{"id":56524,"date":"2019-08-21T10:00:18","date_gmt":"2019-08-21T17:00:18","guid":{"rendered":"http:\/\/in.nau.edu\/news\/?p=56524"},"modified":"2019-08-21T08:15:42","modified_gmt":"2019-08-21T15:15:42","slug":"boreal-forest-carbon-sinks","status":"publish","type":"post","link":"https:\/\/in.nau.edu\/news\/boreal-forest-carbon-sinks\/","title":{"rendered":"Larger, more frequent fires in boreal forest threaten previously protected carbon stores, NAU-led research team reports in Nature"},"content":{"rendered":"\n

Aug. 22, 2019<\/p>\n\n\n\n

Pools of old carbon in the soil of boreal forests historically safe from combustion are being released by more frequent and larger wildfires, a team led by researchers at Northern Arizona University announced in Nature<\/a><\/em> this week. As the climate of these forests in the Northwest Territories of Canada becomes warmer, drier and prone to more frequent fires, the combustion of \u201clegacy carbon,\u201d as the research team calls it, has the potential to shift the global carbon cycle, as boreal forests that have acted as carbon sinks for millennia become sources of atmospheric carbon. <\/p>\n\n\n\n

The research team, which included collaborators from NAU, the government of the Northwest Territories (NWT), four Canadian universities, University of Alaska-Fairbanks and Woods Hole Research Center, found that legacy carbon remained protected from combustion in older stands where the historical fire return interval persisted. But in stands younger than 60 years old, legacy carbon burned.<\/p>\n\n\n\n

\u201cIn older stands that burn, this carbon is protected by thick organic soils,\u201d said Xanthe Walker<\/strong>, lead author and postdoctoral researcher at the Center for Ecosystem Science and Society<\/a> (Ecoss) at Northern Arizona University. \u201cBut in younger stands that burn, the soil does not have time to re-accumulate after the previous fire, making legacy carbon vulnerable to burning. This pattern could shift boreal forests into a new domain of carbon cycling, where they become a carbon source instead of a sink.\u201d<\/p>\n\n\n\n

For Walker and senior author Michelle Mack<\/strong>, who first identified these protected pools of carbon in fire scars in Alaska, a series of mega-fires in the Northwest Territories in 2014 offered an opportunity to ask whether legacy carbon was being combusted, and where. <\/p>\n\n\n\n

\u201cThese\nwere large and severe fires, and we thought: This is when and where it would\nburn,\u201d Walker said. <\/p>\n\n\n\n

\u201cWe know that there is really old carbon in these soils\u2014carbon that is hundreds to thousands of years old, carbon that is irreplaceable,\u201d said Mack, who worked with Walker and NAU collaborators Chris Ebert<\/strong>, Scott Goetz<\/strong> and Ted Schuur<\/strong> on the study. \u201cAs high-intensity fires begin to burn these stores, we think of this as \u2018mining\u2019 soil carbon. Globally, boreal forests store about one-third of terrestrial carbon, primarily in soils, so transferring that carbon from soil to the atmosphere could be a powerful accelerating feedback to climate warming.\u201d<\/p>\n\n\n\n

To\nensure they sampled a full spectrum of burned areas, Steve Cumming of Laval\nUniversity in Quebec identified plots in the burn area with maps derived from\nremote sensing of forest composition. Then Walker and a large field campaign of\nresearchers and students from Canadian universities hiked into the burn areas\nto sample the soil at 211 of these plots. <\/p>\n\n\n\n

\u201cCarbon accumulates in\nthese soils like tree rings, with the newest carbon at the surface and the\noldest carbon at the bottom,\u201d Mack said. \u201cWe thought we could use this layering\nto see how far back in time, in the history of the forest, fires were burning.\u201d\n<\/p>\n\n\n\n

To estimate the age of the\ncarbon in the soil, the team used radiocarbon dating, which measures the\nabundance of 14C carbon isotope in a sample of soil. Carbon dating allows\nresearchers to measure the amount of 14C and gather clues about how long\ncertain carbon stores have been in the soil. This technique requires a\nhigh-precision measurement made by relatively few labs in the world; in early\n2020, Ecoss will install a Mini Carbon Dating System at NAU.<\/p>\n\n\n\n

