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  • 1
    Electronic Resource
    Electronic Resource
    Soil biota and soil properties in the surface rooting zone of mesquite (Prosopis glandulosa) in historical and recently desertified Chihuahuan Desert habitats (1992)
    Springer
    Biology and fertility of soils 14 (1992), S. 90-98 
    Details
    ISSN: 1432-0789
    Keywords: Desertification ; Prosopis glandulosa ; Soil properties ; Mites ; Collembolans ; Nematodes ; Nitrogen mineralization ; Chihuanhuan desert
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The woody legume, mesquite (Prosopis glandulosa) has expanded from its historical habitats (playas and arroyos) to recently occupied grassland and dune habitats during the desertification of perennial grasslands in the Chihuahuan Desert. We studied historical and recently occupied sites, having hypothesized that the trophic structure and population density of soil microarthropods and nematodes associated with the surface root system of mesquite would differ in sites representing historical and recent habitats, and that the N mineralization potential would be lower in the recent habitats. Our results showed that net N mineralization potential did not differ significantly among the sites, even though soil nutrient concentrations and texture varied widely. Concentrations of organic C, N, and P were lowest in the recent dune habitat and highest at the playa. Very low concentrations of P in the dune and grassland soils implicated P as a limiting factor in these systems. The bacterial-feeding and omnivore-predator functional groups made up the largest fraction of the nematode community at most of the sites. The high density of plant-feeding nematodes at the playa indicated that herbivory is potentially most important at this site. Total microarthropod densities did not vary significantly among habitats, with Collembola densities highest in the mesquite dunes. Grazers were the dominant microarthropod functional group. While both C and N pool sizes were higher in the historical habitats, a higher substrate lability in the recent habitats appeared to support biota populations and N mineralization rates equivalent to those in the playa and arroyo. Differences in soil properties and biota among historical and recent mesquite habitats may be important for understanding the changes that have occurred in Chihuahuan Desert ecosystems during desertification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336256
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  • 2
    Electronic Resource
    Electronic Resource
    Asymbiotic dinitrogen fixation by tundra in the Imnavait Creek drainage, Alaska, USA (1989)
    Springer
    Biology and fertility of soils 7 (1989), S. 207-212 
    Details
    ISSN: 1432-0789
    Keywords: Dinitrogen fixation ; Acetylene reduction assay (ARA) ; Tundra ecosystem ; Nitrogen pool
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary N2 fixation by free-living microorganisms was investigated at an intensively studied low Arctic site near Toolik Lake in the northern foothills of the Brooks Range, Alaska, during July 1987. Four characteristic vegetation associations along an elevational gradient were assayed using minimally disruptive in situ acetylene reduction assay methods. The acetylene reduction rates did not differ significantly among vegetation associations. The mean rate for the site was 9.60 μmol m−2 h−1 or 90 μg N m−2 day−1, which is within the range of values given for other Arctic and alpine tundra studies. The complex microtopography and resulting patchy distribution of free-living and phycobiont diazotrophs is the most likely cause of the high spatial variability in acetylene reduction activity. Rates were most variable among samples from the lowest position, a riparian site. The potential contribution of heterotrophic diazotrophs was examined through a laboratory enrichment study. Soils from the two lower slope positions showed dramatic responses to added C, suggesting that heterotrophs may contribute fixed N2 to this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00709650
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  • 3
    Electronic Resource
    Electronic Resource
    The microarthropod fauna associated with a deep rooted legume, Prosopis glandulosa, in the Chihuahuan Desert (1989)
    Springer
    Biology and fertility of soils 7 (1989), S. 330-335 
    Details
    ISSN: 1432-0789
    Keywords: Prosopis glandulosa ; Rhizosphere ; Mites ; Collembolans ; Chihuahuan Desert
