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Black spruce assimilates nitrate in boreal winter
Lina A Koyama1, Knut Kielland2
1Laboratory of Biosphere Informatics, Department of Social Informatics, Graduate School of Informatics, Kyoto University, Kyoto, Japan.
Tree Physiology
|November 22, 2018
Summary
Black spruce trees in Alaska can absorb nitrogen even in freezing winter temperatures, challenging the idea of dormancy. This suggests nutrient acquisition extends beyond the growing season in boreal forests.
Area of Science:
- Forest Ecology
- Plant Physiology
- Biogeochemistry
Background:
- Boreal forests are perceived as dormant in winter regarding plant nutrient uptake.
- Recent data indicate soil remains active, with nutrient transformations occurring post-snowfall.
Purpose of the Study:
- To investigate nitrate assimilation in black spruce (Picea mariana) during winter in Interior Alaska.
- To test if black spruce can assimilate nitrate (NO3--N) at sub-freezing temperatures.
Main Methods:
- Measured nitrate reductase activity (NRA) and nitrate concentration in needles and roots of black spruce.
- Collected samples during summer and winter from two boreal forest sites.
- Assayed NRA at 30 °C and -3 °C for winter samples.
Main Results:
- Nitrate reductase activity and nitrate were detected in black spruce tissues during both summer and winter.
- Season had minimal impact on NRA and nitrate concentration.
- Significant NRA was observed in winter samples, even at -3 °C.
Conclusions:
- Black spruce can assimilate nitrate below freezing temperatures, indicating nitrogen acquisition extends into winter.
- Winter nitrogen uptake should be considered in boreal forest nitrogen budgets.
- Challenges the traditional view of winter dormancy in boreal plant physiology.
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