Redberry Juniper Research Articles

Detection of two intermixed invasive woody species using color infrared aerial imagery and the support vector machine classifier

Both the evergreen redberry juniper (Juniperus pinchotii Sudw.) and deciduous honey mesquite (Prosopis glandulosa Torr.) are destructive and aggressive invaders that affect rangelands and grasslands of the southern Great Plains of the United States. However, their current spatial extent and future expansion trends are unknown. This study was aimed at: (1) exploring the utility of aerial imagery for detecting and mapping intermixed redberry juniper and honey mesquite while both are in full foliage using the support vector machine classifier at two sites in north central Texas and, (2) assessing and comparing the mapping accuracies between sites. Accuracy assessments revealed that the overall accuracies were 90% with the associated kappa coefficient of 0.86% and 89% with the associated kappa coefficient of 0.85 for sites 1 and 2, respectively. Z -statistics (0.102<1.96 ) used to compare the classification results for both sites indicated an insignificant difference between classifications at 95% probability level. In most instances, juniper and mesquite were identified correctly with <7% being mistaken for the other woody species. These results indicated that assessment of the current infestation extent and severity of these two woody species in a spatial context is possible using aerial remote sensing imagery.

Evaluating Biomass of Juniper Trees (Juniperus pinchotii) from Imagery-Derived Canopy Area Using the Support Vector Machine Classifier

Both temporal and spatial magnitude, structure, and distribution of rangeland aboveground biomass (AGB) are important inputs for many necessities, in particular for estimating terrestrial carbon amount, ecosystem productivity, climate change studies, and potential bioenergy uses. Much of the remote sensing research previously completed has focused on determining carbon stocks in forested ecosystems with little attention directed to estimate AGB amount in rangelands. Our objectives were to: 1) identify and delineate individual redberry juniper (Juniperus pinchotii) plants from surrounding live vegetation using the support vector machine method for classifying two-dimensional (2D) geospatial imagery with a 1-m spatial resolution at two sites; and 2) develop regression models relating imagery-derived and fieldmeasured single tree canopy area and diameter for dry AGB estimation. The regression results show that there were very close and significant relationships between field measured juniper plant AGB and canopy area derived from the image classification with r2 > 0.90. These results suggest that spectral reflectance recorded on 2D high resolution imagery is capable to assess and quantify AGB as a quick, repeatable, and unbiased method over large land areas.

Updraft fixed bed gasification of mesquite and juniper wood samples

Biomass gasification is being considered as one of the most promising technologies for converting biomass into gaseous fuel. Here we present results of gasification, using an adiabatic bed gasifier with air as gasification medium, of mesquite (Prosopis glandulosa) and redberry juniper (Juniperus pinchotii), two woody species that dominate uncultivated lands in the Southern Great Plains, U.S.A., that may have potential for bioenergy utilization. The effects of equivalence ratio (ER), particle size, and moisture content on the temperature profile, gas composition (CO, CO2, H2, N2, CH4, and C2H6), and higher heating value (HHV) were investigated. As ER decreased from 4.2 to 2.7, the mole composition of the end product gas for mesquite contained: 13–21% CO, 1.6–3% H2, 1–1.5% CH4, 0.4–0.6% C2H6, 60–64% N2, 11–25% CO2, and 1–2% O2. The mole composition of the end product gas for juniper consisted of 21–25% CO, 2.5–3.5% H2, 1.5–1.8% CH4, 0.3–0.5% C2H6, 58–61% N2, 9–12% CO2, and 1–2% O2. The H2 and CO mole percentages decreased with increasing ER while the CO2 and N2 mole percentage increased. After removing N2, the HHV of the end-product gas for mesquite and juniper reached 26 and 27.5% of natural gas HHV, respectively, when ER ≈ 2.7.

