Soil respiration and its component characteristics under different types of Larix gmelinii forests in the north of Daxing'an Mountains of northeastern China

ObjectiveIn order to provide scientific basis for further research of carbon release and its influence on the regional climate in cold temperate region of China, the characteristics of soil respiration and its components, and their correlations with soil temperature and humidity were analyzed in larch forests of the Daxing'an Mountains of northeastern China.

MethodWe used LI-6400 chamber to measure soil respiration, respiration components and their impacting factors of five typical forest types, which were dominated by larch (pure Larix gmelinii forest, Rhododendron dauricum-Larix gmelinii forest, Ledum palustre Larix gmelinii forest, Betula platyphylla-Larix gmelinii forest, Pinus sylvestris var. mongolica-Larix gmelinii forest) in the north of the Daxing'an Mountains.

ResultThe rates of total soil respiration(R_S), heterotrophic respiration(R_h) and root respiration(R_r)all presented a single-peak curve in growing season, and the peak values all appeared in August for the five kinds of larch forests. The average soil respiration rates of the five communities ranged from 4.71 to 7.41 μmol/(m²·s), and their rank was Pinus sylvestris var. mongolica-Larix gmelinii forest>Ledum palustre-Larix gmelinii forest>Betula platyphylla-Larix gmelinii forest>pure Larix gmelinii forest>Rhododendron dauricum-Larix gmelinii forest (P < 0.05). The R_h and R_r also had significant differences in the five types of larch forest (P < 0.05).The average of R_h ranked as Pinus sylvestris var. mongolica-Larix gmelinii forest (5.56 μmol/(m²·s))>pure Larix gmelinii forest (4.64 μmol/(m²·s))>Betula platyphylla-Larix gmelinii forest (4.55 μmol/(m²·s))>Ledum palustre-Larix gmelinii forest (4.27 μmol/(m²·s))>Rhododendron dauricum-Larix gmelinii forest (3.80 μmol/(m²·s)). The average of R_r ranked as Ledum palustre-Larix gmelinii forest (3.15 μmol/(m²·s))>Pinus sylvestris var. mongolica-Larix gmelinii forest (2.98 μmol/(m²·s))>Betula platyphylla-Larix gmelinii forest (2.76 μmol/(m²·s))>Rhododendron dauricum-Larix gmelinii forest (2.30 μmol/(m²·s))>pure Larix gmelinii forest (1.97 μmol/(m²·s)). R_h was the major component of soil respiration, which accounted for 61.84%-71.76% of the total soil respiration. The soil mineral respiration (R_m) was the main component of R_h, which accounted for 46.28%-58.18% of the total soil respiration. However, the soil litterfall respiration (R_l) only accounted for 8.34%-15.57% of the total soil respiration. R_r accounted for 28.24%-38.16% of the total soil respiration. There was a significantly positive correlation (P < 0.05) between soil respiration rate and the temperature of top 10 cm soil (T₁₀). T₁₀ could explain 43.6%-57.0% of seasonal variation for soil respiration. But the correlations between soil respiration rate and soil humidity were different among the five types of larch forests.

ConclusionThere are significant differences among the soil respiration and its components of the five types of larch forests. Temperature is the dominant factor influencing soil respiration, the influence of humidity on soil respiration is weak in the larch forests in the northern Daxing'an Mountains of northeastern China.