Juniperus Ashei Research Articles

Drought‐induced woody plant mortality in an encroached semi‐arid savanna depends on topoedaphic factors and land management

AbstractQuestionsHow do recent patterns of drought‐induced woody plant mortality in Texas semi‐arid savanna compare to the extended drought of the 1950s? Does the relative composition of the woody plant community shift ubiquitously across the landscape following woody plant mortality and dieback or are shifts dependent on differences among species, soils, land use and plant demography?LocationTexas Agrilife Research Station, Sonora, Texas, USA (30.1° N 100.3° W).MethodsFollowing an exceptional drought from 1951 to 1957, a study was conducted to quantify rates of mortality for various woody plant species. In 2011, we repeated this study within three long‐term grazing treatments that were established in 1948. Ten transects were established in each treatment to quantify the frequency and cover of live and dead woody individuals for all woody species. Rates of woody plant dieback were determined for each species and tested for differences among height classes, soil categories, total woody densities and pastoral treatments.ResultsFlash droughts (defined as rapidly intensifying droughts characterized by moisture deficits and high temperatures) from 2000 to 2011 were the second most severe since 1919 (low PDSI = −4) and were only surpassed by the prolonged drought from 1951 to 1957 (low PDSI = −5.17). Drought‐induced shifts from one woody plant community to another did not occur uniformly across the landscape. Instead, high mortality rates of mature Juniperus ashei trees in deep soils (67.3%, 33 of 49 trees), combined with the recruitment of Quercus species where grazing had been excluded for the last 60 yr, were the only patch types to shift from a Juniperus–Quercus woodland to an alternate state.ConclusionsFlash droughts since 2000 resulted in significant mortality and dieback, but dieback in cover was 28% higher following the more severe drought of the 1950s. Legacies from long‐term land management practices interacted with localized differences in topoedaphic factors to drive patch‐level shifts in woody vegetation following drought.

Refining thresholds in coupled fire–vegetation models to improve management of encroaching woody plants in grasslands

Summary Restoration priorities are typically established without quantitative information on how to overcome the thresholds that preclude successful restoration of desirable ecosystem properties and services. We seek to demonstrate that quantifying ecological thresholds and incorporating them into management‐oriented frameworks provide a more comprehensive perspective on how the threshold concept can be applied to achieve restoration goals. As an example, restoration actions have been largely unsuccessful when based on prevailing ecological knowledge of fire‐based thresholds in nonresprouting Juniperus woodland. We build on previous threshold‐based research and link well‐established models from applied fire physics with a widely applied ecological positive feedback model of woody plant encroachment to introduce a more comprehensive understanding of the mechanism influencing fire intensity and juniper mortality. Our coupling of physical and ecological fire models revealed a critical knowledge gap, a lack of a quantitative estimate on the critical surface fire intensity required to cause mortality of Juniperus ashei trees, which limits the linking of scientific knowledge from these two disciplines. To quantify the relationship between fire intensity and J. ashei mortality, we input data from a previous experiment into Byram's fireline intensity model. This critical surface fire intensity–mortality threshold was estimated to be Is > 160 kJ m−1 s−1. This value establishes a specific threshold that managers should target when attempting to use restoration to collapse J. ashei woodlands. Synthesis and applications. For scientific information associated with the threshold concept to be useful to practitioners, specific information is needed that demonstrates how to use restoration activities to overcome thresholds and collapse the current, degraded state in favour of a more desired ecological state. With this in mind, we present a broadly applicable decision support model within a state and transition framework that identifies the ecological states where the surface fire intensity–mortality threshold is most likely to meet restoration objectives and provides examples of how fuel properties that drive fire intensity should be targeted in restoration to surpass this threshold.

