气候变化领域集成服务门户

Permafrost degradation due to rapid increase in ground surface temperature (GST) in recent years may strongly affect boreal forest ecosystems. However, comparatively few studies have explored how changes in permafrost affect tree growth dynamics in boreal forest. Here, we used a tree ring network of 12 Dahurian larch (Larix gmelinii) sites across permafrost regions in northeast China. We observed an increase in L. gmelinii growth over the past decade, seemingly linked to a shift in their climatic limitations, where winter GST has become the most strongly limiting factor for L. gmelinii growth. The recent increase in growth was particularly strong in older trees (>300years), which could be related to older trees having a more developed root system. GST was the main limiting factor for tree growth. While summer GST had a somewhat consistently positive correlation with tree growth, winter GST has shifted from a negative to a strongly positive correlation with growth in the last decade, coincidental with a sharp increase in winter GST since 2004. Winter GST is also strongly correlated with the rapidly thawing permafrost dynamics. Overall, our results suggest a link between recent changes in the permafrost and shifts in climate-growth correlations for one of the main boreal tree species. As a result, L. gmelinii has experienced an important increase in radial growth that may indicate that, unlike what has been reported for other boreal species, it may temporally benefit from warming climate in the continuous permafrost region of the Asian boreal forests.

Plain Language Summary Dahurian larch (Larix gmelinii) is widely distributed in northeastern Asian boreal forests and the only tree species that can endure the extreme cold climate in the permafrost plains of Asian boreal forests. Permafrost regions have degraded greatly with the rapid warming in the recent decade, posing a serious threat to the survival of larch. We sampled a tree ring network of Dahurian larch from the southern edge of its natural distribution to detect how climate warming has influenced larch growth in the permafrost regions. Our results showed that soil temperature is the dominant climatic factor limiting tree growth. With increasing soil temperatures, larch showed a rapid increase in growth in the last 10years, especially pronounced in older trees. This unusual phenomenon was linked to a sharp increase in winter soil temperature, which determines the soil freezing depth of the permafrost. We also found that the larch grew more quickly in the region where the soil freezing depth is shallow. We concluded that warmer winter soil temperatures have caused an increase in larch growth in recent decades.