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Grassland Fire Effects on Steel Fence Posts
Rangeland Ecology & Management 72 (2019) 411–413
Contents lists available at ScienceDirect
Rangeland Ecology & Management journal homepage: http://www.elsevier.com/locate/rama
Short Communications
Grassland Fire Effects on Steel Fence Posts☆ John R. Weir a,⁎, Heath D. Starns b a b
Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK 74078, USA Texas A&M AgriLife Research, Sonora Research Station, Sonora, TX 76950, USA
a r t i c l e
i n f o
Article history: Received 4 May 2018 Received in revised form 10 October 2018 Accepted 22 October 2018 Key Words: fencing infrastructure prescribed fire range developments T post wildfire
a b s t r a c t Rangeland fire effects on flora, fauna, soils, and water have been studied widely. Fire effects information is limited on rangeland developments such as fencing. Fencing is an integral part of rangeland infrastructure and receives much attention when there is a wildfire or even discussion about conducting prescribed fires. Due to known fence age and fire history, we conducted a study on the Oklahoma State University Research Range located near Stillwater, Oklahoma. Five randomly selected individual metal T posts were sampled from a common fence line of known age and fire treatment. The T posts ranged from 4 to 35 yr since fence construction, with fire activity of 0, 1, 3, or 12 prescribed fires and 0, 1, or 2 wildfire occurrences. Each T post was tested in situ at 40 cm, 80 cm, and 120 cm above ground level for hardness and paint adhesion as set forth by American Society for Testing and Materials (ASTM) International standards for hot wrought metal fence posts. Our results found no differences in post hardness, with all posts tested being higher than the ASTM minimum standard of 83 Rockwell B Hardness Scale. We also found that paint adhesion between burned and unburned T posts did not vary, with age of post being the only significant predictor variable for adhesion. Overall, our results provide evidence that T posts exposed to numerous fires and fire types did not suffer negative effects. This shows that concerns about wildfire and prescribed fires in grasslands having negative effects on metal T posts are unfounded. © 2018 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
Introduction Rangeland fire effects on flora, fauna, soils, and water have been studied widely, with numerous results published from the various ecosystems throughout North America and worldwide. Even with all of this research, information is limited about fire impacts on rangeland developments. Fencing is an integral part of rangeland infrastructure that receives much attention when there is a wildfire (Bechtel, 2018) or even discussion about conducting prescribed fires (Elmore et al., 2010; Morton et al., 2010). Previous fence studies have evaluated fire effects on zinc-coated and older corroded barbed wire, with both finding no impact from fire (Engle et al., 1998; Engle and Weir, 2000). Metal fence post integrity often comes into question following a wildfire or before prescribed burns are conducted. Although other fence post studies have examined the fire resistance of preservative-treated wood posts, we could not find any that examined metal posts (McCarthy et al., 1972; Evans et al., 1994). In the past 40 yr due to availability, ease of handling. and ability to be driven in most soils, hot wrought steel fence posts, often referred to as T posts, have been used on a majority of rangeland fence built (Vallentine, 1989). It is important to determine what impacts fire has on metal T posts because it can limit the ☆ This work was funded by the Oklahoma Agricultural Experiment Station. ⁎ Correspondence: John R. Weir, Natural Resource Ecology and Management, Oklahoma State University, 008C Ag Hall, Stillwater, OK 74078, USA. E-mail address: [email protected] (J.R. Weir).
implementation of prescribed fire due to fear of damaging posts. At the same time, wildfires are often viewed as destructive to metal T posts, with replacement often seen as the only option following these events. A site was available for us to sample T posts that were of a known construction age and fire history. From this we were able to investigate specifically the effects of numerous prescribed fires and wildfires on the metal integrity (hardness) and impact to the paint coating (adhesion) of hot wrought steel T posts.
