The Pinophyta, also known as Coniferophyta or Coniferae, or commonly
as conifers, are a division of vascular land plants containing a
single extant class, Pinopsida. They are gymnosperms, cone-bearing
seed plants. All extant conifers are perennial woody plants with
secondary growth. The great majority are trees, though a few are
shrubs. Examples include cedars, Douglas firs, cypresses, firs,
junipers, kauri, larches, pines, hemlocks, redwoods, spruces, and
yews. As of 1998, the division
Pinophyta was estimated to contain
eight families, 68 genera, and 629 living species.
Although the total number of species is relatively small, conifers are
ecologically important. They are the dominant plants over large areas
of land, most notably the taiga of the Northern Hemisphere, but
also in similar cool climates in mountains further south. Boreal
conifers have many wintertime adaptations. The narrow conical shape of
northern conifers, and their downward-drooping limbs, help them shed
snow. Many of them seasonally alter their biochemistry to make them
more resistant to freezing. While tropical rainforests have more
biodiversity and turnover, the immense conifer forests of the world
represent the largest terrestrial carbon sink. Conifers are of great
economic value for softwood lumber and paper production.
2 Taxonomy and naming
Tree ring structure
3.4 Life cycle
3.5 Female reproductive cycles
Seed dispersal mechanism
4 Invasive species
7 Conditions for growth
8 Economic importance
10 External links
The narrow conical shape of northern conifers, and their
downward-drooping limbs, help them shed snow.
The earliest conifers in the fossil record date to the late
Carboniferous (Pennsylvanian) period (about 300 million years ago),
possibly arising from Cordaites, a genus of seed-bearing Gondwanan
plants with cone-like fertile structures. Pinophytes, Cycadophytes,
and Ginkgophytes all developed at this time. An important
adaptation of these gymnosperms was allowing plants to live without
being so dependent on water. Other adaptations are pollen (so
fertilisation can occur without water) and the seed, which allows the
embryo to be transported and developed elsewhere.
Conifers appear to be one of the taxa that benefited from the
Triassic extinction event, and were the dominant land plants
of the Mesozoic. They were overtaken by the flowering plants, which
first appeared in the Cretaceous, and became dominant in the Cenozoic
era. They were the main food of herbivorous dinosaurs, and their
resins and poisons would have given protection against herbivores.
Reproductive features of modern conifers had evolved by the end of the
Taxonomy and naming
Conifer is a Latin word, a compound of conus (cone) and ferre (to
bear), meaning "the one that bears (a) cone(s)".
The division name
Pinophyta conforms to the rules of the International
Code of Nomenclature for algae, fungi, and plants (ICN), which state
(Article 16.1) that the names of higher taxa in plants (above the rank
of family) are either formed from the name of an included family
(usually the most common and/or representative), in this case Pinaceae
(the pine family), or are descriptive. A descriptive name in
widespread use for the conifers (at whatever rank is chosen) is
Coniferae (Art 16 Ex 2).
According to the ICN, it is possible to use a name formed by replacing
the termination -aceae in the name of an included family, in this case
preferably Pinaceae, by the appropriate termination, in the case of
this division ‑ophyta. Alternatively, "descriptive botanical names"
may also be used at any rank above family. Both are allowed.
