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.

中文翻译：

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覆盖层保留和树种类型影响硬木树冠下未充分种植的短叶松的生存和生长

本研究旨在评估在美国东南部皮埃蒙特地区的干燥高地硬木林分上重新种植短叶松 (Pinus echinata Mill.) 成分的方法。收获重复的处理地块以保留四个水平的剩余覆盖层密度（每公顷约 0、3、7 和 10 平方米的基底面积）。在剩余的覆盖层处理下，将具有较小 (93.4 cm3) 和较大 (113.1 cm3) 插头的一年生容器化幼苗和裸根幼苗种植在地下。经过五个生长季节，幼苗存活率平均为 61%，并且不受剩余覆盖层密度的显着影响。幼苗高度生长范围为 1.42 m 至 2.61 m，与剩余覆盖层密度成反比。具有较大插头的容器化苗木具有最高的成活率（77.4%）和最好的高度生长（2.11 m），其次是具有较小插头的容器化苗木（64.3%，1.76 m）和裸根苗（40.2%，1.85 m）。这项研究的结果表明，在皮埃蒙特地区较干燥、以硬木为主的高地场地种植短叶松，尤其是那些具有较大插塞体积和较大插塞深度的容器化幼苗是一个合适的选择。然而，即使是低水平的覆盖层保留在几年后也会抑制幼苗高度的增长。尤其是那些具有较高栓塞体积和较大栓塞深度的树种，是在皮埃蒙特干燥、以硬木为主的高地地区重建短叶松的合适选择。然而，即使是低水平的覆盖层保留在几年后也会抑制幼苗高度的增长。尤其是那些具有较高栓塞体积和较大栓塞深度的树种，是在皮埃蒙特干燥、以硬木为主的高地地区重建短叶松的合适选择。然而，即使是低水平的覆盖层保留在几年后也会抑制幼苗高度的增长。