Methods We conducted this study on the Oklahoma State University Research Range located 18 km southwest of Stillwater, Oklahoma. The vegetation is dominated by tallgrass prairie species. In May and June 2017 we randomly selected individual metal T posts from burned and unburned areas along five separate fence lines, making sure all selected posts came from original construction materials (Table 1). Five T posts from each burned and unburned section of fence were selected for a total of 45 individual T posts sampled, 25 burned and 20 unburned. The treatments were 1) unburned, 2) burned by prescribed fire only, 3) wildfire only, and 4) wildfire and prescribed fire at various times (see Table 1). The T posts ranged from 4 to 35 yr since fence construction, with fire activity of 0, 1, 3, or 12 prescribed fires and 0, 1, or 2 wildfire occurrences. The time since fire activity at sampling ranged from b 2 mo post fire to 21 yr post fire.
https://doi.org/10.1016/j.rama.2018.10.007 1550-7424/© 2018 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
412
J.R. Weir, H.D. Starns / Rangeland Ecology & Management 72 (2019) 411–413
Table 1 Location, date of installation, type (and number) of fire exposures, and dates of fire occurrence for all posts sampled from the Oklahoma State University Research Range. Site
T posts installed (yr)
Fire treatment (no. of times)
Fire occurrences (yr)
HQ P4
2013
2017
Section 4
1982
Prescribed fire (1) No fire Prescribed fire (1) Wildfire (2) No fire Prescribed fire (3) Wildfire (1) No fire Prescribed fire (12) No fire
CTER P19 East 1983 CTER P19 North 1983 CTER P1
1982
2010 1991, 2009 2000, 2015, 2017 1996 1986, 1987, 1988, 1990, 1993, 1996, 1999, 2002, 2005, 2008, 2013, 2015
The ASTM International has quality standards set in place for consistent manufacturing of steel T posts and the finish applied (ASTM, 2013). These standards include size of posts: ≈35 mm wide, 35 mm deep, and 3.2 mm thick. Lengths available are standard from 1 525 to 3 050 mm, with a nominal weight of 1.49 kg/m. Posts should have a minimum of 83 Rockwell B Hardness. The finish on painted posts is to be one or more coats of weather-resistant enamel paint, which can be air dried or baked on. Hardness was tested with a Model GH100D Hardness Tester (Landmark Industrial, Ramsey, NJ). The Hardness Tester was set to steel and cast steel, with horizontal test setting using the Rockwell B Hardness Scale (HrB). Each of the 45 T posts was tested in situ at 40 cm, 80 cm, and 120 cm above ground level for hardness as set forth by ASTM standards A702-13 (ASTM, 2013). At each of the three heights, five separate hardness readings were recorded. Paint adhesion was tested on the same T post after we conducted the hardness test. One adhesion test was conducted at 40, 80, and 120 cm above ground level on each post, for a total of 135 individual tests. The adhesion test was conducted following the X-cut method using ASTM D3359-09 (ASTM, 2009). The X-cut method involved making sure the site was clean and dry, and then two 40-mm-long cuts were made in
the shape of an X using a sharp razor knife with a metal straight edge through the paint layer down to the metal substrate of the post. Then a 25-mm wide × 75-mm long piece of semitransparent pressure-sensitive tape that met the ASTM standard for adhesion strength of testing tape was placed over the X cut (Intertape LA-26 polyester/rope-fiber laminate tape). The tape was smoothed over the X cut and then rubbed firmly into place with an eraser on the end of a pencil. Within 90 (± 30) seconds of application, the tape was removed by rapidly pulling it back on itself as close to 180 degrees as possible. The tape was placed adhesive side down on a clear plastic sheet to protect the results and allow for examination. The overall temperature ranged from 23 oC to 35 oC, and relative humidity ranged from 35 − 73% during all sampling periods. The following scale was used for determination of paint adhesion as per ASTM D3359-09: 5A No peeling or removal, 4A Trace peeling or removal along incisions or at their intersection, 3A Jagged removal along incisions up to 1.6 mm on either side, 2A Jagged removal along most of incisions up to 3.2 mm on either side, 1A Removal from most of the area of the X under the tape, and 0A Removal beyond the area of the X. We created linear mixed-effects models using the lme4 package in program R (Bates et al., 2013; R Core Team, 2016) to test for differences between burned and unburned posts and to evaluate the effects of total number of fires, fire type, and post age on Rockwell hardness (HrB) and paint adhesion. For each testing height (40, 80, and 120 cm), eight models were created, including global and null models (Burnham and Anderson, 2003). Independent variables of interest included exposure to fire (burned/unburned), total number of fires, fire type (wildfire vs. prescribed), and fence age. All models included a random effect term for location to account for potential unmeasured differences in slope, aspect, and exposure to sunlight. Akaike’s Information Criterion corrected for small sample size (AICC) was used to compare models (Burnham and Anderson, 2003). The model with the lowest AICC score was then analyzed to determine the significance of predictor variables.
