Current Graduate Students
Cassey Edwards, Ph.D. Student
January 2019 - ongoing
B.S. - 2015 - Forestry - Stephen F. Austin State University
M.S. - 2018 - Biology - Stephen F. Austin State University
Committee Members
- Dr. Jeremy Stovall
- Dr. Rebecca Kidd
- Dr. Brian Oswald
- Dr. Dan Unger
Project Abstract
The purpose of this study is to determine vegetative characteristics of the bryophyte community (composition, richness, importance) in an established forest over a series of time on reclaimed lignite coal surface mine land in East Texas. The chronosequence approach of measurement is useful as it replaces time for locations where results should indicate the presence or lack of a linear trajectory of increasing bryophyte establishment and abundance throughout time. This study may provide a baseline of ecological information about the non-vascular plant communities that may assist land managers and researchers in the evaluation of vegetative restoration techniques.
Adam Webb, M.S. Student
June 2020 - ongoing
B.S. - 2020 - Forestry - Texas A&M University
Committee Members
- Dr. Jeremy Stovall (co-advisor)
- Dr. Rebecca Kidd (co-advisor)
- Dr. Brian Oswald
Project Abstract
The goal of this research is to identify how combinations of varying light and hydrology-related factors affect the abundance and diversity of natural regeneration in a BLHF. Identifying areas in these ecosystems that are more favorable to Chinese tallow will allow land managers to recognize areas more susceptible to invasion and assist in current and long-term management practices that are focused around controlling Chinese tallow.
The goal of my second study is to identify how biomass partitioning varies among and between regenerating woody species based on their specific topographic position classification within a BLHF. Identifying how partitioning varies for species based on topographic position can aid in managing such ecosystems with similar species and help determine their response in similar environments.
Austin Morrison, M.F. Student
May 2021 - ongoing
B.S. - 2015 - Forestry - Stephen F. Austin State University
Committee Members
- Dr. Jeremy Stovall (advisor)
- TBD
- TBD
Project Abstract
TBD
Nick Langlois, M.S. Student
August 2021 - ongoing
B.S. - 2021 - Environmental Science - Stephen F. Austin State University
Committee Members
- Dr. Jeremy Stovall (advisor)
- Dr. Rebecca Kidd
- TBD
Project Abstract
Nick is remeasuring the paired plots on the Pineywoods Mitigation Bank examining the impact of herbicides and the 2021 February winter storm on Chinese tallow abundance and density. This is a 10-year re-measurement of the plots first examined by Sam Camarillo in his MS thesis work (scroll down for more on Sam's results).
Jason Lanza, M.S. Student
January 2023 - ongoing
B.S. - 2018 - Biology - Sam Houston State University
Committee Members
- Dr. Jeremy Stovall (co-advisor)
- Dr. Matthew McBroom (co-advisor)
- Dr. Yanli Zhang
Project Abstract
Jason's project will examine the impact of tree planting on infiltration rates in detention basins in Harris County, Texas.
Former Graduate Students
Niyi Ajala, Ph.D. in Forestry
January 2017 - May 2022
Niyi graduated in May 2022, and began a post-doc at Michigan State University.
B.S. - 2011 - Conservation Science - University of Lagos
M.S. - 2016 - Biology - Central Michigan University
Committee Members
- Dr. Jeremy Stovall
- Dr. Brian Oswald
- Dr. Rebecca Kidd
- Dr. Yuhui Weng
- Dr. James Van Kley
Project Abstract
Non-native, invasive species disrupt ecological processes and functions, posing a serious threat to natural ecosystems. By examining the growth metrics of the non-native, invasive tree, Chinese tallow (Triadica sebifera [L.] Roxb.), hereafter tallow, across different flooding and light regimes, I investigated how restructuring native communities with valuable native species will prevent the reestablishment of tallow. I studied the changes in morphological and physiological traits of tallow when growing with water tupelo (Nyssa aquatica L.), sugarberry (Celtis occidentalis L.), and green ash (Fraxinus pennsylvanica Marshall). I found that in the non-flooded and high irradiance treatments, tallow's growth metrics were highest when growing with sugarberry and water tupelo, but decreased when competing with green ash. I concluded that tallow may be less competitive with certain native species and underplanting may be a possible opportunity for improving the success rates of native trees species establishment in areas prone to tallow invasion.
