Black spruce

The black spruce or black spruce or sapinette black , whose scientific name is Picea mariana is a Conifère common to the North-East of the the United States and especially to the Canada. The english-speaking names it Black spruce .

It is one of nearly 40 species to spruces, and one of most resistant to the hard climates (Toundra) of the Arctic; with the “red” spruce (Picea rubens), and the “white” spruce ( Picea glauca ). It is for this reason the symbol of the Northern forest of America, where it pushes until the limit of the Toundra.

It is sometimes victim of important attacks of insects défoliateurs, that the tree generally supports, if it are not repeated more than 4 or 5 years consecutively. Forest fires (natural or of human origin) are another factor of disturbance of the settlements.

Description

The Black spruce has a bulky pyramidal port. It is buissonnante and packed (6 to 8 m in height) in the zones where the climate is hardest, and arborescent is slim (20 m in height) in the zones which are appropriate to him, with branches more and more falling with the age.
Ses branches is rough and its scaly bark.
Le cone is small, of color crimson, transfering with brown clearly with maturity.

Distribution

It is one of the most widespread Conifère S of the Canadian forest, the north of Étast-Plain and Alaska. It dominates the interior region of the Alaska and rarefies until becoming very rare in extreme cases northern of the Northern forest. It is adapted to relatively extreme mediums and pushes as well on dry, acid and sandy grounds as on wet grounds boggy.

Ecology

The virginal reproduces sometimes badly by sowing (very badly in the north of the Tundra, where the diffusion is almost exclusively assured by the natural Marcottage some subjects resulting from seeds brought by the wind or the animals). The reproduction by layering is made with the detriment genetic Diversité, which in this case is however maintained by the Incendie S and epidemics or attacks insects (cf selective pressure). Studies showed that on the level mitochondrial, the black spruce is indeed genetically very homogeneous in the subarctic zone, but not on the level of the cellular core, where it shows a genetic diversity comparable with that of the northern forests more in the south. Its airborne Pollen on long distances would have allowed a redistribution of the nuclear Allèle S of the boreal populations until most Scandinavian, compensating for to some extent low genetic diversity of the genome mitochondrial marked by the youth of this forest (glacial recolonisation post- ).

The operation of the subarctic ecosystem S, characterized by populations of trees including/understanding a great number of individuals and a small number of species is still badly included/understood, but it seems that the climate, fire, and the periodic Défoliation by the insects (such as for example the Tordeuse of the buds of the virginal (TBE) Choristoneura fumiferana ), as well as genetic diversity mainly seem to control the distribution of the virginal and the associated species.

The impacts of the Climate warming and the extension of the Sylviculture and the close-cropped cuts are also badly included/understood. There exist probably loops of Rétroaction S complexes which will take importance, implying for example the défoliateurs, who allow by limiting or blocking evapotranspiration virginal to help of the whole settlements to support periods of Sécheresse, while limiting the fire hazard. The Mushroom S of the ground and the Lichen S could also have a great importance in the adaptation of the ecosystems.

Importance of the fires

A study relating to the recolonisation of sites in the north of Alaska showed that fire stimulated the recruitment of the black spruce, but with a low genetic diversity. The low growth of the species in the cold and acid zones and a weak production of viable seeds is a time compensated by the longevity of the adults, but fires must at least be separated by 350 years so that the population remains stable.

The variations of the severity of the burning of the ground (cf variation related on the wind, the exposure, the moisture of the ground, the drainage, etc) seem to order the owners écopaysagers of Régénération; In the case of a study made afterwards of the various fires of intensity in the center of Alaska, the black spruce was the species whose sowings were most affected by the grounds most degraded by fire, whereas on the contrary the poplar false-trembles (Populus tremuloides Michx.) there produced a air Biomasse (g/m2) was (7 to 8 years after fires) more than 1000 times higher than on the stations where the ground had been the least severely flarings. There, a weak combustion of the ground supported the graminaceous ones and the shrubs with persistent sheets. On the grounds the most strongly flarings, the sheets of the poplar and the foam acrocarpes carpet could accelerate the restoration of the Litière and produce a bed of unfavourable Germination to a monospecific population of conifers to the profit of mixed settlements of conifers dominated by leafy trees.

Deteriorations

As in all the extreme mediums, of the diseases or more often of defoliations vast settlements of trees touch. Certain virginals cover lichens after defoliations and before deteriorations. A colonization unusually important of branches of black spruce decaying by the lichen Bryoria seems to be a good witness (Bioindicateur) owing to the fact that this part of the tree before (up to 30 years front, even more) was strongly défoliées by the tortrix of the virginal, but the Bryoria is not responsible for deterioration. , it simply benefitted from the light and perhaps of excreted of caterpillars.

Adaptation to the warming

It is an increasingly studied question. The increase in CO₂ and the warming seem to be able to dope the reproduction by seed and the growth of the virginal, except to the extreme north or the species is limited by the winds and the estival temperature too fraiche, which can let think that the enforestation of the toundric hills projected by some the scenarios “2 X CO₂” (of doubling of the rate of CO₂ in the air) could be slower than envisaged in north, where the reproduction by seed generally fails the profit of the natural layering which allows only one very slow colonization towards north.

The increase in the estival temperature (nap of the degree-days) seems a determining parameter. Note of Isabelle Gamache). The modifications of the winds at the time of pollination could also have a certain importance, just as the estival fires and the increase in snowing up in winter or pluviometry in spring and in autumn (example of protocol of study for the impact of pluviometry and snowing up on the black spruce)

Uses

With the Canada, its first current use is the exploitation, often in Coupe shaves for the production of Pulp paper

The virginal was used a long time for the Charpente (wood solid, available, right, and light)

One extracts from it from the Young branches (needles) a essential Huile rich in Terpène S (Camphène; 15 to 20%.) and a Ester (Acetate of bornyl; 37 to 45%) famous Sedative, pointing out the odor of the sap of pine.

See too

Pinaceae

External bonds

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