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The rhizosphere microarthropod fauna of a woody, deep-rooted legume, Prosopis glandulosa, was sampled at four sites in the northern Chihuahuan Desert and compared with the rhizosphere microarthropod fauna of a co-dominant shrub, Larrea tridentata. Prostigmatid mites (Speleorchestes sp.,Neognathus sp., Rhagidia sp., Tydaeolus sp., Steneotarsonemus sp., Tarsonemus sp., Nanorchestes sp., Gordialycus sp.), the cryptostigmatid mites (Bankisonoma ovata and Passalozetes neomexicanus), the mesostigmatid (Protogamasellus mica), and the collembolan (Brachystomella arida) characterized the fauna at depths greater than 1 m. Microarthropods were recovered from soils at a depth of 13 m at the edge of a dry lake and at depths of 7 m in a dry wash which were pre-European man P. glandulosa habitats. In habitats where P. glandulosa is a recent invader, root depth and microarthropods were less than 3 m. In most habitats, population densites of microarthropods at depths 0.5 m were more than 100 times those at depths ≫ 0.5 m. Population densities of microarthropods associated with P. glandulosa growing at the edge of a dry wash were not significantly smaller at 0.5−1.0 m depth than at 0−0.5 m. The deep-rhizosphere microarthropod fauna is a reduced subset of the fauna of surficial soils, suggesting that this fauna plays a role in decomposition and mineralization processes functionally similar to that of microarthropods in surficial soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257828
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  • 4
    Electronic Resource
    Electronic Resource
    Depth of root symbiont occurrence in soil (1986)
    Springer
    Biology and fertility of soils 2 (1986), S. 127-130 
    Details
    ISSN: 1432-0789
    Keywords: Prosopis glandulosa ; Sonoran Desert ; N2-fixing nodules ; VA mycorrhizae ; Deep root symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The woody legume Prosopis glandulosa (mesquite) growing in the California Sonoran Desert develops functional root symbiotic associations (N2-fixing nodules, vesicular-arbuscular mycorrhizal fungi) at depths greater than 4 m in moist soil above a seasonally stable water table. Population densities of symbiotic microorganisms are substantially greater at depth than near the surface. Inferences of plant symbiotic dependence based upon examination of surface roots and soil may be incorrect since deep roots can support the symbioses which are critical for plants utilizing deep water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257591
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  • 5
    Electronic Resource
    Electronic Resource
    Climate change (Communication arising) Recent temperature trends in the Antarctic (2002)
    [s.l.] : Nature Publishing Group
    Nature 418 (2002), S. 292-292 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Doran et al. reply — Turner et al. do not find fault with our main focus — the rapid ecological response to recent cooling in the McMurdo Dry Valleys. The essence of their comment is that the spatial interpolation of the Antarctic continental data set (our Fig. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/418292a
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of plant size and water relations on gas exchange and growth of the desert shrub Larrea tridentata (1994)
    Springer
    Oecologia 97 (1994), S. 171-178 
    Details
    ISSN: 1432-1939
    Keywords: Gas-exchange ; Larrea tridentata ; Phenology ; Stomatal conductance ; Water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Larrea tridentata is a xerophytic evergreen shrub, dominant in the arid regions of the southwestern United States. We examined relationships between gasexchange characteristics, plant and soil water relations, and growth responses of large versus small shrubs of L. tridentata over the course of a summer growing season in the Chihuahuan Desert of southern New Mexico, USA. The soil wetting front did not reach 0.6 m, and soils at depths of 0.6 and 0.9 m remained dry throughout the summer, suggesting that L. tridentata extracts water largely from soil near the surface. Surface soil layers (〈0.3 m) were drier under large plants, but predawn xylem water potentials were similar for both plant sizes suggesting some access to deeper soil moisture reserves by large plants. Stem elongation rates were about 40% less in large, reproductively active shrubs than in small, reproductively inactive shrubs. Maximal net photosynthetic rates (Pmax) occurred in early summer (21.3 μ mol m-2 s-1), when pre-dawn xylem water potential (XWP) reached ca. -1 MPa. Although both shrub sizes exhibited similar responses to environmental factors, small shrubs recovered faster from short-term drought, when pre-dawn XWP reached about -4.5 MPa and Pmax decreased to only ca. 20% of unstressed levels. Gas exchange measurements yielded a strong relationship between stomatal conductance and photosynthesis, and the relationship between leaf-to-air vapor pressure deficit and stomatal conductance was found to be influenced by pre-dawn XWP. Our results indicate that stomatal responses to water stress and vapor pressure deficit are important in determining rates of carbon gain and water loss in L. tridentata.