I also investigated the interactive effect of light, flooding, and community types on the growth, dominance, and competitive ability of tallow and water tupelo, sugarberry, green ash, and baldcypress (Taxodium distichum [L.] Rich). I found that mixed community depressed the dominance of tallow in the flooded and low irradiance treatment, however, leaf area and leaf biomass of tallow increased in the mixed community in the non-flooded and high irradiance treatment. I concluded that establishing an appropriate native community in flooded and low irradiance environments may reduce future dominance of tallow.
I additionally tested the competitive ability of tallow, water tupelo, sugarberry, green ash, and baldcypress using the relative interaction index, taking into account the competition of native taxa growing with tallow (effect of natives as competitors) and competition of tallow growing with native taxa (effect of competition on natives). I concluded that with the exception of water tupelo, tallow had no significant impact on the biomass of the native species studied.
Finally, I investigated the growth and survival of water tupelo, baldcypress, water oak (Quercus nigra L.), and loblolly pine (Pinus taeda L.) across the Green Bayou Wetland Mitigation Bank (GBWMB) in Harris County, TX. I found that baldcypress had the highest survival rates that baldcypress and water tupelo had greater tree heights than loblolly pine, and that only loblolly pine and water tupelo had significant increases in tree heights between establishment and final measurements. I concluded that baldcypress is better adapted to the microenvironmental conditions across GBWMB. Overall, the results show that restructuring a native community by planting valuable native hardwood species can be a potential means of reducing future dominance of tallow.
Click for a link to Niyi's 2022 Forest Science Article
Click for a PDF of Niyi's 2022 Forest Science Article
Efosa Egharevba, M.S. in Environmental Science
January 2017 - April 2020
Efosa graduated in May 2020, and began pursuing an MBA from SFA.
B.S. - 2013 - Chemistry - Obafemi Awolowo University
Committee Members
- Dr. Jeremy Stovall
- Dr. Rebecca Kidd
- Dr. Ken Farrish
Project Abstract
Forest productivity on reclaimed mineland is hindered by soil compaction. Different techniques have been used to alleviate the effect of compaction to various degrees of success. The Forestry Reclamation Approach (FRA) was developed in the Appalachians and has been used to improve forest productivity on reclaimed mines in this region. The FRA provides a step by step method designed to reduce compaction, control erosion, provide land stabilization and accelerate forest succession. This method had not been evaluated in the Gulf Coastal Plain, where the pan scraper reclamation method is commonly used. However, using pan scrapers increases minesoil compaction which reduces productivity. This study was carried out on an experimental site in Houston County, Texas managed by the Arthur Temple College of Forestry and Agriculture at Stephen F. Austin State University. The experiment was established as a randomized complete block design containing three treatments: pan scraper reclamation method traditionally used in this region, an FRA low compaction treatment, and an undisturbed control. Loblolly pine (Pinus taeda L.) seedlings of Texas provenance were hand-planted on each treatment.
Loblolly pine (Pinus taeda L.) seedlings were measured, harvested and analyzed to determine dry biomass and nutrient (N, P, K, Ca, Mg) contents for the three treatments. Allometric equations relating dry weights of foliage, stem, branches and roots to diameter at groundline and height were developed to estimate tree biomass. Estimated biomass accumulation improved with FRA treatment which produced a mean of 759 g foliage, 344 g branch, 440 g stem, 273 g root, 1579 g aboveground, and 1865 g total tree mass. On the pan scraper treatment, estimated biomass was: 159 g foliage, 67 g branch, 90 g stem, 77 g root, 334 g aboveground, 420 g total tree mass. On the control treatment, estimated mean biomass was: 244 g foliage, 111 g branch, 154 g stem, 102 g root, 537 g aboveground, 648 g total tree mass. All treatments allocated more biomass to foliage, however, biomass allocation to roots was relatively higher in the pan scraper treatment than FRA treatment.
Nutrient accumulation in tree biomass was highest in FRA treatment and it followed the pattern of biomass accumulation. The nutrient concentrations in different tree tissues decreased in the order foliage > stem > root, except for N and Mg in the pan scraper treatment. Foliage concentrations for all treatments were either at or exceeded the adapted critical concentrations except for N which was slightly lower. However, N was generally the most abundant nutrient in all treatments and was highest in foliage biomass.
