Abstract:Soil respiration, the largest CO2 flux released into the atmosphere from terrestrial ecosystems, is driven by various factors, including substrate properties and environmental conditions. Litter quality and quantity are important factors affecting soil respiration. Using the plant detritus input and removal (DIRT) experiment, we assessed soil and litter respiration in four distinct forest types in Northeast China-namely, Aspen-birch (AB), hardwood (HW), Korean pine (PK), and Mongolian oak (QM) forests-to explore the contributions of litter and roots to soil respiration and the mechanisms influencing them. The results showed consistent trends in the effects of plant detritus on soil respiration. Litter removal delayed the peak time of soil respiration and reduced the seasonal variation of soil respiration. The fluctuation range of soil respiration flux in growing season under the six DIRT treatments was 270-667 gC/m2, 284-598 gC/m2, 234-610 gC/m2 and 274-668 gC/m2 in AB, HW, PK, and QM, respectively. And the underground respiration flux in growing season under the six DIRT treatments were 270-485 gC/m2, 284-505 gC/m2, 131-356 gC/m2, and 186-455 gC/m2, respectively. Doubling litter significantly increased soil and underground respiration fluxes, while litter removal and root cutting significantly reduced them. Litter respiration was more sensitive to environmental factors and was affected by litter quantity, root, litter C/N, soil temperature, and soil moisture, while underground respiration was only affected by soil temperature and root. The fluctuation range of litter respiration per unit mass under the six DIRT treatments was 0.032-0.046 μmol s-1 g-1, 0.041-0.055 μmol s-1 g-1, 0.052-0.059μmol s-1 g-1 and 0.038-0.047 μmol s-1 g-1 in AB, HW, PK, and QM, respectively, there was significant difference only in AB. The litter respiration account for 14%-33%, 9%-21%, 19%-62%, and 16%-46% of the soil respiration for the DIRT treatments in AB, HW, PK, and QM, respectively.The proportion of litter respiration in PK was the highest among them. Root cutting and litter doubling had some inhibitory effects on litter respiration per unit mass. This study provides theoretical basis and data support for the construction of forest carbon cycle model for the temperate forest.