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323146
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  • 7
    Electronic Resource
    Electronic Resource
    Estimates of N2-fixation from variation in the natural abundance of 15N in Sonoran desert ecosystems (1983)
    Springer
    Oecologia 56 (1983), S. 365-373 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The 15N abundance of tissues of five Prosopis specimens at our primary study site (a Prosopis woodland at Harper's Well in the Sonoran desert of Southern California) was determined over two growing seasons 1980 and 1981. The 15N abundance of soil and of tissues of presumed non-N2-fixing (control) plants was also measured. Prosopis tissues were significantly lower in 15N than either soil N or corresponding tissues of presumed non-N2-fixing plants which derive their N entirely from soil. Soil N was also significantly higher in 15N than atmospheric N2. We conclude that it is feasible to use variations in the natural abundance of 15N as an index of N2-fixation in this kind of ecosystem, and that N2-fixation is of considerable importance to Prosopis growing at this site. We also determined the 15N abundance of leaf tissue of presumed N2-fixing and control plants growing at the same site at six additional sites (five in the Sonoran desert of southern California and one in Baja California, Mexico near the town of Catavina). Four of these additional sites were dominated by Prosopis and two were mixed communities. There were statistically significant differences between the 15N abundances of the pooled legume population and control plants at all sites, although not every legume specimen exhibited this difference. From 15N abundance data we estimated the fractional contribution of biologically fixed N to the N economy of desert legumes. We concluded that N2-fixation is very important to Prosopis at six of seven sites in the Sonoran Desert. At the site where Prosopis did not appear to be fixing N2, N2-fixation was important only for legumes of the sub-family Papilionoideae, Lupinus, Dalea, Astragalus and Lotus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379714
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  • 8
    Electronic Resource
    Electronic Resource
    Carbon isotopes reveal soil organic matter dynamics following arid land shrub expansion (1997)
    Springer
    Oecologia 110 (1997), S. 374-386 
    Details
    ISSN: 1432-1939
    Keywords: Key words Carbon isotope ; Carbon cycling ; Mean residence time ; Root distribution ; Desertification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Over the past century, overgrazing and drought in New Mexico’s Jornada Basin has promoted the replacement of native black grama (Bouteloua eriopoda Torr.) grass communities by shrubs, primarily mesquite (Prosopis glandulosa Torr.). We investigated the effects of shrub expansion on the distribution, origin, turnover, and quality of light (LFC) and heavy (HFC) soil organic matter (SOM) fractions using δ13C natural abundance to partition SOM into C4 (grass) and C3 (shrub) sources. Soil organic matter beneath grasses and mesquite was isotopically distinct from associated plant litter, providing evidence of both recent shrub expansion and Holocene plant community changes. Our δ13C analyses indicated that SOM derived from mesquite was greatest beneath shrub canopies, but extended at least 3 m beyond canopy margins, similar to the distribution of fine roots. Specific 14C activities of LFC indicated that root litter is an important source of SOM at depth. Comparison of turnover rates for surface LFC pools in grass (7 or 40 years) and mesquite (11 or 28 years) soils and for HFC pools by soil depth (∼150–280 years), suggest that mesquite may enhance soil C storage relative to grasses. We conclude that the replacement of semiarid grasslands by woody shrubs will effect changes in root biomass, litter production, and SOM cycling that influence nutrient availability and long-term soil C sequestration at the ecosystem level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050172