Cassie Phillips, M.S. in Environmental Science
January 2017 - May 2019
Cassie graduated in August 2019, and began working at New Tech Global Environmental.
B.S. - 2016 - Biological Science - Arkansas State University
Committee Members
- Dr. Jeremy Stovall
- Dr. Hans Williams
- Dr. Ken Farrish
Project Abstract
While land reclamation efforts of surface mines have considerably increased soil stability since the implementation of SMCRA (Surface Mining Control and Reclamation Act), research suggests that resulting soil compaction hinders the productivity of forests post-mining. The Forestry Reclamation Approach (FRA) was developed to improve forest health in the Appalachian region through a five-step process that minimizes soil compaction and establishes a productive forest. The FRA has not yet been tested in the western Gulf Coastal Plain (GCP). The higher clay content of some GCP soils and the dearth of coarse fragments (e.g. cobbles, stones and boulders) may affect reclamation practices and the ability of these methods to create productive forests. Compaction caused by conventional reclamation methods in the GCP has not been studied in great detail. Thus, this study attempts to provide a comparison of two reclamation methods, the FRA low-compaction method used in the Appalachian region with that of conventional scraper-pan (scraper) methods in the GCP.
This study used the FRA with common silvicultural practices of the western Gulf. The two hectare study site was installed with a randomized complete block design with three replicates comparing conventional scraper reclamation used in the region with that of an unmined control and the FRA-style low compaction treatment. Following soil reclamation, containerized loblolly pine (Pinus taeda L.) seedlings of a western Gulf provenance were hand-planted. Soil chemical and physical parameters were assessed on each treatment to determine the effect the FRA and scraper method had on resulting tree seedling growth and survival.
After three growing seasons, seedlings in the FRA plots had significantly higher tree volumes than both the scraper (p=0.0139) and the control (p=0.0247) treatments. The FRA plots also had a 97% survival rate, while scraper plots had a survival of 86%. The FRA plots had significantly lower soil bulk densities than the scraper (p=0.0353) and the control (p<0.0001) which likely influenced growth and survival trends. Soil nutrients were increasingly available on the FRA and scraper plots, likely due to the mixing of the soil profile when compared to the unmined control. Leaf-level water potential and gas exchange were not correlated to growth and survival and did not differ among treatments. These results suggest reclamation practices modeled after FRA methods may benefit tree growth and survival in the Western Gulf.
Click for a link to Cassie's 2021 Forests Article
Click for a PDF of Cassie's 2021 Forests Article
Hannah Angel, M.S. in Forestry
August 2014 - June 2017
Hannah graduated in August 2017, and then pursued her Ph.D. at Virginia Tech.
B.S. - 2014 - Forestry - University of Kentucky
Committee Members
- Dr. Jeremy Stovall (co-adviser)
- Dr. Hans Williams (co-adviser)
- Dr. Ken Farrish
- Dr. Leon Young
- Dr. Brian Oswald
Project Abstract
Since 1974, Luminant Mining Company, LLC (Luminant) has planted over 38.7 million trees on its reclaimed lignite surface mine operations in Texas. For decades, the use of improved reclamation techniques on Luminant’s mined lands have resulted in over 31,160 hectares reclaimed to forests, wildlife habitat, and pastures with productivity levels similar to that found on undisturbed lands. Development of new reclamation methodologies offers opportunities to further improve productivity of planted trees at Luminant’s Martin Lake Oak Hill Mine in east Texas. The conventional haulback or ‘truck-shovel’ reclamation method uses haul trucks for the selective transport and placement of oxidized overburden to serve as the reforestation growth medium. Overburden transport and placement can also be accomplished using tractor pulled scraper pans. Since operating scraper pans are more cost effective than the truck-shovel method, there is considerable interest in reinstituting it as the primary method of reclamation. However, given a lack of information, there are concerns of the effects of scraper pans on mine soil compaction and tree growth.
