Changes in carbon, nitrogen and phosphorus stoichiometry in decaying logs with gap positions in a subalpine forest

Aims: The redistribution of forest gaps based on solar radiation and precipitation (mainly rainfall and snowfall) can create heterogenous microenvironments inside and outside the gaps. Here, we investigated the effects of forest gaps on carbon (C), nitrogen (N) and phosphorus (P) stoichiometry in decaying logs by altering the microenvironments. Methods: Minjiang fir (Abies faxoniana) logs of decay classes I-V were incubated in situ on the floor under the gap center (GC), gap edge (GE) and closed canopy (CC) in a subalpine forest in the eastern Qinghai-Tibet Plateau. The C, N and P concentrations in decaying bark, sapwood and heartwood were measured in August from 2013 to 2016. Important Findings: Our results showed that the N concentration in bark decreased from the CC to the GC, while the opposite trend was found in sapwood and heartwood. Additionally, the C/N ratio in sapwood and heartwood of decay classes IV and V decreased from the CC to the GC, and the N/P ratio in heartwood of decay class V increased from the CC to the GC, implying that forest gaps have strong effects on C/N/P stoichiometry in highly decayed logs. Briefly, highly decayed logs are more susceptible to the microenvironment, and the proportion of highly decayed logs under the CC or the GC should be appropriately adjusted if necessary.