Rhizospheric and heterotrophic components of soil respiration in six Chinese temperate forests

Abstract Partitioning soil respiration ( R S ) into heterotrophic ( R H ) and rhizospheric ( R R ) components is an important step for understanding and modeling carbon cycling in forest ecosystems, but few studies on R R and R H exist in Chinese temperate forests. In this study, we used a trenching plot approach to partition R S in six temperate forests in northeastern China. Our specific objectives were to (1) examine seasonal patterns of soil surface CO 2 fluxes from trenched ( R T ) and untrenched plots ( R UT ) of these forests; (2) quantify annual fluxes of R S components and their relative contributions in the forest ecosystems; and (3) examine effects of plot trenching on measurements of R S and related environmental factors. The R T maximized in early growing season, but the difference between R UT and R T peaked in later summer. The annual fluxes of R H and R R varied with forest types. The estimated values of R H for the Korean pine ( Pinus koraiensis Sieb. et Zucc.), Dahurian larch ( Larix gmelinii Rupr.), aspen‐birch ( Populous davidiana Dode and Betula platyphylla Suk.), hardwood ( Fraxinus mandshurica Rupr., Juglans mandshurica Maxim. and Phellodendron amurense Rupr.), Mongolian oak ( Quercus mongolica Fisch.) and mixed deciduous (no dominant tree species) forests averaged 89, 196, 187, 245, 261 and 301 g C m −2 yr −1 , respectively; those of R R averaged 424, 209, 628, 538, 524 and 483 g C m −2 yr −1 , correspondingly; calculated contribution of R R to R S ( RC ) varied from 52% in the larch forest to 83% in the pine forest. The annual flux of R R was strongly correlated to biomass of roots <0.5 cm in diameter, while that of R H was weakly correlated to soil organic carbon concentration at A horizon. We concluded that vegetation type and associated carbon metabolisms of temperate forests should be considered in assessing and modeling R S components. The significant impacts of changed soil physical environments and substrate availability by plot trenching should be appropriately tackled in analyzing and interpreting measurements of R S components.