This means that if conifers are considered a division, they may be
Pinophyta or Coniferae. As a class they may be called Pinopsida
or Coniferae. As an order they may be called
Pinales or Coniferae or
Conifers are the largest and economically most important component
group of the gymnosperms, but nevertheless they comprise only one of
the four groups. The division
Pinophyta consists of just one class,
Pinopsida, which includes both living and fossil taxa. Subdivision of
the living conifers into two or more orders has been proposed from
time to time. The most commonly seen in the past was a split into two
Taxaceae only) and
Pinales (the rest), but recent
research into DNA sequences suggests that this interpretation leaves
Taxales as paraphyletic, and the latter order is
no longer considered distinct. A more accurate subdivision would be to
split the class into three orders,
Pinales containing only Pinaceae,
Araucariaceae and Podocarpaceae, and
Cupressales containing the remaining families (including Taxaceae),
but there has not been any significant support for such a split, with
the majority of opinion preferring retention of all the families
within a single order Pinales, despite their antiquity and diverse
Phylogeny of the
Pinophyta based on cladistic analysis of molecular
The conifers are now accepted as comprising seven families, with a
total of 65–70 genera and 600–630 species (696 accepted
names). The seven most distinct families are linked
in the box above right and phylogenetic diagram left. In other
Cephalotaxaceae may be better included within the
Taxaceae, and some authors additionally recognize Phyllocladaceae as
Podocarpaceae (in which it is included here). The family
Taxodiaceae is here included in family Cupressaceae, but was widely
recognized in the past and can still be found in many field guides. A
new classification and linear sequence based on molecular data can be
found in an article by Christenhusz et al.
The conifers are an ancient group, with a fossil record extending back
about 300 million years to the
Paleozoic in the late Carboniferous
period; even many of the modern genera are recognizable from fossils
60–120 million years old. Other classes and orders, now long
extinct, also occur as fossils, particularly from the late Paleozoic
Fossil conifers included many diverse forms, the
most dramatically distinct from modern conifers being some herbaceous
conifers with no woody stems. Major fossil orders of conifers or
conifer-like plants include the Cordaitales, Vojnovskyales, Voltziales
and perhaps also the Czekanowskiales (possibly more closely related to
All living conifers are woody plants, and most are trees, the majority
having monopodial growth form (a single, straight trunk with side
branches) with strong apical dominance. Many conifers have distinctly
scented resin, secreted to protect the tree against insect infestation
and fungal infection of wounds. Fossilized resin hardens into amber.
The size of mature conifers varies from less than one meter, to over
100 meters. The world's tallest, thickest, largest, and oldest
living trees are all conifers. The tallest is a Coast Redwood (Sequoia
sempervirens), with a height of 115.55 meters (although one Victorian
mountain ash, Eucalyptus regnans, allegedly grew to a height of 140
meters, although the exact dimensions were not confirmed).[citation
needed] The thickest, or tree with the greatest trunk diameter, is a
Montezuma Cypress (
Taxodium mucronatum), 11.42 meters in diameter. The
largest tree by three-dimensional volume is a Giant Sequoia
Sequoiadendron giganteum), with a volume 1486.9 cubic meters. The
smallest is the pygmy pine (Lepidothamnus laxifolius) of New Zealand,
which is seldom taller than 30 cm when mature. The oldest is
a Great Basin Bristlecone
Pinus longaeva), 4,700 years old.
Pinaceae: needle-like leaves and vegetative buds of Coast Douglas fir
Pseudotsuga menziesii var. menziesii)
Araucariaceae: Awl-like leaves of Cook
Pine (Araucaria columnaris)
Abies grandis (grand fir), and many other species with spirally
arranged leaves, leaf bases are twisted to flatten their arrangement
and maximize light capture.
Cupressaceae: scale leaves of Lawson's Cypress (Chamaecyparis
lawsoniana); scale in mm
Since most conifers are evergreens, the leaves of many conifers are
long, thin and have a needle-like appearance, but others, including
most of the
Cupressaceae and some of the Podocarpaceae, have flat,
triangular scale-like leaves. Some, notably
Agathis in Araucariaceae
Nageia in Podocarpaceae, have broad, flat strap-shaped leaves.
Others such as
Araucaria columnaris have leaves that are awl-shaped.
In the majority of conifers, the leaves are arranged spirally,
exceptions being most of
Cupressaceae and one genus in Podocarpaceae,
where they are arranged in decussate opposite pairs or whorls of 3
(-4). In many species with spirally arranged leaves, such as Abies
grandis (pictured), the leaf bases are twisted to present the leaves
in a very flat plane for maximum light capture.
