Most of the Earth System Models (ESMs) rely on empirical functions for decomposition of litter with multiple soil carbon pools decaying at different rates to estimate Reco variations and its partitioning into autotrophic (Ra) and heterotrophic respiration (Rh) in relation to variation in temperature and soil water content. However, microbially-mediated litter decomposition schemes are very scarce in ESMs. Microbial enzymatic processes are integral parts in litter as well as soil organic matter (SOM) decomposition. Here we developed a mechanistic model comprising of multiple hydro-biogeochemical modules to explicitly incorporate microbially-enzymatic litter decomposition and decomposition of SOM for estimating regional-scale Ra, Rh and Reco. Modeled annual mean Reco values are found varying from 1000 to 8000 kg C ha-1 yr-1 in 2000-2013 within the boreal forest covered sub-basins of the Athabasca River Basin (ARB), Canada. While, for the 2000-2013 period, the annual mean Ra and Rh are varying within 800-6000 kg C ha-1 yr-1 and 500-3500 kg C ha-1 yr-1, respectively. Ra generally dominates Reco with nearly 30-80% contribution in most of the sub-basins in ARB. The model estimates corroborate well with the site-scale and satellite-based estimates reported at similar land use and climatic regions. Modeling the partitioning of Reco to Ra, and Rh are critical to understanding future climate change feedbacks and to help reduce uncertainties in ESMs in the boreal and subarctic regions.

In this study, we developed an integrated cellular automata and thermal lattice Boltzmann model to investigate the effects of different temperatures and velocities in a microbioreactor. Compared with previous studies this model accounted for the direct effects of transient temperature on biofilm growth and indirect effects caused by changes of properties. In addition, the algorithms on variations in solid boundary conditions, detachment and extra mass transport have been improved. Results showed that temperature affected both the maximum biofilm concentration and growth speed. Roughly a 10-75% increase in biofilm concentration was observed, while in some cases the time needed to reach maximum concentration decreased from 30 days to 5 days. Despite of geometrical symmetry, changes in the upper inlet characteristics were more effective on biofilm growth. This demonstrates the capability of the present model to simulate biofilm behaviour in the microbioreactor and its potential industrial and clinical applications.