Canopy Area and Aboveground Mass of Individual Redberry Juniper (Juniperus pinchotii) Trees

There is increasing interest in using canopy area to quantify biomass of invasive woody plants on large land areas of rangelands for a variety of reasons. For those woody species that emphasize lateral canopy growth over vertical growth it may be possible to relate canopy area to aboveground mass (AGM). Our objective was to determine the utility of external canopy measurements (area, volume, and height) for predicting AGM and the percentage of AGM that is wood (PW; i.e., stems > 3 cm diameter) in individual redberry juniper ( Juniperus pinchotii Sudw.) plants in west Texas. The canopy area to height relationship was curvilinear and indicated that at heights > 3 m, there was more lateral (canopy area) than vertical canopy growth. We found a strong linear relationship between canopy area and AGM ( r 2 = 0.94; AGM range 9 kg to 688 kg) and it appeared that AGM could be predicted in individual trees from canopy area. Moreover, the canopy area/AGM relationship developed from smaller trees was able to adequately predict AGM of larger trees. Height was a less effective predictor of AGM ( r 2 = 0.66), and incorporation of height with canopy area to determine canopy volume did little to improve accuracy of estimating AGM over canopy area alone. The canopy area/PW relationship was curvilinear (the rate of increase in PW declined in larger trees) and PW reached 60–70% in the largest trees. Aumenta el interés por usar el área del dosel para cuantificar la biomasa de plantas leñosas invasoras en grandes extensiones de pastizales por diversas razones. Para esas especies leñosas que resaltan el crecimiento lateral del dosel lateral sobre el crecimiento vertical puede ser posible relacionar el área de dosel con la biomasa aérea (BA). Nuestro objetivo fue determinar la utilidad de medir el dosel externo (área, volumen y altura) para predecir BA y el porcentaje de BA que es madera (PW, ejemplo tallos > 3 cm de diámetro) en plantas individuales de junípero rojo ( Juniperus pinchotii Sudw.) en el oeste de Texas. El área del dosel con la relación de altura fue curvilínea e indicaba que la altura > 3 m fue más lateral (área del dosel) que el crecimiento vertical del dosel. Encontramos una fuerte relación linear entre el área del dosel y BA ( r 2 = 0.94; BA rango 9 kg a 688 kg) y esto parece que BA puede ser predicha en arboles individuales de área del dosel. Sin embargo, la relación área del dosel/BA desarrollada de arboles pequeños fue posible predecir adecuadamente BA de arboles grandes. Altura del árbol fue un factor de predicción menos efectivo de BA ( r 2 = 0.66), al incorporar altura con área del dosel para determinar el volumen del dosel mejoro muy poco la exactitud la estimación de BA sobre el área del dosel por sí solo. La relación de área del dosel/madera(PW) fue curvilínea (la tasa de incremento de madera(PW) declino en arboles grandes) y la madera (PW) alcanzo 60–70% en arboles grandes.

Is Red-Berry Juniper an Overlooked Fall Allergen in the Southwest?

Is Red-Berry Juniper an Overlooked Fall Allergen in the Southwest?

Redberry juniper as a roughage source in lamb feedlot rations: Wool and carcass characteristics, meat fatty acid profiles, and sensory panel traits

Effects of replacing cottonseed hulls with juniper leaves on end products were investigated in lambs. Lambs were individually fed diets containing cottonseed hulls (CSH), half of the CSH replaced by juniper (CSHJ), or all the CSH replaced by juniper (JUN). Lambs grew the same amount of wool when measured as greasy fleece ( P > 0.19), clean fleece ( P > 0.46), and clean wool production per unit of BW ( P > 0.54). Average fiber diameter quadratically decreased ( P = 0.04) and became more uniform ( P < 0.04) as percentage of juniper increased in the diet. Carcass characteristics were not affected ( P > 0.16) by diet. Myristic, palmitoleic, and arachidic acids, cis-9, trans-11 CLA, and the ∆9 desaturase index linearly increased ( P < 0.09) and stearic acid linearly decreased ( P = 0.05) as percentage of juniper increased in the diet. Off-flavor linearly increased ( P = 0.02) as juniper increased in the diet.

