@article {JRN55392, title = {The consequences of climate change for dryland biogeochemistry}, journal = {New Phytologist}, year = {2022}, month = {6/15/2022}, abstract = {Drylands, which cover > 40\% of Earth{\textquoteright}s terrestrial surface, are dominant drivers of global biogeochemical cycling and home to more than one third of the global human population. Climate projections predict warming, drought frequency and severity, and evaporative demand will increase in drylands at faster rates than global means. As a consequence of extreme temperatures and high biological dependency on limited water availability, drylands are predicted to be exceptionally sensitive to climate change and, indeed, significant climate impacts are already being observed. However, our understanding and ability to forecast climate change effects on dryland biogeochemistry and ecosystem functions lag behind many mesic systems. To improve our capacity to forecast ecosystem change, we propose focusing on the controls and consequences of two key characteristics affecting dryland biogeochemistry: (1) high spatial and temporal heterogeneity in environmental conditions and (2) generalized resource scarcity. In addition to climate change, drylands are experiencing accelerating land-use change. Building our understanding of dryland biogeochemistry in both intact and disturbed systems will better equip us to address the interacting effects of climate change and landscape degradation. Responding to these challenges will require a diverse, globally distributed and interdisciplinary community of dryland experts united towards better understanding these vast and important ecosystems.}, keywords = {arid lands, global change, islands of fertility, multiple resource limitation, restoration}, doi = {10.1111/nph.18312}, url = {files/bibliography/22-019.pdf}, author = {Brooke B. Osborne and Brandon T Bestelmeyer and Courtney M. Currier and Peter M. Homyak and Heather L. Throop and Kristina Young and Sasha C. Reed} } @article {JRN55042, title = {The interactive role of wind and water in functioning of drylands: what does the future hold?}, journal = {BioScience}, volume = {68}, year = {2018}, month = {09/2018}, pages = {670-677}, chapter = {670}, abstract = {

Feedback mechanisms between abiotic and biotic processes in dryland ecosystems lead to a strong sensitivity to interannual variations in climate. Under a future regime of higher temperatures but potentially increased rainfall variability, drylands are anticipated to experience changes in wind and water transport that will alter plant community composition and feedback on landscape connectivity. Here, we present a conceptual framework for understanding the coupling of vegetation productivity, aeolian transport, and hydrologic connectivity under anticipated changes in future climate, which suggests that a more extreme climatic regime will lead to more connected landscapes with attendant losses in soil, nutrient, and water resources. When enhanced connectivity triggers state changes, irreversible changes in ecosystem functioning can occur, with implications for the future of global drylands.

}, keywords = {aeolian, connectivity, deserts, precipitation, runoff, wind erosion}, doi = {10.1093/biosci/biy067 }, url = {files/bibliography/JRN55042.pdf}, author = {Gregory S. Okin and O. E. Sala and Enrique Vivoni and J. Zhang and Abinash Bhattachan} } @article {JRN54144, title = {Connectivity in dryland landscapes: shifting concepts of spatial interactions}, journal = {Frontiers in Ecology and the Environment}, volume = {13}, year = {2015}, month = {02/2015}, pages = {20-27}, chapter = {20}, abstract = {

Dryland ecosystems are often characterized by patchy vegetation and exposed soil. This structure enhances transport of soil resources and seeds through the landscape (primarily by wind and water, but also by animals), thus emphasizing the importance of connectivity {\textendash} given its relation to the flow of these materials {\textendash} as a component of dryland ecosystem function. We argue that, as with the fertile-islands conceptual model before it, the concept of connectivity explains many phenomena observed in drylands. Further, it serves as an organizing principle to understand dryland structure and function at scales from individual plants to entire landscapes. The concept of connectivity also helps to organize thinking about interactions among processes occurring at different scales, such as when processes at one scale are overridden by processes at another. In these cases, we suggest that state change occurs when fine-scale processes fail to adjust to new external conditions through resource use or redistribution at the finer scale. The connectivity framework has practical implications for land management, especially with respect to decision making concerning the scale and location of agricultural production or habitat restoration in the world{\textquoteright}s drylands.

}, keywords = {conceptual model, dryland landscapes, landscape connectivity, soil transport, spatial interactions, state changes}, doi = {10.1890/140163}, url = {/files/bibliography/15-003.pdf}, author = {Gregory S. Okin and Moreno-de las Heras, Mariano and Patricia M. Saco and Heather L. Throop and Enrique Vivoni and A.J. Parsons and John Wainwright and Debra C. Peters} } @article {JRN54394, title = {Hyperspectral surface reflectance data detect low moisture status of pecan orchards during flood irrigation }, journal = {Journal of the American Society for Horticultural Science}, volume = {140}, year = {2015}, month = {09/2015}, pages = {449-458}, chapter = {449}, abstract = {