To address the potential compacting effects of scraper pans, four soil tillage treatments replicated five times were implemented at the Oak Hill Mine in August 2015 using a randomized complete block design: 1) No Tillage (control); 2) Disking (30-35 cm depth); 3) Single-Ripping (90 cm depth)/Disking (30-35 cm depth); and, 4) Cross-Ripping (90 cm depth)/Disking (30-35 cm depth). Soil physical and chemical properties were investigated at 0-30, 30-60, and 60-90 cm depth intervals. Vegetative response was measured for the winter cover crop in May 2015 and for loblolly pine (Pinus taeda L.) tree seedlings in October 2016 after one growing season.
Aboveground biomass production of the winter cover crop was higher on the ripped treatments. Tree seedling survival was particularly high across treatments for 2016 due to ample rainfall with greatest survivability on the tilled plots (> 90%) compared to the control (85%). Cross ripping was superior in terms of lowering bulk density (1.36 Mg m-3) and soil strength (2,220 kPa), and increasing tree seedling volume index (32 cm3) after one growing season (p < 0.10). Above and belowground biomass of loblolly pine seedlings showed significant treatment effects (p < 0.10), and followed similar trends to seedling volume growth. While disking had a favorable response on wheat and loblolly pine survival, deep dozer ripping, particularly cross-ripping, provided more favorable responses in mine soil physical properties and vegetative growth. These data suggest increased potential for long-term site and tree productivity with subsurface soil tillage.
Click for a link to Hannah's 2019 New Forests Article
Click for a PDF of Hannah's 2019 New Forests Article
Click for a link to Hannah's 2018 Soil Science Society of America Article
Click for a PDF of Hannah's 2018 SSSAJ Article
Click to see Hannah's 2017 BSSRC poster
Hannah won Outstanding Graduate Student Poster at the 19th Biennial Southern Silvicultural Research Conference for her work.
Click to see Hannah's 2017 ASMR poster
Click to see Hannah's 2016 ARRI presentation slides
Click to see Hannah's 2015 SAF poster
Ryan Jacques, M.S. in Forestry
January 2015 - May 2017
Ryan graduated in May 2017, and is now a wildlife biologist for Wisconsin Department of Natural Resources in Rhinelander, WI.
B.S. - 2014 - Biology - University of Wisconsin Whitewater
Committee Members
- Dr. Jeremy Stovall (co-adviser)
- Dr. Chris Comer (co-adviser)
- Dr. Hans Williams
- Dr. Rebbeca Kidd
Project Abstract
Interest in bottomland hardwood forests (BLHW) ecology and restoration has increased over the past 40 years. These communities aid in water quality improvement, streambank stabilization, and urban expansion mitigation. They also provide important habitat for many species of wildlife. Since the majority of remaining BLHW are degraded due to land fragmentation, restoration attempts are becoming commonplace within the Western Gulf Coastal Plain. However, restoration success has been mixed, with managers observing survival rates of <15% for desirable species due to various factors. Over two growing seasons, I investigated multiple factors that have potential to limit BLHW restoration success in East Texas. Specifically, I tested the impacts of herbivory by white-tailed deer (Odocoileus virginianus) and feral swine (Sus scrofa) on Nuttall oak (Quercus texana Buckley), Shumard oak (Q. shumardii Buckley), bur oak (Q. macrocarpa Michx.), and pecan (Carya illinoinensis K. Koch) at BLHW restoration sites at four study areas in east Texas. I also tested the effectiveness of portable electric fences and individual tree shelters in protecting seedlings from herbivory. Herbivory was not the major contributor to seedling mortality, but where it occurred, all protected areas demonstrated higher survival (x̅ = 17%) than non-fenced areas (x̅ = 9%). Feral swine were the major contributors to herbivory, while white-tailed deer did not cause notable amounts of seedling mortality. In areas of high white-tailed deer density, prominent browsing was evident, resulting less growth after two years in non-fenced (x̅ = 2.3 cm) and electric fenced (x̅ = 4.3 cm) plots compared to high fence (x̅ = 13.0 cm) and individual tree shelters (x̅ = 24.2 cm). In addition to seedling survival and growth, we observed reduced survival rates (<10%) on sites that were inundated more than 40 days during the growing season. Matching species of interest to the site conditions, specifically local hydrologic regimes, should carry a higher priority in planning a restoration project within BLHW in the Western Gulf Coastal Plain.
