver fir, which are
shade-demanding during the first two or three years of their existence—has
come to be the exception in place of, as formerly, the rule, though some
maintain that in many cases natural regeneration is the preferable method, and
that better timber crops of pine can be raised from seed shed by parent
standards, if blanks and unregenerated patches be promptly filled up
artificially. Large pine forests on light sandy soil, where sudden clearance
might render it a prey to the winds, ought certainly to be reproduced naturally, and in general
such as show by self-sown seedlings a good capacity for regeneration, even if it
be only in order to escape from the often serious damage caused in very young
plantations by cockchafer grubs (Melolontka). From the actuarial point of view
however—which must always be the principal one, and that most deserving of
attention in the private forests of Britain—speedy artificial reproduction
of regular, equal-aged crops holds out better promise of remunerative results
than the doubtful success of naturally regenerated woodlands of a
light-demanding species on any poor soil liable to deteriorate. And natural
reproduction of our pine forests is seldom quite satisfactory; here the
self-sown seedlings stand too thick, there too sparsely and irregularly, while
in other places again they fail altogether, and the soil becomes covered with
rank undergrowth, which effectually puts an end to all hope of future
spontaneous growth; at best the results are generally such that expensive
assistance has usually to be given by sowing or planting.
Back
to Index
Natural
Reproduction.—No protective standards are necessary for the natural
reproduction of the Scots pine, for on the poorer classes of soil the seedling
growth will not bear shade, and on the better situations it can thrive without
shelter and soon demands, as a light-loving species, the removal of the parent
trees. Natural reproduction under parent standards is therefore only possible on
soils above the average in quality, and can be recommended only on the very best
situations, as otherwise the increase in growth on the standards does not
outweigh the damage done by overshadowing the younger generation. Where,
however, a natural, self-sown growth is to be found with normally-formed leading
shoots, the standing timber should be removed sooner than in other parts of the
forest, so as to ensure the normal development of the young seedlings in groups
or patches: for if once crippled in growth, or hindered in development, such
seedlings never recover completely. Thus a young self-sown crop, which has stood
for more than two or three years under the shade of close canopy, or older plants
under more open cover which show a shortened and impaired growth of the leading
shoot, do not yield suitable material for the formation of future crops, in
addition to which the extraction of the parent trees can seldom be effected
without causing a good deal of damage to the young undergrowth. The retention of
self-sown seedlings occurring only singly here and there on areas that are
intended to be stocked with pure forest of pine, is not advisable, as they are
apt to break into undue branch development, do not form good boles, and
generally interfere with the growth of their neighbours.
In mixed forests
where the pine is grown along with thickly-foliaged trees, or in pine forests
that have been underplanted with shade-bearing species, some soil preparation
is necessary for the purpose of accelerating the decomposition of the layer of
leaves on the ground, and the formation of humus. In pure forests of Scots pine,
however, it is more often the case that reproduction is hindered by a heavy
growth of grass and weeds, amongst which germination of the seed is difficult
and the malformation of the seedling almost certain; for good development of the
young plant can only be expected where the seed rests on the naked soil, and the
rootlets can penetrate immediately into the earth. Even where the ground is only
covered with weeds here and there, some soil preparation is requisite, otherwise
the young crop is patchy, broken, and at best unequal in height, conditions not
at all suitable for the formation of pure forests of a light-loving species like
Scots pine, which only forms good
stems when the density of the crop is sufficient to stimulate growth in height
by interfering with and checking the natural, strongly marked tendency to ramification and coronal
development. Such soil-preparation need not take place over the whole area, but
is at least advisable in bands or strips of twelve to twenty inches broad,
occurring at intervals of three to four feet; the covering of weeds should be
removed till the soil is reached, and this should if possible be broken up
slightly early in spring, so that the seed may find a good bed for germination
on being shed from the cones with the advent of somewhat warmer weather.
Where the quality of
the soil is good enough to make natural reproduction advisable, twelve to twenty
parent standards per acre, equally distributed over the area, will be found
sufficient, especially if high forest of the same species be near the fall and
assist in the distribution of seed. Where, however, it is desirable that the
advantages of increased growth in girth, through freer exposure to light and
air, should be attained by a greater number of sterns before they are felled and
extracted, this can be arranged for by reproducing in circles of forty to
fifty yards diameter with very few standards surrounded by a belt or girdle of
ten to twenty yards broad in which the seed-shedding parent trees are more
numerous. The standards are first removed in three to four years from the
central area, and those from the girdle gradually during the next ten to twelve
years. If under the latter the germination and establishment of the Scots pine
has not been successful other species can be sown, and thus at the end of the
period of reproduction the area will be covered with circular groups, of about
one-third of an acre each, consisting of pine of equal age, surrounded by
belts, ten to twenty yards broad, of shade-bearing species like spruce or silver
fir, in which patches of pine also occur, whereby to a certain extent the
advantages of mixed forests over pure crops will be attained.
