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  • Articles: DFG German National Licenses  (2)
  • 1995-1999  (2)
  • 1970-1974
  • 1915-1919
  • Analysis of covariance  (1)
  • Annual plants  (1)
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  • Articles: DFG German National Licenses  (2)
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  • 1995-1999  (2)
  • 1970-1974
  • 1915-1919
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 20 (1995), S. 137-146 
    ISSN: 1432-0789
    Keywords: Larrea tridentata ; Simulated rainfall ; Precipitation exclusion ; Soil drying effects ; Analysis of covariance ; Chihuahan Desert ; Mineralization rate ; Field capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Irrigation and rain-out shelters were used to simulate precipitation patterns of wet and dry years in the northern Chihuahuan Desert. Irrigation provided approximately double the long-term average monthly precipitation. Rain was excluded during the wet season, July-October, to simulate a dry year. N net mineralization in laboratory incubations was undectable at calculated water potentials less than -1 MPa. Witb increasing moisture, mineralization gradually rose to the highest observed rates near field capacity. There was no mineralization maximum at moisture contents below field capacity. Irrigation significantly increased the water potential and rainfall exclusion reduced water potentials to less than-8 MPa. The general absence of important irrigation effects may have resulted from the high natural precipitation during the experiment or because irrigation inputs were insufficient to increase microbial activity during very dry periods. Precipitation exclusion reduced ion capture during the warm-wet season. After allowing precipitation inputs to resume, NH 4 + -N capture was increased in the cool-dry seasons of both 1987–1988 and 1988–1989. NH 4 + -N capture more than doubled that predicted from the overall covariance of moisture input and ion capture, suggesting increased availability of N. An unusually hot, dry period in May and June 1989 was followed by a threeto fourfold increase in the warm-wet season NO 3 − +NO2−N capture compared to 1988. These data suggest that short droughts of about 3 months in length (both simulated and natural) increased N availability relative to moisture availability.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0789
    Keywords: Annual plants ; Desert ; Harvester ants ; Soil nutrients ; Spatial variability ; Pogonomyrmex rugosus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 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.
    Type of Medium: Electronic Resource
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