In a study published in the journal Nature Plants on Monday, researchers at Lawrence Berkeley National Laboratory projected changes in vegetation types at high latitudes as a result of global warming and increased fire rates.
The research team at Berkeley Lab predicted a shift in the composition of boreal forests in the coming century based on a “well tested mechanistic model,” according to the study. With a warmer climate, the boreal forests, now dominated by evergreen trees, are expected to transition to mostly deciduous broadleaf trees.
Deciduous broadleaf trees shed their leaves annually, while evergreens do not.
“The expansion of deciduous broadleaf forests will have several ecological and climatic feedbacks that affect the carbon cycle, and surface energy fluxes of the boreal forest,” said postdoctoral research fellow and co-author of the study Zelalem Mekonnen in an email.
Climate change already affects higher latitudes in northern regions of North America through a process called Arctic amplification, according to a Berkeley Lab press release. This phenomenon indicates that at higher latitudes, temperatures will increase faster than the global average.
Taking climatic predictions into account, the study projects that by the year 2060 the relative number of deciduous broadleaf trees, or aspen, will grow by 50 percent, while the evergreen conifer trees, or black spruce, will decline concurrently.
Although past studies have addressed potential vegetation changes, the Berkeley Lab study is detailed and hinges on a rigorously tested model, according to Mekonnen. He added that the results of the model were compared to observations from flux towers in “many high latitude sites across multiple years and against large-scale remote-sensing vegetation observations.”
The results also addressed potential changes to the forest ecosystem, including effects on soil, nutrients, and carbon cycling. Since evergreen trees shed their leaves, they decompose quickly, which leads to faster “carbon turnover.” Broadleaf deciduous trees are also known to be more resilient to forest burns, which are expected to occur more frequently with climate change, according to the press release.
The study focused on the Alaskan boreal forest and drew from paleoecological data from the Holocene epoch. During the early Holocene, the Alaskan climate was drier and hotter than it is today. During this period, aspen trees flourished in the region. By contrast, in the late Holocene, which became cooler and exhibited similar precipitation patterns to the modern day, the forest became dominated by the black spruce.
The predictive model could be useful in understanding vegetation changes after disturbances such as fires, according to Mekonnen. Mekonnen added that although the dominant measurements that dictate vegetation dynamics might differ, the fundamental mechanisms such as nutrient and carbon cycling are similar in other regions.
“Our modeling approach is applicable to other regions because the fundamental mechanisms that control these dynamics are similar everywhere,” Mekonnen said.