@article {JRN54899, title = {Playa-wetlands effects on dryland biogeochemistry: space and time interactions}, journal = {Journal of Geophysical Research - Biogeosciences}, year = {2018}, abstract = {

Playas are ephemerally flooded wetlands found in hydrologically closed dryland catchments. Recent research showed how upland-catchment biophysical characteristics control the amount of organic carbon and nutrients that accumulates in playas from upland grasslands and shrublands. Here we further explored the role of allochthonous and autochthonous processes in fixing carbon and accruing soil nutrients in playas across a desert basin. We assessed whether playas contribute soil nutrient, organic-carbon stocks, and primary productivity rates in amounts disproportionately higher or lower than upland grasslands and shrublands. We found that playas had higher soil carbon and nutrient storage but no difference in mean annual primary production. Playas, on average, had similar primary productivity than upland systems, because they exhibited lower productivity during extremely wet years that offset the larger productivity during average or below average precipitation years. These results suggest that playas contain higher carbon and soil nutrient stocks because of runoff-mediated allochthonous inputs, rather than autochthonous sources, since long-term average productivity was similar to upland ecosystems. We also used the precipitation-aboveground net primary production (ANPP) relationships to accurately measure run-on in playas using differences between playa and upland grassland ANPP. The dependence of playa ANPP on surface-water inputs from upland catchments makes them susceptible to future changes in extreme precipitation events.

}, keywords = {climate change, desert playas, groundwater recharge, Jornada LTER, organic carbon, precipitation variability, soil nutrients, watershed ecology}, doi = {10.1029/2017JG004176}, url = {files/bibliography/JRN54899.pdf}, author = {Owen P. McKenna and O. E. Sala} } @article {JRN52687, title = {Soil organic carbon enrichment of dust emissions: Magnitude, mechanisms and its implications for the carbon cycle}, year = {2013}, abstract = {

Soil erosion is an important component of the global carbon cycle. However, little attention has been given to the role of aeolian processes in influencing soil organic carbon (SOC) flux and the release of greenhouse gasses, such as carbon-dioxide (CO2), to the atmosphere.\  Understanding the magnitude and mechanisms of SOC enrichment in dust emissions is necessary to evaluate the impact of wind erosion on the carbon cycle. This research examines the SOC content and enrichment of dust emissions measured using Big Spring Number Eight (BSNE) wind-vane samplers across five land types in the rangelands of western Queensland, Australia. Our results show that sandy soils and finer particulate quartz-rich soils are more efficient at SOC emission and have larger SOC dust enrichment than clay-rich aggregated soils. The SOC enrichment ratios of dusts originating from sites with sand-rich soil ranged from 2.1-41.9, while the mean enrichment ratio for dusts originating from the clay soil was 2.1. We hypothesise that stronger inter-particle bonds and the low grain density of the aggregated clay soil explain its reduced capacity to release SOC during saltation, relative to the particulate sandy soils. We also show that size-selective sorting of SOC during transport may lead to further enrichment of SOC dust emissions. Two dust samples from regional transport events were found to contain 15-20\% SOC. These preliminary results provide impetus for additional research into dust SOC enrichment processes to elucidate the impact of wind erosion on SOC flux and reduce uncertainty about the role of soil erosion in the global carbon cycle.

}, keywords = {aeolian dust, carbon cycle, rangelands, soil nutrients, wind erosion}, doi = {10.1002/esp.3404}, url = {/files/bibliography/13-032.pdf}, author = {Nicholas Webb and Craig Strong and A. Chappell and Samuel K. Marx and Grant McTainish} } @article {49868, title = {Aeolian process effects on vegetation communities in an arid grassland ecosystem}, journal = {Ecology and Evolution}, volume = {2}, year = {2012}, month = {04/01/2012}, pages = {809-821}, abstract = {