Using Experience and Supplementation to Increase Juniper Consumption by Three Different Breeds of Sheep

In the southwestern United States, redberry (Juniperus pinchotii Sudw.) and ashe (Juniperus ashei Buchholz) juniper are two invasive species that dominate some rangelands. Goats will consume up to 30% of their diet in juniper, but it is unknown if sheep will accept juniper to the same extent. The objectives of this study were to determine if sheep can be conditioned to consume juniper and to compare intake among different breeds. Rambouillet (n = 10), Suffolk (n = 10), and Dorper-cross (n = 10) lambs were randomly placed in individual pens for 31 d. A basal diet of alfalfa pellets (2.5% body weight [BW]) and juniper were fed. Juniper was fed each morning from 0800 to 0830 hours. The basal diet was fed for the remainder of the day. Intake of each was measured daily. Following the first 17 d, the basal diet was reduced to 2% BW for 7 d and then reduced to 1.5% BW for the final 7 d. Serum aspartate transaminase (AST), gamma glutamyltransferase (GGT), blood urea nitrogen (BUN), creatinine, and bilirubin levels, and live body weight were measured to assess any adverse physiological effects from juniper consumption. In a second trial, lambs were again fed alfalfa (2.5% BW) and juniper. One half of the lambs were also fed a 36% protein supplement to determine if supplementation with protein sources that escape rumen degradation would improve juniper consumption. Lambs received alfalfa, juniper, and protein supplement for 22 d with intake of each recorded daily. Intake of juniper was similar (P > 0.05) among breeds of sheep. Lambs readily consumed juniper and increased (P < 0.05) intake of juniper as the amount of alfalfa fed was reduced. Weight change was also similar among treatments. Protein supplementation did not improve juniper consumption. We contend that sheep will consume a diet consisting of 24% juniper without experiencing any adverse effects.

Juniper Pollen Hotspots in the Southwest

Rationale: Juniperus pollen is a major allergen in Texas, Oklahoma, and New Mexico. While the bulk of pollen may be released in rural areas, large amounts of pollen can be transported to urban areas. Major juniper species in the region include: Juniperus ashei, J. virginiana, J. pinchotii, and J. monosperma. Pollen release is virtually continuous beginning in late September with J. pinchotii and ending in May with J. monosperma. Urban areas in the region were evaluated for the potential of overlapping seasons in order to inform sensitive individuals. Methods: Burkard volumetric pollen traps were established for two consecutive spring seasons at 6 sites in northern New Mexico and 6 sites for two consecutive winter and fall seasons in Texas and Oklahoma Standard methods were used in the preparation and analysis of slides. Results: The Dallas-Fort Worth Metroplex is home to over 6 million people. It is adjacent to populations of J. pinchotii, J. virginiana, and J. ashei. Peak concentration near Dallas for J. ashei in 2011 was 5891 pollen grains/m3 in January 7th. The peak date for J. pinchotii at an upwind sampling location in San Marcos, TX was November 1, 2010 and peak for J. virginiana at a nearby station in Tulsa, OK was November 1, 2010 and peak for J. virginiana at a nearby station in Tulsa, OK was February 20, 2011. Amarillo, TX is adjacent to J. pinchotii, J. ashei, and J. monosperma populations and may be subject to juniper pollen from September through May. Conclusions: Considering the overlapping distributions of juniper trees and the overlapping temporal release of pollen, sensitive patients may benefit from avoiding hotspots.

Exposure to Juniperus Ashei (Mt. Cedar) and Virginia Live Oak Pollen in a Pollen Challenge Chamber Elicits Similar Symptomology When Compared to Natural Season

Exposure to Juniperus Ashei (Mt. Cedar) and Virginia Live Oak Pollen in a Pollen Challenge Chamber Elicits Similar Symptomology When Compared to Natural Season

Exposure to Juniperus Ashei (Mt. Cedar) Pollen in a Pollen Challenge Chamber Elicits Changes in White Blood Cell Counts and Cytokines in Mountain Cedar Positive and Negative Subjects

Exposure to Juniperus Ashei (Mt. Cedar) Pollen in a Pollen Challenge Chamber Elicits Changes in White Blood Cell Counts and Cytokines in Mountain Cedar Positive and Negative Subjects

Topical Wound-Healing Effects and Phytochemical Composition of Heartwood Essential Oils ofJuniperus virginianaL.,Juniperus occidentalisHook., andJuniperus asheiJ. Buchholz

