• A truck-mounted mobile screen for photodigital estimation of whole plant leaf area

      Ansley, R. J.; Price, D. L.; Lawrence, B. K.; Jacoby, P. W. (Society for Range Management, 1988-07-01)
      A large, truck-mounted screen was constructed to aid in measurement of total leaf area of individual honey mesquite (Prosopis glandulosa Torr.) trees. The screen, which measured 4.6 m × 6.2 m, was constructed with a white tarp supported by a PVC and steel frame, and mounted via steel brackets to one side of a crew-cab truck. To alleviate problems with wind and to facilitate transport, the tarp was attached only at the top of the frame and could be raised and lowered as required. The screen could be transported in the unassembled condition using a standard truck transport frame. The assembled screen was used in a natural rangeland setting to provide a consistent background for photography of individual trees. A 35-mm camera and a portable VCR recorder were used to obtain 2 dimensional images of the tree canopy, which were then digitized. These values were related to whole plant leaf area by harvesting entire trees. A crew of 4 was required to assemble the screen and photograph about 35 trees within 4 hours.
    • An improved method for measuring temperatures during range fires

      Jacoby, P. W.; Ansley, R. J.; Trevino, B. A. (Society for Range Management, 1992-03-01)
      A technique for recording time-temperature curves within field-scale range fires was accomplished using a commercially available data logger capable of rapidly reading large numbers of thermocouples. A specially designed fireproof box was utilized to house and protect the data logger within the center of the burned area. Programming features allowed temperatures to be measured and recorded rapidly (each second) during the passage of the fire front and recorded as 1-minute means before and after the combustion interval. Strategic placement of thermocouples provided time-temperature profiles for various heights above ground, rate of spread, and duration of heat above specific temperatures. Additionally, measurement of preheating prior to the actual flame passage was obtained by placement of the recorder and thermocouples well within the burned area. This technique may provide better quantification of fire effects on vegetation, especially woody weeds targeted for control with fire, by documenting temperature extremes and their duration at critical growing points on plants.
    • Control of honey mesquite with herbicides: influence of plant height

      Jacoby, P. W.; Meadors, C. H.; Ansley, R. J. (Society for Range Management, 1990-01-01)
      Stands of honey mesquite (Prosopis glandulosa var. glandulosa) were treated with aerially applied herbicides at 16 locations in western and northwestern Texas over an 8-year period to determine influence of plant height on herbicide efficacy. Plant height was not found to significantly (P<0.05) influence effectiveness of a particular herbicide, but taller plants were found consistently to be more resistant. No basis was found for delaying control of honey mesquite with herbicides until plants reach a particular height.
    • Control of honey mesquite with herbicides: influence of stem number

      Jacoby, P. W.; Ansley, R. J.; Meadors, C. H.; Cuomo, C. J. (Society for Range Management, 1990-01-01)
      Following aerial application of herbicides, stands of honey mesquite (Prosopis glandulosa var. glandulosa) were evaluated to determine the influence of individual plant stem number on herbicide efficacy. A highly significant (P<0.01) relationship was found between stem number and plant mortality, with herbicide resistance increasing sharply in plants with greatest numbers of stems. This relationship was consistent among all herbicides and plant heights, which suggests that stem number may be useful in selecting the type of control method employed on specific sites.
    • Design of rain shelters for studying water relations of rangeland shrubs

      Jacoby, P. W.; Ansley, R. J.; Lawrence, B. K. (Society for Range Management, 1988-01-01)
      A low-cost, fixed-place, subcanopy rain shelter was constructed to facilitate studying water relations of honey mesquite (Prosopis glandulosa) growing in north Texas rangeland. This shelter, combined with a supplemental irrigation system and a barrier to contain lateral roots, permitted the study of moisture influences on transpiration, xylem pressure potential, and leaf temperature on large woody plants in the field.
    • Effects of Herbicides on Germination and Seedling Development of Three Native Grasses

