DOI: 10.5061/dryad.3bk3j9kkj
title: Effects of wildfire and Paulownia tomentosa on native tree regeneration

description: A wildfire occurred in Shawnee State Forest located in southern Ohio that
 consumed 1215 hectares. Based on earlier forest inventories it was known
 that paulownia (Paulownia tomentosa), a non-native invasive tree species,
 occurred in the forest. The objective of this study was to determine if
 paulownia heavily colonized areas two years after the fire where the burn
 occurred, and if its presence had a negative impact on the regeneration
 (&lt;137 cm height) of native species—red and white oaks (Quercus
 sp.), red maple (Acer rubrum), and yellow-poplar (Liriodendron
 tulipifera). Two years after the fire, paulownia had invaded the burned
 areas but not at significantly higher densities than occurred in the
 unburned areas. Fire significantly reduced the number of regenerating
 stems of white oak and red maple two years after the fire, whereas the
 number of regenerating stems of red oak increased slightly and that of
 yellow-poplar increased significantly. In areas where paulownia occurred
 that experienced wildfire, all species studied displayed a reduction in
 the number of regenerating stems compared to paulownia’s absence in the
 burn areas. Where paulownia occurred in areas not affected by the
 wildfire, all the native species studied displayed a reduction in the
 number of regenerating stems. The average heights of red oak, white oak,
 and red maple were significantly taller when growing in areas affected by
 the wildfire due to a more open canopy. However, there was no significant
 change in the average heights of yellow-poplar. The presence of paulownia
 in both the burned and unburned areas reduced the number of regenerating
 stems of the native species studied.
description: Paulownia specimens for this study were first located in the
 burned areas off of hiking trails, logging trails, and dozer lines both in
 the burned and unburned areas. Each located specimen was tagged, and its
 GPS location saved and logged for future reference. Paulownia specimens in
 unburned areas were located along the outer boundaries of the burned area
 to try to ensure similar soil, topographic, geologic, and moisture
 characteristics for proper comparison between burned and unburned areas.
 Of the more than 200 paulownia specimens that were located in both the
 burned and unburned areas, a total of 61 specimens were randomly
 selected—28 and 33 specimens in the burned and unburned areas,
 respectively. Each of the randomly selected paulownia stems served as the
 plot center, and the minimum possible density of paulownia within a plot
 was one stem. Plots without paulownia trees were established and paired
 with the plots containing paulownia trees within 75 m of the paulownia
 plots in the respective burned and unburned areas, having similar slope
 steepness, aspect, elevation, and soil type as the paired paulownia plot.
 The 61 plots containing paulownia trees and the corresponding paired plots
 without paulownia trees provided a total of 122 sample plots. Accordingly,
 three treatments were evaluated: fire and paulownia present (F-P), fire
 and no paulownia present (F-NP), and no fire and paulownia present (NF-P).
 Plots established in unburned areas with no paulownia present (NF-NP)
 served as a control. Sample plots were 10 X 4 m in size
 and were divided into 5 X 2 m quadrants to facilitate measurements. Within
 each plot, the total height (to the nearest 1 cm) of each paulownia stem
 was recorded with the use of a telescoping height pole. Paulownia stems
 that split below 137 cm height were counted as multiple stems. Canopy
 closure was measured at the center of each plot with the use of a
 densiometer. For this study four important native
 species or species groups were evaluated. These species were red maple
 (<i>Acer rubrum</i>), yellow-poplar (<i>Liriodendron
 tulipifera</i>), the red oak group (<i>Q.
 marilandica</i>, <i>Q. rubra</i>, <i>Q.
 velutina</i>), and the white oak group (<i>Q. alba</i>,
 <i>Q. montana</i>). The focus of this study was on the early
 regeneration of these native species, which was defined as all stems less
 than 137 cm in height. A count of each species or species group was
 performed in each quadrant and summed for the total plot. Three seedlings
 per species or species group were randomly selected from each quadrant,
 providing 12 stems per species per plot, and the total height to the
 nearest 1 cm was measured and recorded. The recorded heights from each
 quadrant were combined to determine an average height for the plot by
 species or species groups.
description: The following provides further explanation of variables contained
 in the dataset: PLOT: This is the paired plot
 identifier. FIRE: This variable indicates whether the
 plot was located in the burned area (FIRE) or unburned area
 (NOFIRE). PATO PRESENCE: This variable indicates
 whether paulownia was present (PATO) or absent (NOPATO) on the plot. Note:
 PATO is the designation for paulownia (<b>PA</b>lownia
 <b>TO</b>mentosa) SPECIES: This variable
 contains the native tree species selected for analysis in this study. RMAP
 = red maple, ROAK = red oak, WOAK = white oak, YPOP =
 yellow-poplar. SPECIES COUNT: This variable contains
 the number of individual stems of species the occurred on the
 plot SPECIES HT: This variable contains the average
 height (cm) based on the 12 randomly selected stems less than 137 cm
 height of each species on the plot. If no stems of a species occurred on
 the plot, then a null ( _N_ ) value is placed in the variable.
 PATO COUNT: This variable contains the number of paulownia stems
 that occurred on the plot. PATO HT: This variable
 contains the average height (cm) of all paulownia stems that occurred on
 the plot. If no stems of paulownia occurred on the plot, then a null ( _N_
 ) value is placed in the variable. TREATMENT: This
 variable contains the treatment represented by the plot. F-P = Fire and
 presence of Paulownia, F-NP = Fire and no Paulownia present, NF-P = No
 Fire and presence of paulownia, NF-NP = No fire and No Paulownia
 present. SPECIES STEM/HA: This variable contains the
 number of species stems on a plot converted to the number of stems per
 hectare. PATO STEM/HA: This variable contains the
 number of paulownia stems on a plot converted to the number of stems per
 hectare.