Table 2 Paired comparison tests for burn and control treatments comparing 1989 baseline data to 2017 sample data for eight vegetation parameters at Gibbons Creek Barrens Natural Area, Pope County, Illinois, USA. se = standard error. If “mean ±” is shown, data were analyzed with paired t-tests; if “mdn” (median) is shown, data were analyzed with related samples Wilcoxon signed-rank tests because either 1989 or 2017 data were not normally distributed. GCB = Gibbons Creek Barrens, FSB = Forest Service Barrens, Change (%) = difference between 1989 and 2017, df = degrees of freedom, Test stat = test statistic, P = probability, NA = not applicable. P values shown in bold are significant (<0.05)
Parameter | Treatment: Burn (GCB) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
1989 (mean ± se) | 2017 (mean ± se) | Change (%) | Test stat | df | P | |||||
Overstory | ||||||||||
Tree density (stems per 0.05 ha) | 47.27 | ± | 12.50 | 21.87 | ± | 7.18 | −53.74 | 8.40 | 14 | <0.001 |
Tree basal area (m2 per 0.05 ha) | 0.89 | ± | 0.06 | 0.76 | ± | 0.06 | −15.04 | 4.60 | 14 | <0.001 |
Shrub and sapling density (stems per 0.005 ha) | 27.73 | ± | 3.70 | 46.27 | ± | 5.35 | 66.83 | −5.68 | 14 | <0.001 |
Ground layer | ||||||||||
Species density (species per 0.25 m) | 4.37 | ± | 0.60 | 6.75 | ± | 0.42 | 54.45 | −6.66 | 14 | <0.001 |
Species richness (total species per plot [12 quadrats]) | 21.00 | mdn | NA | 26.00 | mdn | NA | 23.81 | 113.00 | 0.003 | |
Species diversity (H' per 0.25 m2) | 2.76 | mdn | NA | 2.90 | mdn | NA | 5.07 | 108.00 | 0.006 | |
Dominance (C per 0.25 m2) | 0.08 | mdn | NA | 0.07 | mdn | NA | −13.75 | 8.50 | 0.003 | |
Cover (%) | 90.42 | ± | 13.06 | 55.31 | ± | 4.93 | −38.83 | 2.85 | 14 | 0.013 |
Parameter | Treatment: Control (FSB) | |||||||||
1989 (mean ± se) | 2017 (mean ± se) | Change (%) | Test stat | df | P | |||||
Overstory | ||||||||||
Tree density (stems per 0.05 ha) | 50.25 | ± | 3.02 | 46.75 | ± | 2.17 | −6.97 | 3.44 | 7 | 0.011 |
Tree basal area (m2 per 0.05 ha) | 0.92 | ± | 0.05 | 0.94 | ± | 0.08 | 2.03 | −0.48 | 7 | 0.644 |
Shrub and sapling density (stems per 0.005 ha) | 25.50 | ± | 5.31 | 29.13 | ± | 3.92 | 14.22 | −1.09 | 7 | 0.311 |
Ground layer | ||||||||||
Species density (species per 0.25 m) | 4.38 | mdn | NA | 4.42 | mdn | NA | 1.03 | 8.50 | 0.352 | |
Species richness (total species per plot [12 quadrats]) | 22.50 | ± | 2.76 | 18.63 | ± | 2.03 | −17.22 | 1.53 | 7 | 0.169 |
Species diversity (H' per 0.25 m2) | 2.69 | ± | 0.13 | 2.55 | ± | 0.13 | −5.20 | 1.38 | 7 | 0.210 |
Dominance (C per 0.25 m2) | 0.10 | ± | 0.01 | 0.11 | ± | 0.01 | 9.74 | −0.91 | 7 | 0.392 |
Cover (%) | 98.42 | ± | 7.26 | 41.12 | ± | 7.27 | −58.22 | 9.30 | 7 | <0.001 |