Carbon dynamics and nutrients in different decay stages of coarse woody debris in natural Hyrcanian forests, Northern Iran

The relationship between the degree of decay, carbon dynamics, and nutrients of coarse woody debris (CWD) were examined in the experimental forest of Kheirudkenar – Nowshahr as a part of Hyrcanian forests in Northern Iran. CWD (snag and log) with an average middle diameter more than 7.5 cm was recorded in 50 ha. For snag CWD, species type, diameter at the breast height and height, while for log CWD, species type, the average diameter and their length were determined and recorded. In the case of non-circular CWD cross-sections especially in the higher decay stages, diameter was determined by tape. All CWD were categorized in three diameter classes and the degree of their decay (snag and log) was determined. The CWD nutrients examined throughout taking a piece from each CWD and analysing them in the laboratory (60 specimens). The C/N ratio of CWD was obtained separately for diameter classes and degrees of decay. All data were tested for probability of fit to normal distribution. To identify the most influential gradients, principal component analysis (PCA) was applied. The nutrients in the trunk CWD in different diameter classes and degrees of decay showed that in most cases, there is a significant difference between them. The results of the C/N ratio of the total trunk of CWD showed that this ratio decreases by elevating the degree of decay and by upraising the diameter classes of CWD. The degrees of decay of CWD were majority related to N, C/N ratio, C and K respectively. This research demonstrated that the nitrogen and carbon concentrations among the decay classes and species type of CWD should be considered.