Ethnobotanical surveys indicated that in the traditional medicines worldwide, several Juniperus species are utilized as antihelmintic, diuretic, stimulant, antiseptic, carminative, stomachic, antirheumatic, antifungal, and for wound healing. In the present study, essential oils obtained from heartwood samples of Juniperus virginiana L., Juniperus occidentalis Hook. and Juniperus ashei J. Buchholz were evaluated for wound healing and anti-inflammatory activities by using in vivo experimental methods. The essential oils were obtained by the supercritical carbon dioxide extraction method. Linear incision and circular excision wound models were performed for the wound-healing activity assessment. The tissues were also evaluated for the hydroxyproline content as well as histopathologically. To evaluate the anti-inflammatory activity of the essential oils, the test used was an acetic acid-induced increase in capillary permeability. The essential oil of J. occidentalis showed the highest activity on the in vivo biological activity models. Additionaly, the oil of J. virginiana was found highly effective in the anti-inflammatory activity method. The experimental data demonstrated that essential oil of J. occidentalis displayed significant wound-healing and anti-inflammatory activities.

Species‐specific water use by woody plants on the Edwards Plateau, Texas

ABSTRACTWoody encroachment is of great socio‐economic and ecological importance in semiarid savannas because it is presumed to alter the water balance in such ecosystems. We compared two encroachers, Ashe juniper (Juniperus ashei) and honey mesquite (Prosopis glandulosa), with the less invasive live oak (Quercus fusiformis) to ascertain whether soil depth or species‐specific water use strategy is most important in determining transpirational losses on shallow soils underlain by fractured limestone bedrock on the Edwards Plateau. Sap fluxes, leaf water potentials, soil moisture and meteorological information were monitored during spring 2009 at three sites with differing soil depths and were used in a non‐spatial soil–vegetation–atmosphere water transfer model to predict different rooting depths. Sap flux responses and soil water stress were compared using multivariate statistical analysis. At two relatively deep‐soil savanna sites, we found that dominant tree species had similar water use behaviour. However, at the shallow‐soil forest containing Ashe juniper and live oak, juniper transpiration was much higher early in the season than oak transpiration, indicating that juniper benefited more from early spring rainfall than oaks. The model predicts that maximum rooting depths for the woody vegetation were mostly constrained by site soil depths. This study provides new evidence that these species perform similarly on shallow soils and that their water use is restricted by soil depth. The only species‐specific strategy found important in determining transpirational losses was juniper's ability to withstand low soil water potentials in very shallow soils. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Water‐storage capacity controls energy partitioning and water use in karst ecosystems on the Edwards Plateau, Texas

ABSTRACTWoody plants are encroaching into grasslands and savannas of the karst Edwards Plateau, but their impacts on climate and hydrology are unclear because of high variability in soil depth and uncertainties about the contribution of water in fractured limestone to the water available to trees. Water use is controlled by available energy (AE) and its partitioning between latent (λE) and sensible (H) heat fluxes. We hypothesized that the partitioning of AE depends on soil depth, with greater depth leading to more λE and less H. We compared energy fluxes of a deep soil savanna with ~50% woody cover dominated by Ashe juniper (Juniperus ashei) and a shallow soil woodland dominated by live oak (Quercus virginiana) and juniper over a 5‐year period, which included periods of unusually high rainfall and severe drought. Although AE was 7% higher in the woodland, λE was about 2% higher at the savanna over the 5‐year study. Site differences in evapotranspiration were maximal during dry periods between rainfall events, suggesting greater storage of water at the savanna site. During periods of high rainfall, the impact of water storage limitations was minimal, and site differences in evapotranspiration were controlled mainly by AE and its partitioning into H. Both sites were characterized by rapid reductions in λE and reciprocal increases in H during drying cycles following rainfall, indicating that neither of these ecosystems had access to easily utilized sources of deep water. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Differences in chemical composition between browsed and non-browsed Juniperus ashei Buch. Trees

