Performance of white oak (Quercus alba) and three pine species in novel multi-cropped plantations in eastern Tennessee, USA

Abstract

Loblolly pine (Pinus taeda L.), shortleaf pine (Pinus echinata Mill.), and eastern white pine (Pinus strobus L.) seedlings were multi-cropped with standard and large-diameter white oak (Quercus alba L.) seedlings to test for neutral or positive effects of multi-cropping. The study was established in 2014 in three complete blocks within recent clearcuts in eastern Tennessee, USA. Each block consisted of six multi-cropped treatments and four monocultures randomly assigned to ten 14.63 × 21.95 m plots. Within each block, monocultures of white oak and each pine species were planted in four control plots. Multi-cropped treatments included loblolly pine planted with white oak at a 0.31 m spacing, loblolly pine planted with white oak in alternating rows at a 1.74 m spacing, shortleaf pine planted with white oak at a 0.31 m spacing, shortleaf pine planted with white oak at a 1.74 m spacing, eastern white pine planted with white oak at a 0.31 m spacing, and eastern white pine planted with white oak at a 1.74 m spacing. Each plot with white oak received 20 standard (~0.127 cm in basal diameter) and 20 large-diameter (~0.632 cm in basal diameter) white oak seedlings that were randomly assigned to planting locations. Initial height, basal diameter, and early survival were recorded for each seedling just after planting. Height growth, basal diameter growth, survival, herbivory, and insect damage were recorded in early December 2014, 2015, 2016, 2017, 2018, and 2019. In 2019, percent survival among treatments did not differ significantly for white oak (p = 0.152), loblolly pine (p = 0.396), shortleaf pine (p = 0.246), or eastern white pine (p = 0.065). In addition, mean height growth and mean basal diameter growth did not differ significantly among treatments for white oak (p = 0.698 and 0.437, respectively), loblolly pine (p = 0.630 and 0.762, respectively), shortleaf pine (p = 0.324 and 0.251, respectively), or eastern white pine (p = 0.623 and 0.823, respectively). Survival was greater for large-diameter white oak seedlings than standard seedlings (p < 0.001). Mean height and mean basal diameter growth in large-diameter white oak seedlings were significantly greater than in standard seedlings ((p < 0.001) and (p < 0.001), respectively). Although these plantings are in the early stages of development, the lack of significant differences in seedling performance among treatments suggests species compatibility and no net negative impact of multi-cropping white oak with the three pine species.