Effects of forest gaps on the humification process of deadwood in the subalpine forest

In this study, we in-situincubated Minjiang fir (Abies faxoniana) logs of I-V decay classes on the forest floor across gap positions (gap center, gap edge and closed canopy) to measure the concentrations of humic substance (HS), humic acid (HA), fulvic acid (FA), and humification degree (HD) of deadwood in February and August, and calculated the net accumulation of HS, HA, and FA in cooling (Aug-Feb) and warming (Feb-Aug) seasons.Our results showed that the effect of forest gaps on deadwood humification depends strongly on wood tissuesand that forest gaps shift the contribution of deadwood humification to forest carbon sequestration from heartwood toward bark, while sapwood humification remains relatively consistent in different gap positions.Furthermore, warmer winter and prolonged summer favor humus accumulation in bark but reduce the carbon sequestration potential in heartwood, especially in the gap center. Thisstudy have animportant implication for further understanding the impact of the deadwood humification to soil organic matter accumulation under different microclimate conditions.