Abstract Leaf secondary compounds were examined in browsed and non-browsed Juniperus ashei trees to identify selective browsing patterns by goats and deer. Analysis of volatile leaf oils (terpenoids) revealed that the browsed trees were lower in total oil than non-browsed trees (2.18 vs. 3.46%, DW basis). Extractable and fiber-bound condensed tannins (CT) were not different but protein-bound CT concentrations were greater in browsed trees. Among digestibility measures (NDF, ADF, IVDMD), IVDMD was greater in non-browsed leaves. Terpene components analyzed on a percent total oil basis had 3 differences versus 12 significant differences on a mg/g DW basis. The terpenoid components profile differed little between browsed and non-browsed trees. Total CT are negatively associated with oil yields. No association was found between crude protein and oil yields or between digestibility (IVDMD, NDF, ADF) and oil yields. The question of whether individual plants or populations may invest less in CT when greater amounts of terpenes are produced (or vice-versa) may have evolutionary implications since individual browsers or populations may adapt to consuming or avoiding either CT or terpenes. The fact that browsed tree leaves were less digestible than non-browsed tree leaves may be a result of complex interactions between CT, terpenes, fiber, and nutrients.

Hydraulic responses to extreme drought conditions in three co-dominant tree species in shallow soil over bedrock

An important component of the hydrological niche involves the partitioning of water sources, but in landscapes characterized by shallow soils over fractured bedrock, root growth is highly constrained. We conducted a study to determine how physical constraints in the root zone affected the water use of three tree species that commonly coexist on the Edwards Plateau of central Texas; cedar elm (Ulmus crassifolia), live oak (Quercus fusiformis), and Ashe juniper (Juniperus ashei). The year of the study was unusually dry; minimum predawn water potentials measured in August were -8 MPa in juniper, less than -8 MPa in elm, and -5 MPa in oak. All year long, species used nearly identical water sources, based on stable isotope analysis of stem water. Sap flow velocities began to decline simultaneously in May, but the rate of decline was fastest for oak and slowest for juniper. Thus, species partitioned water by time when they could not partition water by source. Juniper lost 15-30 % of its stem hydraulic conductivity, while percent loss for oak was 70-75 %, and 90 % for elm. There was no tree mortality in the year of the study, but 2 years later, after an even more severe drought in 2011, we recorded 34, 14, 6, and 1 % mortality among oak, elm, juniper, and Texas persimmon (Diospyros texana), respectively. Among the study species, mortality rates ranked in the same order as the rate of sap flow decline in 2009. Among the angiosperms, mortality rates correlated with wood density, lending further support to the hypothesis that species with more cavitation-resistant xylem are more susceptible to catastrophic hydraulic failure under acute drought.

Removing woody vegetation has little effect on conduit flow recharge

ABSTRACTIn drylands across the globe, grasslands and savannas have succumbed to encroachment by woody plants. There is a concern that, in some cases, these changes may lead to lower groundwater recharge and streamflow. In karst landscapes, the effect of woody plants on recharge is difficult to determine because of the shallow and rocky soils. In our study, we estimated the amount of water entering a shallow cave (3–5 m deep) as a surrogate measurement for groundwater recharge, to evaluate whether the removal of Ashe juniper (Juniperus ashei) above the cave would affect recharge. Three sets of large‐scale rainfall simulations were conducted in 2005, before removal of the overstory juniper; seven were conducted in 2008, soon after the juniper were removed; and two were conducted in 2009, one year after juniper removal. We found that recharge occurred mainly via conduits or macropores and, as such, was extremely dynamic and responsive to rainfall. The amount of recharge ranged from 3% to 17% of the water applied, the higher percentages being measured when antecedent soil conditions were wet. At least in this case of recharge taking place via conduit flow, removal of the juniper had little if any effect. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Herbivore species and grazing intensity regulate community composition and an encroaching woody plant in semi-arid rangeland

Grazing by livestock can influence ecosystems in various ways, including altering plant communities, influencing woody plant encroachment, and determining livestock productivity. Evaluating long term effects of grazing on plant composition is valuable not only to understand herbivory on rangelands but to be able to address the primary factors that can threaten long term livestock productivity. We examined plant species composition and woody plant encroachment 45 years after the initiation of differing grazing treatments within a semiarid savanna of the southern Great Plains, USA. Grazing treatments varied in herbivore type (domestic cattle, sheep, and goats vs. goats only) and grazing intensity (heavy, moderate, and no-herbivory). All individual trees of Juniperus ashei Buchholz, the encroaching woody plant of the area, were removed prior to treatment initiation. Moderate and heavy grazing by a combination of species resulted in similar plant communities, while a history of heavy browsing by goats only and no-herbivory resulted in more distinct communities. Cover of J. ashei did not differ between mixed grazing and no-herbivory treatments, indicating that grazing was not responsible for woody plant encroachment. J. ashei cover within the browsed treatment was a third less compared to other treatments; compositional differences within this treatment are possibly due to reduced cover of woody vegetation. Declines in livestock productivity of the area are likely related to compositional changes resulting from increased woody plants. Livestock production within this semi-arid rangeland is likely unsustainable without management of woody plant encroachment, as communities tend to a closed canopy woodland.