For large fields, remote sensing might permit plant low moisture status to be detected early, and this may improve drought detection and monitoring. The objective of this study was to determine whether canopy and soil surface reflectance data derived from a handheld spectroradiometer can detect moisture status assessed using midday stem water potential (csmd) in pecan (Carya illinoinensis) during cyclic flood irrigations. We conducted the study simultaneously on two mature pecan orchards, a sandy loam (La Mancha) and a clay loam (Leyendecker) soil. We were particularly interested in detecting moisture status in the L0.90 to L1.5 MPa csmd range because our previous studies indicated this was the critical range for irrigating pecan. Midday stem water potential, photosynthesis (A) and canopy and soil surface reflectance measurements were taken over the course of irrigation dry-down cycles at csmd levels of L0.40 to L0.85 MPa (well watered) and L0.9 to L1.5 MPa (water deficit). The decline in A averaged 34\% in La Mancha and 25\% in Leyendecker orchard when csmd ranged from L0.9 to L1.5 MPa. Average canopy surface reflectance of well-watered trees (csmd L0.4 to L0.85 MPa) was significantly higher than the same trees experiencing water deficits (csmd L0.9 to L1.5 MPa) within the 350- to 2500-nm bands range. Conversely, soil surface reflectance of well-watered trees was lower than water deficit overall bands. At both orchards, coefficiet of determinations between csmd and all soil and canopy bands and surface reflectance indices were less than 0.62. But discriminant analysis models derived from combining soil and canopy reflectance data of well-watered and water-deficit trees had high classification accuracy (overall and cross-validation classification accuracy \>80\%). A discriminant model that included triangular vegetation index (TVI), photochemical reflectance index (PRI), and normalized soil moisture index (NSMI) had 85\% overall accuracy and 82\% cross-validation accuracy at La Mancha orchard. At Leyendecker, either a discriminant model weighted with two soil bands (690 and 2430 nm) or a discriminant model that used PRI and soil band 2430 nm had an overall classification and cross-validation accuracy of 99\%. In summary, the results presented here suggest that canopy and soil hyperspectral data derived from a handheld spectroradiometer hold promise for discerning the csmd of pecan orchards subjected to flood irrigation.

}, url = {/files/bibliography/15-020.pdf}, author = {Othman, Yahia and Caitriana Steele and D. VanLeeuwen and St. Hilaire, Rolston} } @conference {JRN53988, title = {Surface water and shallow groundwater interactions in semiarid agro-ecosystems of western USA}, booktitle = {EGU General Assembly 2014}, year = {2014}, month = {04/2014}, publisher = {European Geosciences Union}, organization = {European Geosciences Union}, address = {Vienna, Austria}, abstract = {

Surface water and groundwater interactions in agro-ecosystems of semiarid regions can translate into multiple hydrological benefits including aquifer recharge, temporary storage, and delayed return flow. Our ongoing research effort aimed to better understand surface water and shallow groundwater interactions and their contribution to aquifer recharge and stream flow is being conducted in five relatively narrow floodplains in the semiarid western United States. Over the last several years, we have monitored multiple hydrologic parameters in three flood irrigated valleys of northern New Mexico. This year we are monitoring two sprinkler-irrigated floodplain valleys in semiarid landscapes of eastern Oregon. At all locations, we measure multiple hydrologic parameters including irrigation diversions, soil moisture, shallow groundwater fluctuations, and weather variables. Data collected are being used to quantify different water budget components such as deep percolation, waterway seepage, evapotranspiration, and aquifer recharge. Results from one of our study sites in New Mexico showed that on average, canal seepage was 12\%, and deep percolation ranged from 9 to 32\% out of total canal inflow during the irrigation season. Also, shallow aquifer recharge ranged from 1044 to 1350 mm yr-1 during a 3-year evaluation period. At a second study site, canal seepage was 59\% and deep percolation averaged 30\% of total water diverted. Timing and magnitude of surface water and shallow groundwater interactions is also being evaluated. Results show that replenishment of the shallow aquifer follows a seasonal pattern, driven primarily by canal seepage and irrigation percolation contributions. At one of our study sites, each year the water table reaches a peak of up to 0.8 m within three to five weeks after the onset of irrigation; this increase in water table levels is maintained throughout most of the irrigation season that ends in October. After the end of irrigation season, in the winter time, the river acts as a drain and the water table drops to baseline levels. This is similar to the other two study sites being evaluated in New Mexico. For the two study sites in Oregon, because of the use of the use of less-water application systems we expect to see a more muted response regarding water table response to irrigation percolation inputs. Results from this research effort enhance understanding of surface water and groundwater interactions and the role that irrigation plays in providing soil and aquifer recharge in agro-ecosystems of arid and semiarid environments.

}, author = {Carlos Ochoa and Guldan, Steve and Alexander Fernald and Tidwell, Vince and Emile H. Elias and Gutierrez, Karina and Borman, Mike} } @proceedings {JRN54044, title = {The southern Kalahari as a dust source: preliminary results from the field}, year = {2014}, month = {07/2014}, pages = {p. 326}, publisher = {International Society of Aeolian Research (ISAR)}, address = {Lanzhou, China}, abstract = {

The Kalahari encompasses one of the largest drylands in the Southern Hemisphere and it is a potentially large source of atmospheric dust in its relatively low-dust region.\  The severe iron depletion in the southern Indian and Atlantic Oceans, the ocean basins that receive much of the Kalahari dust, suggests that even incremental increases in dust export to these basins could have significant impact on ocean productivity. The Kalahari also provides an excellent \“natural laboratory\”, due to its consistent Kalahari Sands existing along a strong precipitation gradient (from ~850 mm in southern Zambia to ~150 mm in southwestern Botswana) with a range of different land uses and land use intensities. A large-scale field campaign to evaluate the potential of the southern Kalahari to produce atmospheric dust was established in August, 2013. The goal of the experiment is to evaluate the potential of climate change and land-use to contribute to dust production. The experiment includes measurement of horizontal flux, vegetation structure, and meteorological variables. Novel estimates were made of dust production efficiency (vertical flux produced per unit of horizontal flux) through the coordinated use of active aerosol samplers and passive horizontal sediment traps.\  In addition, a new stereophotographic method using an unmanned aerial vehicles for the estimation of wind-relevant vegetation parameters has been developed for this project. Our preliminary field data and modeling results indicate that land use and climate can have a significant impact on the potential for dust emission from the region, but new field estimates of dust emission efficiency suggest that the absolute magnitude of dust emitted from the region might, at present, be lower than previously thought.