Supplements Containing Escape Protein Improve Redberry Juniper Intake by Goats

Abstract Redberry juniper ( Juniperus pinchotii Sudw.) is a common invasive plant species in west-central Texas. Goats will consume redberry juniper, but intake is limited by monoterpenoids found in the plant. Previous research has shown that goats will increase juniper intake through 1) conditioning and 2) protein supplementation. This study compared intake of juniper when goats received different protein supplements either with or without protein sources that are high in amino acids that escape digestion in the rumen. Recently weaned Boer-cross goats ( n = 47) were randomly placed into five treatments. Treatments 1, 2, 3, and 4 received a protein supplement and juniper for 1 h daily for 14 d, along with a basal diet of alfalfa pellets (2% body weight). Treatment 5 received only a basal diet of alfalfa pellets and juniper. All supplements were formulated to be isonitrogenous (37% crude protein [CP]). Treatment 1 contained cottonseed meal (high CP escape value), treatment 2 contained cottonseed meal and distiller’s dried grain (higher CP escape value), treatment 3 contained soybean meal (low CP escape value), and treatment 4 contained soybean meal and distiller’s dried grain (moderate CP escape value). Refusals of juniper, supplements, and alfalfa were weighed daily to determine intake. Supplementation with 1) cottonseed meal, 2) soybean meal, or 3) soybean meal and distillers dried grain did not influence ( P > 0.05) juniper intake. Conversely, goats supplemented with cottonseed meal and distiller’s dried grain ate more ( P

Feeding Redberry Juniper (Juniperus pinchotii) at Weaning Increases Juniper Consumption by Goats on Pasture

Redberry (Juniperus pinchotii Sudw.) and ashe (Juniperus ashei Buchh.) juniper dominate rangelands throughout central Texas. Our objective was to attempt to improve the efficacy of goats as a biological control mechanism for juniper through behavioral training. Conditioning sheep and goats to increase the palatability of chemically defended plants can be a useful tool in brush control. Previous research illustrated that goats can be conditioned to consume more juniper while in individual pens when foraging choices are limited. To test whether this creates a longer-lasting increase in juniper preference, we determined if goats would continue to consume juniper on pasture for one year after being fed juniper in individual pens for 14 d. Female Boer-cross goats (n = 40) were randomly divided into two treatments: conditioned and naive to juniper. At approximately 12 mo of age, conditioned goats were placed in individual pens and fed redberry juniper 1 h daily for 14 d, while naive goats received only alfalfa pellets to meet maintenance requirements. After the pen-feeding phase of the study, goats were placed in one of four pastures (10 goats · pasture−1) for 12 mo. Two pastures housed conditioned goats, and two pastures housed naive goats at a moderate stocking rate (1 animal unit · yr−1 · 8 ha−1). Bite count surveys were conducted twice per month, while herbaceous standing crop and monoterpene levels were measured once per month. Juniper preference varied monthly; however, conditioned goats consistently ate more (P < 0.05) juniper than naive goats except for April, when the study began, and March, when the study ended. When selection of herbaceous forages decreased, conditioned goats increased selection of juniper, while naive goats increased selection of other palatable shrubs. Seasonal changes of monoterpene levels in juniper had no apparent effect on juniper preference. We contend that feeding juniper at weaning will increase use of the plant in grazing situations. Juniperus pinchotii Sudw y J. ashei Buchh son dominantes en pastizales naturales del centro de Texas. Nuestro objetivo fue intentar mejorar la eficacia del pastoreo de caprinos como mecanismo de control biológico de Juniperus mediante entrenamiento de comportamiento ingestivo. El condicionamiento de ovejas y cabras para que incrementen la palatabilidad de plantas que contienen defensas químicas podría ser una herramienta útil en el control de especies arbustivas. Trabajos de investigación previos demostraron que se puede condicionar un incremento en el consumo de Juniperus en cabras mantenidas en bretes individuales cuando las opciones de forrajeo son limitadas. A fin de determinar si este protocolo crea un incremento duradero en la preferencia de Juniperus, determinamos si las cabras continuarían consumiendo Juniperus en condiciones de pastoreo durante un año luego de haber recibido Juniperus en bretes individuales por 14 días. Hembras cruza Boer (n = 40) se dividieron al azar en 2 tratamientos, uno condicionado y el otro sin experiencia previa. A los 12 meses de edad aproximadamente, las cabras condicionadas fueron ubicadas en bretes individuales y alimentadas J. pinchotii durante una hora diaria por 14 días mientras que las cabras en el tratamiento sin experiencia previa recibieron solamente pellets de alfalfa para suplir sus requerimientos de mantenimiento. Luego de la fase de alimentación a corral las cabras fueron puestas en 1 de 4 potreros (10 cabras · potrero−1) durante 12 meses. Dos potreros fueron pastoreados por cabras condicionadas y dos por cabras sin experiencia previa con una carga animal moderada (1 Unidad Animal Año · 8 ha−1). Se realizaron conteos de bocados bimestrales y monitoreos mensuales de disponibilidad herbácea y niveles de monoterpenos. La preferencia por Juniperus varió mes a mes; sin embargo, las cabras condicionadas consumieron consistentemente más (P < 0.05) Juniperus que las cabras sin experiencia previa excepto durante abril cuando comenzó el estudio y durante marzo cuando el estudio finalizó. En momentos de menor preferencia por forrajes herbáceos, las cabras condicionadas mostraron un incremento en la selección de Juniperus, mientras que las cabras sin experiencia previa incrementaron la selección de otros arbustos palatables. Cambios estacionales en los niveles de monoterpenos aparentemente no tuvieron un efecto sobre la preferencia de Juniperus. Sostenemos que alimentado Juniperus al destete incrementará el uso de esta planta en situaciones de pastoreo.

