Nursery Management Modulates Biomass Allocation and Early Field Establishment of Pinus douglasiana Martínez

Nursery decisions influence the condition of seedlings before outplanting, but their practical value depends on whether those traits remain evident during early field establishment. We evaluated Pinus douglasiana Martínez seedlings grown under eight combinations of container volume, fertilization, and irrigation regime. Seedlings were conditioned for six months in the nursery and then assessed after 12 months under field conditions. Container volume was the clearest source of variation. Compared with 1 L containers, 5 L containers produced seedlings with larger root collar diameter, greater shoot, root, and total biomass, and higher Dickson quality index. Total biomass was 2.2-fold greater in 5 L stock. Final survival was retained as a descriptive field variable and averaged 76.7% in 5 L treatments and 27.5% in 1 L treatments. Correlations based on treatment means associated total biomass with field diameter and descriptive survival, although these patterns were exploratory because only eight treatment means were available. Proline increased mainly under non-continuous irrigation, indicating a water-related nursery response, but it was not aligned with biomass production or first-year field performance. The treatment-level PCA separated biomass and field-growth variables from proline and lignification. These results show that larger containers improved the structural condition of P. douglasiana planting stock, although nursery costs, planting-site constraints, and longer monitoring should be considered before operational adoption.