Leaf size varies from
2 mm in many scale-leaved species, up to 400 mm long in the
needles of some pines (e.g. Apache Pine,
Pinus engelmannii). The
stomata are in lines or patches on the leaves, and can be closed when
it is very dry or cold. The leaves are often dark green in colour,
which may help absorb a maximum of energy from weak sunshine at high
latitudes or under forest canopy shade. Conifers from hotter areas
with high sunlight levels (e.g. Turkish
Pinus brutia) often have
yellower-green leaves, while others (e.g. blue spruce,
have a very strong glaucous wax bloom to reflect ultraviolet light. In
the great majority of genera the leaves are evergreen, usually
remaining on the plant for several (2-40) years before falling, but
five genera (Larix, Pseudolarix, Glyptostrobus,
Taxodium) are deciduous, shedding the leaves in autumn and leafless
through the winter. The seedlings of many conifers, including most
of the Cupressaceae, and
Pinus in Pinaceae, have a distinct juvenile
foliage period where the leaves are different, often markedly so, from
the typical adult leaves.
Tree ring structure
The internal structure of conifer
Tree rings are records of the influence of environmental conditions,
their anatomical characteristics record growth rate changes produced
by these changing conditions. The microscopic structure of conifer
wood consists of two types of cells: parenchyma, which have an oval or
polyhedral shape with approximately identical dimensions in three
directions, and strongly elongated tracheids. Tracheids make up more
than 90% of timber volume. The tracheids of earlywood formed at the
beginning of a growing season have large radial sizes and smaller,
thinner cell walls. Then, the first tracheids of the transition zone
are formed, where the radial size of cells and thickness of their cell
walls changes considerably. Finally, the latewood tracheids are
formed, with small radial sizes and greater cell wall thickness. This
is the basic pattern of the internal cel structure of conifer tree
Main article: Conifer cone
Most conifers are monoecious, but some are subdioecious or dioecious;
all are wind-pollinated. Conifer seeds develop inside a protective
cone called a strobilus. The cones take from four months to three
years to reach maturity, and vary in size from 2 mm to
600 mm long.
In Pinaceae, Araucariaceae,
Sciadopityaceae and most Cupressaceae, the
cones are woody, and when mature the scales usually spread open
allowing the seeds to fall out and be dispersed by the wind. In some
(e.g. firs and cedars), the cones disintegrate to release the seeds,
and in others (e.g. the pines that produce pine nuts) the nut-like
seeds are dispersed by birds (mainly nutcrackers, and jays), which
break up the specially adapted softer cones. Ripe cones may remain on
the plant for a varied amount of time before falling to the ground; in
some fire-adapted pines, the seeds may be stored in closed cones for
up to 60–80 years, being released only when a fire kills the parent
In the families Podocarpaceae, Cephalotaxaceae, Taxaceae, and one
Cupressaceae genus (Juniperus), the scales are soft, fleshy, sweet and
brightly colored, and are eaten by fruit-eating birds, which then pass
the seeds in their droppings. These fleshy scales are (except in
Juniperus) known as arils. In some of these conifers (e.g. most
Podocarpaceae), the cone consists of several fused scales, while in
others (e.g. Taxaceae), the cone is reduced to just one seed scale or
(e.g. Cephalotaxaceae) the several scales of a cone develop into
individual arils, giving the appearance of a cluster of berries.
The male cones have structures called microsporangia that produce
yellowish pollen through meiosis.
Pollen is released and carried by
the wind to female cones.
Pollen grains from living pinophyte species
produce pollen tubes, much like those of angiosperms. The gymnosperm
male gametophytes (pollen grains) are carried by wind to a female cone
and are drawn into a tiny opening on the ovule called the micropyle.
It is within the ovule that pollen-germination occurs. From here, a
pollen tube seeks out the female gametophyte and if successful,
fertilization occurs. The resulting zygote develops into an embryo,
which along with its surrounding integument, becomes a seed.