Redberry juniper as a roughage source in lamb feedlot rations: Performance and serum nonesterified fatty acids, urea nitrogen, and insulin-like growth factor-1 concentrations1

Effects of replacing cottonseed hulls with dry redberry juniper leaves on performance and serum NEFA, urea N, and IGF-1 were investigated in Rambouillet lambs (n = 24, initial BW = 28.6 +/- 4.94 kg). In a study with 2 feeding periods (period 1 = 65% concentrate ration, 28 d; period 2 = 85% concentrate ration, 49 d), lambs were individually fed ad libitum treatment diets containing cottonseed hulls (control; CSH), one-half of the cottonseed hulls replaced by dry juniper leaves (CSHJ), or all the cottonseed hulls replaced by dry juniper leaves (JUN). Lamb BW was similar on d 0 and 14, but increasing juniper in the diet linearly reduced (P = 0.04) BW on d 28. Differences in BW during period 1 are attributed to ADG and average daily DMI linearly decreasing (P < 0.001) with increasing concentrations of juniper, with lambs fed CSH, CSHJ, or JUN diets having ADG of 0.34, 0.30, and 0.14 kg, respectively. Differences in average daily DMI are attributed to secondary compounds in the cottonseed hulls and juniper and nutrient-toxin interactions. Lambs fed CSHJ diets had the greatest (P = 0.04) G:F compared with lambs fed CSH and JUN during period 1. Lambs fed JUN diets tended to have the greatest (P = 0.09) NEFA concentrations during period 1, and increasing juniper in the diet linearly reduced (P = 0.006) serum urea N and IGF-1 on d 14 and 28, respectively. During period 2, intake and growth of lambs fed JUN diet rapidly increased, resulting in all lambs having similar ADG, DMI, G:F, and BW. When period 2 began (d 33), serum NEFA and urea N were similar (P > 0.12) among lambs, but serum IGF-1 tended to be linearly reduced (P = 0.09) by increasing juniper in the diet. At times during period 2, lambs fed CSHJ had the greatest (P < 0.02) serum urea N (d 40 and 82) and IGF-1 (d 54) concentrations. Results were interpreted to indicate that air-dried redberry juniper leaves can replace all of the cottonseed hulls in lamb feedlot rations. Feeding 30% juniper in the diet for a longer period of time during the initial feeding period probably would have further reduced growth performance.

