The role of environmental, root, and microbial biomass characteristics in soil respiration in temperate secondary forests of Northeast China

For secondary forests, the major forest resources in China (accounting for more than 50% of the national total), soil respiration (R (S)) and the relationship between R (S) and various biotic/abiotic factors are poorly understood. The objectives of the present study were to examine seasonal variations in soil respiration during the growing season, and to explore the factors affecting the variation in soil respiration rates for three forest types (Mongolian oak, Manchurian walnut and mixed forests) of temperate secondary forest in Northeast China. The results showed that (1) the maximum total R (S) rate occurred in July, following a bell-shaped curve with season, (2) for all forest types, the total R (S) was significantly influenced by soil temperature (P < 0.01), and did not significantly correlate with soil moisture, (3) compared with fine root biomass, coarse root biomass was more closely related with the root respiration in mixed forest (R (2) = 0.711, P = 0.017) and in Manchurian walnut forest (R (2) = 0.768, P = 0.010), and (4) microbial biomass carbon (MBC) and nitrogen were significantly correlated with heterotrophic R (S) in Mongolian oak forest (R (2) = 0.664, P = 0.026; R (2) = 0.784, P = 0.008, respectively) and in mixed forest (R (2) = 0.918, P = 0.001; R (2) = 0.967, P = 0.001, respectively). We can conclude that in temperate secondary forests: (1) the R (S) rate and the relationships between R (S) and abiotic/biotic factors change greatly with forest types, and (2) R (S) is strongly influenced by soil temperature, MBC, microbial biomass nitrogen and coarse root biomass in temperate secondary forests.