Arctic pines grow fastest at midnight and stay stunted for days after hot spells
Tumajer J, Grudd H, Kuželová H, Lange J, Treml V
Climate Adaptation
The pines at the edge of the Arctic forest are telling us that hotter, drier days don't just slow growth in the moment; they suppress it for up to four days afterward, a lag that reshapes how the entire northern treeline will respond as summers get longer and warmer.
Scientists placed tiny sensors on Scots pine trees growing at the cold, dry edge of the Arctic forest in northern Sweden to track exactly when the trees added new wood. They found the trees grew fastest around midnight in summer, not during warm sunny afternoons, because midday heat and dry air actually shut growth down. Even more surprising, a hot dry day can suppress growth for up to four days afterward, meaning short-term weather events have longer consequences for the forest than anyone realized.
Key Findings
Stem radius increment peaked during cool, moist midnight hours (air temp 4-16°C, vapor pressure deficit near 0 kPa), with two optimal growth windows jointly accounting for 68% of total annual growth.
Immediate correlations between summer growth rates and temperature/humidity were negative, but those correlations flipped to positive when accounting for meteorological conditions up to 4 days prior.
Peak wood cell production occurred in warm summer months on an annual scale, but within summer days, midday warmth and rising solar altitude consistently suppressed radial growth.
chevron_right Technical Summary
Scots pine trees near the Arctic Circle grow fastest not at midday in summer, but during the cool, moist hours around midnight. This frequency-dependent growth pattern, driven by temperature and humidity, may explain why boreal forests aren't responding to warming as simply as climate models predict.
Abstract Preview
Original paper
Frequency-dependent climate sensitivity of sub-daily radial growth of tree stems at the dry Arctic treeline.
Radial growth of tree stems shows remarkable variability over the year but also within individual days. Understanding the frequency-dependent growth sensitivity, i.e., the shifting responses of woo...
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Pinus sylvestris is a species of tree in the pine family Pinaceae that is native to Eurasia. It is commonly known as the Scots pine in English; it is also known as the Scotch pine in the United States, and occasionally called the Baltic pine or European red pine. It can readily be identified by i...