In nearly half (45\npercent) of the young stands the researchers sampled, legacy carbon burned. And\nwhile the amount of legacy C didn\u2019t alter total carbon emitted from these\nfires, the pattern the researchers identified has global implications for future\nclimate scenarios. <\/p>\n\n\n\n

\u201cThe frequency of boreal forest fires is projected\nto increase even more with expected climate warming and drying, and as a result\ntotal burned area is expected to increase 130-350 percent by mid-century,\u201d the\nauthors write, expanding the proportion of young forests vulnerable to burning\nand loss of legacy carbon. <\/p>\n\n\n\n

\u201cBy defining and analyzing \u2018legacy carbon,\u2019 this paper offers a new way to think about long-sequestered carbon stocks in boreal forests and how vulnerable they are to being burned during increasingly frequent and severe wildfires,\u201d said Brendan Rogers, a scientist at Woods Hole Research Center who co-authored the Nature<\/em> study. \u201cThis tool helps us understand when burning goes \u2018outside the norm\u2019 from a historical perspective and begins to combust carbon stocks that survived past fires.<\/p>\n\n\n\n

\u201cSecond, this study further emphasizes why more frequent burning in the boreal forest is bad from a climate perspective.”<\/p>\n\n\n\n

\u201cThe\n2014 wildfires were unlike anything the Northwest Territories had experienced, and\nafter them, the Government of the NWT sought to understand the impacts of\nextreme wildfire on the lands and people of the NWT so they could better plan\nand adapt,\u201d said\nJennifer Baltzer, a researcher at Wilfrid Laurier University in\nOntario and co-author of the Nature<\/em>\nstudy. \u201cThis\nresearch, with their help and partnership, has really advanced our\nunderstanding of these fires and the tremendous impact extreme wildfire years\nhave on globally critical stores of carbon.\u201d<\/p>\n\n\n\n

\u201cThe good news here is that this landscape in the Northwest Territories is comprised primarily\u00a0of old forests,\u00a0and legacy carbon stayed protected there,\u201d said Walker, who earned her PhD. with biologist and co-author Jill Johnstone at the University of Saskatchewan. \u201cYoung stands lack accumulated fuel and acted as a kind of fire break. But as the climate continues to warm and grow drier, we may see that change, and young stands may begin to carry fire and threaten legacy carbon.\u201d<\/p>\n\n\n\n

This project was a collaborative effort primarily supported by funding awarded to Michelle Mack by the NASA Arctic Boreal Vulnerability Experiment (ABoVE) and a National Science Foundation (NSF) Division of Environmental Biology (DEB) Rapid grant. Additional funding was provided by: Natural Sciences and Engineering Research Council (NSERC) Discovery Grants awarded to Jill Johnstone and Merritt Turetsky; the Northwest Territories Cumulative Impacts Monitoring Program awarded to Jennifer Baltzer; an NSERC postdoctoral fellowship awarded to Nicola Day; and Polar Knowledge, Canada\u2019s Northern Science Training Program awarded to Canadian field assistants. Logistical support was provided by the Government of the Northwest Territories\u2013Wilfrid Laurier University Partnership Agreement.<\/em><\/p>\n\n\n\n

Above graphic by Victor O. Leshyk<\/em>, Ecoss<\/em><\/p>\n\n\n\n

\"NAU<\/figure>
\n

Kate Petersen | Center for Ecosystem Science and Society<\/p>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"

Aug. 22, 2019 Pools of old carbon in the soil of boreal forests historically safe from combustion are being released by more frequent and larger wildfires, a team led by researchers at Northern Arizona University announced in Nature this week. As the climate of these forests in the Northwest Territories of Canada becomes warmer, drier…<\/a><\/p>\n","protected":false},"author":59,"featured_media":56527,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[11],"tags":[],"class_list":["post-56524","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research-academics"],"acf":[],"_links":{"self":[{"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/posts\/56524","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/users\/59"}],"replies":[{"embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/comments?post=56524"}],"version-history":[{"count":0,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/posts\/56524\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/media\/56527"}],"wp:attachment":[{"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/media?parent=56524"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/categories?post=56524"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/in.nau.edu\/news\/wp-json\/wp\/v2\/tags?post=56524"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}