Many arid grassland communities are changing from grass dominance to shrub dominance, but the mechanisms involved in this conversion process are not completely understood. Aeolian processes likely contribute to this conversion from grassland to shrubland. The purpose of this research is to provide information regarding how vegetation changes occur in an arid grassland as a result of aeolian sediment transport. The experimental design included three treatment blocks, each with a 25 {\texttimes} 50 m area where all grasses, semi-shrubs, and perennial forbs were hand removed, a 25 {\texttimes} 50 m control area with no manipulation of vegetation cover, and two 10 {\texttimes} 25 m plots immediately downwind of the grass-removal and control areas in the prevailing wind direction, 19{\textdegree} north of east, for measuring vegetation cover. Aeolian sediment flux, soil nutrients, and soil seed bank were monitored on each treatment area and downwind plot. Grass and shrub cover were measured on each grass-removal, control, and downwind plot along continuous line transects as well as on 5 {\texttimes} 10 m subplots within each downwind area over four years following grass removal. On grass-removal areas, sediment flux increased significantly, soil nutrients and seed bank were depleted, and Prosopis glandulosa shrub cover increased compared to controls. Additionally, differential changes for grass and shrub cover were observed for plots downwind of vegetation-removal and control areas. Grass cover on plots downwind of vegetation-removal areas decreased over time (2004{\textendash}2007) despite above average rainfall throughout the period of observation, while grass cover increased downwind of control areas; P. glandulosa cover increased on plots downwind of vegetation-removal areas, while decreasing on plots downwind of control areas. The relationships between vegetation changes and aeolian sediment flux were significant and were best described by a logarithmic function, with decreases in grass cover and increases in shrub cover occurring with small increases in aeolian sediment flux.

}, keywords = {aeolian processes, grassland community, sediment flux, seed bank, soil nutrients, vegetation change, vegetation community, vegetation cover}, doi = {10.1002/ece3.205}, url = {/files/bibliography/12-020.pdf}, author = {Lorelei Alvarez and Howard Epstein and Junran Li and Gregory S. Okin} } @article {50092, title = {Badger (Taxidea taxus) disturbances increase soil heterogeneity in a degraded shrub-steppe ecosystem}, journal = {Journal of Arid Environment}, number = {73}, year = {2009}, month = {01/2009}, pages = {66-73}, chapter = {66}, abstract = {

In the western United States, overgrazing, weed invasion and wildfire have resulted in the conversion of shrub-steppe to annual grasslands, with substantial effects on ecosystem function. In these lands capes, badgers disturb large areas of soil while foraging for fossorial animals. Mounds created by badgers contained the lowest concentrations of total carbon, nitrogen and sulphur, mineral nitrogen and mineralizable nitrogen, inter-mound soils had the highest concentrations, and excavation pits had intermediate levels. Soil C:N ratio and pH were greater, and electrical conductivity and soluble Ca2{\th}, Mg2{\th} and K{\th} were lower on mound soils compared with either pit or inter-mound soils. Larger pits generally trapped more litter, and increased litter mass equated with greater concentrations of active carbon, but only at the burned sites. Older mounds supported more vascular plants and cryptogamic crusts. Our results demonstrate reduced levels of nutrients and a higher C:N ratio on the mounds compared with either the pits or inter-mounds. Alteration to the homogeneous post-fire landscape by badgers contributes to patchiness in soils and vegetation, which is critical to the functioning of arid systems. Given their effect on soil C:N ratios, mounds may be important sites for recovery of indigenous shrub-steppe plant species.