On the poorer
classes of soil natural reproduction is not advisable, although where groups or
large patches of well-developed self-sown
seedlings have asserted themselves on blanks occasioned by windfall, &c.,
their retention is often advisable. Where a recent fall of timber has taken
place, a natural growth can often be obtained if bands be prepared for the
reception of seed whenever numerous cones on the neighbouring trees to the
windward side show prospect of a large supply of seed being shed in the
following spring in the direction of the area to be re-wooded. But such natural
reproduction cannot be relied on for more than 100 to 120 yards, and is often
extremely irregular and unsatisfactory, necessitating considerable outlay for
the filling up of blanks. As germination can only be secured on dry soil when
the seed has some soil-covering, it is advisable either to break up the soil
before the time of seed-shedding, or to go over it lightly with the rake or
harrow after the seed has fallen. A favourable germinating-bed is afforded by
places where the stumps of the trees have been grubbed out to decrease the
number of breeding-places available for such dangerous insect enemies as are
found among the Curculionidae and Bostrichini.
In the enormous pine
forests of northern Germany, natural reproduction over large areas has long been
given up, and total clearance of the mature crop is at once followed by sowing
or planting operations, except near the edge of next year’s fall, where, for
the distance of about 100 to 200 yards, there is sometimes a growth of self-sown
seedlings from the seed shed during the last year, which is often capable of
forming close canopy with more or less of artificial assistance.
Back
to Index
Artificial
Formation and Reproduction.—Whether the artificial formation or
reproduction should take place by sowing or planting is a question dependent
mainly on local circumstances in each case. In northern Germany, for example, it
has received a practical answer in the fact that whilst about twenty or thirty
years ago there was at least as much sowing as planting, the latter has now
become the rule, except where want of
available labour has settled the question in favour of sowing. No hard and fast
rules can be framed for the pine more than for any other kind of forest tree, as
in each case soil and situation and other circumstances must all be taken into
consideration before any dictum can have genuine practical value; but in general
the formation or the reproduction of pine forests is best undertaken by means of
planting, as then the distances at which the plants shall stand, and the time at
which the young crop shall form canopy, are most easily determinable by the
owner: When the first and early thinnings are remunerative, tolerably close
planting and dense plantations will naturally recommend themselves.
Back
to Index
Sowing.—Under
certain circumstances, however, sowing has its recommendations. The supply of
seedlings may fail owing to grubs in the nurseries or other causes, the
available supply of labour may not be securable, or the soil is perhaps not
suitable for planting out young seedlings, whilst the necessarily higher costs
of planting up with older transplants from nurseries may for one reason or
another not be considered desirable.
Sowings are not
always cheaper than planting, for a certain amount of preparation of the soil
for the reception of seed is imperative to secure any fair measure of success;
the filling up of blanks may at times be costly, and after all the results may
show that it would have proved a saving both in time and money to have
determined in favour of planting at the outset.
It is difficult to
hit the happy medium in sowings of the pine ; they are usually either too dense
or too thin. In the latter case, even with some assistance in the way of
planting, the crops often stand too open, and from the very first,
branch-development is unduly great; in the former, even with the frequent
assistance of the bill in the way of weeding an~1 clearing, the
individual struggle for predominance begins early and is long continued,
especially on the poorer classes of soil, and in it is often dissipated the
general energy in growth during the period when that vital energy is at its
greatest.
Where pure forests of
Scots pine are desired, sowing (
See table on p. 50.) in mountainous tracts usually takes place
broadcast along lines cleared of weeds to a breadth of 1 to 1˝ feet and 3˝ to
4˝ feet apart. Where the soil is dry, hard, or covered with a thick layer of
incompletely formed or inferior humus, some little soil-preparation is advisable
in order to enable the rootlets to penetrate quickly into the ground, so that
they may the better withstand drought. Where there is a strong growth of heath,
heather or weeds, the area should be burned over before any soil-preparation
takes place, but caution must be used to ensure that the fire does not spread
into the forests. On level tracts the best soil-preparation can be effected by
the plough during autumn, when sowing follows in spring, about 5 to 6 lbs. per
acre being used, and germination assisted by the use of the rake or the harrow.
On low-lying tracts where the soil is wet, or in localities with impermeable
subsoil of moorpan or ironband, trenching with the subsoil plough is requisite,
the seed being sown on the top and sides of the beds or mounds between the
trenches.
Cones were often
formerly sown out, but as in cold wet weather the scales did not open to let the
seed issue, the results were at times very unsatisfactory.
