Tree regeneration on stumps in second-growth temperate rainforests of British Columbia, Canada

The significance of stumps and other coarse woody debris in maintaining biodiversity has been widely recognized in temperate rainforests, however, there is a paucity of research on the role of stumps in tree regeneration. We studied vascular plant diversity, island species area-relationship, and tree regeneration on stumps in temperate rainforests across three sites in British Columbia, Canada (Malcom Knapp Research Forest, MKRF; Pacific Spirit Regional Park, PSRP; and Stanley Park, SP). Our results were: 1) identification of 19 vascular plant species on stumps, including eight tree species, 2) the number of plants established on stumps observed convex up shape in MKRF and sigmoid shape for PSRP and SP, 3) the overall species established on stumps were positively associated in MKRF (Variance ratio = 2.74) and SP (Variance ratio = 1.37), but negatively associated in PSRP (Variance ratio = 0.57), and 4) tree species appeared to compete with each other on stumps and likely to co-occur with understorey species. Our results highlight species relationships and stumps diameter are major factors affecting tree regeneration on stumps in these second-growth temperate rainforests. We synthesized our results in a schematic of tree regeneration processes on stumps, which could be used to stimulate ideas for new hypothesis generation and for studies relevant to conservation and management.