Figure 1. Upper panel: Boxplots of hardness (HrB,) of steel posts at testing heights of 40 cm (A), 80 cm (B), and 120 cm (C) above ground level, for unburned posts and posts burned multiple times. Dashed line is ASTM minimum requirement for hot wrought steel T posts, HrB 83. Lower panel: Paint adhesion scores from tape testing at heights of 40 cm (D), 80 cm (E), and 120 cm (F) above ground level for unburned posts (circles) and posts burned multiple times (triangles).
J.R. Weir, H.D. Starns / Rangeland Ecology & Management 72 (2019) 411–413 Table 2 Results of AICC model comparison procedures for mean hardness and paint adhesion of steel T posts at each testing height (40 cm, 80 cm, and 120 cm). Display restricted to top three models. Response HrB @ 40 cm
HrB @ 80 cm
HrB @ 120 cm
Paint @ 40 cm
Paint @ 80 cm
Paint @ 120 cm
Model
ΔAICc
df
Weight
Burned NULL Total burns + burned Burned NULL Total burns + burned Burned NULL Total burns + burned Fence age NULL Fence age + burned NULL Fence age Burned NULL Fence age Burned
0.0 0.4 3.1 0.0 1.4 3.4 0.0 0.5 2.8 0.0 1.1 5.6 0.0 1.4 2.6 0.0 1.6 5.1
5 4 6 5 4 6 5 4 6 5 4 6 4 5 5 4 5 5
0.4341 0.3621 0.0938 0.5357 0.2680 0.0961 0.4110 0.3130 0.1000 0.6002 0.3400 0.0364 0.5907 0.2498 0.1422 0.6355 0.2850 0.0485
Results We found no differences in HrB between burned and unburned posts (Fig. 1). Mean hardness of posts in all treatments was higher than the ASTM minimum post hardness standard of 83 HrB. Although burn treatment (burned/unburned) was included in the “best” model for hardness at all testing heights, the null model was a competing model (AICC b 2.0, Table 2) at each testing height. Further investigation of the models revealed that burn treatment was not statistically significant at any testing height (P = 0.65 at 40 cm, P = 0.27 at 80 cm, P = 0.27 at 120 cm). Five individual posts, three burned and two unburned, did have averages just below 83 HrB at the 40-cm height only (Burned HrB—80.8, 82.0, 82.9, Unburned HrB—81.0, 82.0). Similar to hardness, we found no differences in paint adhesion between burned and unburned posts (see Fig. 1). Paint adhesion was higher (less paint removed by tape) on older posts in both burned and unburned treatments. The null model was the best model for paint adhesion at 80 cm and 120 cm above ground level (see Table 2), with fence age included in a competing model at both heights. Fence age was included in the best model for paint adhesion at 40 cm above ground level, with the null a competing model (see Table 2). Fence age was a significant predictor in the model for paint adhesion at 40 cm (P b 0.001) Discussion Our results indicate that prescribed fires or wildfires have no effect on hardness or paint adhesion of hot wrought steel fence posts commonly used for rangeland fencing. Regardless of age, hardness of T posts sampled in our study was greater than the minimum ASTM re-
413
