PARENT SESSION
Contributed Oral Session 125: Soil Ecology: Carbon - Nitrogen Cycling
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 524 B, Level 5, Palais des congrès de Montréal

Elevated Carbon Dioxide Stimulates Net Accumulations of Carbon and Nitrogen in Terrestrial Ecosystems: A Meta-Analysis.

Luo, Yiqi^*,1, Hui, Dafeng ², Zhang, Deqiang³, ¹ University of Oklahoma, Norman, OK² Duke University, Durham, NC³ South China Botanical Gardan, Guanzhou, China

ABSTRACT- The capability of terrestrial ecosystems to sequester carbon (C) plays a critical role in regulating future climatic change yet depends on nitrogen (N) availability. To predict long-term ecosystem C storage, it is essential to examine whether soil N becomes progressively limiting as C and N are sequestered in long-lived plant biomass and soil organic matter. A critical parameter to indicate the long-term progressive N limitation (PNL) is net change in ecosystem N content in association with C accumulation in plant and soil pools under elevated CO₂. We compiled data from 104 papers that study C and N dynamics at ambient and elevated CO₂. The compiled database contains C contents, N contents, and C/N ratio in shoot, root, whole plant, litter, and soil pools; and root/shoot ratio. Carbon and N pool sizes in plant and soil all significantly increase at elevated CO₂ in comparison to those at ambient CO₂, ranging from 5% in shoot N content to 32% in root C content. The C and N contents in litter pools are consistently higher in elevated than ambient CO₂ among all the surveyed studies whereas C and N content in the other pools increase in some studies and decrease in other studies. The averaged C/N ratios are higher by 3% in litter and soil pools and 11% in root and shoot pools at elevated than ambient CO₂. Elevated CO₂ slightly increases root/shoot ratio. The net N accumulation in plant and soil pools at least helps prevent complete downregulation of, and likely supports, long-term CO₂ stimulation of C sequestration. Nevertheless, larger percent increments in C than N contents at elevated CO₂ suggest that N may still partially limit ecosystem C processes under elevated CO₂. The coupled C and N accumulations in response to rising atmospheric CO₂ may reflect intrinsic nature of ecosystem development as revealed before by studies of succession over hundreds and millions of years

Key words: Global change, biogeochemical cycles, ecosystem, carbon and nitrogen