}, author = {Gregory S. Okin and Nicholas Webb and Abinash Bhattachan and Dintwe, Kebonye and Paolo D{\textquoteright}Odorico} } @article {49895, title = {Relationship between plant lipid bodies and fungal endophytes}, journal = {Terra Latinoamerica}, volume = {30}, year = {2012}, month = {03/01/2012}, pages = {39-45}, chapter = {39}, abstract = {Lipid bodies are universal components of plant cells and provide a mobilized carbon source for essential biological processes.\  Plant oils harvested for food and fuel often reside in these lipid bodies.\  Plants also host diverse populations of endophytic fungi, which easily escape microscopic detection.\  This study reviews data from previous surveys of endophyte distribution in native plants to specifically examine the physical association between endophytic fungi and plant lipid bodies.\  Plant tissues stained with trypan blue and sudan IV prior to differential interference contrast microscopy revealed lipid bodies tightly associated with fungal hyphae and with trypan blue stained fungal networks.\  The abundance of endophyte-associated lipids in healthy plant tissues suggests endophyte involvement in carbon (oil) metabolism and transport.\  More research, particularly at the molecular level, is merited to assess the significance of this plant feature which is conserved in grasses and shrubs.\  Exploring the interfaces where plant cells and endophyte cells exchange organic carbon using modern imaging, molecular and genomic analysis could transform current understanding of plant carbon metabolism.}, keywords = {arid zones, biofuel, endophyte, fungi, stress resistance}, url = {/files/bibliography/12-011.pdf}, author = {P. Osuna-Avila and J.R. Barrow and M.E. Lucero and Aaltonen, R.E.} } @article {49967, title = {Dust: small-scale processes with global consequences}, journal = {EOS Transactions, American Geophysical Union}, volume = {92}, year = {2011}, pages = {241-243}, abstract = {

[1] Desert dust, both modern and ancient, is a critical component of the Earth system. Atmospheric dust has important effects on climate by changing the atmospheric radiation budget, while deposited dust influences biogeochemical cycles in the oceans and on land. Dust deposited on snow and ice decreases its albedo, allowing more light to be trapped at the surface, thus increasing the rate of melt and influencing energy budgets and river discharge. In the human realm, dust contributes to the transport of allergens and pathogens and when inhaled can cause or aggravate respiratory diseases. Dust storms also represent a significant hazard to road and air travel. Because it affects so many Earth processes, dust is studied from a variety of perspectives and at multiple scales, with various disciplines examining emissions for different purposes using disparate strategies. Thus, the range of objectives in studying dust, as well as experimental approaches and results, has not yet been systematically integrated. Key research questions surrounding the production and sources of dust could benefit from improved collaboration among different research communities. These questions involve the origins of dust, factors that influence dust production and emission, and methods through which dust can be monitored.

}, keywords = {desert dust, dust emissions, remote sensing, small-scale processes}, doi = {10.1029/2011EO290001 }, url = {files/bibliography/JRN00562.pdf}, author = {Gregory S. Okin and Joanna E. Bullard and Reynolds, R. L. and Ballantine, J.-A. C. and Schepanski, K. and Todd, M. C. and Jayne Belnap and Matthew C. Baddock and Thomas E. Gill and M. Miller} } @article {49968, title = {Impacts of atmospheric nutrient deposition on marine productivity: Roles of nitrogen, phosphorus, and iron}, journal = {Global Biogeochemical Cycles}, volume = {25}, year = {2011}, pages = {GB2022}, keywords = {atmospheric deposition, iron, marine productivity, nitrogen, nutrient deposition, phosphorus}, author = {Gregory S. Okin and Baker, A. R. and Tegen, I. and Mahowald, N. M. and Dentener, F. J. and Duce, R. A. and Galloway, J. N. and Hunter, K. A. and Kanakidou, M. and Kubilay, N. and Prospero, J. M. and Sarin, M. M. and Surapipith, V. and Uematsu, M. and Zhuo, T.} } @article {50052, title = {The contribution of brown vegetation to vegetation dynamics}, journal = {Ecology}, volume = {91}, year = {2010}, pages = {743-755}, chapter = {743}, abstract = {

Indices of vegetation dynamics that include both green vegetation (GV) and non-photosynthetic vegetation (NPV), that is, brown vegetation, were applied to MODIS surface reflectance data from 2000 to 2006 for the southwestern United States. These indices reveal that the cover of NPV, a measure of vegetation brownness and a component of ecosystems worldwide, is highly variable in both space and time in the study region. In the more mesic regions of the study area, the timing of peaks in NPV appears to result from simple senescence of GV at the end of the growing season. In these regions, the amplitude of GV cyclicity dominates the total vegetation signal. In contrast, in arid and semiarid regions, the amplitude of cyclicity of NPV dominates the total vegetation signal, showing the vegetation of these regions to be unexpectedly dynamic. Shrublands of southwestern United States exhibit temporal behavior in which the annual peak in NPV cover precedes the annual peak in GV cover by a few months. Several explanations for this behavior are offered. This study shows the importance of vegetation indices that include NPV, or vegetation brownness, in understanding terrestrial ecosystem dynamics, as well as the response to change for these ecosystems.

}, keywords = {deserts, grasslands, green photosynthetic, non photosynthetic, phenology remote sensing, savannas, shrublands, stress vegetation dynamics, vegetation, woodlands}, doi = {10.1890/09-0302.1}, url = {/files/bibliography/10-051.pdf}, author = {Gregory S. Okin} } @article {50126, title = {Do changes in connectivity explain desertification?}, journal = {BioScience}, volume = {59}, number = {3}, year = {2009}, month = {March 2009}, pages = {237-244}, abstract = {Desertification, broad-scale land degradation in drylands, is a major environmental hazard facing inhabitants of the world{\textquoteright}s deserts as well as an important component of global change. There is no unifying framework that simply and effectively explains different forms of desertification. Here we argue for the unifying concept that diverse forms of desertification, and its remediation, are driven by changes in the length of connected pathways for the movement of fire, water and soil resources. Biophysical feedbacks exist that increase the length of connected pathways explaining the persistence of desertified landscapes around the globe. Management of connectivity in the context of environmental and socioeconomic change is essential to understand, and potentially reverse, the harmful effects of desertification.Desertification, broad-scale land degradation in drylands, is a major environmental hazard facing inhabitants of the world{\textquoteright}s deserts as well as an important component of global change. There is no unifying framework that simply and effectively explains different forms of desertification. Here we argue for the unifying concept that diverse forms of desertification, and its remediation, are driven by changes in the length of connected pathways for the movement of fire, water and soil resources. Biophysical feedbacks exist that increase the length of connected pathways explaining the persistence of desertified landscapes around the globe. Management of connectivity in the context of environmental and socioeconomic change is essential to understand, and potentially reverse, the harmful effects of desertification.}, keywords = {connectivity, desertifiction, erosion, fire, vegetation dynamics}, url = {/files/bibliography/09-007.pdf}, author = {Gregory S. Okin and A.J. Parsons and John Wainwright and Jeffrey E. Herrick and Brandon T Bestelmeyer and Debra C. Peters and E.L. Fredrickson} } @article {50127, title = {Mountain Snow Equals River Flow}, volume = {Spring}, year = {2009}, month = {2009}, pages = {22-23}, publisher = {New Mexico State University}, abstract = {Research use $15 million EPSCoR grant to track impact of climate change on water supplies (Rango)}, url = {http://researchmag.nmsu.edu/2009_SP/feature_mountain.html}, author = {Olmsted, A.} } @article {50249, title = {A multi-source portable light emiting diode spectrofluorometer}, journal = {Applied Speactroscopy}, volume = {62}, year = {2008}, month = {March 1, 2008}, pages = {327-332}, abstract = { A portable luminescence spectrofluorometer weighing only 1.5 kg that uses multiple light emitting diodes (LEDs) as excitation sources was developed and evaluated. Excitation using a sequence of seven individual broad-band LED emission sources enabled the generation of excitation-emission spectra using a light weight (\<1.5 kg) spectrometer. Limits of detection for rhodamine 6G, rhodamine B and fluorescein were 2.9, 3.2, and 11.0 nM, respectively. Generation of excitation-emission matrices (EEMs) enabled the analysis of samples containing mixtures of rhodamine B and fluorescein. Buffered saline plant and animal feed extracts were also analyzed using this instrument. These samples included the woody plants Pistacia lentiscus (Evergreen pistache or Mastic) and Philyria latifolia, and the herbaceous species Medicago sativa (alfalfa), Trifolium spp. (clover), and a feed concentrate. Application of multi-way principal component analysis (MPCA) to the resulting three-dimensional data sets enabled discernment among these various diet constituents.}, keywords = {LED, spectrofluorometer}, url = {/files/bibliography/08-006.pdf}, author = {S. Obeidat and B. Bai and G.D. Rayson and D.M. Anderson and Puscheck, A.D. and Landau, S.Y. and Glasser, T.} } @conference {50250, title = {Feedbacks between aeolian processes, vegetation productivity, and nutrient flux in deserts}, booktitle = {Geological Society of America Meetings}, series = {Geological Society of America Meetings}, year = {2008}, abstract = {Wind is a key abiotic factor that influences the dynamics of arid and semiarid systems. A series of experiments and models will be presented that show the important feedbacks that exist between Aeolian processes and biotic process in deserts. Wind impacts vegetation by both changing the composition of the soils, mainly by winnowing fines from erosional areas and redeposition of fines in deposition areas, and by direct physical effects on plants. The former leads to significant loss and redistribution of soil organic matter and plant nutrients as well as the disruption of nutrient cycling process. The latter leads to burial, pedestaling, leaf stripping and branch abrasion that lead to increased plant mortality. There is significant evidence that this leads to state changes in deserts, namely replacement of grasses by shrubs, which in turn create landscapes that are far larger emitters of dust. Changes in aridity have, in the past, caused changes variations in dust emission associated with vegetation state changes and, models suggest, aeolian processes will be increasingly important in vegetation change and dust emissions in deserts.}, keywords = {abstract, aeolian, arid, biotic, semiarid, wind}, author = {Gregory S. Okin and Junran Li and Lorelei Alvarez and Debra C. Peters and Paolo D{\textquoteright}Odorico} } @article {50251, title = {Spatial patterns of soil nutrients in two southern African savannas}, journal = {Journal of Geophysical Research - Biogeosciences}, volume = {113}, year = {2008}, pages = {G02011}, doi = {10.1029/2007JG000584}, author = {Gregory S. Okin and Mladenov, N. and L. Wang and Cassel, D. and Caylor, K. K. and Ringrose, S. and Stephen A. Macko} } @article {50365, title = {Application of multi-way data analysis on excitation-emission spectra for plant identification}, journal = {Talanta}, volume = {72}, year = {2007}, month = {April 1, 2007}, pages = {682-690}, abstract = {The ability to distinguish among diets fed to Damascus goats using excitation-emission luminescence spectra was investigated. These diets consisted of Medicago sativa L. (Alfalfa), Trifolium spp (Clover), Pistacia lentiscus (P.lentiscus), Phyllirea latifolia (P.latifolia), and Pinus brutia (P. brutia). The three dimensional luminescence response surface from phosphate buffered saline extracts of each material was analyzed using muti-way analysis chemometric tools (MPCA) and parallel factor analysis (PARAFAC). Using three principle components, the spectra from each diet component was distinguished. Additionally, fecal samples from goats fed diets of either alfalfa or clover hays were investigated. The application of MPCA and PARAFAC to these samples using models derived from the pre-digested diet materials was strongly suggestive of the utility of similarly derive training samples for the elucidation of botanical diet composition for animals.}, keywords = {luminescence spectroscopy, multi-way principal component analysis (MPCA), parallell factor analysis (PARAFAC), phosphate buffered saline plant extracts}, url = {/files/bibliography/07-007.pdf}, author = {S. Obeidat and G.D. Rayson and D.M. Anderson and Landau, S.Y. and Glasser, T.} } @article {50480, title = {Multiscale controls on and consequences of aeolian processes in landscape change in arid and semi-arid environments}, journal = {Journal of Arid Environments}, volume = {65}, year = {2006}, month = {April 1, 2006}, pages = {253-275}, abstract = {Aeolian processes are tightly linked to soil and vegetation change in deserts at multiple spatial and temporal scales. Wind influences patterns of vegetation and soil within the landscape, while these patterns control wind erosion at patch to landscape scales. Aggregated at larger scales, patterns in soil and vegetation distributions influence global distributions of dust and its biogeochemical impacts. Understanding the controls on aeolian processes is, therefore, important not only in understanding the biogeochemistry and land cover patterns in dryland environments but also in understanding global land cover, climate, and biogeochemistry. These relationships are poorly understood, particularly for structurally complex plant communities such as shrub-invaded grasslands. The objective of this paper is to review the controls on aeolian processes and their consequences at plant-interspace, patch-landscape, and regional-global scales. Based on this review, we define the requirements for a cross-scale model of wind erosion in structurally complex arid and semi-arid ecosystems. http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6WH9-4H1004J-1-1N\&_cdi=6845\&_user=1496926\&_orig=browse\&_coverDate=04\%2F30\%2F2006\&_sk=999349997\&view=c\&wchp=dGLbVtb-zSkWA\&md5=e74666463d89e6fd5315d4fde2958934\&ie=/sdarticle.pdf}, keywords = {aeolian processes, desertification, dust emission, landscape change, wind erosion}, url = {/files/bibliography/06-010.pdf}, author = {Gregory S. Okin and D. E. Gillette and Jeffrey E. Herrick} } @proceedings {50586, title = {Soil microorganisms and their importance in plant establishment and growth}, year = {2005}, month = {April 20-23, 200}, address = {Zacatecas, Mexico}, abstract = {Shrubs and grasses of the Chihuahuan Desert are more extensively colonized by atypical dark septate endophytes (DSE) than by common mycorrhizal fungi. DSE fungi are identified as stained or dark hyphae and microesclorotia in the root cortex by utilizing traditional trypan blue staining. Staining with Sudan IV, DSE fungi reveals lipid bodies attached to fungal structures indicating a higher incidence of fungal colonization that than previously observed. These fungi are intrinsically integrated with all the cells of the native and regenerated BOER plants. The transfer of fungi from BOER or SPCR calluses to nonhost plants indicated remarkable changes in root morphology and shoots biomass, chlorophyll content, and fruit and seed production. This study shows that plant-associated microbes can influence plant health and promote establishment and growth in different ecosystems.}, keywords = {Mycorrhizal fungi, plant establishment, plant growth, soil microorganisms}, author = {P. Osuna-Avila and J.R. Barrow} } @inbook {50696, title = {Modelling wind erosion and dust emission on vegetated surfaces}, booktitle = {Spatial Modeling of the Terrestrial Environment}, year = {2004}, note = {//USDA//LTER IV// Listed in LTER IV 2004 annual report}, month = {2004}, pages = {137-156 pp}, publisher = {Wiley, and Sons, Ltd}, organization = {Wiley, and Sons, Ltd}, abstract = {

Summary

This chapter contains sections titled:

}, keywords = {book, books, chapter, chapters, model, dust emission, model, wind erosion, report, reports, wind erosion, dust emission, wind erosion, modelling}, doi = {10.1002/0470094001.ch7}, author = {Gregory S. Okin and D. E. Gillette}, editor = {R. Kelly and Drake, N. A. and Barr, S. L. eds.} } @conference {50697, title = {Regeneration of black grama (Bouteloua eriopoda Torr. Torr) plants via somatic embryogenesis and the internal colonization of endophytic fungi}, booktitle = {2004 World Congress on In Vitro Biology}, year = {2004}, month = {May 2004}, address = {San Francisco, CA}, abstract = {Black grama (Bouteloua eriopoda) is an important forage grass in southwestern USA rangelands. Plants were regenerated by somatic embryogenesis. Surface disinfested seeds were germinated and the embryonic shoots were excised and cultured on Murashige and Skoog (MS) medium gelled with agar. Callus was induced from apical meristems. Calluses were cultured on MS solid medium with six concentrations of 2,4, D (2,4-dichlorophenoxyacetic acid) or Dicamba (6-dichloro-o-anisic acid) for 6 weeks under light or dark conditions. Somatic embryo induction was greatest on 4.52 um Dicamba, under light, after transferring to an auxin- free medium. Embryo development progressed from globular, torpedo to mature embryos phenotypically identical to those naturally produced in seed that developed into intact plants and were established in soil and grown to maturity. Two fungal species, Aspergillus ustus and Puccinia cacabata consistently associated with native populations were also found to be intimately integrated with meristematic mother cells from germinating seedlings and were associated with cells, tissues and regenerated plants. Fungi form protective biofilms on cells and tissues in culture and on root and leaf surfaces of regenerated and native plants. The ecological role of these endophytes is to protect plant surfaces from hostile external environmental conditions.}, keywords = {black grama}, author = {P. Osuna and J.R. Barrow} } @article {50698, title = {Regeneration of black grama (Bouteloua eriopoda Torr. Torr) plants via somatic embryogenesis}, journal = {In Vitro Cellular and Developmental Biology - Plant}, volume = {40}, year = {2004}, month = {May 1, 2004}, pages = {299-302}, abstract = {Seeds of Bouteloua eropida, (Torr.) Torr. were surface disinfested and germinated on a carbon mineral rich medium. Callus was initiated from embryonic shoots excised from the roots on auxin supplemented medium. After callus multiplication, embryos were induced from callus. They developed into normal embryos and caryopses that subsequently developed into intact plants. Regenerated plants were transplanted into soil and grown in the growth chamber. The utilization of regenerated plants for plant-fungus associations is discussed.}, keywords = {black grama, Bouteloua eriopoda, regeneration, somatic embryogenesis}, url = {/files/bibliography/04-009.pdf}, author = {P. Osuna and J.R. Barrow} } @conference {50802, title = {Black grama grass under the microscope; anatomical festures of a native palnt from southwestern United States}, booktitle = {Microscopy and Microanalysis}, volume = {9}, number = {2}, year = {2003}, month = {2003}, pages = {1348-1349}, abstract = {Black grama grass (Bouteloua eriopoda) is a perennial desert grass native to the arid Southwestern United States. It is most common in the Chihuahuan Desert, occupying large areas of New Mexico and Arizona, where occurrence of drought conditions are high. Black grama tends to grow in sandy loam soils low in organic matter. However, it contains one of the highest protein contents of any desert grass, thus offering very nutritious forage for livestock and wildlife. Due to its bunchgrass-like nature, black grama aids in reducing soil erosion from rainfall. Some drought tolerance adaptive features include a root system that extends four or more feet into the soil and a small leaf blade size (2mm wide). Unfortunately, abundance of black grama is being greatly reduced by factors such as overgrazing and invasion of Honey mesquite plants. Due to the importance of black grama grass and its easily observable adaptive features, we investigated its cellular structures to find more specialized components of this plant that allow it to survive in drought conditions.}, keywords = {Arizona, black grama, grass, native, New Mexico}, url = {/files/bibliography/03-040.pdf}, author = {O{\textquoteright}Donnell, B. and Kersey, S. and Gallegos, L. and J.R. Barrow and Ghoshroy, S.} } @article {50920, title = {Desert dogma revisited: coupling of stomatal conductance and photosynthesis in the desert shrub, Larrea tridentata}, journal = {Plant, Cell and Environment}, volume = {25}, year = {2002}, note = {//NMSU//LTER IV//}, month = {2002}, pages = {909-921}, abstract = {The success of the desert shrub Larrea tridentata (creosotebush) has been largely attributed to temperature acclimation and stomatal control of photosynthesis (A) under drought stress. However, there is a paucity of field data on these relationships. To address this void, we conducted a joint field and modeling study that encompassed a diverse set of environmental conditions. At a Larrea-dominated site in southern New Mexico we manipulated soil moisture during the growing season over a 2-year period and measured plant pre-dawn water potential ({\O}pd), stomatal conductance (g) and A of individual shrubs. We used these data to develop a semi-mechanistic photosynthesis model (A-Season) that explicitly couples internal CO2 (Ci) and g. Vapor pressure deficit (VPD) and {\O}pd affect instantaneous g in a manner that is consistent with a biophysical model of stomatal regulation of leaf water potential. Ci is modeled as a function of g, derived from a simplification of a typical A-Ci curve. After incorporating the effects of growing temperature on stomatal behavior, the model was able to capture the large diurnal fluctuations in A, g and Ci and the observed hysteresis in g versus Ci dynamics. Our field data and application of the A-Season model suggest that dogma attributed to Larrea{\textquoteright}s success is supported with regard to stomatal responses to VPD and {\O}pd but not for mechanisms of temperature acclimation and CO2 demand.}, keywords = {article, articles, journal, journals, Larrea, evapotranspiration, Larrea, photosynthesis, Larrea, transpiration, Larrea,gas-exchange, model, A-Season, model, Ball-Berry, model, Larrea, model, Leuning, model, Pitman, photosynthesis, Larrea, physiology, Larrea}, author = {Ogle, K. and J. F. Reynolds} } @mastersthesis {50921, title = {The development of an in vitro system to determine the role of endophytic fungus (Aspergillus ustus) on Daucus carota roots}, year = {2002}, note = {//NONE//LTER IV//ProCite field[12]: Not in File (11/08/2005)}, month = {2002}, pages = {134}, school = {New Mexico State University}, type = {Ph.D. Dissertationpp}, address = {Las Cruces, New Mexico}, keywords = {dissertation, fungi, Aspergillus, fungi, endophytic, thesis}, author = {P. Osuna-Avila} } @article {51027, title = {Degradation of sandy arid shrubland environments: observations, process modelling, and management implications}, journal = {Journal of Arid Environments}, volume = {47}, year = {2001}, note = {//USDA//LTER IV// In file and Updated 12/15/2005}, month = {2001}, pages = {123-144}, abstract = {

Field remote sensing, and modelling observations from a degraded Mojave Desert shrubland were used to develop a model of the progressive degradation of areas adjacent to sites of direct anthropogenic disturbance. Aeolian removal and transport and dust, sand, and litter are the primary mechanisms of degradation, killing plants by burial and abrasion, interrupting natural processes of nutrient accumulation, and allowing the loss of soil resources by abiotic transport. It is concluded that any arid shrubland with wind-erodible soils is susceptible to degradation, and where possible development of these lands should be avoided.

}, keywords = {agriculture, article, articles, desertification, journal, journals, landscape, ecosystem dynamics, management, shrublands, model, process, Mojave Desert, paleolakes, shrubland, degradation, shrublands, wind erosion}, doi = {10.1006/jare.2000.0711}, url = {files/bibliography/JRN00324.pdf}, author = {Gregory S. Okin and Murray Bruce and W. H. Schlesinger} } @inbook {51026, title = {Desertification in an arid shrubland in the southwestern United States}, booktitle = {Land Degradation}, year = {2001}, note = {//NMSU,USDA//LTER IV//ProCite field[6]: In}, month = {2001}, pages = {53-70}, publisher = {Kluwer Academic Publishers}, organization = {Kluwer Academic Publishers}, address = {Dordrecht}, abstract = {

In the Mojave Desert of the southwestern U.S. human destruction of soil crusts and removal of vegetation have led to progressive, expanding degradation of adjacent arid shrublands. Aeolian mobilisation of dust, sand and litter triggered by anthropogenic disturbance contributes to the destruction of islands of fertility in adjacent areas by killing shrubs through burial and abrasion. This interrupts nutrient-accumulation processes and allows the loss of soil resources by abiotic transport. Thus the processes of degradation spread across the landscape driven largely by abiotic processes.

Soil chemical analyses and remote sensing observations presented here are designed to test a model hypothesis of degradation of arid shrublands. Nutrient and non-nutrient chemical species in the soil act as tracers of material transport and provide clues as to the nature of progressive anthropogenic degradation in arid shrublands. Remote sensing yields information about short- and long-term effects on the landscape as well as important constraints on the magnitude of degradation. Field, chemical and remote sensing observations argue for an extension of recent definitions and models of desertification to include the loss of islands of fertility in established shrublands. This extended model places arid shrublands in a continuum of physical and ecological processes and ecosystems that links semiarid grasslands with Sahara-like hyperarid barren lands.

}, keywords = {book, books, chapter, chapters, desertification, shrubland, Model Hypothesis, Mojave Desert, report, reports, Semiarid Grassland, shrubland, desertification, soil crust, wind erosion}, doi = {10.1007/978-94-017-2033-5_4}, url = {files/bibliography/JRN00325.pdf}, author = {Gregory S. Okin and Murray, B. and W. H. Schlesinger}, editor = {Conacher, A. J. ed.} } @article {51025, title = {Distribution of vegetation in wind-dominated landscapes: implications for wind erosion modeling and landscape processes}, journal = {Journal of Geophysical Research}, volume = {106}, year = {2001}, note = {//USDA//LTER IV//}, month = {2001}, pages = {9673-9684}, abstract = {

Dust emission and wind erosion from arid and semiarid environments provide a major source of global atmospheric aerosols. Well-known relations between wind stress and saltation sand flux for sand sheets and relations between sand flux and dust emission by sandblasting have enabled construction of dust models that have only been partly successful in predicting atmospheric mineral dust concentrations. Most models of wind erosion assume that vegetation is evenly distributed. Through the use of field, Fourier transform, and semivariogram analysis, we show that mesquite dunelands in the Chihuahuan Desert of southern New Mexico, United States, have anisotropic shrub distributions. Elongated areas of bare soil, {\textquotedblleft}streets,{\textquotedblright} which are aligned with the prevailing winds may partially explain discrepancies between observed and predicted atmospheric dust concentrations. Soils in the streets are not protected from winds blowing down the streets and may therefore produce more dust than if vegetation were more evenly distributed. Currently, few desert landscape evolution models take the role of wind explicitly into account. The existence of streets implies that wind plays a major role in the evolution of vegetated arid and semiarid landscapes with wind-erodible soils. Here wind acts in tandem with water to enforce islands of fertility centered around individual shrubs and may provide an explanation for reduced soil fertility observed in shrublands. Furthermore, in order for mathematical models of dust flux to be successful in these landscapes, new landscape models are required which incorporate the existence and orientation of streets.

}, keywords = {aeolian processes, vegetation effects, aeolian processes, wind erosion, article, articles, journal, journals, model, wind erosion, wind erosion, }, doi = {10.1007/978-94-017-2033-5_4}, url = {files/bibliography/JRN00327.pdf}, author = {Gregory S. Okin and D. E. Gillette} } @article {51741, title = {Growth of Gutierrezia sarothrae seedlings in the field}, journal = {Journal of Range Management}, volume = {41}, number = {1}, year = {1988}, note = {//NMSU//NONE//}, month = {1988}, pages = {92-93}, abstract = {Broom snakeweed (Gutierrezia sarothrae [Pursh] Britt. and Rusby) has increased in density and distribution on many southwestern ranges. The objective of this study was to determine root and shoot development of snakeweed seedlings as an aid in understanding the establishment of the species. Broom snakeweed seedlings were excavated from the field from March through September at approximately monthly intervals to determine biomass of roots and shoots. Root and shoot biomass growth was comparable from March to July, but shoot growth exceeded that by roots of the rest of the growing season. Root:shoot ratios were below 0.6 for the entire growing season, suggesting that rapid root development is not the primary mechanism for colonizing disturbed areas.}, keywords = {article, articles, Gutierrezia, root:shoot ratios, journal, journals, seedling,Gutierrezia}, author = {Abdelgader Osman and Pieper, Rex D.} } @article {51792, title = {Soil seed banks associated with individual broom snakeweed plants}, journal = {Journal of Range Management}, volume = {40}, number = {5}, year = {1987}, note = {//NMSU//NONE//}, month = {1987}, pages = {441-443}, abstract = {The influence of individual broom snakeweed (Gutierrezia sarothrae [Push] Britt. \& Rushby) plants on the distribution of buried viable seed and the distribution of plants in the field was studied in a desert grassland in southern New Mexico. Surface soil samples collected at 3 distances from a central broom snakeweed plant were watered in pots in a greenhouse and numbers of each specie emerging were counted. Densities of each species were also determined in the field. Some species (Sporobolus flexuosus [Thrub.] Rybd., S. contractus Hitche., Descurainia pinnata [Walt.] Britton, and Dithyre wislizenii Engelm.) emerged in greatest numbers from soil collected in the zones closest and at the greatest distances from the broom snakeweed. Emergence of other species declined in relation to distance from the central snakeweed plant. In the field, grasses generally increased in relation to distance from the central broom snakeweed plant while the pattern for forbs was not consistent.}, keywords = {article, articles, Gutierrezia, effects on forbs and grasses, Gutierrezia,seed bank associations, Gutierrezia,vegetational zonation, journal, journals, seed bank,Gutierrezia association, soil, Gutierrezia, soil, seed banks, vegetational zonation,Gutierrezia}, author = {Abdelgader Osman and Pieper, Rex D. and K. C. McDaniel} } @mastersthesis {52012, title = {Establishment of broom snakeweed (Xanthocephalum sarothrae (Pursh) Shinners) and other species on semidesert grasslands of southern New Mexico}, year = {1982}, note = {//??//NONE//}, month = {1982}, pages = {207}, school = {New Mexico State University}, type = {Ph.D. Dissertationpp}, address = {Las Cruces, New Mexico}, keywords = {dissertation, dissertations, theses, thesis, Xanthocephalum,establishment}, author = {Abdelgader Osman} } @mastersthesis {52244, title = {The distribution and productivity of Flourensia cernua D.C. (tarbush) in southern New Mexico}, year = {1975}, note = {//LOCAL//NONE//}, month = {1975}, pages = {74}, school = {New Mexico State University}, type = {M.S. Thesispp}, address = {Las Cruces, New Mexico}, abstract = {The absolute cover and productivity pre new growth shoot of Flourensia cernua D.C. were looked at with respect to 16 selected soil variables and xylem sap potential along a 1400 m belt transect traversing 5 different plant communities near an enclosed basin in southern New Mexico.... Productivity per new growth shoot, xylem sap potentials, and soil water potentials were observed to be their highest in a Hilaria community with the lowest absolute cover value of Flourensia. The low absolute cover of Flourensia in this community was attributed primarily to the large absolute cover of Hilaria for it had been found by others that Flourensia will increase in disturbed Hilaria communities.}, keywords = {dissertation, dissertations, Flourensia, distribution, Flourensia, plant cover, Flourensia, productivity, productivity,Flourensia, soil, Flourensia, theses, thesis}, author = {T. O{\textquoteright}Laughlin} } @article {52341, title = {Proteolytic activity of soil microorganisms}, year = {1972}, note = {//??//US-IBP//}, month = {1972}, institution = {Utah State University}, address = {Logan, Utah}, keywords = {book, books, chapter, chapters, proteolytic activity,microorganisms, report, reports, soil microorganisms}, isbn = {Research Memorandum 72-42}, author = {R. T. O{\textquoteright}Brien} }