Arboriculture & Urban Forestry 46(6): November 2020 397 Table 1. Liters of herbicide applied/hectare (ha) in 2012, native flowering plant species richness, and number of trees/ha (< 0.3 m in height) in wire zones of 14 treatment sections on State Game Lands 33 Rights-of-Way Research and Demonstration Area, Centre County, PA, USA in 2016. Dominant (> 50% of area) cover type (forb, grass, or shrub) for wire zone is also presented. Liters of herbicide applied/ha (2012 treatment cycle) 0 0 0 0 0.75 0.75 0.75 6.27 29.93 31.99 168.37 241.33 436.82 436.82 Mechanical treatments versus herbicide treatments did not differ (t = 1.06, df = 1, p = 0.31); mechanical treatments versus glyphosate herbicide treatments dif- fered slightly (t = 1.81, df = 1, p = 0.09); mechanical treatments versus non-glyphosate treatments did not differ (t = 0.19, df = 1, p = 0.86); glyphosate versus non-glyphosate herbicide treatments differed significantly (t = −2.44, df = 1, p = 0.04). c Mechanical treatments versus herbicide treatments differed significantly (t = 3.10, df = 1, p = 0.009); mechanical treatments versus glyphosate herbicide treatments differed slightly (t = 2.18, df = 1, p = 0.06); mechanical treatments versus non-glyphosate herbicide treatments differed slightly (t = 2.03, df =1, p = 0.08); glyphosate versus non-glyphosate herbicide treatments did not differ (t = −0.74, df =1, p = 0.481). b a Accord concentrate (glyphosate) 7% + Arsenal (imazapyr) 1% dGarlon 3A (triclopyr) 5 pints/100 gal (2 L/380 L) + Milestone (aminopyralid) 7 oz/100 gal (210 mL/380 L) + Arsenal (imazapyr) 1% eMilestone (aminopyralid) 5 oz/100 gal (150 mL/380 L) + Arsenal (imazapyr) 4 oz/100 gal (120 mL/380 L) f Milestone (aminopyralid) 7 oz/100 gal (210 mL/380 L) + Rodeo (glyphosate) 1% + Arsenal (imazapyr) 1% + Tordon K (picloram) 4% + Garlon 3A (triclopyr) 5 pints/100 gal (2 L/380 L) correlation coefficient (r) to determine if there was a relationship between herbicide application rate in 2012 and stems of tree species and/or compatible native flowering plant species richness measured in 2016. We also used a two-tailed t-test (α = 0.05) for unequal sample sizes (and unequal variances) to determine if mechanical or chemical treatment influ- enced tree species abundance or the species richness of compatible native flowering plants at our plots. We also compared the effects of herbicide type on plant response; in particular, we examined the effects of herbicide mixes that contained glyphosate with those that did not. All statistical analyses were performed using Minitab® 17 (2010). RESULTS We documented a total of 29 compatible native flow- ering plant species on our plots (Table 2). Not all spe- cies were present in each section. We also documented 7 different species of trees within our vegetation plots (Table 2). There was no correlation between herbi- cide application rate (liters of herbicide applied) and the number of both trees (r = −0.30, n = 14, p = 0.29) and native flowering plant species richness (r = 0.21, n = 14, p = 0.46). There also was no difference in com- patible native flowering plant species richness between mechanically treated plots and herbicide-treated plots (t = 1.06, df = 1, p = 0.31; Table 1). However, when we compared herbicide treatments that contained ©2020 International Society of Arboriculture 1482 2718 11,613 3459 494 741 494 247 1729 741 0 494 200 100 Number of stems of trees/haa Native species richness of compatible flowering plant speciesb 7 9 11 25 8 8 6 7 15 10 19 10 5 7 M (Mowing) M (Mowing) M (Hand cutting) M (Hand cutting) H (Glyphosate, Imazapyr)c H (Glyphosate, Imazapyr) H (Glyphosate, Imazapyr) H (Aminopyralid, Imazapyr, Triclopyr)d H (Aminopyralid, Imazapyr, Triclopyr) H (Aminopyralid, Imazapyr, Triclopyr) H (Aminopyralid, Imazapyr)e H (Aminopyralid, Imazapyr) H (Aminopyralid, Glyphosate, Imazapyr, Picloram, Triclopyr)f H (Aminopyralid, Glyphosate, Imazapyr, Picloram, Triclopyr) Integrated vegetation management herbicide (H) versus mechanical (M) treatment Herbicide application (selective [backpack spray] or nonselective [broadcast spray]) N/A N/A N/A N/A Selective Selective Selective Selective Broadcast Broadcast Broadcast Selective Broadcast Broadcast Shrub Forb Shrub Shrub Grass Forb Forb Forb Forb Shrub Forb Shrub Grass Forb Cover type
November 2020
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