Subalpine-fir Adapts Poorly to Warmer Climate

Subalpine-fir seedlings from high elevations in central British Columbia are less adaptable to warmer temperatures than are seedlings of lodgepole pine or interior spruce.

To determine how three tree species might adjust to climatic warming, seeds collected over an 1100 m elevation gradient were grown in greenhouses under 25 °C daytime temperatures.

Pine and spruce showed similar adaptive behaviours regarding allocation of growth and the date that height growth ended.

In comparison, subalpine-fir responded more conservatively. Subalpine-fir seedlings originating from higher elevations put less emphasis on developing photosynthetic capacity, by reducing foliage production, to grow more shoot and root tissue. Spruce and pine do not make trade-offs between foliage and shoot growth. Pine from all elevations had the highest proportion of foliage to shoot mass, a reflection of its fast-growing, pioneer strategy.

Decreasing daylight hours trigger conifers to terminate a season's height growth, but in the warmer temperature, height growth continued up to a month longer in pine and spruce seedlings. Fir, particularly from higher elevations, extended its growing season much less, and overall ceased growing earlier than did pine or spruce. Of the three conifer species, pine's growth response to warm temperatures was the least influenced by the elevation from which its seed originated.