Surface Fuel Sampling Strategies: Linking Fuel Measurements and Fire Effects

Abstract We assessed the effectiveness of different sampling strategies in linking fine fuel load and crown scorch of ashe (Juniperus ashei) and redberry juniper (J. pinchotii) for prescribed fires conducted in wet and dry periods of the growing season on the Edwards Plateau, Texas, USA. Our aim was to determine if spatial and temporal variation in crown scorch was best predicted by estimates of fuel load sampled with spatially explicit, multiscale sampling strategies or with traditional, simple random sampling of fuel load. We found that multiscale sampling of fuel load underneath and adjacent to juniper crowns was more effective than simple random sampling in predicting crown scorch for the 14 fires conducted in the wet period and the five conducted in the dry period. The type of sampling strategy employed was critical in relating fuel load to crown scorch during the wet period. Percent crown volume scorched ranged from 0% to 100% in these conditions. In contrast, the type of sampling strategy was less ...

Age and Body Condition of Goats Influence Consumption of Juniper and Monoterpene-Treated Feed

Abstract Redberry juniper (Juniperus pinchotii Sudworth) is an invasive, evergreen tree that is rapidly expanding throughout western and central Texas. Goats will consume some juniper on rangelands; however, intake is limited. The objective of our research was to determine how the age and body condition of goats influence their consumption of juniper and an artificial feed containing 4 monoterpenes. Two separate experiments were conducted. Experiment 1 examined the intake of redberry juniper foliage and used 39 goats either young (2 yr) or mature (> 6 yr). One-half of each age group was fed appropriate basal rations to reach either a high (HBC) or low body condition (LBC). Goats in LBC ate more (P < 0.01, 8.6 g · kg−1 body weight [BW] ± 0.7 SE) juniper than those in HBC (2.3 g · kg−1 BW ± 0.3 SE), and young animals consumed more (P < 0.05, 7.2 g · kg−1 BW ± 0.7 SE) juniper than mature goats (3.9 g · kg−1 BW ± 0.5 SE) across body condition treatments. In experiment 2, 36 goats, either young (2 yr) or matur...

Effects of Supplementation on Juniper Intake by Goats

Abstract The potential for winter supplementation to increase juniper intake by goats on rangelands in the Edwards Plateau region of Texas was assessed in two experiments. The first experiment evaluated the effect on juniper intake of either no supplementation (negative control) or supplementation with corn, alfalfa, or cottonseed meal fed at an isonitrogenous protein level of 1.5 g · kg body weight−1 for 12 days. Redberry juniper (Juniperus pinchotii Sudw.) consumption by individually penned Spanish, Boer × Spanish, Spanish × Angora, and Angora goats was measured on days 11 and 12. Each goat received each supplement in a complete 4 × 4 Latin square design. Juniper intake increased for goats supplemented with alfalfa and cottonseed meal (P = 0.001), but not for those supplemented with corn (P = 0.944). Boer × Spanish goats did not differ in levels of consumption (P = 0.085) from the other breeds. A second study investigated the effect of either no supplementation or soybean meal supplementation on juniper...