quirement for hot-wrought steel posts. Our findings are contrary to prevailing views and suggest that replacement of T posts is not necessary after a wildfire. Even the three burned and two unburned posts that recorded just below industry standard readings at the 40-cm height only showed no signs of reducing fence integrity or need for replacement. We also conclude that steel T posts should not be a topic of concern when planning prescribed burns in rangeland settings. It should be noted that several samples were from posts burned 21 yr before testing; therefore, any time-lagged impacts of fire should have been manifested before sampling. Fence age was the only predictor variable with an influence on paint adhesion, with a seemingly positive correlation between the two. A plausible explanation for this is that older posts in our study had less paint remaining intact as a function of age; therefore, less paint was available to adhere to the tape. Paint adhesion scores were slightly lower for newer posts, again probably because older (N 30-yr) posts in our study had less paint remaining. The results of the paint adhesion tests were not consistent for all three testing heights, possibly as a result of different amounts of sun exposure. Overall, our results provide evidence that T posts exposed to numerous fires and fire types do not suffer negative effects. Our findings are also consistent with the previous investigations into effects of fire on rangeland improvements that revealed no negative impacts to barbed wire (Engle et al., 1998; Engle and Weir, 2000). References ASTM, 2009. ASTM D3359-09. Standard test methods for measuring adhesion by tape test. ASTM International, West Conshohocken, PA, USA, p. 8. ASTM, 2013. ASTM A702-13. Standard specification for steel fence posts, hot wrought. ASTM International, West Conshohocken, PA, USA, p. 3. Bates, D., Maechler, M., Bolker, B., Walker, S., 2013. . [computer program]. lme4: linear mixed-effects models using Eigen and S4. R package version 1.0-5. Bechtel, W., 2018. Oklahoma Wildfires cause $26 million in damage to cattle ranchers. Drovers 7 May. Available at:. https://www.drovers.com/article/oklahoma-wildfirescause-26-million-damages-cattle-ranchers, Accessed date: 10 July 2018. Burnham, K.P., Anderson, D.R., 2003. Model selection and multimodel inference: a practical information-theoretic approach. Springer Science & Business Media, New York, NY, USA, p. 488. Elmore, R.D., Bidwell, T.G., Weir, J.R., 2010. Prescribed fire public perception and education perceptions of Oklahoma residents to prescribed fire. In: Robertson, K.M., Galley, K.E.M., Masters, R.E. (Eds.), Proceedings of the 24th Tall Timbers Fire Ecology Conference: The Future of Prescribed Fire: Public Awareness, Health, and Safety. Tall Timbers Research Station, Tallahassee, FL, USA, pp. 50–61. Engle, D.M., Weir, J.R., 2000. Grassland fire effects on corroded barbed wire. Journal of Range Management 53, 611–613. Engle, D.M., Weir, J.R., Gay, D.L., Dugan, B.P., 1998. Grassland fire effects on barbed wire. Journal of Range Management 51, 621–624. Evans, P.D., Beutel, P., Cunningham, R.B., Donnelly, C.F., 1994. Fire resistance of preservative-treated slash pine fence posts. Forest Products Journal 44, 37–39. McCarthy, D.F., Bezemer, L.D., Seaman, W.G., Dacosta, E.W.B., 1972. Development and evaluation of a leach resistant fire retardant preservative for pine fence posts. Institute of Wood Science Journal 6, 24–31. Morton, L.W., Regen, E., Engle, D.M., Miller, J.R., Harr, R.N., 2010. Perceptions of landowners concerning conservation, grazing, fire and eastern redcedar management in tallgrass prairie. Rangeland Ecology & Management 63, 645–654. R Core Team, 2016. . [computer program]. R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. Vallentine, J.F., 1989. Range development and improvements. Academic Press, Inc., San Diego, CA, USA, p. 524.
