PARENT SESSION
Oral Session # 35: Biogeochemistry III: Arctic, Alpine, and Tundra Systems.
Presiding: A Hartley
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Meeting Room 203.
Transfers of carbon across the landscape: The controls on dissolved C production in soils.
Kling, George*,1, Judd, Kristi1, Sommerkorn, Martin2, Nadelhoffer, Knute2, Rastetter, Edward2, Johnson, Loretta3, 1 University of Michigan, Ann Arbor, MI2 Marine Biological Laboratory, Woods Hole, MA3 Kansas State University, Manhattan, KS
ABSTRACT- Much of the world′s plant production is returned to the soil within seasons to decades. Labile fractions of this material are dissolved in soils and then transported from uplands to lowlands and eventually deposited in the oceans or exhaled to the atmosphere. Although this transported material is important for regional to global carbon and nutrient budgets, our understanding of the integrated mechanisms responsible for this cycling, and our ability to predict the sources and rates of production of dissolved materials in soils, is rudimentary. We used pulse-labeling of 14C-CO2 added through photosynthesis to intact plant-soil mesocosms and to field plots in order to trace the movement of carbon through the plant-soil system of arctic tundra. We found that the bulk of recent photosynthate lost from the plant is returned to the atmosphere through plant respiration in less than 10 days. Recently-fixed plant carbon is also transferred immediately to roots, and within 1-2 hours enters the dissolved pool in soils. The pool of dissolved organic carbon (DOC) is most rapidly enriched with 14C from root exudation, followed closely by dissolved CO2. Dissolved CH4 labeled with 14C is produced in the soil within hours of the label addition. Nutrient fertilization did not alter the rate of 14C transfer to the dissolved pool, but did alter the magnitude of transfer for different C species. Dissolved organic or inorganic carbon production dominated the dissolved soil pool, depending on the overlying vegetation type. Estimated transfer rates of C from roots to DOC, CO2, and CH4 pools were high, and ranged from 5-25% per day of the total pool size in the soils. We propose that this flux derived from recently-fixed organic matter, versus from older organic matter, dominates the total production of dissolved material even in soils with high organic matter content.
Key words: biogeochemistry, arctic, carbon, ecosystem