Eventually the seed may fall to the ground and, if conditions permit,
grow into a new plant.
In forestry, the terminology of flowering plants has commonly though
inaccurately been applied to cone-bearing trees as well. The male cone
and unfertilized female cone are called male flower and female flower,
respectively. After fertilization, the female cone is termed fruit,
which undergoes ripening (maturation).
It was found recently that the pollen of conifers transfers the
mitochondrial organelles to the embryo, a sort of meiotic drive that
perhaps explains why
Pinus and other conifers are so productive, and
perhaps also has bearing on (observed?) sex-ratio bias
Pinaceae: unopened female cones of subalpine fir (
Taxaceae: the fleshy aril that surrounds each seed in the European Yew
Taxus baccata) is a highly modified seed cone scale
Pinaceae: pollen cone of a Japanese
Larch (Larix kaempferi)
Conifers are heterosporous, generating two different types of spores:
male microspores and female megaspores. These spores develop on
separate male and female sporophylls on separate male and female
cones. In the male cones, microspores are produced from
microsporocytes by meiosis. The microspores develop into pollen
grains, which are male gametophytes. Large amounts of pollen are
released and carried by the wind. Some pollen grains will land on a
female cone for pollination. The generative cell in the pollen grain
divides into two haploid sperm cells by mitosis leading to the
development of the pollen tube. At fertilization, one of the sperm
cells unites its haploid nucleus with the haploid nucleus of an egg
cell. The female cone develops two ovule, each of which contains
haploid haploid megaspores. A megasporocyte is divided by meiosis in
each ovule. Each winged pollen grain is a four celled male gametophyte
Three of the four cells break down leaving only a single surviving
cell which will develop into a female multicellular gametophyte. The
female gametophytes grow to produce two or more archegonia, each of
which contains an egg. Upon fertilization, the diploid egg will give
rise to the embryo, and a seed is produced. The female cone then
opens, releasing the seeds which grow to a young seedling.
To fertilize the ovum, the male cone releases pollen that is carried
on the wind to the female cone. This is pollination. (Male and female
cones usually occur on the same plant.)
The pollen fertilizes the female gamete (located in the female cone).
Fertilization in some species does not occur until 15 months after
A fertilized female gamete (called a zygote) develops into an embryo.
A seed develops which contains the embryo. The seed also contains the
integument cells surrounding the embryo. This is an evolutionary
characteristic of the Spermatophyta.
Mature seed drops out of cone onto the ground.
Seed germinates and seedling grows into a mature plant.
When the plant is mature, it produces cones and the cycle continues.
Female reproductive cycles
Conifer reproduction is synchronous with seasonal changes in temperate
zones. Reproductive development slows to a halt during each winter
season, and then resumes each spring. The male strobilus development
is completed in a single year. Conifers are classified by three
reproductive cycles, namely; 1-, 2-, or 3- . The cycles refers to the
completion of female strobilus development from initiation to seed
maturation. All three types or reproductive cycles have a long gap in
between pollination and fertilization.
One year reproductive cycle:The genera includes Abies, Picea, Cedrus,
Keteleeria (Pinaceae) and Cupressus, Thuja,
Cunninghamia and Sequoia (Cupressaceae). Female strobili
are initiated in late summer or fall in a year, then they overwinter.
Female strobili emerge followed by pollination in the following spring
Fertilization takes place in summer of the following year, only
3–4 months after pollination. Cones mature and seeds are then shed
by the end of that same year.
Pollination and fertilization occurs in
a single growing season.
Two-year reproductive cycle:The genera includes Widdringtonia,
Sequoiadendron (Cupressaceae) and most species of Pinus. Female
strobilus initials are formed in late summer or fall then overwinter.