Monoterpene Production in Redberry Juniper Foliage Following Fire

Prescribed fire is commonly used to initiate redberry juniper (Juniperus pinchotti Sudw.) suppression, and herbivory by goats presents a potentially effective mechanism to prolong the efficacy of the reclamation treatment. Monoterpenes in redberry juniper leaves serve as a barrier to effective herbivory, but fire has the potential to reduce this barrier through reversion of aboveground growth to juvenile tissue. Traditional optimal defense theory predicts that because of the assumed fitness value of vegetative regrowth, plant secondary chemicals will be higher in this tissue than mature growth. This study was designed to measure the monoterpene concentration and composition from redberry juniper foliage sampled from 3 different ages of plant tissue. Prescribed fire was used to create 3- and 11-month regrowth juniper foliage, and mature growth of juniper was sampled as a control. Total monoterpene levels were lowest in the 3-month regrowth (P = 0.018). Monoterpene concentration and composition was similar for the 11-month and mature foliage. Concentration of terpinen-4-ol (P = 0.001) and alpha-terpineol (P = 0.007), identified as particularly aversive monoterpenoids to goats, was lowest in the 3-month regrowth but increased to levels found in mature leaves by 11 months of age. There was a trend in changes in composition of total oil as relative concentrations of monoterpene hydrocarbons (α-pinene, β-pinene/sabinene) decreased and monoterpene alcohols and oxygenated monoterpenes increased. These results identify a short period of time following a burn during which monoterpene levels in regrowth are low. This suggests a period of vulnerability in plant biochemical defenses that has the potential to be utilized by strategic herbivory by goats for more effective juniper management. El fuego prescrito es comunmente usado para iniciar la supresión del “redberry juniper” (Juniperus pinchotti Sudw.) y la herbivoría de las cabras se presenta como un mecanismo potencialmente efectivo para prolongar la eficacia del tratamiento de mejoramiento. Los monoterpenos de las hojas del “redberry juniper” sirven como una barrera a la herbivoría, pero el fuego tiene el potencial de reducir esta barrera a través de la reversión del crecimiento aéreo a tejido juvenil. La téoria tradicional de defensa óptima predice que debido al valor de aptitud asumido en el rebrote vegetativo, los compuestos químicos secundarios serán más altos en este tejido que en el maduro. Este estudio se diseño para medir la concentración y composición de monoterpenos del follaje del “redberry juniper” en tres edades del tejido de la planta. El fuego prescrito se utilizó para crear follaje de reborte de “redberry juniper” de 3 y 11 meses de edad, mientras que el follaje maduro fue muestrado como tratamiento control. Los niveles totales más bajos de monoterpenos se presentaron en el rebrote de 3 meses (P = 0.018). La concentración y composición de monoterpenos fue similar en el rebrote de 11 meses y el follaje maduro. La concentracion más baja de terpineno-4-ol (P = 0.001) y el alfa-terpineol (P = 0.007), identificados como monoterpenoides particularmente aversivos para las cabras, se presentó en el rebrote de 3 meses, pero a los 11 meses de edad del rebrote se incrementó a los niveles encontrados en el follaje maduro. Hubo una tendencia en los cambios de la composición del aceite total porque la concentración de hidrocarburos monoterpénicos (α-pineno, β-pineno/sabineno) decreció y la de alcohol monoterpenoides y monoterpenoides oxigenados se incrementó. Estos resultados identifican un periodo corto de tiempo después de la quema en el cual los niveles de monoterpenos del rebrote son bajos. Esto sugiere un periodo de vulnerabilidad en las defensas bioquímicas de la planta que tiene el potencial para ser utilizado con herbivoría estrátegica con cabras para un manejo más efectivo del “Redberry juniper.”

Herbaceous Restoration of Juniper Dominated Grasslands With Chaining and Fire

Juniper (Juniperus spp.) encroachment in grasslands usually progresses toward a stable woody state of mature trees that requires a significant disturbance to shift succession in another direction. Fire alone is often inadequate to shift succession in dense stands of mature juniper and must be preceded by a mechanical treatment such as chaining to reduce juniper competition and increase herbaceous growth that fuels a subsequent fire. However, little long-term data are available that measure combined effects of mechanical and fire treatments on restoration of juniper-dominated grasslands. Here, on a degraded (40% bare ground) north Texas site dominated by redberry juniper (Juniperus pinchotii Sudw), we quantify long-term herbaceous responses to mechanical chaining followed by fire. Two types of chaining, ground-level and elevated, were evaluated and all chained plots were burned 4 years after chaining. Herbaceous and woody responses were measured for several years after both chaining and fire treatments and compared to untreated controls. At study termination, both of the chaining + fire treatments reduced juniper cover from 32% to < 6%, but mortality was < 10%, because most plants basal-sprouted. Total grass production did not increase in chained treatments over the untreated until 3 growing seasons after chaining. Grass production declined the first growing season following the fire treatment, but increased in treated plots to 3 times the untreated the second and third year postfire. Total grass cover in treated plots did not increase over the untreated until the second year after the fire treatment. There was no difference in juniper or herbaceous responses between the 2 chain types. Results suggest increases in herbaceous production from chaining alone were due to increased growth of existing vegetation patches whereas the fire treatment appeared to stimulate herbaceous recruitment into bare soil areas.

