Growth of Black Spruce at its Northern Range Limit in Arctic Quebec, Canada

Abstract

The northernmost black spruce (Picea mariana) outpost in the Ungava Peninsula (arctic Quebec) is about 80 km north of the treeline. It is a confined (440 m²), low-growth krummholz stand with a fragmented cover of creeping ramets about 50 ± 15 cm high. The spruce patches probably belong to the same clone and resulted from lateral spread as suggested by the widespread distribution of connecting ramets. The krummholz stand developed in a sedge-shrub fen influenced by sheet flow promoting higher soil temperatures than nearby exposed permafrost soils. Stem analysis of the two largest ramets indicated slow horizontal, creeping growth during the 19th century, and relatively rapid upslope growth from 1880 to 1900 and vertical growth since the 1930s, most likely associated with recent warming. Periods of relatively fast lateral and vertical stem growth were recorded in the oblique sequences by larger annual rings below the stem apex; narrow and uniform annual rings developed during periods of slow stem growth. Because the outlier is at the arctic spruce line and far north from the treeline, the species probably established from long-distance seed transport.