Leveraging observed soil heterotrophic respiration fluxes as a novel constraint on global‐scale models

Abstract

Microbially explicit models may improve understanding and projections of carbon dynamics in response to future climate change, but their fidelity in simulating global-scale soil heterotrophic respiration (R H ), a stringent test for soil biogeochemical models, has never been evaluated. We used statistical global R H products, as well as 7821 daily site-scale R H measurements, to evaluate the spatiotemporal performance of one firstorder decay model (CASA-CNP) and two microbially explicit biogeochemical models (CORPSE and MIMICS) that were forced by two different input datasets. CORPSE and MIMICS did not provide any measurable performance improvement; instead, the models were highly sensitive to the input data used to drive them. Spatial variability in R H fluxes was generally well simulated except in the northern middle latitudes (~50°N) and arid regions; models captured the seasonal variability of R H well, but showed more divergence in tropic and arctic regions. Our results demonstrate that the next generation of biogeochemical models shows promise but also needs to be improved for realistic spatiotemporal variability of R H . Finally, we emphasize the importance of net primary production, soil moisture, and soil temperature inputs, and that jointly evaluating soil models for their spatial (global scale) and temporal (site scale) performance provides crucial benchmarks for improving biogeochemical models.

Vertically Divergent Responses of SOC Decomposition to Soil Moisture in a Changing Climate

“…We demonstrate that SOC decomposition models which consider one soil depth with average SOC density, temperature, and moisture changes could poorly reflect the overall response of SOC turnover, because soil moisture at different depths can cause both accelerations and slowdowns of SOC turnover. So, while our study highlights the possible magnitude of decomposition rate changes with projected soil moisture (and temperature) changes, a quantitative assessment of the predicted changes in heterotrophic respiration and associated changes in SOC stocks additionally depends on the dynamic modeling of the feedback between climate change and SOC stocks (i.e., feedbacks of temperature and soil moisture on substrate availability, as well as fresh carbon inputs [NPP; Jian et al., 2021]).…”

“…As microbes continuously change their behavior in response to soil drying and re‐wetting, they alter soil carbon cycling at the ecosystem level (Schimel, 2018). Representing these mechanisms in more detail inside SOC decomposition models is therefore very important for improved estimates of future SOC turnover times (Jian et al., 2021). The DAMM equations provide one model representation of the interactions between microbes, SOC decomposition and soil temperature and moisture.…”

Twenty Years of Progress, Challenges, and Opportunities in Measuring and Understanding Soil Respiration

“…New mechanisms have been identified and incorporated in (5) process-based models (Abramoff et al, 2022;Sulman et al, 2018), building on a widening pool of global researchers (D.-G. Kim et al, 2022). Finally, these new approaches have (6) improved predictions of soil respiration from local to global scales (Jian et al, 2021a;H. Lu et al, 2021;Stell et al, 2021a).…”

“…Kim et al., 2022). Finally, these new approaches have (6) improved predictions of soil respiration from local to global scales (Jian et al., 2021a; H. Lu et al., 2021; Stell et al., 2021a).…”

Biome-scale temperature sensitivity of ecosystem respiration revealed by atmospheric CO2 observations

“…This feedback depends on the difference between the responses of photosynthesis and respiration to a changing climate 5 . Estimates of photosynthesis 6 , 7 and respiration 8 – 10 vary substantially across terrestrial biosphere models (TBMs) 11 , however. Furthermore, whereas there has recently been a proliferation of novel measurement techniques to better constrain photosynthesis from regional to global scales, such as solar-induced chlorophyll fluorescence 12 , near-infrared reflectance of vegetation 13 and carbonyl sulfide 14 , 15 , respiration remains difficult to constrain at large scales due to the absence of a unique spectral signature or atmospheric tracer.…”