}, keywords = {Badger, Biopedturbation, disturbance, ecosystem engineering, mounding, soil nutrients}, doi = {10.1016/j.jaridenv.2008.09.004}, url = {/files/bibliography/09-002.pdf}, author = {D.J. Eldridge and Walter G. Whitford} } @article {50229, title = {Landscape position moderates how ant nests affect hydrology and soil chemistry across a Chihuahuan Desert watershed}, journal = {Landscape Ecology}, volume = {23}, year = {2008}, month = {11/2008}, pages = {961-975}, chapter = {961}, abstract = {

Ants moderate the supply of critical resources such as water and nutrients in desert environments by changing the physical arrangement of soils during nest construction. We measured water infiltration and soil physical and chemical properties on and off the nests of two ant species (Pogonomyrmex rugosus, Aphaenogaster cockerelli) across five sites at differing landscape positions within a Chihuahuan Desert watershed. Our aim was to test whether the effects of these long-lived ant nests on water infiltration and soil chemistry varied between ant species or across sites within a watershed. Water flow was generally slowest at the site with the highest silt and clay contents, and fastest at the site with sandy soils. Flow was generally greater through ant nest soils than adjacent non-nest soils, and we attribute this to increases in macropores in the nests. However, the effects of both ant nests and species varied among sites. Despite wide variation in soil chemical properties across all sites, ant nests had a consistent effect on soil chemical properties, with higher levels of carbon, nitrogen, sulphur, phosphorus and electrical conductivity on nests compared with non-nest soils. Our results demonstrate that while we can generalise about the effects of ant nests on water flow and nutrient levels, differences in soil type, nest density and ant species across sites are likely to moderate these effects.

}, keywords = {infiltration, Landscape scale, macropores, soil nutrients, Sorptivity}, doi = {10.1007/s10980-008-9251-6}, url = {/files/bibliography/08-039.pdf}, author = {Angela James and Edridge, D.J. and T. B. Koen and Walter G. Whitford} } @article {50236, title = {Effects of wind erosion on the spatial heterogeneity of soil nutrients in two desert grassland communities}, journal = {Biogeochemistry}, volume = {88}, number = {1}, year = {2008}, note = {//USDA//LTER-V//entered 06/06/2008; PDF on file}, month = {2008}, pages = {73}, abstract = {

Wind is known to affect the spatial heterogeneity of soil resources in arid and semiarid systems, but multi-year, quantified observations are largely absent. We studied the effects of wind erosion on the spatial distribution of soil organic carbon (SOC) and other soil nutrients at the Jornada Experimental Range, in southern New Mexico. Enhanced wind erosion was encouraged by grass cover reduction in a Sporobolus-mesquite dominated site (SM) and a Bouteloua-mesquite dominated site (BM). The scale and magnitude of spatial dependence for the soil analytes were quantified using geostatistical analyses. Results of this study show that soil organic matter related analytes such as SOC, TN, Navail, and SO4 2 are among the first to be eroded and redistributed; cations such as Ca2+ and Mg2+ may not be removed and redistributed significantly; and other ions such as K+, Na+ and Cl- showed no discernible pattern of change. Geostatistics show that wind appeared to increase the scale of spatial autocorrelation, but decrease the scale of spatial dependence of most soil analytes over 2{\textendash}3 windy seasons. In the wind enhanced plot of the SM site, up to 99\% of the spatial dependence of SOC was autocorrelated at the distance of 1.45 m before the initiation of wind erosion, but the spatial dependence dropped significantly to only 60\% at a larger autocorrelation distance of 2.76 m after three windy seasons. Similar but less significant changes were observed for SOC in the BM site. Despite the differential effects of wind on the soil analytes, we conclude that the overall results of wind on the grass cover reduction plots are the disappearance of small, strong fertile islands, which may be related to grasses; and the reinforcement of large fertile islands, which are likely related to mesquite shrubs. In addition, the change of the spatial patterns of SOC and other soil nutrients induced by enhanced wind erosion may persist and reinforce soil islands associated with shrubs, thus allowing a positive feedback for further desertification in this arid grassland.

