Abstract
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 (CH4) uptake in forest soils. Here, we present how freezing treatment and glucose, as a DOC source, can affect the roles of NH4+-N and NO3−-N in inhibiting soil CH4 uptake, by using soil-core incubation experiments. A long-term freezing at low temperature reduced cumulative CH4 uptake in the soils sampled from two temperate forest stands without carbon (C) and N addition. The inhibition effects of N addition as NH4Cl and KNO3 on the soil CH4 uptake were much larger than C addition. Freezing treatment eliminated the inhibition effect of NH4Cl and KNO3 addition on CH4 uptake, and this response was affected by glucose addition and forest types. The addition of glucose eliminated the inhibition effect of NO3−-N on CH4 uptake in the forest soils without and with freezing treatment, while the addition of NH4+-N and glucose inhibited synergistically the soil CH4 uptake. The results highlight the importance of synergistic effects of DOC and N inputs on the soil CH4 uptake under forest stands during soil wetting and thawing periods.
Highlights
The relationship between CH4 uptake and dissolved organic carbon (DOC) concentration in soil is generally elusive[17]
NH4+-N concentration in the two forest soils treated with KNO3 alone significantly increased without and with freezing treatment, especially in the white birch forest (WBF) soil (P < 0.05) (Tables S2–S4)
Freezing treatment caused a release of DOC and dissolved organic N (DON) (P < 0.0001) and a significant decrease in microbial biomass C (MBC) and the MBC:MBN ratios of the two forest soils in all treatments (P < 0.001) (Tables S2–S4)
Summary
The relationship between CH4 uptake and DOC concentration in soil is generally elusive[17]. We hypothesized that freezing treatment and glucose, as a DOC source, can affect the roles of NH4+ and NO3− in inhibiting soil CH4 uptake For this purpose, a series of laboratory incubation experiments were done to study (1) the single and interactive effect of C and N addition on CH4 uptake in WBF and KBPF soils without and with freezing treatment; (2) the main driving mechanisms of CH4 uptake during soil wetting and thawing periods by considering the variations of soil properties such as labile C and N pools. The results improve our understanding of how DOC input from forest organic layers and in combination with N deposition can affect the soil CH4 uptake under forest stands during soil wetting and thawing periods
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