It emerges and receives pollen in the first year spring and become
conelets. The conelet goes through another winter rest and in the
spring of the 2nd year. The
Archegonia form in the conelet and
fertilization of the archegonia occurs by early summer of the 2nd
year, so the pollination-fertilization interval exceeds a year. After
fertilization, the conelet is considered an immature cone. Maturation
occurs by autumn of the 2nd year, at which time seeds are shed. In
summary, the 1-year and the 2-year cycles differ mainly in the
duration of the pollination- fertilization interval.
Three-year reproductive cycle: Three of the conifer species are pine
Pinus torreyana) which have
pollination and fertilization events separated by a 2-year interval.
Female strobili initiated during late summer or autumn in a year, then
overwinter until the following spring. Female strobili emerge then
pollination occurs in spring of the 2nd year then the pollinated
strobili become conelets in same year (i.e. the second year). The
female gametophytes in the conelet develop so slowly that the
megaspore does not go through free-nuclear divisions until autumn of
the 3rd year. The conelet then overwinters again in the free-nuclear
female gametophyte stage.
Fertilization takes place by early summer of
the 4th year and seeds mature in the cones by autumn of the 4th
The growth and form of a forest tree are the result of activity in the
primary and secondary meristems, influenced by the distribution of
photosynthate from its needles and the hormonal gradients controlled
by the apical meristems (Fraser et al. 1964). External factors
also influence growth and form.
Fraser recorded the development of a single white spruce tree from
1926 to 1961. Apical growth of the stem was slow from 1926 through
1936 when the tree was competing with herbs and shrubs and probably
shaded by larger trees. Lateral branches began to show reduced growth
and some were no longer in evidence on the 36-year-old tree. Apical
growth totalling about 340 m, 370 m, 420 m, 450 m, 500 m, 600 m, and
600 m was made by the tree in the years 1955 through 1961,
respectively. The total number of needles of all ages present on the
36-year-old tree in 1961 was 5.25 million weighing 14.25 kg. In
1961, needles as old as 13 years remained on the tree.The ash weight
of needles increased progressively with age from about 4% in
first-year needles in 1961 to about 8% in needles 10 years old. In
discussing the data obtained from the one 11 m tall white spruce,
Fraser et al. (1964) speculated that if the photosynthate used in
making apical growth in 1961 was manufactured the previous year, then
the 4 million needles that were produced up to 1960 manufactured food
for about 600,000 mm of apical growth or 730 g dry weight, over
12 million mm3 of wood for the 1961 annual ring, plus 1 million new
needles, in addition to new tissue in branches, bark, and roots in
1960. Added to this would be the photosynthate to produce energy to
sustain respiration over this period, an mount estimated to be about
10% of the total annual photosynthate production of a young healthy
tree. On this basis, one needle produced food for about 0.19 mg
dry weight of apical growth, 3 mm3 wood, one-quarter of a new
needle, plus an unknown amount of branch wood, bark and roots.
The order of priority of photosynthate distribution is probably: first
to apical growth and new needle formation, then to buds for the next
year's growth, with the cambium in the older parts of the branches
receiving sustenance last. In the white spruce studied by Fraser et
al. (1964), the needles constituted 17.5% of the over-day weight.
Undoubtedly, the proportions change with time.
Seed dispersal mechanism
Wind and animals dispersals are two major mechanisms involved in the
dispersal of conifer seeds.
Wind bore seed dispersal involves two
processes, namely; local neighborhood dispersal (LND) and long-
distance dispersal (LDD). Long-distance dispersal distances ranges
from 11.9–33.7 kilometres (7.4–20.9 mi) from the source.
