Partitioning of root respiration into growth, maintenance, and ion uptake components in a young larch-dominated forest

Purpose Fine roots play an essential role in global carbon cycles, but phenological variations in root function and metabolism are poorly understood. To illustrate the dynamics of fine root function and metabolism in the field, we partitioned root respiration (R-r) into growth (R-g), maintenance (R-m), and ion uptake (R-ion) components using a modified traditional model. Methods A year-round experiment was conducted in a young larch-dominated forest regrowing on bare soil. Soil respiration was measured with a chamber method and partitioned into R-r and heterotrophic respiration by trenching. Fine root biomass and production were measured simultaneously. Using the field data, the model was parameterized, and R-r was further partitioned. Results Annually, R-r (210-253 g C m(-2) yr(-1)) accounts for 45-47% of the total soil respiration. The contribution of fine root R-g, fine root R-m, coarse root R-m, and fine root R-ion were 26-40, 46-51, 10-16, and 12%, respectively. The R-g contribution showed a clear seasonal variation, with a peak in mid-spring and a minimum in early fall, mainly because of different seasonality between fine root production and soil temperature. Conclusion The model parameters were consistent with those from our previous study conducted by the same method in the same site. Thus, we believe that our approach was robust under a relatively simple condition. However, our growth respiration parameter resulting from only field data was much higher than those from laboratory experiments. To further improve our understanding of root respiration, more field data should be accumulated.