The future of Portland’s forests: conifer regeneration and barriers to recruitment in urban and rural forests

Some reports suggest that Portland’s urban forests have low conifer regeneration rates. If so, this could be due either to a shortage of viable seeds or to a shortage of viable habitat. Nurse logs, in particular, have been identified as a substrate that increases conifer germination and survival rates. My study aims to determine 1) if there is less conifer regeneration in urban forests compared to rural forests, and, if so, 2) do urban forests produce less conifer seeds than rural forests, and 3) do urban forests have less nurse log surface area than rural forests. I sampled five of Portland’s second-growth urban forests and five nearby rural second-growth forests. In each site, I quantified the size structure of the conifer community, collected and counted the conifer seed rain, and quantified the surface area amount and decay state of downed wood. Preliminary analyses suggest that the urban forest sites have fewer young conifers and lower seed rain than the rural sites. Nurse log availability, while differing among sites, is less clearly predicted by a site\u27s urban vs. rural location. These results could have important implications for the management of Portland’s urban forests and the long term outlook on these parks’ conifer populations