Synergistic effects of dissolved organic carbon and inorganic nitrogen on methane uptake in forest soils without and with freezing treatment

There is limited knowledge about how the interaction of dissolved organic carbon (DOC) and inorganic nitrogen (N) released into the soil just after freezing can affect methane (CH(4)) uptake in forest soils. Here, we present how freezing treatment and glucose, as a DOC source, can affect the roles of NH(4)(+)-N and NO(3)(−)-N in inhibiting soil CH(4) uptake, by using soil-core incubation experiments. A long-term freezing at low temperature reduced cumulative CH(4) uptake in the soils sampled from two temperate forest stands without carbon (C) and N addition. The inhibition effects of N addition as NH(4)Cl and KNO(3) on the soil CH(4) uptake were much larger than C addition. Freezing treatment eliminated the inhibition effect of NH(4)Cl and KNO(3) addition on CH(4) uptake, and this response was affected by glucose addition and forest types. The addition of glucose eliminated the inhibition effect of NO(3)(−)-N on CH(4) uptake in the forest soils without and with freezing treatment, while the addition of NH(4)(+)-N and glucose inhibited synergistically the soil CH(4) uptake. The results highlight the importance of synergistic effects of DOC and N inputs on the soil CH(4) uptake under forest stands during soil wetting and thawing periods.