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.