• ucsantabarbara twitter avatar
    From theory to practice, this week's #GauchoCourse prepares soon-to-be professors for the real world. https://t.co/DAj0nUIwAw
    6 hours 41 min ago
  • UCSBgauchos twitter avatar
    MVB: Gauchos snap 7 match losing streak with emphatic sweep of UCSD on Friday night. RECAP >>>… https://t.co/Cee1KbeXOh
    16 hours 32 min ago
  • UCSBgauchos twitter avatar
    Women's Tennis: UC Santa Barb. 2, Oregon 5 (Final)
    19 hours 16 sec ago
  • UCSBgauchos twitter avatar
    WBB: Gauchos Face First-Place UC Davis Looking to End Two-Game Skid https://t.co/wRGTYxtxDC
    20 hours 1 min ago
  • ucsantabarbara twitter avatar
    Called “tama” or “tamashii,” the belief in spirits of deceased ancestors goes back centuries. https://t.co/KUJg2oGc7k
    20 hours 26 min ago
  • UCSBgauchos twitter avatar
    Muno (2 H, 2 R), Corey (3-4, 2 R), Davis (7 IP, 2 ER, 10 K) lead @UCSB_Baseball to 7-4 win in home opener! RECAP >>… https://t.co/I32qmDSuZB
    20 hours 53 min ago
  • ArtsandLectures twitter avatar
    Fascinating! #Sapiens + #HomoDeus author #YuvalNoahHarari predicts humankind’s future: https://t.co/5P25xtpyRQ via… https://t.co/TIAzFchgfI
    21 hours 25 min ago
  • ArtsandLectures twitter avatar
    RT @AshleyyySb: Only on Twitter to continue to absorb all insight and research from @DrSidMukherjee || Stoked to attend his lecture @Artsan
    21 hours 41 min ago
  • brenucsb twitter avatar
    Does location affect how pines react to climate change? Bren PhD student Ian McCullough shares answer #BrenPhDTalks https://t.co/6zVyQetm2t
    21 hours 46 min ago
  • UCSBgauchos twitter avatar
    Softball: Fifth-Inning Dooms Gauchos in 6-4 Loss to Purdue https://t.co/XWYKVl9UPx
    21 hours 48 min ago
  • UCSB_GradPost twitter avatar
    Register for 2017 Graduate Division Commencement before May 5! https://t.co/IDP1WGLGik #UCSB #ucsbgradpost
    21 hours 54 min ago
  • brenucsb twitter avatar
    Bren PhD student Jessica Perkins' research answers: "What Makes an #LCA Study Influential?" https://t.co/HatfwVTKV4 #BrenPhDTalks
    21 hours 55 min ago
  • brenucsb twitter avatar
    Runsheng Song shares strategies to estimate chemicals' life cycle inventories with little data #BrenPhDTalks https://t.co/gUsRney8nC #LCI
    22 hours 6 min ago
  • brenucsb twitter avatar
    #BrenPhDTalks: Bren PhD student Ying Wang looks at nanomaterial accumulation in soybeans & nitrogen-fixing bacteria https://t.co/85xiy6EmAY
    22 hours 16 min ago
  • brenucsb twitter avatar
    Bren PhD student Yuwei Qin uses US potato production to show how to model marginal production in #LCA https://t.co/jDyW0Fkzbx #BrenPhDTalks
    22 hours 26 min ago

Research into Carbon Storage in Arctic Tundra Reveals Unexpected Insight into Ecosystem Resiliency

Thursday, May 16, 2013 - 17:00
Santa Barbara, CA

When UC Santa Barbara doctoral student Seeta Sistla and her adviser, environmental studies professor Josh Schimel, went north not long ago to study how long-term warming in the Arctic affects carbon storage, they had made certain assumptions.

"We expected that because of the long-term warming, we would have lost carbon stored in the soil to the atmosphere," said Schimel. The gradual warming, he explained, would accelerate decomposition on the upper layers of what would have previously been frozen or near-frozen earth, releasing the greenhouse gas into the air. Because high latitudes contain nearly half of all global soil carbon in their ancient permafrost –– permanently frozen soil –– even a few degrees' rise in temperature could be enough to release massive quantities, turning a carbon repository into a carbon emitter.

"The Arctic is the most rapidly warming biome on Earth, so understanding how permafrost soils are reacting to this change is of major concern globally," Sistla said.

To test their hypothesis, the researchers visited the longest-running climate warming study in the tundra, the U.S. Arctic Long-Term Ecological Research site at Toolik Lake in northern Alaska. This ecosystem-warming greenhouse experiment was started in 1989 to observe the effects of sustained warming on the Arctic environment.

What they initially found was typical of Arctic warming: low-lying, shallow-rooted vegetation giving way to taller plants with deeper roots; greater wood shrub dominance; and increased thaw depth. What they weren't expecting was that two decades of slow and steady warming had not changed the amounts of carbon in the soil, despite changes in vegetation and even the soil food web.

The answer to that mystery, according to Sistla, might be found in the finer workings of the ecosystem: Increased plant growth appears to have facilitated stabilizing feedbacks to soil carbon loss. Their research is published in the recent edition of the journal Nature.

"We hypothesize that net soil carbon hasn't changed after 20 years because warming-accelerated decomposition has been offset by increased carbon inputs to the soil due to a combination of increased plant growth and changing soil conditions," Sistla said.

The increased plant productivity, caused by the warmer temperatures –– on average 2 degrees Celsius in the air and 1 degree in the soil to the permafrost –– has increased plant litter inputs to the soil. Unexpectedly, the soils in the greenhouse experiment developed higher winter temperatures, while the summer warming effect declined.

"These changes reflect a complicated feedback," Sistla said. "Shrubs trap more snow than the lower-lying vegetation, creating warmer winter soil temperatures that further stimulate both decomposers and plant growth. Shrubs also increase summer shading, which appears to have reduced decomposer activity in the surface soil by reducing the greenhouse effect during the summer."

The increased plant growth and deeper thaw, meanwhile, also may have enabled increased carbon availability in the deeper mineral layer that overlies the permafrost. In fact, the researchers found the strongest biological effects of warming at depth, a "biotic awakening," with mineral soil decomposers showing more activity, along with the increased carbon stock at that level. "It's a surprising counterbalance," said Schimel. "It may be that those soil systems are not quite as vulnerable to warming as initially expected."

However, whether or not this phenomenon –– no net loss of soil carbon despite long-term warming –– is a transient phase that will eventually give way to increased decomposition activity and more carbon release, is not yet known. Future studies will include investigation into the mineral soil to determine the age of the carbon, which may in turn yield clues into how the carbon cycle is changing at depth, where the majority of tundra soil carbon is stored.

Funding for this study came from the National Science Foundation Long Term Ecological Research (LTER) Program, DOE Global Change Education Program Graduate Fellowship, a Leal Anne Kerry Mertes scholarship, and Explorer's Club.

According to Sistla and Schimel, this research paradigm validates the NSF LTER program's commitment to supporting long-term experiments, because it creates opportunities for younger scientists to observe effects and condition decades after experiments are established –– results that could not have been foreseen when the experiments were started.

Researchers participating in this study include John C. Moore and Rodney T. Simpson from Colorado State University, Fort Collins; Laura Gough from the University of Texas at Arlington; and Gaius R. Shaver from the Marine Biological Laboratory at Woods Hole, Mass.

U.S. Arctic LTER
Josh Schimel
Seeta Sistla

Topics: