@article {JRN54560, title = {Defoliation of Flourensia cernua (tarbush) with high-density mixed-species stocking}, journal = {Journal of Arid Environments}, volume = {130}, year = {2016}, month = {04/2016}, pages = {62-67}, chapter = {62}, abstract = {

Interest in shrub use by livestock is increasing along with the rising demands placed on rangelands worldwide. Historically, Flourensia cernua (tarbush) has increased in the Chihuahuan Desert but receives limited use by cattle. Cattle, sheep and goats co-grazed eight 0.6 ha tarbush-dominated paddocks during two periods for up to nine days during two consecutive years. Cumulative tarbush defoliation across periods and years averaged 75.6\%, with a mean increase of 9.3\%/day (P \< 0.0001). Defoliation of individual shrubs varied from 5 to 99\% in 1989 and 0 - 100\% in 1990, indicating highly variable palatability among individual plants. Sheep lost 2.3 - 5.5 kg/hd (P \< 0.0001) across periods and years when forced to browse tarbush. In 1989, goats gained (P . 0.0345) 0.6 kg/hd in period 1, but the gain in period 2 was not significant (P . 0.2934). During 1990, goats lost 3.1 kg/hd (P . 0.0001) across periods. High-density mixed-species stocking of small areas for short time periods resulted in extensive tarbush use, primarily due to browsing by sheep and goats. Targeted use of tarbush for short time intervals may increase use of this highly nutritious forage and potentially serve as a form of biocontrol for this shrub.

}, keywords = {biocontrol, browsing, cattle, goats, sheep, shrubs}, doi = {10.1016/j.jaridenv.2016.03.013}, url = {/files/bibliography/16-008.pdf}, author = {Richard E. Estell and D.M. Anderson and D. K. James} } @article {JRN52696, title = {Coping with shrub secondary metabolites by ruminants}, journal = {Small Ruminant Research}, volume = {94}, year = {2010}, month = {10/2010}, pages = {1-9}, chapter = {1}, abstract = {

Rangelands throughout the world contain varying but often substantial proportions of shrubs. Shrubs are generally heavily chemically defended, and herbivores must either contend with their plant secondary metabolites (PSM) or avoid a significaant component of the available forage. Browsing ruminants are exposed to thousands of chemicals in infinite combinations and concentrations that are constantly changing both temporally and spatially. The success with which a herbivore navigates this complex environment is in part attributed to its ability to cope with PSM. Plant secondary metabolites can affect a number of physiological and metabolic processes (e.g., altered microbial activity, reduced digestion, compromised acid/base balance, toxicity), although negative consequences to the herbivore range from harmless to lethal, depending factors such as dose, animal species, plane of nutrition, and physiological state. Herbivores have a variety of intertwined mechanisms to cope with consumption of PSM, ranging from physiological (e.g., salivary proteins, detoxification pathways) to behavioral (e.g., avoidance, regulation of intake below critical threshold, cautious sampling, altering size and pattern of feeding bouts, diet switching, consuming diverse and/or complementary diets). Secondary compounds may affect requirements for nutrients (e.g., protein, minerals, and glucose) and water, and may alter basal metabolic rate. Energy requirements may also increase to accommodate increased travel to water and supplementation sites to counter these negative effects, particularly on arid rangelands.

}, keywords = {foraging behavior, herbivory, intake, plant secondary metabolites, ruminants, secondary chemistry, shrubs}, doi = {10.1016/j.smallrumres.2010.09.012}, url = {/files/bibliography/10-033.pdf}, author = {Richard E. Estell} } @conference {50326, title = {Effects of individual terpenes and terpene mistures on intake of lambs}, booktitle = {American Society of Animal Science}, volume = {85}, number = {Suppl. 1}, year = {2007}, month = {July 9, 2007}, pages = {287-288}, abstract = {Rangeland degradation due to shrub encroachment is a major concern to livestock producers and land managers in the western United States and in arid and semiarid regions worldwide. Most invasive shrubs contain secondary compounds that reduce their consumption by herbivores, but knowledge concerning the effects of specific compounds is limited. Four experiments were conducted to determine the effects of individual terpenes or mixtures of monoterpenes or sesquiterpenes on intake by lambs. After a 10-day adaptation period with untreated alfalfa pellets, lambs were individually fed treated alfalfa pellets for 20 min. each morning for 5 days. Five treatments (0X, .5X, 1X, 2X, and 10X; multiples of the concentrations of the same terpenes in Flourensia cernua) were applied to alfalfa pellets (637 g, DM basis) in an ethanol carrier. Except during the 20-m,in test, lambs were maintained outdoors and fed untreated alfalfa pellets (total mean intake = 4.7\%) in Exp. 1 and 4 because of greater intake of OX than other treatments on day 1 and lower intake for the 10XZ treatment on day 1 and 2. A trend for decreased intake (g/kg BW) as concentration of the sesquiterpene mixture increased was observed. Although there was a tendency for a sesquiterpene mixture to decrease intake, and the monoterpene mixture did not appear to affect intake by lambs.}, keywords = {alfalfa, alfalfa pellet, intake, lambs, shrubs, terpene}, author = {Richard E. Estell and E.L. Fredrickson and D.M. Anderson and M.D. Remmenga} } @proceedings {50540, title = {Geometric-Optical Modeling of Desert Grassland Canopy Structure with MISR}, year = {2005}, month = {October 17, 2005}, pages = {141-143}, address = {Bejing, China}, abstract = {A new method is described for the retrieval of fractional cover of large woody plants (shrubs) at the landscape scale using moderate resolution multiangle remote sensing data from the Multiangle Imaging SpectroRadiometer (MISR) and an hybrid geometric-optical (GO) canopy reflectance model. The major difficulty in applying such models in desert grasslands if the spatially dynamic nature of the combined soil and understory background reflectance. The best method found was multiple regression on the weights of a kernel-driven model and MISR nadir camera blue, green, and near infra-red bidrectional reflectance factors. The results of forward modeling for a 5.15 km2 area in the USDA, ARS Jornada Experimental Range (n=441) showed excellent agreement with the MISR data in both shape and magnitude. Inversion of the model allowed estimation of fractional shrub cover with an RMSE of 0.03.}, keywords = {MISR, remote, remote sensing, sensing, shrubs}, url = {/files/bibliography/05-051Proc.pdf}, author = {M. Chopping and J. V. Martonchik and A. Rango and Debra C. Peters and L. Su and Andrea S. Laliberte} } @article {50591, title = {Using historic data to assess effectiveness of shrub removal in southern New Mexico}, journal = {Journal of Arid Environments}, volume = {62}, number = {1}, year = {2005}, month = {July 1, 2005}, pages = {75-91}, abstract = {

In the late 1930{\textquoteright}s, the presence of a highly organized labor force, the Civilian Conservation Corps (CCC), in the Jornada Basin of southern New Mexico provided the capability for rangeland scientists to conduct experiments to determine the effectiveness of various techniques for remediating or reversing the encroachment of shrubs into grasslands. Unfortunately, soon after the treatments were performed, the CCC disbanded and most records of the treatments were lost. Despite sketchy documentation, some rangeland treatments left legacies on the landscape, and effects on water retention, erosion, and vegetation dynamics remained long after the CCC work ended. The discovery of historical documents from long-closed files and aerial photography in widely scattered archives allowed some of the experiments to be located and reexamined. Two research areas established in the mid-1930s were of particular interest, namely a tarbush (Flourensia cernua) site where shrubs were grubbed and quadrats established and a creosote (Larrea tridentata) site where both creosote and tarbush shrubs were grubbed. Here we outline how these sites were rediscovered, how historical measurements were repeated for the first time since the late l930s, and conclusions drawn regarding specific rangeland remediation strategies and vegetation dynamics. Our results show that shrub populations recovered from a radical removal treatment in less than 65 years. Remediation of these sites so that grass will recover to pre-shrub-dominated amounts will require measures additional to just removal of shrubs in order to restore hydrologic function. The fact that we were able to relocate, revisit, and resample these treatment areas provided unique opportunities to understand the long-term vegetation dynamics of these arid ecosystems. It is evident that woody plant populations have a high degree of resilience, that density dependence or interference appears to limit plant size in arid shrub communities, and that shrub populations had not reached any stable equilibrium state at the time of treatment in the 1930s. These insights would have been impossible to gain from short-term studies and without long-term studies initiated in the 1930s combined with recent discoveries of original documentation and historical aerial photography. http://authors.elsevier.com/sd/article/S0140196304002411

}, keywords = {aerial, grasslands, historical, photography, remediation, shrubs}, doi = {10.1016/j.jaridenv.2004.11.001}, url = {/files/bibliography/05-002.pdf}, author = {A. Rango and L. Huenneke and M. Buonopane and Jeffrey E. Herrick and Kris Havstad} } @conference {50967, title = {A method for analyzing active internal colonization of dark septate fungal endophytes in grasses and shrubs native to arid southwestern USA rangelands}, booktitle = {Third International Conference on Mycorrhizae}, year = {2001}, month = {July 8-13, 2001}, pages = {Abstract No. P1-68}, address = {Adelaide, Australia}, abstract = {Dominant native grasses and shrubs in arid southwestern USA rangelands are more extensively colonized by dark septate fungal endophytes (DSE) than by conventional mycorrhizal fungi. These endophytes are widespread colonizers in most ecosystems, but their ecological function is currently unresolved. They are readily observed as stained or melanized septate hyphae and microsclerotia on the root surface and in the cortex using fungus specific stains that bind to chitin, a common wall component. Roots of grasses and shrubs native to the northern Chihuahuan Desert were stained with sudan IV, specific for lipids, and analyzed with high magnification differential interference microscopy. Inconspicuous internal hyphal extensions of stained or pigmented hyphae were observed that were not visible using fungus specific stains. These structures were observed in a much greater frequency than the commonly recognized stained or pigmented structures in physiologically active roots. Differential responses to staining were attributed to structural differences and levels of chitin incorporation in the fungal wall. Internal hyphae varied in diameter, wall thickness, and visibility and in many cases were detectable only because of the positive staining of lipids in fungal vacuoles. Internal hyphae grew both inter and intracellularly within the cortex and sieve elements of the vascular cylinder and at time contained substantial quantities of lipids. This method promises to be effective for studying the extent, nature, and possible function of DSE fungi in native ecosystems.}, keywords = {analyzing, arid rangelands, dark septate, fungal endophytes, grasses, internal colonization, shrubs}, author = {J.R. Barrow and Aaltonen, R.E.} } @article {50988, title = {Root systems of some Chihuahuan Desert plants}, journal = {Journal of Arid Environments}, volume = {49}, number = {2}, year = {2001}, month = {October 1, 2001}, pages = {221-263}, abstract = {Root systems of 11 shrub or shrub-like species, 11 grass species, 19 perennial forb species and 4 annual forb species were excavated on the Jornada Experimental Range in the northern Chihuahuan Desert in southern New Mexico, USA. Maximum radial horizontal spread of shrub root systems usually occurred above calcic and petrocalcic horizons at depths above 1 m. .With one exception, all shrub species roots were traced through calcic and petrocalcic horizons to depths down to 5 m. Upward growing roots reaching very shallow depths (\< 10 cm) were common for most shrub species. Thus, the shrubs can readily access soil water and nutrients from both surface and deep soil horizons. Grass root systems on sandy soils extended radially up to 1.4 m, perhaps an adaptation to capture more soil water from the frequent small rainfall events. Grass roots did not extend through calcic or petrocalcic horizons and none penetrated deeper than 1.6 m. Perennial forb root systems varied in depth of branching but often penetrated into o through calcic and petrocalcic horizons and, like shrubs, have an advantage over grasses during droughts. Root systems of the annual forbs, excavated at the end of a season of above average precipitation, reached depths of 0.5 to 1.2 m. At each of the 18 excavation sites the roots of all the plant life forms were highly intermingled in the upper soil horizons, indicating that competition for water and soil nutrients is intense. It is believed that the plasticity and architecture of the shrub root systems, enabling them to compete with the grasses for soil water in the upper soil horizons and also access soil water at depths beyond the reach of grass roots, has been a major reason for the increase of shrubs during the historical period in this arid environment.}, keywords = {Chihuahuan Desert, competition, forbs, grasses, Jornada, root systems, shrubs, soil resources}, doi = {10.1006/jare.2000.0784}, url = {/files/bibliography/01-023.pdf}, author = {Gibbens, Robert P. and J.M. Lenz} } @article {51304, title = {Variation in Creosotebush (Larrea tridentata) canopy morphology in relation to habitat, soil fertility and associated annual plant communities}, journal = {American Midland Naturalist}, volume = {137}, year = {1997}, month = {1997}, pages = {13-26}, abstract = {

Differences in creosotebush (Larrea tridentata) crown morphology may reflect chances in relative demand for water vs. nutrient resources, coinciding with shrub growth and development. Creosotebushes with inverted, cone-shaped crowns were more abundant in water-limited environments; whereas, hemispherical-shaped creosotebushes were more abundant in less water-limited environments. Cone-shaped creosotebushes accumulated substantially less litter under their canopies than did creosotebushes with hemispherical-shaped crowns. Soil nutrient concentrations under conical shrubs were similar to those in intershrub spaces and both of these were less than soil nutrient concentrations under hemispherical shrubs. In ecosystems where overland flow of water exerted a greater influence on movement of organic litter than did wind, shrub shape had little effect on long-term litter accumulation. No persistent differences in the biomass or diversity of ephemeral taxa exploiting undershrub areas were found, probably because the positive effects of greater nutrient resources under hemispherical shrubs were offset by the limitations imposed by the larger, more dense canopies of hemispherical shrubs. Overall, creosotebush morphology affected litter accumulation patterns and soil nutrient patterns and must be considered when assessing the heterogeneity of desert ecosystems in the southwestern U.S.

}, keywords = {desert soils, deserts, nitrogen, Plant morphology, plants, shrubs, soil morphology, soil nutrients, Stems, Vegetation canopies}, doi = {10.2307/2426751 }, url = {/files/bibliography/510.pdf}, author = {A.G. de Soyza and Walter G. Whitford and E. Martinez-Meza and Justin Van Zee} } @article {51375, title = {Effects of plant size on photosynthesis and water relations in the desert shrub Prosopis glandulosa (Fabaceae)}, journal = {American Journal of Botany}, volume = {83}, number = {1}, year = {1996}, month = {1996}, pages = {99-105}, abstract = {

The Jornada del Muerto Basin of southern New Mexico has undergone a marked transition of plant communities. Shrubs now dominate areas that were previously dominated by perennial grasses. The replacement of grasses by shrubs requires an establishment phase where small shrubs must compete with similar-sized grass plants. This is followed by a phase in which established shrubs sequester nutrients and water within their biomass and alter soil resources under their canopy, creating {\textquotedblleft}islands{\textquotedblright} of fertility. We studied gas exchange and water relations of small and large shrubs growing in the Jornada del Muerto as a function of varying soil moistsure during the season. The small shrubs had greater net assimilation, stomatal conductance, transpiration, and xylem water potential than large shrubs following high summer rainfall in July and highest seasonal soil moisture. High rates of carbon assimilation and water use would be an advantage for small shrubs competing with grasses when shallow soil moisture was plentiful. Large shrubs had greater net assimilation and water-use efficiency and lower xylem water potential than small shrubs following a dry period in September when soil moisture was lowest. Low xylem water potentials and high water-use efficiency would allow large shrubs to continue acquiring and conserving water as soil moisture is depleted. Although the study provides evidence of differences in physiological responses of different-sized shrubs, there was not support for the hypothesis that small shrubs are more closely coupled to variation in soil moisture availability than large shrubs. Small shrubs may actually be less coupled to soil moisture than large shrubs and thus avoid conditions when continued transpiration could not be matched by equivalent water uptake.

}, keywords = {Atmospheric moisture, desert soils, deserts, grasses, plants, Rain, shrubs, soil depth, soil water, Water use efficiency}, doi = {10.2307/2445960}, url = {/files/bibliography/471.pdf}, author = {A.G. de Soyza and A. C. Franco and R. A. Virginia and J. F. Reynolds and Walter G. Whitford} } @article {51438, title = {Relationship of tarbush leaf surface secondary chemistry to livestock herbivory}, journal = {Journal of Range Management}, volume = {47}, year = {1994}, note = {Permission to post articles granted by the Society for Range Management; www.rangelands.org.}, month = {1994}, pages = {424-428}, abstract = {

Tarbush (Flourensia cernua DC.) is an abundant shrub native to the Chihuahuan desert. Limited use as a forage by ruminants has been observed. The objective of this studey was to eexamine the leaf surface chemistyr of tarbush inrelation to degree of use by ruminants. Mature tarbush leaves were collected on 2 sites during 2 periods approximately 2 weeks apart from plants exhibiting either high (\>45\%) or low (\<10\%) use when browsed by cattle, sheep, and goats confined to a small area (5 plants per use category for each site/period combination). A greater (P\<0.05) concentration of epicuticular wax was detected on the leaf surface of plants used to a lower degree. Epicuticular wax concentration was 8.2 and 10.3\% of the leaf dry matter for high and low used plants, repectively. Several leaf surface compounds were related to period, while site and degree of use were seldom related to individual mon- and sesquiterpenes measure in this study. Camphene and 10 unidentified compounds differed between periods (P 0.10). Two unidentified compounds were related to site (P \< 0.10) and 2 others were related to use (P\<.0.10). In summary, individual leaf surface compounds on tarbush do not appear to greatly affect degree of us of tarbush by livestock, but collectively ( based on epicuticular wax data), these compunds may influence the diet selected by browsing ruminants.

}, keywords = {Epicuticular wax, herbivores, Leaves, livestock, monoterpenes, Plant biochemistry, plants, shrubs, terpenes, terpenoids}, doi = {10.2307/4002991 }, url = {/files/bibliography/418.pdf}, author = {Richard E. Estell and E.L. Fredrickson and D.M. Anderson and W. Mueller and M.D. Remmenga} } @inbook {51829, title = {Seeding shrubs in the field}, booktitle = {Forage and Fuel Production from Salt-Affected Wasteland}, year = {1986}, month = {1986}, pages = {377-385}, publisher = {Elsevier Science Publisher}, organization = {Elsevier Science Publisher}, address = {Amsterdam, The Netherlands}, abstract = {

Production from degraded rangeland may be increased by sowing with shrubs. Before reseeding an area it should be established that a change in plant cover is desirable and that the terrain is suitable for seeding. Rainfall or water supply should be adequate to ensure survival of seeded species. It may be desirable to sow mixtures of species. Care should be taken in the preparation of the seed bed and in optimizing seeding rate, spacing and depth. Factors which may be important in ameliorating harsh environmental conditions include the use of mulches, water ponding and soil compaction.

}, keywords = {mulches, seeding methods, shrubs, temperature, water conservation}, url = {/files/bibliography/293.pdf}, author = {C.H. Herbel}, editor = {Barrett-Lennard, E.G. and Malcolm, C.V. and Stern, W.R. and Wilkins, S.M.} }