Herbaceous Restoration of Juniper Dominated Grasslands With Chaining and Fire

Juniper (Juniperus spp.) encroachment in grasslands usually progresses toward a stable woody state of mature trees that requires a significant disturbance to shift succession in another direction. Fire alone is often inadequate to shift succession in dense stands of mature juniper and must be preceded by a mechanical treatment such as chaining to reduce juniper competition and increase herbaceous growth that fuels a subsequent fire. However, little long-term data are available that measure combined effects of mechanical and fire treatments on restoration of juniper-dominated grasslands. Here, on a degraded (40% bare ground) north Texas site dominated by redberry juniper (Juniperus pinchotii Sudw), we quantify long-term herbaceous responses to mechanical chaining followed by fire. Two types of chaining, ground-level and elevated, were evaluated and all chained plots were burned 4 years after chaining. Herbaceous and woody responses were measured for several years after both chaining and fire treatments and compared to untreated controls. At study termination, both of the chaining + fire treatments reduced juniper cover from 32% to &lt; 6%, but mortality was &lt; 10%, because most plants basal-sprouted. Total grass production did not increase in chained treatments over the untreated until 3 growing seasons after chaining. Grass production declined the first growing season following the fire treatment, but increased in treated plots to 3 times the untreated the second and third year postfire. Total grass cover in treated plots did not increase over the untreated until the second year after the fire treatment. There was no difference in juniper or herbaceous responses between the 2 chain types. Results suggest increases in herbaceous production from chaining alone were due to increased growth of existing vegetation patches whereas the fire treatment appeared to stimulate herbaceous recruitment into bare soil areas.

Sire Influence on Juniper Consumption by Goats

Goats avoid eating redberry juniper (Juniperus pinchottii Sudw.) when other palatable forages are available but will increase intake of juniper when exposed to the plant for several days. Intake of redberry juniper also differs among breeds and individual goats. Selection based on foraging habits could further improve juniper intake. The purpose of this study was to determine the influence of sires on juniper consumption. Heritability of redberry juniper intake was assessed for 3 years (1997, 1998, 2000) by placing male Boer-Spanish cross goats from 4–8 sires (the number of sires differed among years) in individual pens and feeding juniper (200 g) daily for 2 hours over 5 to 10 days. Feeding juniper was done after weaning kid goats each year. Juniper intake was similar among sire groups within years. Heritability of juniper consumption was low (11%) across the 3 years of this study. Goats increased juniper intake daily while in individual pens. These results suggest that an acceptance of juniper by goats can be conditioned through exposure to the plant after weaning, and that juniper consumption does not appear to be a highly heritable trait.

Sire Influence on Juniper Consumption by Goats

Goats avoid eating redberry juniper (Juniperus pinchottii Sudw.) when other palatable forages are available but will increase intake of juniper when exposed to the plant for several days. Intake of redberry juniper also differs among breeds and individual goats. Selection based on foraging habits could further improve juniper intake. The purpose of this study was to determine the influence of sires on juniper consumption. Heritability of redberry juniper intake was assessed for 3 years (1997, 1998, 2000) by placing male Boer-Spanish cross goats from 4-8 sires (the number of sires differed among years) in individual pens and feeding juniper (200 g) daily for 2 hours over 5 to 10 days. Feeding juniper was done after weaning kid goats each year. Juniper intake was similar among sire groups within years. Heritability of juniper consumption was low (11%) across the 3 years of this study. Goats increased juniper intake daily while in individual pens. These results suggest that an acceptance of juniper by goats can be conditioned through exposure to the plant after weaning, and that juniper consumption does not appear to be a highly heritable trait.