}, keywords = {article, geostatistics, journal, soil carbon, soil nitrogen, soil nutrients, spatial heterogeneity, wind erosion, soil carbon, wind erosion, soil nitrogen, wind erosion, soil nutrients}, doi = {10.1007/s10533-008-9195-6}, url = {files/bibliography/JRN00499.pdf}, author = {Junran Li and Gregory S. Okin and Lorelei Alvarez and Howard Epstein} } @article {50323, title = {Changes in the spatial variation of soil properties following shifting cultivation in a Mexican tropical dry forest}, journal = {Biogeochemistry}, volume = {84}, year = {2007}, pages = {99-113}, keywords = {goestatistics, Mexico, shifting cultivation, soil nutrients, spatial heterogeneity, tropical dry forest}, author = {Diekmann, Lucy O. and Lawrence, Deborah and Gregory S. Okin} } @article {51128, title = {Arroyo water storage and soil nutrients and their effects on gas-exchange of shrub species in the northern Chihuahuan Desert}, journal = {Journal of Arid Environments}, volume = {43}, number = {1}, year = {1999}, month = {1999}, pages = {21-33}, abstract = {

A variable fraction of the rain falling on desert landscapes runs off and accumulates in ephemeral channels (arroyos), where some of the water is transported downslope. Relatively large amounts of water are stored in arroyo sediments. This water may support high rates of gas-exchange in some riparian species. We examined differences in the timing of flow events, soil water storage, and soil nutrients on gas-exchange rates of shrubs growing on arroyo margins and in adjacent piedmont areas in the Chihuahuan Desert of southern New Mexico, USA. The semi-riparian shrub, Fallugia paradoxa (Apache plume), had very different photosynthetic rates between two arroyos, but transpiration rates did not differ. This may result from nutrient limitation differences between arroyos. At one site, the semi-riparian shrub, Prosopis glandulosa (mesquite), on arroyo margins had access to more water and showed higher rates of gas-exchange compared with non-arroyo mesquite located on nearby piedmont areas. The obligate riparian shrub, Chilopsis linearis (desert willow), had intermediate gas-exchange rates when compared with Apache plume and mesquite, and neither soil water nor nutrient concentrations appeared to affect photosynthesis during the growing season. Variation between and within arroyos was high; however, our data suggest that stored water enabled mesquite of arroyo margins to maintain relatively high rates of gas-exchange. When water was relatively abundant, nutrient availability appeared to limit photosynthetic rates of Apache plume. (C) 1999 Academic Press.

}, keywords = {Chihuahuan Desert, Chilopsis linearis, fallugia paradoxa, photosynthesis, prosopis glandulosa, soil nutrients, soil water storage, transpiration}, doi = {10.1006/jare.1999.0530}, url = {/files/bibliography/643.pdf}, author = {Atchley, M.C. and A.G. de Soyza and Walter G. Whitford} } @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} } @book {51351, title = {Ecosystem function of biodiversity in arid ecosystems}, series = {Functional roles of biodiversity: A global perspective}, year = {1996}, note = {//NMSU,USDA//LTER-III//ProCite field[6]: InProCite field[30]: Mooney, H. A.Cushman, J. H.Medina, E.Sala, O. E.Schulze, E.-D. , eds.}, month = {1996}, pages = {99-128}, publisher = {John Wiley \& Sons Ltd}, organization = {John Wiley \& Sons Ltd}, address = {New York}, abstract = {Our discussion applies to both so-called hot or semi-tropical deserts and to cool or temperate arid zones; we exclude from discussion the polar deserts, where temperature constrains plant growth during most of the year. We recognize that aridity may arise from different combinations of regional climate, topography, and so on.... In this chapter we focus on a description of the nature and function of biodiversity, at several levels of organization, within these systems.}, keywords = {biodiversity, ecosystem, book, books, chapter, chapters, ecosystem dynamics, abiotic factors, ecosystem dynamics, biotic responses, ecosystem dynamics, invertebrates, ecosystem dynamics, water, ecosystem function, ecosystem, biodiversity, ecosystem, fungal community, ecosystem, plant production, ecosystem, processes, ecosystem, soil microorganisms, grazing, ecosystem function, plant production, report, reports, soil nutrients, soil structure}, author = {L. Huenneke and I. R. Noble} } @article {51370, title = {On the spatial pattern of soil nutrients in desert ecosystems}, journal = {Ecology}, volume = {77}, number = {2}, year = {1996}, note = {//NMSU, USDA//LTER III//}, month = {1996}, pages = {364-374}, abstract = {

