Overstory retention and stock type impact survival and growth of underplanted shortleaf pine beneath a hardwood canopy

Abstract

This study was established to evaluate underplanting as a method of reestablishing a shortleaf pine (Pinus echinata Mill.) component to a dry upland hardwood stand in the Piedmont region of the southeastern United States. Replicated treatment plots were harvested to retain four levels (approximately 0, 3, 7, and 10 m² of basal area per hectare) of residual overstory density. One-year-old containerized seedlings with both smaller (93.4 cm³) and larger (113.1 cm³) plugs and bareroot seedlings were underplanted beneath the residual overstory treatments. After five growing seasons, seedling survival averaged 61% and was not meaningfully affected by residual overstory density. Seedling height growth ranged from 1.42 m to 2.61 m and was inversely related to residual overstory density. Containerized seedlings with larger plugs had the highest survival (77.4%) and best height growth (2.11 m), followed by containerized seedlings with smaller plugs (64.3%, 1.76 m) and bareroot seedlings (40.2%, 1.85 m). The results of this study indicated that underplanting containerized seedlings, particularly those with higher plug volume and greater plug depth, was a suitable option for reestablishing shortleaf pine on drier, hardwood dominated upland sites in the Piedmont. However, even low levels of overstory retention suppressed seedling height growth after a few years.

Keywords

underplanting, shortleaf pine, pine-hardwood mixtures, stock type, Piedmont

Citation

Schnake, David K.; Roberts, Scott D.; Willis, John L.; Kushla, John D.; Munn, Ian A. 2021. Overstory retention and stock type impact survival and growth of underplanted shortleaf pine beneath a hardwood canopy. Forest Science. 67(2): 219-230.