Students of global warming know most plants flourish in an enriched carbon dioxide environment. They also know many plants will benefit from a longer growing season, when winter ends earlier and begins later with a warming so concentrated in the high latitudes and the cool season.
But prior research suggested these benefits would not transfer to some high-latitude species, since earlier thaws and warmer springs would result in a net loss of carbon from boreal spruce and tundra ecosystems.
A recent study counters that claim. As part of a major multiyear project, researchers measured carbon uptake in a heavily instrumented deciduous forest site in Saskatchewan, focusing on the trembling aspen, balsam poplar, and hazelnut species.
The aspen leaf emergence date was highly significantly correlated to higher spring air and soil temperatures. Likewise, the annual sequestration of carbon was related to spring warmth. Comparing their seasonal relationships to those based on annual data, they found spring temperature was more important in determining carbon sequestration than yearly average temperature.
The last year of their published research was 1998, when the latest major El Niño event was in full force. In that season, they measured a doubling of carbon sequestration (along with much higher spring air temperatures and very early leaf emergence). The authors noted
these results are in contrast with findings at a boreal spruce site showing that earlier spring thaws can decrease carbon sequestration as a result of increased soil respiration. The large increase in carbon sequestration by this ecosystem is considered a significant and unexpected benefit from spring weather attributed to the 1997–98 [El Niño] event.
Reference
Black, T.A. et al., 2000. Increased carbon sequestration by a boreal deciduous forest in years with a warm spring. Geophysical Research Letters, 27, 1271-1274.