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  • 9
    Electronic Resource
    Electronic Resource
    Influences of microclimatic conditions and water relations on seasonal leaf dimorphism of Prosopis glandulosa var. torreyana in the Sonoran Desert, California (1986)
    Springer
    Oecologia 69 (1986), S. 95-100 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seasonal measurements of microclimatic conditions were compared to seasonal indices of leaf structural components and plant water relations in Prosopis glandulosa var. torryana. P. glandulosa had two short periods of leaf production which resulted in two distinct even aged cohorts of leaves. The two leaf cohorts (summer, winter) were concurrent in the summer and fall, contrasting to previous studies on other species in which one leaf form replaces a previous leaf type. The structural characteristics of these two cohorts differed significantly in two replicate year cycles. The leaves of the spring cohort were larger in weight and area but similar to the summer cohort in specific leaf weight and leaflet number. The second growth period leaves constituted only a small proportion of the total plant leaf area. The dimorphism between the two cohorts was best associated with plant water relations and not energy load. Second growth period leaves maintained turgor to greater water deficits but lost turgor at higher leaf water potentials. Seasonal osmotic adjustment occurred for first growth period leaves but not second growth period leaves. The small leaves produced during the hot climate were most likely the result of low turgor potential during development rather than an adaptation to tolerate stressful environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399043
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  • 10
    Electronic Resource
    Electronic Resource
    Seasonal dynamics of nitrogen cycling for a Prosopis woodland in the Sonoran Desert (1982)
    Springer
    Plant and soil 67 (1982), S. 343-353 
    Details
    ISSN: 1573-5036
    Keywords: Desert woodland ; N-cycling ; N2fixation ; Prosopis glandulosa ; Sonoran Desert
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Resumen Los bosques de Prosopis en el desierto Sonorense tienen niveles de producción de biomasa (parte aérea) y productividad mucho mayores que las predecibles para comunidades de plantas de desierto con muy bajos niveles de precipitación. Los bosques freatofiticos deP. glandulosa cerca del Mar de Salton, California, producen 13 000 kg ha−1 de biomasa aérea con una productividad 3700 kg ha−1 año−1. Tan alto nivel de productividad es posible porque Prosopis no es afectado por los factores que limitan la aprovechabilidad de agua y nitrógeno. Los primeros 60 cm del perfil del suelo bajo el dosel de Prosopis contienen 1020 g m−2 de nitrógeno total, el 25% existe en la forma de nitrato. Tales acumulaciones de nitrógeno pueden ser el resultado de la fijación simbiótica activa. Los primeros valores estimados sugieren que son fijados entre 25–30 kg N ha−1 año−1 en estos bosques. Puesto que Prosopis cubre solamente 34% de esta área y sus recursos de agua no son limitantes, puede ser posible la obtención de mayores niveles de fijación de nitrógeno y productividad de los cultivos si se manejan con mayores densidades.
    Notes: Abstract Prosopis woodlands in the Sonoran Desert have levels of above-ground biomass and productivity much higher than those predicted for desert plant communities with such low levels of precipitation. A stand ofP. glandulosa near the Salton Sea, California, has 13,000 kg ha−1 aboveground biomass and a productivity of 3700 kg ha−1 yr−1. Such a high level of productivity is possible because Prosopis is decoupled from the normal limiting factors of water and nitrogen availability. Soil nitrogen contents for the upper 60 cm of soil beneath Prosopis canopies have 1020 g m−2 total nitrogen, 25 per cent of which is in the form of nitrate. Such accumulations of nitrogen may be the result of active symbiotic nitrogen fixation. Early estimates suggest that about 25–30 kg N ha−1 yr−1 is fixed in these stands. Since Prosopis covers only 34% of the ground surface and its water resources are not limiting, much higher levels of nitrogen fixation and productivity may be possible in managed stands at greater densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02182781
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