Contents lists available at ScienceDirect
Rangeland Ecology & Management journal homepage: http://www.elsevier.com/locate/rama
Short Communications
Grassland Fire Effects on Steel Fence Posts☆ John R. Weir a,⁎, Heath D. Starns b a b
Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK 74078, USA Texas A&M AgriLife Research, Sonora Research Station, Sonora, TX 76950, USA
a r t i c l e
i n f o
Article history: Received 4 May 2018 Received in revised form 10 October 2018 Accepted 22 October 2018 Key Words: fencing infrastructure prescribed fire range developments T post wildfire
a b s t r a c t Rangeland fire effects on flora, fauna, soils, and water have been studied widely. Fire effects information is limited on rangeland developments such as fencing. Fencing is an integral part of rangeland infrastructure and receives much attention when there is a wildfire or even discussion about conducting prescribed fires. Due to known fence age and fire history, we conducted a study on the Oklahoma State University Research Range located near Stillwater, Oklahoma. Five randomly selected individual metal T posts were sampled from a common fence line of known age and fire treatment. The T posts ranged from 4 to 35 yr since fence construction, with fire activity of 0, 1, 3, or 12 prescribed fires and 0, 1, or 2 wildfire occurrences. Each T post was tested in situ at 40 cm, 80 cm, and 120 cm above ground level for hardness and paint adhesion as set forth by American Society for Testing and Materials (ASTM) International standards for hot wrought metal fence posts. Our results found no differences in post hardness, with all posts tested being higher than the ASTM minimum standard of 83 Rockwell B Hardness Scale. We also found that paint adhesion between burned and unburned T posts did not vary, with age of post being the only significant predictor variable for adhesion. Overall, our results provide evidence that T posts exposed to numerous fires and fire types did not suffer negative effects. This shows that concerns about wildfire and prescribed fires in grasslands having negative effects on metal T posts are unfounded. © 2018 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
Introduction Rangeland fire effects on flora, fauna, soils, and water have been studied widely, with numerous results published from the various ecosystems throughout North America and worldwide. Even with all of this research, information is limited about fire impacts on rangeland developments. Fencing is an integral part of rangeland infrastructure that receives much attention when there is a wildfire (Bechtel, 2018) or even discussion about conducting prescribed fires (Elmore et al., 2010; Morton et al., 2010). Previous fence studies have evaluated fire effects on zinc-coated and older corroded barbed wire, with both finding no impact from fire (Engle et al., 1998; Engle and Weir, 2000). Metal fence post integrity often comes into question following a wildfire or before prescribed burns are conducted. Although other fence post studies have examined the fire resistance of preservative-treated wood posts, we could not find any that examined metal posts (McCarthy et al., 1972; Evans et al., 1994). In the past 40 yr due to availability, ease of handling. and ability to be driven in most soils, hot wrought steel fence posts, often referred to as T posts, have been used on a majority of rangeland fence built (Vallentine, 1989). It is important to determine what impacts fire has on metal T posts because it can limit the ☆ This work was funded by the Oklahoma Agricultural Experiment Station. ⁎ Correspondence: John R. Weir, Natural Resource Ecology and Management, Oklahoma State University, 008C Ag Hall, Stillwater, OK 74078, USA. E-mail address: [email protected] (J.R. Weir).
implementation of prescribed fire due to fear of damaging posts. At the same time, wildfires are often viewed as destructive to metal T posts, with replacement often seen as the only option following these events. A site was available for us to sample T posts that were of a known construction age and fire history. From this we were able to investigate specifically the effects of numerous prescribed fires and wildfires on the metal integrity (hardness) and impact to the paint coating (adhesion) of hot wrought steel T posts.