We examined the spatial distribution of soil nutrients in desert ecosystems of the southwestern United States to test the hypothesis that the invasion of semiarid grasslands by desert shrubs is associated with the development of "islands of fertility" under shrubs. In grasslands of the Chihuahuan Desert of New Mexico, 35-76\% of the variation in soil N was found at distances \<20 cm, which may be due to local accumulations of soil N under Bouteloua eriopoda, a perennial bunchgrass. The remaining variance is found over distances extending to 7 m, which is unlikely to be related to nutrient cycling by grasses. In adjacent shrublands, in which Larrea tridentata has replaced these grasses over the last century, soil N is more concentrated under shrubs and autocorrelated over distances extending 1.0-3.0 m, similar to mean shrub size and reflecting local nutrient cycling by shrubs. A similar pattern was seen in the shrublands of the Mojave Desert of California. Soil PO4, Cl, SO4, and K also accumulate under desert shrubs, whereas Rb, Na, Li, Ca, Mg. and Sr are usually more concentrated in the intershrub spaces. Changes in the distribution of soil properties may be a useful index of desertification in arid and semiarid grasslands worldwide.

}, keywords = {Artemisia, nitrogen cycling, Artemisia, soil heterogeneity, article, articles, Bouteloua, nitrogen cycling, Bouteloua, soil heterogeneity, Bromus, nitrogen cycling, Bromus, soil heterogeneity, geostatistics, Great Basin Desert, Bouteloua community, Great Basin Desert, Larrea community, journal, journals, Larrea, nitrogen cycling, Larrea, soil heterogeneity, Mojave Desert, Larrea community, nitrogen cycling, phosphorous, soil heterogeneity, soil nutrients, soil, nitrogen, soil, phosphorus}, doi = {10.2307/2265615 }, url = {files/bibliography/JRN00213.pdf}, author = {W. H. Schlesinger and Raikes, Jane A. and Anne E. Hartley and Cross, Anne F.} } @article {51427, title = {Variability in soils and vegetation associated with harvester ant (Pogonomyrmex rugosus) nests on a Chihuahuan Desert watershed}, journal = {Biology and Fertility of Soils}, volume = {20}, year = {1995}, month = {1995}, pages = {169-173}, abstract = {

The effects of harvester ant (Pogonomyrmex rugosus) nests on the density and cover of spring annual plants and on soil characteristics were measured at three locations characterized by different soils and dominant vegetation on a desert watershed. There were few differences in vegetation and soils associated with harvester ant nests at locations at the base of the watershed where brief periods of flooding and sediment deposition occur at periodic intervals. At mid-slope locations, there were significant increases in total nitrogen, inorganic phosphorus, and cover (biomass) of four species of spring annuals at the edges of nest disks when compared with reference sites. The spring annuals that exhibited increased cover were species that increase biomass as a function of available nitrogen. At a clay-loam, Scleropogon-Hilaria, grassland site, there were significant reductions in the concentrations of Ca2+ and Mg2+, significant increases in nitrate and total nitrogen, but a significant increase in cover in only one species of annual plant. The data demonstrate that the effects of ants on soil properties and vegetation vary with site location and soil type.

}, keywords = {annual plants, desert, Harvester ants, Pogonomyrmex rugosus, soil nutrients, spatial variability}, doi = {10.1007/BF00336554}, url = {/files/bibliography/463.pdf}, author = {Walter G. Whitford and DiMarco, R.} }