      Huffman, A. H.; Jacoby, P. W. (Society for Range Management, 1984-01-01)
      Two experiments conducted in growth chambers examined influences of 2,4,5-T [(2,4,5-trichlorophenoxy) acetic acid], chlopyralid (3,6-dichloropicolinic acid), picloram (4-amino-3,5,6-trichloropicolinic acid), and triclopyr {[3,5,6-trichloro-2-pyridinyl)-oxy]acetic acid} on germination and early seedling development of buffalograss [Buchloe dactyloides (Nutt.) Engelm.], blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Griffiths], and sideoats grama [Bouteloua curtipendula (Michx.) Torr.]. Germination and plumule growth were largely unaffected chlopyralid but were significantly reduced by 2,4,5-T, picloram, and triclopyr, especially at rates greater than 1.1 kg/ha. Blue grama was less affected by herbicides than either buffalograss or sideoats grama.
    • Epicuticular wax in honey mesquite: seasonal accumulation and intraspecific variation

      Jacoby, P. W.; Ansley, R. J.; Meadors, C. H.; Huffman, A. H. (Society for Range Management, 1990-07-01)
      Epicuticular wax on the leaves of honey mesquite (Prosopis glandulosa) increased rapidly from May to July and stabilized or decreased by late summer. Pattern of accumulation best fit a second order polynomial regression equation using day of year as the independent variable. Considerable variation in wax accumulation was found among individual trees within populations and appeared to be consistent from year to year. Wax generally increased from about 0.35 g m-2 to more than 1.00 g m-2 during the growing season. A difference in maximum wax accumulation was detected between the 2 years of study and was attributed to differing environmental conditions. These findings may partially explain resistance of honey mesquite to folk-applied herbicides.
    • Herbaceous Vegetation-Lotebush (Ziziphus obtusifolia (T. & G.) Gray var. obtusifolia) Interactions in North Texas

      Foster, M. A.; Scifres, C. J.; Jacoby, P. W. (Society for Range Management, 1984-07-01)
      Basal cover and standing crop of herbaceous vegetation were measured during 1979 and 1980 at 0.3-m intervals along transects radiating from individual lotebush canopies in each cardinal direction. Basal covers and standing crops were generally least near the shrubs, regardless of season. However, buffalograss was less abundant in the shrub-free zones than near the lotebush plants. Texas wintergrass basal cover and standing crop were greatest in shrub-free areas except at the north and east driplines, where environmental conditions were apparently ameliorated by the lotebushes. Japanese brome and sand dropseed were most abundant in those zones where buffalograss and Texas wintergrass influences were least. These results indicate that lotebush has a minimal influence on grass cover, and that the major impact is concentrated beneath the shrub canopies.
    • Honey Mesquite Control and Forage Response in Crane County, Texas

      Jacoby, P. W.; Meadors, C. H.; Foster, M. A.; Hartmann, F. S. (Society for Range Management, 1982-07-01)
      Replicated field plots of honey mesquite (Prosopis glandulosa var. glandulosa) were aerially treated with herbicides in 1977 near Crane, Texas. Plots were evaluated for 3 years to determine efficacy of nine herbicide formulations. Of the herbicides studied 3,6-dichloropicolinic acid was the most effective. Sprayed plots produced twice as much forage as unsprayed areas with several species of grass showing significant increases in production. Forb response was not significantly different between treated and untreated plots. Most of the forage response occurred 1 m from the tree base rather than at 3 and 5 m from the tree.
    • Honey mesquite transpiration along a vertical site gradient