Urban Heat And Humidity Islands And The Preferential Deposition Of Airborne Pollen

Juniperus ashei, is a highly allergenic winter pollinating tree, common across the Edwards Plateau in Texas. Pollen from these populations travel long distances when atmospheric and meso-scale weather patterns prevail and affect downwind communities. Increasing urbanized areas are affected, perhaps preferentially. Whereas it is assumed that entrained pollen travels over these areas, the advent of urban heat and humidity islands may significantly affect the characteristics of the pollen causing increased deposition.

Long-Term Effects of Fire, Livestock Herbivory Removal, and Weather Variability in Texas Semiarid Savanna

We examined how the occurrence and structure of grasses and woody plants changed after 12 yr of a fire season manipulation and removal of livestock herbivores. Applying high intensity fires in the summer preserved the structural integrity of this semiarid live oak (Quercus virginiana Mill.) savanna while decreasing or eliminating numerous problematic plants in the understory and overstory, such as prickly pear cactus (Opuntia spp.), sacahuista (Nolina texana S. Watson), Ashe juniper (Juniperus ashei J. Buchholz), Pinchot's juniper (J. pinchotii Sudw.), and honey mesquite (Prosopis glandulosa Torr.). In the less intense repeat winter burning treatments, undesirable woody plants were generally maintained at pretreatment levels in the overstory but all woody plants except Ashe juniper increased in the understory. Alternatively, areas excluded from fire in the control treatment rapidly transitioned from a grass-tree codominated savanna environment to one that is heavily dominated by woody plants. In the grass community, the most frequently occurring grass species in the winter burn treatment differed from summer burn and control treatments, whereas the summer burn treatment was not different from the control. Of the herbaceous plants, only little bluestem (Schizachyrium scoparium &lsqb;Michx.] Nash) responded to fire treatments. Little bluestem increased in the winter burn treatment, remained fairly constant in the summer burn treatment, and decreased in the control. Other grasses varied largely as a function of annual weather variability, the removal of livestock, and legacy effects resulting from pre-existing variability. These findings suggest that fire can reduce or eliminate woody plant species that threaten the stability of live oak savannas while having little long-term effect on grasses desired by rangeland managers.

Validation of the biogenics research chamber for Juniperus ashei (mountain cedar) pollen

Pollen challenge chambers have been used to evaluate medication in allergic rhinoconjunctivitis under controlled conditions. To validate a facility for the study of subjects' responses to inhalational challenges with Juniperus ashei (mountain cedar) pollen. Two chambers, 307 m(3) and 188 m(3), seating 50 and 25 individuals, respectively, were constructed with clean room materials. The computer-controlled air handler used powered diffusers and exhausts to maintain a laminar flow. Pollen was delivered by a feeder into a vortex created by an eductor through a series of stainless steel tubes. Nonprimed mountain cedar sensitive and healthy control subjects were exposed to a masked sham air run and increasing increments of pollen during a 5-hour period outside the natural season. These individuals were then exposed for 2-hour periods for up to 4 sequential days at fixed pollen counts to demonstrate effects of priming. Airflow from diffusers and exhausts maintained 12 exchange cycles per hour. Pollen counts ranged from 1,300 to 12,000 grains/m(3). None of the subjects responded during the masked sham run. Healthy controls did not respond. Nonprimed subjects had an inadequate response. Primed subjects responded symptomatically within a period adequate for entry into studies. There were no serious adverse responses. The chambers functioned within the parameters for which they were designed. Subjects did not respond to a sham run. Priming runs were required to stimulate symptoms at levels in a timeframe sufficient for pharmacologic studies. Pollen counts 3 to 4 times the average seasonal counts were required to elicit significant symptoms.