Mesquite and Grass Interference with Establishing Redberry Juniper Seedlings

Excessive cover of juniper (Juniperus pinchotii Sudw.) reduces forage production, interferes with livestock management, and diminishes the watershed and wildlife habitat values of rangelands. We studied whether juniper seedlings were differentially suppressed in the presence of different grass species, and to what extent established mesquite (Prosopis glandulosa Torr.) trees facilitated or competed with establishing juniper seedlings. Seedlings growing with any of the grasses (RGR = 0.23 to 0.43 cm cm(-1)) grew significantly less than those with no grass competition (RGR = 0.72 cm cm(-1))(P 0.05), indicating that mesquite root competition with juniper is probably inconsequential. Since junipers grow mainly in fall, winter and spring when mesquite trees are dormant and leafless, the lack of competition may largely be due to these 2 species using resources at different times of the year. Greater nutrient availability beneath mesquite canopies, reduction of summer temperatures, and temporal separation of resource use clearly benefit juniper seedlings growing in the presence of mesquite. Managing for a vigorous grass component with low densities and cover of mesquite is the best way to limit the rate of invasion by juniper. DOI:10.2458/azu_jrm_v54i6_teague

Redberry Juniper Canopy Cover Dynamics on Western Texas Rangelands

Knowledge of the rate woody plant canopy cover increases is essential for understanding the ecology of rangeland plant communities, determining the economic feasibility of brush management practices, and for scheduling initial and maintenance control practices. We determined rates of change in redberry juniper (Juniperus pinchotii Sudw.) canopy cover from the mid 1950s through the late 1990s at 5 locations in western Texas on rangeland that had been chained or grubbed for juniper control and on adjacent untreated areas. Juniper cover was estimated from aerial photographs by the line intercept method using a 10-X monocular lens with a vernier. Juniper cover increased at 0.35 +/- 0.06 percentage units year(-1) on untreated sites and at 1.01 +/- 0.07 percentage units year(-1) following chaining or grubbing. Juniper cover returned to pre-treatment levels in an average of 20 years (range 11 to 25) following chaining or grubbing. Herbage production on untreated rangeland was predicted to decline slowly (2.4 to 5.0 kg ha(-1) year(-1)) as juniper cover increased from 6 to 14% and rapidly (> 8 kg ha(-1) year(-1)) as juniper cover increased from 30 to 38%. Herbage production was predicted to decline at a constantly increasing rate following mechanical control of juniper, from < 2 kg ha(-1) year(-1) in year 1 to 23 kg ha(-1) year(-1) in year 29. Potential additional livestock carrying capacity due to juniper control would be under estimated by more than 40%, assuming forage production without treatment remained constant during the entire planning horizon of an economic analysis. To avoid significant reductions in livestock carrying capacity, redberry juniper control should be implemented before its canopy cover exceeds about 20%. DOI:10.2458/azu_jrm_v54i5_ueckert

Remote Sensing of Redberry Juniper in the Texas Rolling Plains

Redberry juniper (Juniperus pinchotii Sudw.) is a noxious shrub or small tree that invades rangelands in northwest Texas. Field reflectance measurements showed that redberry juniper had lower visible and higher near-infrared (NIR) reflectance than associated species and mixtures of species in February. The low visible reflectance of redberry juniper was due to its darker green foliage than associated species, whereas its high NIR reflectance was attributed to its greater vegetative density than associated vegetation. Redberry juniper had a distinct reddish-brown image tonal response on color-infrared aerial photographs obtained in February. Computer analysis of a color-infrared photographic transparency showed that redberry juniper infestations could be quantified. An accuracy assessment performed on the classified image had a user's accuracy of 100% and a producer's accuracy of 94% for redberry juniper. DOI:10.2458/azu_jrm_v54i3_everitt