Methods We conducted this study on the Oklahoma State University Research Range located 18 km southwest of Stillwater, Oklahoma. The vegetation is dominated by tallgrass prairie species. In May and June 2017 we randomly selected individual metal T posts from burned and unburned areas along five separate fence lines, making sure all selected posts came from original construction materials (Table 1). Five T posts from each burned and unburned section of fence were selected for a total of 45 individual T posts sampled, 25 burned and 20 unburned. The treatments were 1) unburned, 2) burned by prescribed fire only, 3) wildfire only, and 4) wildfire and prescribed fire at various times (see Table 1). The T posts ranged from 4 to 35 yr since fence construction, with fire activity of 0, 1, 3, or 12 prescribed fires and 0, 1, or 2 wildfire occurrences. The time since fire activity at sampling ranged from b 2 mo post fire to 21 yr post fire.
https://doi.org/10.1016/j.rama.2018.10.007 1550-7424/© 2018 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
412
J.R. Weir, H.D. Starns / Rangeland Ecology & Management 72 (2019) 411–413
Table 1 Location, date of installation, type (and number) of fire exposures, and dates of fire occurrence for all posts sampled from the Oklahoma State University Research Range. Site
T posts installed (yr)
Fire treatment (no. of times)
Fire occurrences (yr)
HQ P4
2013
2017
Section 4
1982
Prescribed fire (1) No fire Prescribed fire (1) Wildfire (2) No fire Prescribed fire (3) Wildfire (1) No fire Prescribed fire (12) No fire
CTER P19 East 1983 CTER P19 North 1983 CTER P1
1982
2010 1991, 2009 2000, 2015, 2017 1996 1986, 1987, 1988, 1990, 1993, 1996, 1999, 2002, 2005, 2008, 2013, 2015
The ASTM International has quality standards set in place for consistent manufacturing of steel T posts and the finish applied (ASTM, 2013). These standards include size of posts: ≈35 mm wide, 35 mm deep, and 3.2 mm thick. Lengths available are standard from 1 525 to 3 050 mm, with a nominal weight of 1.49 kg/m. Posts should have a minimum of 83 Rockwell B Hardness. The finish on painted posts is to be one or more coats of weather-resistant enamel paint, which can be air dried or baked on. Hardness was tested with a Model GH100D Hardness Tester (Landmark Industrial, Ramsey, NJ). The Hardness Tester was set to steel and cast steel, with horizontal test setting using the Rockwell B Hardness Scale (HrB). Each of the 45 T posts was tested in situ at 40 cm, 80 cm, and 120 cm above ground level for hardness as set forth by ASTM standards A702-13 (ASTM, 2013). At each of the three heights, five separate hardness readings were recorded. Paint adhesion was tested on the same T post after we conducted the hardness test. One adhesion test was conducted at 40, 80, and 120 cm above ground level on each post, for a total of 135 individual tests. The adhesion test was conducted following the X-cut method using ASTM D3359-09 (ASTM, 2009). The X-cut method involved making sure the site was clean and dry, and then two 40-mm-long cuts were made in
the shape of an X using a sharp razor knife with a metal straight edge through the paint layer down to the metal substrate of the post. Then a 25-mm wide × 75-mm long piece of semitransparent pressure-sensitive tape that met the ASTM standard for adhesion strength of testing tape was placed over the X cut (Intertape LA-26 polyester/rope-fiber laminate tape). The tape was smoothed over the X cut and then rubbed firmly into place with an eraser on the end of a pencil. Within 90 (± 30) seconds of application, the tape was removed by rapidly pulling it back on itself as close to 180 degrees as possible. The tape was placed adhesive side down on a clear plastic sheet to protect the results and allow for examination. The overall temperature ranged from 23 oC to 35 oC, and relative humidity ranged from 35 − 73% during all sampling periods. The following scale was used for determination of paint adhesion as per ASTM D3359-09: 5A No peeling or removal, 4A Trace peeling or removal along incisions or at their intersection, 3A Jagged removal along incisions up to 1.6 mm on either side, 2A Jagged removal along most of incisions up to 3.2 mm on either side, 1A Removal from most of the area of the X under the tape, and 0A Removal beyond the area of the X. We created linear mixed-effects models using the lme4 package in program R (Bates et al., 2013; R Core Team, 2016) to test for differences between burned and unburned posts and to evaluate the effects of total number of fires, fire type, and post age on Rockwell hardness (HrB) and paint adhesion. For each testing height (40, 80, and 120 cm), eight models were created, including global and null models (Burnham and Anderson, 2003). Independent variables of interest included exposure to fire (burned/unburned), total number of fires, fire type (wildfire vs. prescribed), and fence age. All models included a random effect term for location to account for potential unmeasured differences in slope, aspect, and exposure to sunlight. Akaike’s Information Criterion corrected for small sample size (AICC) was used to compare models (Burnham and Anderson, 2003). The model with the lowest AICC score was then analyzed to determine the significance of predictor variables.
