Preliminary findings on silvicultural techniques and early growth assessment of Podocarpus pilgeri Foxw., 1907 in Quang Ninh Province

Abstract

Podocarpus pilgeri Foxw. (1907) is a rare and highly valuable timber species currently lacking a standardized planting protocol in Quang Ninh province. This study aims to evaluate ecological conditions, establish experimental models, and propose suitable local planting techniques. Initial results indicate that the suitable site condition is yellowish-red ferralic soil (pH 5.6–6.5; soil depth > 50 cm). The planting density is 625 trees/ha (4 × 4 m) for pure plantations and 250 trees/ha for under-canopy planting. Seedlings used for planting are 12–18 months old, with a height of  ≥ 15 cm and a root-collar diameter ≥ 0.3 cm. After one year, the survival rate exceeded 85% (the pure plantation model achieved 532/625 trees/ha; the under-canopy model achieved 218/250 trees/ha). The growth in height and root-collar diameter was stable, with the under-canopy model exhibiting lower variation. Growth prediction analysis showed that the Gompertz function is more suitable than the Mitscherlich function in the first five years (R²: 0.987–0.99; low RMSE); however, this requires further verification using long-term data. The study proposed preliminary technical criteria (site conditions, seedlings, planting, and tending), providing a scientific basis for the conservation and development of this species in Quang Ninh.