Partitioning Autotrophic and Heterotrophic Respiration at Howland Forest
Abstract:Terrestrial ecosystem respiration is the combined flux of CO2 to the atmosphere from above- and below-ground, plant (autotrophic) and microbial (heterotrophic) sources. Flux measurements alone (e.g., from eddy covariance towers or soil chambers) cannot distinguish the contributions from these sources, which may change seasonally and respond differently to temperature and moisture. The development of improved process-based models that can predict how plants and microbes respond to changing environmental conditions (on seasonal, interannual, or decadal timescales) requires data from field experiments to distinguish among these respiration sources.
We tested the viability of partitioning of soil and ecosystem respiration into autotrophic and heterotrophic components with different approaches at the Howland Forest in central Maine, USA. These include an experimental manipulation using the classic root trenching approach, combined with continuous measurements of d13CO2 as well as targeted ∆14CO2 measurements. For the isotopic measurements, we used a two-end member isotope mass balance approach to determine the fraction of soil respiration from autotrophic and heterotrophic sources. Results from these approaches will be compared, and together used in a model-data fusion context to better constrain the partitioning of ecosystem respiration in the ecosystem model, FöBAAR.