Back
to Index
Planting.—A great
impetus was given to planting by the use of one, or at most two-year-old naked
seedlings in districts with loose or mild soils, where notching could be carried
out. Nursery costs, and the dangers incident to life in a nursery, were thereby
reduced to a minimum, packing and transport were rendered
cheap and easy, the actual operation of planting was of the simplest and
cheapest possible description, and the success was satisfactory, as good results
could be achieved with the young material at a very reasonable outlay. And
whenever possible, notching of naked seedlings has other advantages besides
cheapness over planting with transplants having balls of earth attached, for in
the loose or light soils where alone it is practicable, the seedlings maintain
themselves better against drought than if planted out with earth around the
roots,—a fact that has its explanation in the greater ease with which the
comparatively undamaged and undiminished tender root-system can establish itself
in the easily penetrable soil.
When notching is the
method employed, as is usual on moist soils except those that are tenacious,
the use of yearling seedlings has a decided advantage over older plants, as the
roots are much less likely to get damaged during the planting operations.
Yearling seedlings should be pricked out in rows not more than 4˝ feet apart, and
should be set from 2˝ to 3˝ feet apart in the rows; but where trenching has been
carried out, the rows are usually further apart, and the plants closer together
in the lines. Long, thick, wedge-shaped notching spades should be used, so that
the rootlets may not be damaged, and because planting too deep is in the case of
the Scots pine less of a mistake than planting too shallow On very dry or light
soils, indeed, the seedlings are put in so far that only the top bud appears
above the ground - a method that would of course not be applicable in moist
localities or on stiff soils.
Planting with
two-year-old plants is dearer, without being necessarily more successful, than
when good yearling seedlings have been used. Transplants over two years old, and
in unfavourable circumstances even two-year-old plants, are put out with balls
of earth attached to the roots; but as this method is comparatively more
expensive, it is usually adopted only on wet moors and other places where there
is danger of the plants being lifted out of the ground by frost, or where, as in
the case of shifting sand, the soil is extremely poor. The larger transplants
are, however, to be recommended in the filling up of blanks,—a measure that
should be promptly attended to in the formation of young pine woods, as can
easily be understood when one considers their rapid growth in early years, and
the tendency towards branch-development on any side offering the enjoyment of
light and air. Young plants round blanks soon tend to assume branching and
abnormal development, and if they have an advantage of two or three years in
growth, they prevent younger plants from thriving. The filling up of blanks with
transplants of four and five-year-old and older plants can only take place with
large balls of earth, owing to the development of the tap-root, and is as a rule
very expensive. But in such cases the filling up of blanks with Weymouth pine,
black pine, spruce, or silver fir will generally recommend itself in preference
to Scots pine, unless the soil and situation be distinctly unsuitable for any of
these other species.
In its demand for
light is explainable the mistake of too close planting of the pine. Thick sowing
or dibbling in of many seeds in patches here and there is contrary to the
natural habit of the species, more especially on the poorer classes of soil
where the youthful energy of the pole stage of growth is squandered in an
unprofitable struggle for individual supremacy. One or two-year-old seedlings
should not be put out closer than 3 feet x 3 feet, three and four-year-old
transplants with balls of earth attached not nearer than 4 feet x 4 feet, or in
rows of 5 feet x 3 feet to make clearing and thinning out easier and cheaper.
When seedlings are to
be used, they can be raised in temporary nurseries in any sheltered locality
with good mild soil. The seed is sown in
rills about one inch deep and 4 to 4˝ inches apart, and lightly covered with
soil. If two-year-old seedlings are to be used, the rows are put six inches
apart, the quantity of seed being of course reduced to ˝ to two-third of what
is found most suitable in the former case. When the seedlings are intended for
very dry soil, bastard-trenching is advisable in order to loosen the soil and
stimulate the young plants to the development of long roots; the work of
trenching should be carried out as early as possible, so as to let the ground
settle again before the seed is sown. If no sheltered locality be available, the
nursery must have some artificial protection from the wind, such as dykes or
hedges, whilst on poor soil manuring with leaf-mould or the ashes of weeds is
advisable. Where such temporary nurseries have been well chosen, no covering or
protection for the young seedlings is necessary, and in no case should twigs or
sprays of Scots pine be used for such a purpose, as their needles are often
infected with the fungous disease occasioned by Hysterium pinastri, which may
only too easily be thus communicated to the seedlings.
In order to provide a
supply of transplants for the filling up of blanks, or for the introduction of
Scots pine as a subordinate tree in forests of other species, one must adopt the
usual method of schooling the plants in nurseries, which should of course be
located as near to the ultimate destination as practicable, in order to reduce to
a minimum the costs of transport and the risk of damage during the final
operations of planting out.
All planting
operations with Scots pine on dry soils should be carried out as early as
possible in spring, so that the young plants may have a fair chance of
establishing themselves before the usual period of drought sets in. The better
and the fresher the soil, the less danger is there of late operations proving
unsuccessful.
Back
to Index
|