The bird family,
Corvidae is the primary distributor of the conifer
seeds. These birds are known to cache 32,000 pine seeds and transport
the seeds as far as 12–22 kilometres (7.5–13.7 mi) from the
source. The birds store the seeds in the soil at depths of 2–3
centimetres (0.79–1.18 in) under conditions which favor
Main article: Wilding conifer
A number of conifers originally introduced for forestry have become
invasive species in parts of New Zealand, including Radiata pine
Pinus radiata), Lodgepole pine (P. contorta), Douglas fir
Pseudotsuga mensiezii) and European larch (Larix decidua). In
parts of South Africa,
Pinus pinaster, P. patula and P. radiata have
been declared invasive species. These wilding conifers are a
serious environmental issue causing problems for pastoral farming and
At least 20 species of roundheaded borers of the family Cerambycidae
feed on the wood of spruce, fir, and hemlock (Rose and Lindquist
1985). Borers rarely bore tunnels in living trees, although when
populations are high, adult beetles feed on tender twig bark, and may
damage young living trees. One of the most common and widely
distributed borer species in
North America is the whitespotted sawyer
(Monochamus scutellatus). Adults are found in summer on newly fallen
or recently felled trees chewing tiny slits in the bark in which they
lay eggs. The eggs hatch in about 2 weeks, and the tiny larvae tunnel
to the wood and score its surface with their feeding channels. With
the onset of cooler weather, they bore into the wood making oval
entrance holes and tunnel deeply. Feeding continues the following
summer, when larvae occasionally return to the surface of the wood and
extend the feeding channels generally in a U-shaped configuration.
During this time, small piles of frass extruded by the larvae
accumulate under logs. Early in the spring of the second year
following egg-laying, the larvae, about 30 mm long, pupate in the
tunnel enlargement just below the wood surface. The resulting adults
chew their way out in early summer, leaving round exit holes, so
completing the usual 2-year life cycle.
A cultivar of
Pinus sylvestris with a narrow "fastigiate" growth habit
Conifers – notably
Abies (fir), Cedrus, Chamaecyparis
lawsoniana (Lawson's cypress),
Cupressus (cypress), juniper, Picea
Thuja - have been the subject of
selection for ornamental purposes (for more information see the
silviculture page). Plants with unusual growth habits, sizes, and
colours are propagated and planted in parks and gardens throughout the
Conditions for growth
Conifers can absorb nitrogen in either the ammonium (NH4+) or nitrate
(NO3−) form, but the forms are not physiologically equivalent. Form
of nitrogen affected both the total amount and relative composition of
the soluble nitrogen in white spruce tissues (Durzan and Steward
Ammonium nitrogen was shown to foster arginine and amides
and lead to a large increase of free guanidine compounds, whereas in
leaves nourished by nitrate as the sole source of nitrogen guanidine
compounds were less prominent. Durzan and Steward noted that their
results, drawn from determinations made in late summer, did not rule
out the occurrence of different interim responses at other times of
Ammonium nitrogen produced significantly heavier (dry weight)
seedlings with higher nitrogen content after 5 weeks (McFee and Stone
1968) than did the same amount of nitrate nitrogen. Swan
(1960) found the same effect in 105-day-old white spruce.
The general short-term effect of nitrogen fertilization on coniferous
seedlings is to stimulate shoot growth more so than root growth
(Armson and Carman 1961). Over a longer period, root growth is
also stimulated. Many nursery managers were long reluctant to apply
nitrogenous fertilizers late in the growing season, for fear of
increased danger of frost damage to succulent tissues. A presentation
at the North American
Tree Nursery Soils Workshop at Syracuse
in 1980 provided strong contrary evidence: Bob Eastman, President of
the Western Maine
Forest Nursery Co. stated that for 15 years he has
been successful in avoiding winter “burn” to Norway spruce and
white spruce in his nursery operation by fertilizing with
50-80 lb/ac (56–90 kg/ha) nitrogen in September, whereas
previously winter burn had been experienced annually, often severely.
Eastman also stated that the overwintering storage capacity of stock
thus treated was much improved (Eastman 1980).
