Picea Mariana - Ecology

Ecology

Growth varies with site quality. In swamp and muskeg it shows progressively slower growth rates from the edges toward the centre. The roots are shallow and wide spreading with fallen trees are colloquially called "drunken trees", and are often associated with thawing of permafrost. In the northern part of its range, ice pruned asymmetric Black Spruce are often seen, with diminished foliage on the windward side.

In the southern portion of its range it is found primarily on wet organic soils, but farther north its abundance on uplands increases. In the Great Lakes States it is most abundant in peat bogs and swamps, also on transitional sites between peatlands and uplands. In these areas it is rare on uplands, except in isolated areas of northern Minnesota and the Upper Peninsula of Michigan.

Most stands are even-aged due to frequent fire intervals in Black Spruce forests. It commonly grows in pure stands on organic soils and in mixed stands on mineral soils. It is tolerant of nutrient-poor soils, and is commonly found on poorly drained acidic peatlands. It is considered a climax species over most of its range. However, some ecologists question whether Black Spruce forests truly attain climax because fires usually occur at 50-150 year intervals, while "stable" conditions may not be attained for several hundred years.

The frequent fire return interval, a natural fire ecology, perpetuates numerous successional communities. Throughout boreal North America, Paper Birch Betula papyrifera and Quaking Aspen Populus tremuloides are successional hardwoods that frequently invade burns in Black Spruce. Black Spruce typically seeds in promptly after fire, and with the continued absence of fire, will eventually dominate the hardwoods.

It is a pioneer that invades the sedge mat in filled-lake bogs, though often preceded slightly by Tamarack Larch, Larix laricina, with which it may in time form a stable forest cover in swamps. However, as the peat soil is gradually elevated by the accumulation of organic matter, and the fertility of the site improves, Balsam Fir and Eastern Arborvitae Thuja occidentalis will eventually replace Black Spruce and Tamarack.

The larvae of the Spruce Budworm moth cause defoliation and if it occurs several years in a row will lead to death, though Black Spruce is less susceptible than White Spruce or Balsam Fir. Trees most at risk are those growing with Balsam Fir and White Spruce.