2018 ASHS Annual Conference

Two-year-old (plug+1) balsam fir [Abies balsamea (L.) Mill.], and concolor fir [Abies concolor], and one-year-old bare-root Eastern White Pine [Pinus strobus (L.)] transplants were grown under three irrigations treatments (low, medium, and high) and two fertilization treatments (low and high) in greenhouse conditions. The goal was to determine the biomass allocation and nutrient use efficiency in response to the interactive effect of irrigation and fertilization under water stress. Relative root collar diameter (RRCD), relative height growth (RHG), relative root length (RRL), fresh and dry shoot mass (FSM and DSM), fresh and dry root mass (FRM, DRM), root number, and shoot/root (S/R) ratio were measured as growth parameters. We analyzed total nitrogen concentration of needles, stems, and roots and calculated resource-use efficiency parameters, such as assimilatory nutrient efficiency (ANUE), whole plant nutrient efficiency (NUE), index of nitrogen (N) availability (N/RW) and root weight ratio (RWR) to evaluate nutrient use physiology of the three species. Results obtained indicate significant differences between the two fir and white pine seedlings for stem water potential (SWP), growth parameters, biomass allocation, and nutrient use physiology. Specifically, concolor fir had a greater capacity to hold acquired water and improve water uptake compared to white pine. Furthermore, concolor fir showed higher aboveground growth and S/R ratio. The fir species had a higher nitrogen concentration compared to white pine. All species had higher N concentrations in their needles followed by roots and stems. White pine seedlings showed the highest ANUE, NUE and RWR values but the lowest N/RW value. These findings have strong implications for the management of these species in horticultural systems.