The concentrations of nutrient in plant tissues depend on many
factors, including growing conditions. Interpretation of
concentrations determined by analysis is easy only when a nutrient
occurs in excessively low or occasionally excessively high
concentration. Values are influenced by environmental factors and
interactions among the 16 nutrient elements known to be essential to
plants, 13 of which are obtained from the soil, including nitrogen,
phosphorus, potassium, calcium, magnesium, and sulfur, all used in
relatively large amounts (Buckman and Brady 1969). Nutrient
concentrations in conifers also vary with season, age and kind of
tissue sampled, and analytical technique. The ranges of concentrations
occurring in well-grown plants provide a useful guide by which to
assess the adequacy of particular nutrients, and the ratios among the
major nutrients are helpful guides to nutritional imbalances.
The softwood derived from conifers is of great economic value,
providing about 45% of the world’s annual lumber production. Other
uses of the timber include the production of paper and plastic from
chemically treated wood pulp. Some conifers also provide foods such as
pine nuts and
Juniper berries, used to flavor gin.
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from phyla Coniferophyta, Cycadophyta, Gnetophyta, and Ginkgophyta:
characteristics of early seed plants". 80 (9): 954–961.
^ a b c Henry, R.J.(2005)
Plant Diversity and evolution. London: CABI.
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^ Derived from papers by A. Farjon and C. J. Quinn & R. A. Price
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Ecology of the southern
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Tree Improvement in
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^ a b c Singh, H. 1978. Embryology of gymnosperms. Berlin, Gebruder
^ a b c Fraser, D.A.; Belanger, L.; McGuire, D.; Zdrazil, Z. 1964.
Total growth of the aerial parts of a white spruce tree at Chalk
River, Ontario, Canada. Can. J. Bot. 42:159–179.
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dispersal distances: implications for transgenic
Ecological Applications 16:117-124
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Ecology 4: 185-219
^ a b "South Island wilding conifer strategy". Department of
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^ Rose, A.H.; Lindquist, O.H. 1985. Insects of eastern spruces, fir
and, hemlock, revised edition. Gov’t Can., Can. For. Serv., Ottawa,
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^ Farjon, Aljos (2010). A handbook of the world's conifers. Brill
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^ Durzan, D.J.; Steward, F.C. 1967. The nitrogen metabolism of Picea
glauca (Moench) Voss and
Pinus banksiana Lamb. as influenced by
mineral nutrition. Can. J. Bot. 45:695–710.
^ McFee, W.W.; Stone, E.L. 1968.
Ammonium and nitrate as nitrogen
Pinus radiata and
Picea glauca. Soil Sci. Soc. Amer. Proc.
^ Swan, H.S.D. 1960. The mineral nutrition of Canadian pulpwood
species. 1. The influence of nitrogen, phosphorus, potassium and
magnesium deficiencies on the growth and development of white spruce,
black spruce, jack pine and western hemlock seedlings grown in a
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^ Armson, K.A.; Carman, R.D. 1961.
Forest tree nursery soil
management. Ont. Dep. Lands & Forests, Timber Branch, Ottawa ON.
^ Eastman, B. 1980. The Western Maine
Forest Nursery Company. pp.
291-295 In Proc. of the North American
Tree Nursery Soils
Workshop, July 28-August 1, 1980, Syracuse, New York. Environment
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^ Buckman, H.O.; Brady, N.C. 1969. The Nature and Properties of Soils,
7th ed. Macmillan NY. 653 p.
Seed sex ratio in dioecious plants depends on relative dispersal of
pollen and seeds: an example using a chessboard simulation model - T.
DE JONG 2002
Wikimedia Commons has media related to Pinophyta.
Wikispecies has information related to Pinophyta
300 million-year-old conifer in Illinois - 4/2007
World list of conifer species from Conifer Database by A. Farjon in
the Catalogue of Life
Tree browser for conifer families and genera via the Catalogue of Life
Royal Horticultural Society Encyclopedia of Conifers: A Comprehensive
Guide to Cultivars and Species.
DendroPress: Conifers Around the World.
Knee, Michael. "Gymnosperms". Retrieved 14 January 2016.
Plantae sensu lato
& land plants)
& land plants)
Angiosperms or flowering plants
† = extinct. See also the list of plant orders.