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

Abstract

AbstractPartitioning soil respiration (RS) into heterotrophic (RH) and rhizospheric (RR) components is an important step for understanding and modeling carbon cycling in forest ecosystems, but few studies on RR and RH exist in Chinese temperate forests. In this study, we used a trenching plot approach to partition RS in six temperate forests in northeastern China. Our specific objectives were to (1) examine seasonal patterns of soil surface CO2 fluxes from trenched (RT) and untrenched plots (RUT) of these forests; (2) quantify annual fluxes of RS components and their relative contributions in the forest ecosystems; and (3) examine effects of plot trenching on measurements of RS and related environmental factors. The RT maximized in early growing season, but the difference between RUT and RT peaked in later summer. The annual fluxes of RH and RR varied with forest types. The estimated values of RH 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 RR averaged 424, 209, 628, 538, 524 and 483 g C m−2 yr−1, correspondingly; calculated contribution of RR to RS (RC) varied from 52% in the larch forest to 83% in the pine forest. The annual flux of RR was strongly correlated to biomass of roots <0.5 cm in diameter, while that of RH 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 RS 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 RS components.