PARENT SESSION
Contributed Oral Session 146: Biogeochemistry: Nutrient Dynamics; Carbon Sequestration
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 524 C, Level 5, Palais des congrès de Montréal

Carbon allocation and the contribution of C from pools of varying age in a P. deltoides plantation during a simulated drought.

Trueman, Rebecca^*,1, Gonzalez-Meler, Miquel¹, Berry, Joseph², ¹ University of Illinois at Chicago, Chicago, IL, USA² Carnegie Institution of Washington, stanford, ca, USA

ABSTRACT- As atmospheric carbon dioxide concentration increases global temperature will rise causing a shift in environmental conditions and amplifying extreme events such as drought. Understanding the effects of drought in a changing environment is important for C mitigation strategies. This study used ¹³C pulse-chase experiments to label photoassimilate from one day (C*) and analyze the response of soil C allocation and sequestration in a P. deltoides plantation during a simulated drought. Under drought conditions soil respiration decreased with soil VWC and soil type. The response of C* in soil respiration to a simulated drought event was not as expected. The allocation of C* respired from soil changed as a function of moisture stress. The contribution of C in soil respired CO₂ was determined for three age classes (C* less than 7 days, C_intermediate greater than 7 days and less than 5 years and C_old greater than 5 years) and was found to change under moisture stress. There was an unexpected increase in C_old loss from the soil C pool under drought conditions even though root mortality increased. The age of C in soil respiration was determined by stable isotope partitioning of ¹³C. The effect of drought on plantation C sequestration can vary significantly depending on the direct and indirect responses of trees and soil to moisture.

Key words: C allocation, MRT of C, ¹³C partitioning, drought