Experimental evidence of host race formation inMitourabutterflies (Lepidoptera: Lycaenidae)

A population of herbivorous insects that shifts to a novel host can experience selection pressures that result in adaptation to the new resource. Host race formation, considered an early stage of the speciation process, may result. The current study investigates host shifts and variation in traits potentially involved in the evolution of reproductive isolation among populations of the juniper hairstreak butterfly,Mitoura gryneus. Mitouraare closely associated with their host trees (Cupressaceae) and exhibit host plant fidelity: in addition to larval development and oviposition, host trees support male leks and mating. Female oviposition preference for the natal host, and differential fitness of larvae when reared on natal versus alternate hosts, are indications that specialization and local adaptation to the natal host plant are occurring. Populations with single host plant associations (Juniperus ashei,J. pinchotiiandJ. virginiana) as well as populations with multiple hosts (bothJ. asheiandJ. pinchotii) were examined. Concordance between female preference and larval performance was found forJ. ashei‐associated populations. Population‐level variation in the patterns of female preference and larval performance, both within and among host associations, may reflect differences in the timing and direction of colonization of hosts. For a single nominal species that otherwise exhibits no morphological or phenological differences, the experimental assessment of specialization and host fidelity inM. gryneusprovides strong support for the hypothesis of ongoing host race formation in these butterflies.

Mountain cedar pollen induces IgE-independent mast cell degranulation, IL-4 production, and intracellular reactive oxygen species generation

Cedar pollens cause severe allergic disease throughout the world. We have previously characterized allergenic pollen glycoproteins from mountain cedar ( Juniperus ashei) that bind to allergen-specific immunoglobulin E (IgE). In the present report, we investigated an alternative pathway of mast cell activation by mountain cedar pollen extract through IgE-independent mechanisms. We show that mountain cedar pollen directly induces mast cell serotonin and IL-4 release and enhances release induced by IgE cross-linking. Concomitant with mediator release, high levels of intracellular reactive oxygen species (ROS) were generated, and both ROS and serotonin release were inhibited by anti-oxidants. These findings suggest that alternative mechanisms exist whereby pollen exposure enhances allergic inflammatory mediator release through mechanisms that involve ROS. These mechanisms have the potential for enhancing the allergenic potency of pollens.

Chemical Composition and Antibacterial Activity of Selected Essential Oils and Some of Their Main compounds

The chemical composition of essential oils of cabreuva (Myrocarpus fastigiatus Allemao, Fabaceae) from Brazil, cedarwood (Juniperus ashei, Cupressaceae) from Texas, Juniper berries (Juniperus communis L., Cupressaceae) and myrrh (Commiphora myrrha (Nees) Engl., Burseraceae) were analyzed using GC/FID and GC/MS. The antimicrobial activity of these essential oils and some of their main compounds were tested against eleven different strains of Gram-positive and Gram-negative bacteria by using agar diffusion and agar serial dilution methods. Animal and plant pathogens, food poisoning and spoilage bacteria were selected. The volatile oils exhibited considerable inhibitory effects against all tested organisms, except Pseudomonas, using both test methods. Higher activity was observed against Gram-positive strains in comparison with Gram-negative bacteria. Cabreuva oil from Brazil showed similar results, but in comparison with the other oils tested, only when higher concentrations of oil were used.

Herbaceous Cover and Biomass of Carex planostachys in Juniperus ashei Woodlands of Central Texas

Abstract In the understory of many Juniperus woodlands, herbaceous cover and biomass are reduced or eliminated compared to interstitial grasslands. However, there are some exceptions. Carex planostachys (cedar sedge) is a widespread herbaceous species associated with J. ashei and occurs in the understory of these woodlands in central Texas. The purpose of this paper was to compare cover and biomass of herbaceous vegetation along a gradient from below the canopy of J. ashei into an associated intercanopy patch or grassland. Levels of light are reduced below the canopy, whereas litter and moisture in the soil are higher. Cover and biomass of C. planostachys were higher below the J. ashei canopy and canopy edge. Total cover and biomass of grasses were higher in the intercanopy at elevated levels of light, reduced litter, and lower soil moisture. Spatial distribution of C. planostachys below the canopy suggests that this species is tolerant of shade and may require a woodland canopy for growth and development.