Changes in soil moisture drive soil XXXX uptake along a fire regeneration chronosequence in a eucalypt forest landscape.

@entity577 @entity578
UNASSIGNED: Disturbance associated with severe wildfires (WF) and WF simulating harvest operations can potentially alter soil @entity577 ( @entity578 ) oxidation in well-aerated forest soils due to the effect on soil properties linked to diffusivity, methanotrophic activity or changes in methanotrophic bacterial community structure. However, changes in soil @entity578 flux related to such disturbances are still rarely studied even though WF frequency is predicted to increase as a consequence of global climate change. We measured in-situ soil-atmosphere @entity578 exchange along a wet sclerophyll eucalypt forest regeneration chronosequence in Tasmania, Australia, where the time since the last severe fire or harvesting disturbance ranged from 9 to >200  years. On all sampling occasions, mean @entity578 uptake increased from most recently disturbed sites (9  year) to sites at stand 'maturity' (44 and 76  years). In stands >76  years since disturbance, we observed a decrease in soil @entity578 uptake. A similar age dependency of potential @entity578 oxidation for three soil layers (0.0-0.05, 0.05-0.10, 0.10-0.15  m) could be observed on incubated soils under controlled laboratory conditions. The differences in soil @entity578 uptake between forest stands of different age were predominantly driven by differences in soil moisture status, which affected the diffusion of atmospheric @entity578 into the soil. The observed soil moisture pattern was likely driven by changes in interception or evapotranspiration with forest age, which have been well described for similar eucalypt forest systems in south-eastern Australia. Our results imply that there is a large amount of variability in @entity578 uptake at a landscape scale that can be attributed to stand age and soil moisture differences. An increase in severe WF frequency in response to climate change could potentially increase overall forest soil @entity578 sinks.