Figure 1. Upper panel: Boxplots of hardness (HrB,) of steel posts at testing heights of 40 cm (A), 80 cm (B), and 120 cm (C) above ground level, for unburned posts and posts burned multiple times. Dashed line is ASTM minimum requirement for hot wrought steel T posts, HrB 83. Lower panel: Paint adhesion scores from tape testing at heights of 40 cm (D), 80 cm (E), and 120 cm (F) above ground level for unburned posts (circles) and posts burned multiple times (triangles).
J.R. Weir, H.D. Starns / Rangeland Ecology & Management 72 (2019) 411–413 Table 2 Results of AICC model comparison procedures for mean hardness and paint adhesion of steel T posts at each testing height (40 cm, 80 cm, and 120 cm). Display restricted to top three models. Response HrB @ 40 cm
HrB @ 80 cm
HrB @ 120 cm
Paint @ 40 cm
Paint @ 80 cm
Paint @ 120 cm
Model
ΔAICc
df
Weight
Burned NULL Total burns + burned Burned NULL Total burns + burned Burned NULL Total burns + burned Fence age NULL Fence age + burned NULL Fence age Burned NULL Fence age Burned
0.0 0.4 3.1 0.0 1.4 3.4 0.0 0.5 2.8 0.0 1.1 5.6 0.0 1.4 2.6 0.0 1.6 5.1
5 4 6 5 4 6 5 4 6 5 4 6 4 5 5 4 5 5
0.4341 0.3621 0.0938 0.5357 0.2680 0.0961 0.4110 0.3130 0.1000 0.6002 0.3400 0.0364 0.5907 0.2498 0.1422 0.6355 0.2850 0.0485
Results We found no differences in HrB between burned and unburned posts (Fig. 1). Mean hardness of posts in all treatments was higher than the ASTM minimum post hardness standard of 83 HrB. Although burn treatment (burned/unburned) was included in the “best” model for hardness at all testing heights, the null model was a competing model (AICC b 2.0, Table 2) at each testing height. Further investigation of the models revealed that burn treatment was not statistically significant at any testing height (P = 0.65 at 40 cm, P = 0.27 at 80 cm, P = 0.27 at 120 cm). Five individual posts, three burned and two unburned, did have averages just below 83 HrB at the 40-cm height only (Burned HrB—80.8, 82.0, 82.9, Unburned HrB—81.0, 82.0). Similar to hardness, we found no differences in paint adhesion between burned and unburned posts (see Fig. 1). Paint adhesion was higher (less paint removed by tape) on older posts in both burned and unburned treatments. The null model was the best model for paint adhesion at 80 cm and 120 cm above ground level (see Table 2), with fence age included in a competing model at both heights. Fence age was included in the best model for paint adhesion at 40 cm above ground level, with the null a competing model (see Table 2). Fence age was a significant predictor in the model for paint adhesion at 40 cm (P b 0.001) Discussion Our results indicate that prescribed fires or wildfires have no effect on hardness or paint adhesion of hot wrought steel fence posts commonly used for rangeland fencing. Regardless of age, hardness of T posts sampled in our study was greater than the minimum ASTM re-
413
