States Labrum

photo of States Labrum

Columbia State student States Labrum was chosen to participate in Harvard’s Forest Summer Research Program during summer 2017. Their research objective was to investigate the relationship between long term soil warming and subsequent soil carbon release into the atmosphere, within the context of the impact of global warming. 

Currently, soil organic matter (SOM) holds the largest carbon pool in the terrestrial ecosystem. The rise of global temperatures accelerates microbial respiration and potentially increases carbon release from the soil. Here, we conducted soil-warming experiments to examine how various soil temperatures affect carbon release through soil microbial respiration, and whether the soil microbes may compensate for the effects of rising temperatures by the phenomenon of thermal acclimation. Our field experimental results showed a pattern of decreased soil respiration in the heated plots relative the control plots. To understand what factors drive thermal acclimation, we incubated heated and control soil samples at six separate temperatures (6°C-36°C) in the laboratory. 

We found that the relationships between temperature and respiration were similar in field and laboratory data. The observed decrease in microbial biomass in heated soils caused the decrease in respiration relative to controls. Additionally, to remove potential bearing of substrate limitation, we amended the soils with sucrose which further minimized the difference in respiration between treatments. The results indicated that microbial biomass and substrate limitations are the factors primarily responsible for thermal acclimation, correlating with the prior conducted 26-year long experimental observations. We hypothesized that structural and functional changes in soil microbial communities drive the patterns of thermal acclimation of SOM decomposition, directly impacting soil carbon release.

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