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Why can black spruce survive on bogs and mountaintops but struggle to compete on richer sites?

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Tall giant sequoia trees with reddish bark and thick trunks rise closely together in a dense forest at Sequoia National Park, California. — Tree A stand of giant sequoia trees (*Sequoiadendron giganteum*) in Sequoia National Park, California.

The black spruce (Picea mariana) is highly tolerant of environmental extremes, allowing it to thrive in challenging habitats like bogs and mountaintops where other species may struggle. However, it possesses a low threshold for competition, meaning it is easily outcompeted by other tree species on more favorable, nutrient-rich sites.1

In extreme environments, a tree's survival is primarily dictated by its ability to withstand physical stressors, such as temperature extremes or poor soil conditions. In contrast, on moderate or richer sites, biotic factors—specifically the ability to compete for resources like light, water, and nutrients—become the primary determinants of success. Because the black spruce is specialized for survival in harsh conditions rather than for aggressive resource acquisition, it is typically displaced by more competitive species in less stressful environments.1