quirement for hot-wrought steel posts. Our findings are contrary to prevailing views and suggest that replacement of T posts is not necessary after a wildfire. Even the three burned and two unburned posts that recorded just below industry standard readings at the 40-cm height only showed no signs of reducing fence integrity or need for replacement. We also conclude that steel T posts should not be a topic of concern when planning prescribed burns in rangeland settings. It should be noted that several samples were from posts burned 21 yr before testing; therefore, any time-lagged impacts of fire should have been manifested before sampling. Fence age was the only predictor variable with an influence on paint adhesion, with a seemingly positive correlation between the two. A plausible explanation for this is that older posts in our study had less paint remaining intact as a function of age; therefore, less paint was available to adhere to the tape. Paint adhesion scores were slightly lower for newer posts, again probably because older (N 30-yr) posts in our study had less paint remaining. The results of the paint adhesion tests were not consistent for all three testing heights, possibly as a result of different amounts of sun exposure. Overall, our results provide evidence that T posts exposed to numerous fires and fire types do not suffer negative effects. Our findings are also consistent with the previous investigations into effects of fire on rangeland improvements that revealed no negative impacts to barbed wire (Engle et al., 1998; Engle and Weir, 2000). References ASTM, 2009. ASTM D3359-09. Standard test methods for measuring adhesion by tape test. ASTM International, West Conshohocken, PA, USA, p. 8. ASTM, 2013. ASTM A702-13. Standard specification for steel fence posts, hot wrought. ASTM International, West Conshohocken, PA, USA, p. 3. Bates, D., Maechler, M., Bolker, B., Walker, S., 2013. . [computer program]. lme4: linear mixed-effects models using Eigen and S4. R package version 1.0-5. Bechtel, W., 2018. Oklahoma Wildfires cause $26 million in damage to cattle ranchers. Drovers 7 May. Available at:. https://www.drovers.com/article/oklahoma-wildfirescause-26-million-damages-cattle-ranchers, Accessed date: 10 July 2018. Burnham, K.P., Anderson, D.R., 2003. Model selection and multimodel inference: a practical information-theoretic approach. Springer Science & Business Media, New York, NY, USA, p. 488. Elmore, R.D., Bidwell, T.G., Weir, J.R., 2010. Prescribed fire public perception and education perceptions of Oklahoma residents to prescribed fire. In: Robertson, K.M., Galley, K.E.M., Masters, R.E. (Eds.), Proceedings of the 24th Tall Timbers Fire Ecology Conference: The Future of Prescribed Fire: Public Awareness, Health, and Safety. Tall Timbers Research Station, Tallahassee, FL, USA, pp. 50–61. Engle, D.M., Weir, J.R., 2000. Grassland fire effects on corroded barbed wire. Journal of Range Management 53, 611–613. Engle, D.M., Weir, J.R., Gay, D.L., Dugan, B.P., 1998. Grassland fire effects on barbed wire. Journal of Range Management 51, 621–624. Evans, P.D., Beutel, P., Cunningham, R.B., Donnelly, C.F., 1994. Fire resistance of preservative-treated slash pine fence posts. Forest Products Journal 44, 37–39. McCarthy, D.F., Bezemer, L.D., Seaman, W.G., Dacosta, E.W.B., 1972. Development and evaluation of a leach resistant fire retardant preservative for pine fence posts. Institute of Wood Science Journal 6, 24–31. Morton, L.W., Regen, E., Engle, D.M., Miller, J.R., Harr, R.N., 2010. Perceptions of landowners concerning conservation, grazing, fire and eastern redcedar management in tallgrass prairie. Rangeland Ecology & Management 63, 645–654. R Core Team, 2016. . [computer program]. R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. Vallentine, J.F., 1989. Range development and improvements. Academic Press, Inc., San Diego, CA, USA, p. 524.