      Cuomo, C. J.; Ansley, R. J.; Jacoby, P. W.; Sosebee, R. E. (Society for Range Management, 1992-07-01)
      Honey mesquite (Prosopis glandulosa Torr.) occurs on a variety of sites varying in soil depth and moisture availability. The objective of this study was to compare water use by honey mesquite on upland, lowland, and riparian sites which were assumed to represent increasing levels of available soil moisture within a single watershed. Effects of the upland and lowland sites were evaluated in 1985. The riparian site was evaluated with the other 2 sites in 1986. Soil moisture and average daily transpiration were greater (P < 0.05) on the upland than on the lowland site from mid-May to July in both years, and from mid-August through September 1986. These differences were attributed mainly to soil surface characteristics which created greater infiltration on the upland site. The riparian site was near an ephemeral stream and had a water table as shallow as 1.5 m. Soil water content was much greater for this site compared to the other 2 sites throughout 1986. Mesquite transpiration was greater on the riparian site than on the other sites during July 1986, when seasonal vapor pressure deficit was at maximum. However, transpiration was less on the riparian site than on the upland site during May and June 1986. Soil temperature was significantly lower on the riparian than on the upland site and potentially inhibited transpiration on the riparian site in May and June. The study demonstrated a positive relationship between water availability and transpiration by mesquite but did not support the hypothesis that water availability or transpiration was lowest on upland sites.
    • Intraspecific competition in honey mesquite: Leaf and whole plant responses

      Ansley, R. J.; Trevino, B. A.; Jacoby, P. W. (Society for Range Management, 1998-05-01)
      Leaf and whole plant responses of honey mesquite (Prosopis glandulosa Torr.) to intraspecific competition were compared under low (LD) or high (HD) stand density in a semi-arid region of north Texas. The HD trees occurred within a stand of 300 trees ha-1. The LD trees occurred in areas of the dense stand that were thinned to 80 trees ha-1 with no neighbors within 10 m of study trees. Tree size was similar in each treatment at study initiation. Five years after thinning, tree height, canopy volume, basal stem diameter, leaf area, and leaf area index were significantly greater in LD than HD trees. No differences in leaf predawn water potential, stomatal conductance, and photosynthesis were found between LD and HD trees during growing seasons 4 or 6 years after study initiation. Results indicate resources necessary for growth of individual mesquite plants were limiting under increased stand density and suggest the occurrence of intraspecific competition. Limitations were manifest at the whole plant level via modification of tree size and leaf area per tree, and not through adjustment of leaf physiological processes. The limiting factor appeared to be soil water. Daily water loss tree-1 was 2.5 to 4 times greater in LD than HD trees, and ranged from 119 to 205 kg and 46 to 59 kg in LD and HD trees, respectively. Projected daily water loss by mesquite at the stand level was similar between treatments, however, and ranged from 9,500 to 17,700 kg ha-1.
    • Late season control of honey mesquite with clopyralid

      Jacoby, P. W.; Ansley, R. J.; Meadors, C. H. (Society for Range Management, 1991-01-01)
      Herbicides were applied aerially to honey mesquite (Prosopis glandulosa Torr.) in the Rolling Plains and Edwards Plateau land resource areas of Texas to evaluate efficacy during late season applications. Although other herbicides gave higher levels of above ground mortality, clopyralid caused higher whole plant mortality throughout the growing season than 2,4,5-T + picloram, both of which were ineffective when applied in September. Mixtures of clopyralid + picloram also were less effective when applied during later periods in the growing season, suggestiong picloram added little or even reduced the efficacy of clopyralid for late season control of honey mesquite. Triclopyr alone or in combination with picloram was ineffective in controlling honey mesquite in the fall. Clopyralid in the fall was most effective when applied at rates of 0.56 kg ha-1 or more. Dosage response of honey mesquite in late season applications (late August to October) was practically identical to that found for applications made in June and July, which indicates that clopyralid provides constant levels of mortality throughout the growing season. This research supports the practice of extending the season of applications with clopyralid into the fall. Applications in the fall might allow more rangeland to be treated for honey mesquite reduction and also reduce risks associated with drift damage to crops during their most susceptible periods of growth in early to mid-summer.
    • Leaf and whole plant transpiration in honey mesquite following severing of lateral roots