Click for a link to Ryan's 2021 Forestry Article
Click for a PDF of Ryan's 2021 Forestry Article
Click to see Ryan's 2017 BSSRC poster
Click to see Ryan's 2016 TWS poster
Click to see Ryan's 2015 SAF poster
Luke Oliver, M.S. in Forestry
August 2013 - May 2017
Luke graduated in May 2017, and began working at New Tech Global Environmental.
B.S.F. - 2013 - Timber Management - SFASU
Committee Members
- Dr. Jeremy Stovall
- Dr. Hans Williams
- Dr. Chris Comer
Project Abstract
Removal and degradation of bottomland hardwood forests (BLHW) in the southern United States has been extensive for the past 200 years. BLHW provide valuable ecological functions, including habitat unique to a number of birds, reptiles, small, and large mammals. Large mast-production is crucial to the survival of many of these animals and is also valued by landowners interested in improving habitat for game species. The alteration of the natural flooding regime has shifted species composition of some of these BLHW. It is impractical to consider restoration of the natural flooding regime for most of these BLHW, and so, the question becomes: Which heavy-seeded species are suited to the new flooding regime of these sites?
A two-year study monitored survival and growth of planted seedlings receiving different levels of canopy reduction, competition control, and species at different positions on the Trinity River floodplain. Uprooting by feral hogs, and extended flooding during the second growing season resulted in mortality of >99% of seedlings planted on the two sites in the first bottom. On the site in the transition zone between the first bottom and Terrace I, canopy reduction improved survival of seven of the nine species/competition control method combinations. No benefits of competition control on survival or height growth were realized by the oak species. Pecan seedlings receiving the weed barrier mat treatment (in the mulched and the un-mulched treatments) had greater survival than pecan seedlings receiving the herbicide treatment, or those receiving no competition control.
A greenhouse experiment examined oak and pecan seedlings subjected to two-phase flooding/drought treatments to measure the effects of flooding and drought stress, and changes in stressors over time on gas-exchange, growth, and survival of planted seedlings. The soil had a pH value of 7.7 that may have resulted in an iron deficiency for all planted seedlings. Flooding reduced light-saturated photosynthetic rate (Asat) on most of the measurement dates. Stomatal conductance (gs) and transpiration (E) were higher for pecan than bur oak on most of the measurement dates. Survival was higher for the unflooded seedlings, but most of the unflooded seedlings dropped their leaves which greatly reduced the sample size for gas-exchange measurements, and may have had adverse effects on growth.
Click for a link to Luke's 2018 Restoration Ecology Article
Click to see Luke's 2015 SAF poster
Jeremy Priest, M.S. in Forestry
August 2012 - August 2015
Jeremy graduated in August 2015, and is now working as an asset analysty for the city of Tyler, Texas.
B.S.F. - 2012 - Forest Range Management - SFASU
Committee Members
- Dr. Jeremy Stovall
- Dr. Hans Williams
- Dr. Brian Oswald
- Dr. Dean Coble
Project Abstract
Strip-mining is a common practice in the Gulf Coastal Plain, with some individual mines spanning over 5,000 hectares. Federal surface mining regulations require land be restored to a productive state capable of supporting pre-existing land-uses. Loblolly pine (Pinus taeda L.) plantations are a widespread reclamation land-use in east Texas; however, the productivity of these plantations compared to those on unmined lands is not well-documented. The first objective of our study was to quantify current site quality of loblolly pine plantations on two mines as compared to stands on unmined soils. The two mines differ in the method of overburden replacement. Substituting mixed overburden for topsoil generally results in no distinction of original soil layers following reclamation (Beckville Mine), while removing and mixing the pre-mining upper, oxidized soil layers for topsoil in the post-mining reclamation areas creates some stratification (Oak Hill Mine). Non-linear modeling of stem analysis data indicated the current site indices are 18.6 and 18.9 m at 25 years for Beckville Mine (mixed overburden) and Oak Hill Mine (mixed oxidized material), respectively. Pre-mining site indices were approximated from soil surveys at 21.3 (Beckville Mine) and 20.1 (Oak Hill Mine) m. The current site indices (post-mining) for each mine did not differ statistically from pre-mining site indices, nor was height statistically different between pre-mining and post-mining at any age. The two mine sites did not statistically differ by height at any age, nor were site index model parameters statistically different. Site index calculated from both mines’ data was found to be significantly lower (p < 0.05) than east Texas’ average site index of 21.6 m at 25 years.
