Dr. Namjin Noh1, Dr Elise Pendall1, Mr Jinquan Li1,2, Dr. Georgia Koerber3, Dr Wayne Meyer3, Dr Will Woodgate4, Dr Stefan Arndt5, Dr Eric Davidson6
1Western Sydney University, Penrith, Australia, 2Fudan University, Shanghai, China, 3University of Adelaide, Adelaide, Australia, 4CSIRO, Canberra, Australia, 5University of Melbourne, Melbourne, Australia, 6University of Maryland, Frostburg, USA
Understanding temperature sensitivity of soil organic carbon (SOC) decomposition in relationship to substrate availability and priming effects is critical for predicting climate-carbon feedbacks. Here, thermal response of SOC decomposition and substrate-induced priming were investigated using 13C-labeled Eucalyptus leaf litter for surface soils sampled in six eucalypt forests and woodlands across the Southeast Australian Temperate Transect (SATT). The selected sites belong to the Australian Terrestrial Ecology Research Network and form a gradient of increasing productivity with mean annual precipitation increasing from 300 to >1000 mm. The priming effect was computed from respired CO2 flux and associated δ13C, which were measured for 3 weeks in laboratory microcosms at incubation temperatures of 5, 15, and 25°C. Litter addition resulted in stimulation of total soil CO2 flux as substrate-induced respiration (SIR) for all forest soils, but the magnitude of the SIR was dependent on substrate availability across the sites, indicating SIR was higher at the sites with lower productivity. Addition of fresh litter significantly decreased temperature sensitivity (Q10) of SOC decomposition due to the negative correlation between Q10 and carbon quality. The Q10 of litter C was lower than that of SOC suggesting that soil C is relatively more vulnerable to climate warming, potentially due to its greater complexity. On the other hand, the priming effect of litter substrate on SOC decomposition was negative and more pronounced at higher temperature, indicating reduced SOC loss with warming in the presence of fresh litter. Our results demonstrate that temperature sensitivity of SOC decomposition was lower and (negative) priming was greater at the sites with more SOC across the SATT productivity gradient. These results suggest potential substrate-dependent mechanisms that may enhance SOC stabilization in future climates.
Elise Pendall is Professor of Soil Science at Western Sydney University and serves as Theme Leader for the Soil Biology and Genomics research group at Hawkesbury Institute for the Environment. She studies responses of biogeochemical cycling to climate change, ecological disturbances and land management. She uses field and lab experiments and modelling to evaluate linkages between aboveground and belowground ecosystem components and how they regulate carbon, water and nutrient cycling in forests, grasslands, and crops.