Abstract:Soil surface CO2 flux (RS) is overwhelmingly the product of respiration by roots (autotrophic respiration, RA) and soil organisms (heterotrophic respiration, RH). Partitioning soil carbon dioxide efflux with highly variable results has received considerable attention, as differential responses of these components to environmental change have profound implications for soil and ecosystem C balance. The contribution of each group needs to be understood to evaluate implications of environmental change on soil carbon cycling and sequestration. We present results of a strict literature search of soil surface CO2 flux and partitioning studies and analyze global trends in soil carbon dioxide flux and partitioning between biomes, and age classes. There are statistically different and increasing trends in soil surface CO2 flux between biomes following the sequence of biome types as boreal< temperate coniferous0.05). While chronosequence studies report mild increase in the RH/RS ratio with age, for the mean of RH/RS ratio and variance, of young class is larger than that of intermediate and mature groups, no significant difference could be detected for different age groups in the global data set (α>0.05). Site-specific measurements are always more desirable than the application of inferred broad relationships. Measuring RS is straightforward and commonly done; however, belowground measurements are difficult and expensive. Thus the relationships and RH/RS rate for each biome presented here provide a new approach and useful baselines that can help constrain estimates of terrestrial carbon budgets.