The second objective was to evaluate biomass partitioning and C sequestration in loblolly pine grown on reclaimed mineland at Beckville Mine. Through strip-mining and subsequent reclamation practices, soil processes are disrupted and many physical and biological changes occur. These impacts create site conditions which are not typically experienced by loblolly pine grown throughout the Southeast and therefore have the potential to alter biomass partitioning between above- and belowground biomass (i.e. root:shoot ratio). Allometric analyses have determined Biomass partitioning patterns in loblolly pine are related to development, not site conditions (Coyle et al. 2008). Stand level biomass estimates for forty-eight stands at Beckville Mine were determined using individual tree prediction equations developed by destructive sampling of above- and belowground components. Log-linear allometric analysis determined young trees on reclaimed mineland partitioned greater biomass to belowground components than trees on unmined sites (p < 0.05), indicating optimal partitioning. Further analysis indicated that only young trees experience optimal partitioning and larger trees on reclaimed mineland return to an allometric partitioning pattern found on unmined sites. The results are indicative of optimal partitioning theory for young loblolly pine on reclaimed mineland, although older trees appear to partition biomass according to allometric partitioning theory. The stand level estimates of total aboveground biomass and stem volume were comparable to unmined datasets from the literature (Coble and Pendergast 2014; Gonzalez-Benecke et al. 2014). Site quality and productivity of loblolly pine plantations grown on reclaimed mineland in east Texas do not appear to be significantly impacted by strip-mining under current reclamation techniques.
Click to see Jeremy's 2019 New Forests Article
Click to see a PDF of Jeremy's 2019 New Forests Article
Click to see Jeremy's 2016 Forest Science Article
Click to see a PDF of Jeremy's 2015 Forests Article
Click to see the Forests Article on MDPI
Click to see Jeremy's 2013 SAF poster
Click to see Jeremy's 2014 SRM poster
Click to see an interactive google map Jeremy created for silvopasture markets in east Texas
Click to see slides of Jeremy's 2014 ASMR presentation
Samuel Camarillo, M.S. in Forestry
June 2012 - December 2014
Sam graduated in December 2014, and is now Assistant Principal of Culture at Austin Achieve Public Schools in Texas.
Committee Members
- Dr. Jeremy Stovall
- Dr. Hans Williams
- Dr. Dean Coble
- Dr. Warren Conway
Project Abstract
Chinese tallow (Triadica sebifera (L.) Small) is an invasive tree species that competes with native species in bottomland hardwood forests in the western Gulf Coastal Plain of the southern United States. While much research has been done on Chinese tallow in coastal prairie ecosystems focusing on its establishment ecology, there is little known about its impacts on stand dynamics in forested ecosystems, where it is a growing problem. A paired-plot design was employed in 23 different stands along the Neches River, near Diboll, Texas, to compare sites with contrasting abundance in Chinese tallow. The objectives were to 1) determine the impacts of Chinese tallow on stand dynamics, 2) examine its impact on the light environment, and 3) determine if edaphic factors were correlated with stand structure on sites with varying stocking of Chinese tallow. Stand structural metrics were measured in 2012 and 2013, and the below-canopy light environment was estimated using hemispherical canopy analysis. Soil samples were collected for analysis in 2013. For all species, stand density was greater in plots with abundant Chinese tallow, while basal area, quadratic mean diameter, and relative density were lower (p < 0.10). Chinese tallow presence was negatively correlated with overstory diversity, density of native species, oak density. We observed a greater maximum stand density index for bottomland hardwoods than has previously been reported (1200 trees ha-1 at 25 cm QMD). Stand structure was most correlated to soil metal availability, yet relationships were weak (R2 < 0.30), potentially indicating minimal differences in edaphic conditions across our stands. Management to prevent Chinese tallow from replacing native species in bottomland hardwood forests includes proper density management of stands in areas where Chinese tallow is likely to grow and early detection of gap formation to allow treatment of establishing Chinese tallow before it outcompetes regenerating native species.
