Shifting Biomes in Alaska
Scientists have hypothesized that evergreen forests will increase their growth at the margin of present tundra areas, while simultaneously declining at the margins of temperate forests to the south. New research highlights this shift in biomes caused by a warming climate by combining data gathered from satellite imagery and tree rings.
The study, which will be published in the journal Ecology Letters, provides a regional picture of forest productivity in Alaska which previously did not exist.
“The results provide evidence for the initiation of a biome shift in response to climate change, and indicate that some ecosystem models may be missing fundamental changes taking place in the circumpolar region,” said lead author Pieter Beck, a post-doctoral fellow at WHRC. He adds that “while the findings contrast with some recent model predictions of increased high latitude vegetation productivity, they are consistent with longer-term projections of global vegetation models.”
The team behind the research studied change sin forest productivity since 1982 across boreal Alaska by combining satellite estimates of primary productivity with a large tree-ring data set.
They found that both records showed a consistent growth increase at the boreal-tundra borders, while simultaneously seeing a drought-induced productivity declines throughout the interior of Alaska, supporting the underlying hypothesis of a biome shift.
“Most people don’t think of high latitudes forests as being drought stressed – and they are not in the traditional sense of having soils dry up and blow away – but their growth is negatively impacted by hot dry air masses and those have increased in recent years,” said Scott Goetz, a senior scientist at WHRC who proposed the study and co-authored the manuscript. “This paper shows those drought impacts are captured in both the satellite and the tree ring record. Of course the tree rings go back in time much further than the satellite observations, which only extend about 30 years, but the changes that we observe from satellites are clearly supported not only by the tree rings but also by carbon isotope analysis of the wood.”