Warming alters soil respiration and soil organic matter fractions throughout the whole soil profile

Dr Jennifer Soong1, Dr Caitlin Hicks Pries2, Dr Margaret Torn1

1Lawrence Berkeley National Laboratory, Berkeley, United States, 2Dartmouth University, Hanover, United States

As the climate warms, heat is transferred to the land surface, warming soils throughout the whole soil profile. The impact of warming on soil organic matter (SOM) formation and decomposition may differ with soil depth. The decomposition signal is typically measured as fluxes from the soil surface but the effect on underlying SOM itself is harder to observe. Over five years of a whole-soil warming experiment in a mixed coniferous forest, we found that +4 ˚C warming led to a 30% increase in soil respiration. This increased respiration originated from microbial activity, measured from 5-90 cm deep, throughout all seasons and years of the experiment. After 3.5 years of warming, carbon and nitrogen stocks in the SOM light fraction showed a significant treatment effect, mainly driven by changes in the mass of these fractions with the warming treatment. We will also present results from a one-year decomposition experiment of 13C labeled root litter at three soil depths in the heated and unheated plots. Initial results show a clear decrease in SOM formation from root litter with depth. Together, results on soil respiration, SOM composition, and SOM formation from litter decomposition will be used to present a depth-resolved picture of warming impacts on SOM dynamics and carbon fluxes over five years of soil warming.

Biography: Jennifer Soong is a postdoctoral fellow at Lawrence Berkeley National Laboratory. She earned her PhD in Ecology from Colorado State University and her B.A. from Oberlin College. Dr. Soong’s research focuses on biogeochemistry and ecosystem ecology with an emphasis on how terrestrial ecosystems function under natural and human-influenced environmental conditions. She conducts observational and experimental studies in field and laboratory across a broad range of ecosystem types, using techniques such as stable isotope probing, molecular techniques and modeling to quantify how organic and inorganic materials are transported and transformed as they move through plant-soil-microbial-atmospheric interfaces. Dr. Soong works closely with modelers to scale new mechanistic insights to ecosystem and global scales and help improve predictions of future ecosystem functioning.


7th International Symposium
Soil Organic Matter

6 – 11 October 2019

Hilton Adelaide

Adelaide, South Australia


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