¹⁵N-uptake in Abies lasiocarpa and Abies nordmanniana at low root temperatures

Abstract

Low soil temperatures limit nutrient uptake with negative consequences for growth and foliage quality. A better understanding of the temperature sensitivity of root N uptake is required to improve the best management practices for fertilization of conifers. Uptake of ¹⁵N in saplings of Abies lasiocarpa (Hook) Nutt and Abies nordmanniana (Steven) Spach was studied at root temperatures of 3–15°C in hydroponics. ¹⁵N accumulation in shoots increased with temperature, showing accelerated accumulation from 7°C upward. At 3°C, uptake rates were low for both species. Between 7 and 12°C, ¹⁵N accumulation in shoots increased by a factor of 5 in A. lasiocarpa and by a factor of 3 in A. nordmanniana. The temperature response of N uptake was similar to root growth responses to temperature documented by previous studies. The results have implications for early season fertilization, where fertilization of both species should be withheld until soil temperatures reach 10–12°C.

Keywords:

• Nitrogen
• nordman fir
• nutrient uptake
• subalpine fir
• soil temperature