      Ansley, R. J.; Jacoby, P. W.; Hicks, R. A. (Society for Range Management, 1991-11-01)
      This study examined water loss by fully grown honey mesquite (Prosopis glandulosa var. glandulosa Torr.) trees at 2 levels of resolution, the whole plant (canopy) and the individual leaf. Trees were manipulated by severing lateral roots during winter dormancy. Leaf transpiration and photosynthesis were measured in root-severed and unsevered (control) trees for 2 growing seasons following treatment. An empirical model which integrated leaf transpiration, whole plant leaf area, and influence of shading within the canopy on leaf transpiration was used to calculate daily water loss from individual trees. During the first growing season leaf abscision occurred on root-severed, but not control trees, in early July, resulting in a 50% reduction in whole plant leaf area. Following abscission, transpiration and photosynthesis of remaining leaves on root-severed trees were significantly greater than on control trees from July through September. Because of increased transpiration of remaining leaves on root-severed trees, daily water loss per tree was not significantly different between root-severed and similar-size control trees before or after leaf abscission. No differences in leaf or canopy transpiration were found between root-severed or unsevered honey mesquite during the second growing season. Daily water loss per tree ranged from 30 to 75 liters during the study. These responses illustrate that water loss from mesquite may be regulated by various combinations of stomatal control and adjustment of transpirational surface area.
    • Long-term grass yields following chemical control of honey mesquite

      Ansley, R. J.; Pinchak, W. E.; Teague, W. R.; Kramp, B. A.; Jones, D. L.; Jacoby, P. W. (Society for Range Management, 2004-01-01)
      Long-term herbaceous response data following herbicidal treatment of honey mesquite (Prosopis glandulosa Torr.) are needed to develop more accurate projections regarding economic feasibility of these treatments and to model ecological interactions between woody and herbaceous plants in rangeland systems. Our objective was to measure herbaceous yield and mesquite regrowth 10 or 20 years after mesquite was aerially sprayed with either mesquite top-killing or root-killing herbicides. Treatments evaluated included mesquite top-killing herbicides at 10-12 years (T10) and 19-21 years (T20) post-treatment, mesquite root-killing herbicides at 10-12 years (R10) and 19-21 years (R20) post-treatment, and an untreated control where mesquite were 30 years old (C30). Treatments were applied in the late 1970's or late 1980's. Grass yields, measured annually from 1998 through 2000, were quantified within patches of 3 perennial grass functional groups: cool-season mid-grasses, warm-season mid-grasses, or warm-season short-grasses. Cool-season annual grass yields were also quantified within these perennial grass patches. By 1998, mesquite canopy cover was 55, 47, 36, 24, and 12% in C30, T20, T10, R20, and R10 treatments, respectively. Warm-season mid-grass yields were most sensitive to differences in mesquite cover in all 3 years and declined sharply when mesquite cover exceeded 30%. Cool-season mid-grass yields declined slightly with increasing mesquite cover. Warm-season short-grass and cool-season annual grass yields were not related to mesquite cover, except in 2000 when warm-season short-grass yield beneath mesquite canopies increased with increasing mesquite cover. Results suggest that herbicide treatment life (defined by increased perennial grass yield in response to mesquite treatments) was at least 20 years for the root-killing herbicide, but no longer than 10 years for the top-killing herbicide.
    • Revegetation Treatments for Stand Establishment on Coal Spoil Banks

      Jacoby, P. W. (Society for Range Management, 1969-03-01)
      Coal spoil banks near Kemmerer, Wyoming were subjected to several treatments designed to facilitate revegetation. These included the use of snowfence, jute net, and straw mulch applied to banks of three different ages. Evaluation by seedling density suggested that the older the spoil the more suitable for planting. All treatments produced seedling stands but a combination of jute netting and mulch gave best results.
    • Root biomass and distribution patterns in a semi-arid mesquite savanna: Responses to long-term rainfall manipulation

