Inconsistent interannual variations between net primary production and soil CO_2 effluxes in a Moso bamboo forest

Understanding the link between interannual variations in net primary production (NPP) and soil CO_2 efflux (R_s) is essential for evaluating carbon dynamics in forest ecosystems, particularly in ecosystems such as Moso bamboo (Phyllostachys pubescens) forests with distinctive 2-year cycles of new shoot production. In this study, we measured NPP and R_s components in a Moso bamboo forest over a 5-year period to clarify the consistency of their interannual variation patterns. Our results revealed significant year-to-year variations in NPP (CV = 41%), primarily attributable to above-ground productivity, while R_s components (i.e. autotrophic (R_a) and heterotrophic (R_h) respiration) exhibited less year-to-year variations (CV = 10%–22%). Although NPP and R_s did not exhibit synchronized interannual variations, we observed marginal positive correlations between litterfall, fine root production, and R_a (Spearman’s correlation coefficient = 0.9, p < 0.1). These findings suggest that while current-year NPP components may influence R_a, R_h variations appear to be relatively independent from NPP variations in Moso bamboo forests. We discuss the simplification of net ecosystem production (NEP = NPP − R_h) estimates in Moso bamboo forests for regional C assessment, highlighting the importance of long-term monitoring of above- and below-ground processes in these ecosystems.