Click to see an author's version of Sam's 2015 Forest Ecology & Management Article
Click to see the Forest Ecology and Management Article on Elsevier
Click to see Sam's 2014 BCUENR poster
Click to see Sam's 2013 BSSRC poster
Research Associates
Undergraduate Research Assistants
Stefni Deaton
Summer 2012 - Spring 2013
B.S.F. - 2013 - Forestry - SFASU
Project Abstract
Chinese tallow tree is an invasive non-native species that grows and reproduces quickly by way of a large number of seedlings or by root and stump sprouting. It is well-adapted to varying nutrient and water availabilities along a wide gradient typical to forested bottomland ecosystems. It can also withstand animal predation effectively. The ability to sprout limits the efficacy of control via mechanical means or fire, leaving herbicide treatment as the preferred option from both ecological and economical viewpoints. Operational treatments of Garlon® (Triclopyr) and Arsenal® (Imazapyr) have been imposed to control tallow on several newly established patch clearcuts in bottomland hardwood covertypes on Pineywoods Mitigation Bank in East Texas south of Diboll. Treatment efficacy was assessed pre- and post-application based on percent tallow treated and percent mortality in small plots with a range of tallow densities that were further stratified by grass competition (heavy grass and light grass). The recruitment of new tallow in these plots was then subsequently quantified following treatment. The hypothesis being tested is that areas of low grass competition and dense tallow are not effectively treated, while areas of low tallow density with heavy grass competition are more effectively controlled. Results will guide recommendations on areas that may require more effort to effectively control tallow invasions.
Stefni won Outstanding Graduate Student Poster at the 17th Biennial Southern Silvicultural Research Conference for her work, despite the fact that she was an undergraduate at the time.
Click to see Stefni's 2013 BSSRC poster
Tamara Bennett & Hollis Gregory
Fall 2012 - Spring 2013
Honors Project Abstract
Bark texture has been proposed as a method of differentiating between high and low vigor trees in bottomland oak species. Generally it is reported that faster growing, more vigorous trees should have smoother bark than slower growing, less vigorous trees. Texture also differs between red and white oaks. Bark traits can be rapidly visually assessed while cruising and marking timber, while growth rates require more labor-intensive, invasive measurements like increment boring that degrade timber quality and increase costs. The objective of this project was to test whether observed patterns in bark roughness were correlated to growth rates in cherrybark (Quercus pagoda), willow (Q. phellos), and overcup (Q. lyrata) oaks.
On November 10, 2012, the 860 acre Naconiche Mitigation Area (NMA) in Angelina County, Texas was sampled. The NMA, located on the floodplain of the Angelina River, is dominated by 55-year-old bottomland oaks mixed with other hardwoods. A total of 39 trees from the NMA, 13 of each species, were selected. Trees were chosen based on subjective criteria including a high quality butt log with minimal apparent defects that could then or would in the future be capable of producing sawtimber. Measurements in the field included total height, diameter at breast height (dbh), bark thickness, and crown class. To assess bark roughness a 17 gauge wire was wrapped around each tree at dbh. Wires were pressed into each fissure in the bark, clipped to length, and stored. A regression between wire weight and length (R2 > 0.99, p < 0.05) was used to convert wire weights to straightened lengths. These lengths were used with tree circumference calculated from dbh to create a bark roughness index (BRI). An increment core (bark to pith) was obtained by boring each tree. Cores were sanded and analyzed with winDENDRO to determine age at dbh height, average radial growth per year, and radial growth for the past 5 and 10 year periods.
Linear regression showed that the BRI was not significantly (p > 0.05) influenced for any of the three species by tree age, height, dbh, crown class, bark thickness, or radial growth (average annual and 5 or 10 year periods). This may have been due to difficulty in accurately assessing the BRI. Despite careful measurements made in the field, the wire length was slightly less than the diameter tape length for 17 of the 39 sampled trees by a mean of 4.7% ± 1.7 (standard error) . Examination of photos taken of each tree revealed that these were generally trees with the smoothest bark and the least obvious ridges or fissures. Despite problems with BRI, bark thickness was also unrelated to growth variables (R2 < 0.03, p > 0.05). Bark roughness and thickness are not useful indicators of tree vigor based on the population sampled in this study. Further work developing a better BRI and evaluating greater sample sizes across a broader range of stand ages, site qualities, and oak species is required before broadly inferring bark roughness or thickness are not predictive of vigor.
Tamara presented their work at the Undergraduate Research Conference in April 2013.
Click to see Tamara and Hollis' 2013 URC poster
Other Undergraduate Student Researchers