      Ansley, R. J.; Boutton, T. W.; Jacoby, P. W. (Society for Range Management, 2014-03)
      Expansion of woody plants in North American grasslands and savannas is facilitated in part by root system adaptation to climatic extremes. Climatic extremes are predicted to become more common with global climate change and, as such, may accelerate woody expansion and/or infilling rates. We quantified root biomass and distribution patterns of the invasive woody legume, honey mesquite (Prosopis glandulosa), and associated grasses following a long-term rainfall manipulation experiment in a mixed grass savanna in the southern Great Plains (United States). Root systems of mature trees were containerized with vertical barriers installed to a depth of 270 cm, and soil moisture was manipulated with irrigation (Irrigated) or rainout shelters (Rainout). Other treatments included containerized, precipitation-only (Control) and noncontainerized, precipitation-only (Natural) trees. After 4 yr of treatment, soil cores to 270 cm depth were obtained, and mesquite root length density (RLD) and root mass, and grass root mass were quantified. Mesquite in the Rainout treatment increased coarse-root (->-2 mm diameter) RLD and root mass at soil depths between 90 cm and 270 cm. In contrast, mesquite in the Irrigated treatment increased fine-root (-<-2 mm diameter) RLD and root mass between 30 cm and 270 cm depths, but did not increase total root mass (fine-+-coarse) compared to the Control. Mesquite root-to-shoot mass ratio was 2.8 to 4.6 times greater in Rainout than the other treatments. Leaf water stress was greatest in the Rainout treatment in the first year, but not in subsequent years, possibly the result of increased root growth. Leaf water use efficiency was lowest in the Irrigated treatment. The increase in coarse root growth during extended drought substantially increased mesquite belowground biomass and suggests an important mechanism by which woody plant encroachment into grasslands may alter below ground carbon stocks under climate change scenarios predicted for this region. © 2014 The Society for Range Management.
    • Root containerization for physiological studies of shrubs and trees on rangeland

      Ansley, R. J.; Jacoby, P. W.; Lawrence, B. K. (Society for Range Management, 1988-01-01)
      The use of metal and plastic barriers to contain root systems of woody plants is presented as a method to study water relations and other physiological responses of field-grown shrubs. This method has permitted the study of plant dependence on lateral root systems and provides a convenient method to isolate plant roots in an equal volume of soil for replicated studies of large plants under field conditions.
    • Some observations from the excavation of honey mesquite root systems

      Heitschmidt, R. K.; Ansley, R. J.; Dowhower, S. L.; Jacoby, P. W.; Price, D. L. (Society for Range Management, 1988-05-01)
      A single, mature and 12 smaller honey mesquite (Prosopis glandulosa Torr. var. glandulosa) trees were partially excavated during 1986 to examine root distributional patterns. The mature tree had an extensive lateral root system and a large tap root that subdivided into 3 smaller tap roots at a depth near 1 m. The lateral root system of all trees was concentrated in the upper 0.3 m of the soil profile. Results from the excavations provide evidence in support of honey mesquite's classification as a facultative phreatophyte.
    • Technical Notes: A Tool for Sampling Flat Jointed Opuntia

      Huffman, A. H.; Jacoby, P. W. (Society for Range Management, 1985-01-01)
      A section of automobile exhaust pipe was machined to produce a tool for sampling prickly pear. The tool provides a method to quickly and easily remove a section of the cladophyll. This method produces samples with a uniform surface area.
    • Vegetational Responses Following Control of Sand Shinnery Oak with Tebuthiuron

      Jacoby, P. W.; Slosser, J. E.; Meadors, C. H. (Society for Range Management, 1983-07-01)
      Tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thia-diazol-2-yl]-N,N′-dimethylurea} pellets were applied aerially in April 1979 at rates of 0.5 and 1.0 kg ai./ha to rangelands supporting a uniform stand of sand shinnery oak (Quercus havardii Rydb.) near Andrews, Texas. Tebuthiuron pellets were applied at 1.1 kg ai/ha to a second location near Jayton, Texas, in March 1980. Sand shinnery oak was significantly reduced (P is lesser than or equal to 0.05) in treated plots at both locations. Yields of annual and perennial grasses were significantly greater (P is lesser than or equal to 0.05) and those of forbs significantly less (P is less than or equal to 0.05) on tebuthiuron-treated plots at Andrews. Untreated plots at Andrews had more bare soil than those treated with tebuthiuron after 18 and 30 months. Grass yields at the Jayton site were greater, although no significant (P is less than or equal to 0.05) differences occurred with forb yields.