Abundance and diversity of deadwood and tree-related microhabitats in a Caledonian pine forest, Scotland

Old-growth forests provide a key biodiversity reservoir due to their high amount of deadwood and abundance of tree-related microhabitats (TreMs). This research investigates the abundance and diversity of deadwood and TreMs in old-growth Caledonian pine forests located in the Cairngorms National Park, Scotland. The study area is a Scots pine (Pinus sylvestris L.)-dominated forest. A field survey campaign was conducted in 15 sample plots to collect data on stand and deadwood characteristics, and TreMs by category. Within circular plots of 531 m2, the diameter at breast height, height, and insertion height of the canopy of all the living trees were measured, and the three deadwood components (snags, fallen deadwood, and stumps) and TreMs were recorded. The results showed a total deadwood volume of 37.53 ± 32.39 m3 ha−1, mostly in the form of snags (68.9% of total volume) and in the lowest degree of decay (first decay class equals 36.8%). The average number of deadwood elements is 217 ha−1, distributed to 127 snags ha−1, 64 fallen deadwood ha−1, and 26 stumps ha−1. The results showed an average of 89.1 TreMs ha−1 on snags and 26.4 ha−1 on living trees. The abundance and diversity of TreMs are significantly related to the volume of snags (R2 = 0.712), the deadwood diversity (R2 = 0.664), and the degree of decomposition (R2 = 0.416).