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  • Succession  (2)
  • Diversity  (1)
  • Soil nitrogen  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 71 (1987), S. 481-485 
    ISSN: 1432-1939
    Keywords: Cedar Creek ; Minnesota ; Nitrogen mineralization ; Old fields ; Succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nitrogen availability and its response to fertilizer amendments was measured by in situ incubation in four old fields ranging in age from 16 to 〉100 years at Cedar Creek Natural History Area. Net nitrogen mineralization in control plots increased with field age, from 4.4 g/m2 in the youngest field to 6.5 g/m2 in the oldest field. The proportion of total N mineralized decreased with field age, from 6.2% of total N mineralized in the youngest field to 4.8% mineralized in the oldest field, suggesting a decrease in organic matter quality with time. Unlike many forests in the region, nitrogen mineralization was correlated with total soil nitrogen content. Greater than 90% of the mineralized N was nitrified in most months. Analyses of variance indicate significant effects of field age and month of year on N mineralization and nitrification, but not effect of fertilizer treatment except in the oldest field. Fertilizer additions did not significantly increase standing pools of mineral N in the youngest or oldest fields but did in the 26 and 50 year old fields. However, changes in mineral N pools did not account for the amount added in fertilizer. Strong plant and microbial sinks for fertilizer and possibly leaching losses may be the reasons why fertilizer additions did not stimulate N mineralizations during the first two years in most fields.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Keywords: Geomys ; Soil nitrogen ; Gopher mounds ; Succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Pocket gophers (Geomys bursarius: Geomyidae Rodentia) are shown to affect soil resources and thus, indirectly, vegetation. Gophers reduce average soil nitrogen near the surface and increase point-to-point heterogeneity of soil nitrogen by moving nitrogen-poor subsurface soil to the soil surface. Data from 22 old fields at Cedar Creek Natural History Area, Minnesota, USA show correlations of soil nitrogen, vegetation, and gopher mounds that are consistent with this indirect mechanism by which gophers affect local species composition and old field succession.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 89 (1992), S. 257-264 
    ISSN: 1432-1939
    Keywords: Drought ; Extinctions ; Species richness ; Diversity ; Colonization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The local species richness of four different grassland fields fell an average of 37% during a 1988 drought that decreased above-ground living plant mass by an average of 47%. Despite the return to more normal plant mass and precipitation during the next two years, there was no significant recovery in species richness in the 46 permanent plots, suggesting that local species richness became recruitment limited. The drought led to the loss of annual species independent of their abundance. For perennial grasses, perennial forbs, legumes and woody species, the probability of a species being lost from a plot was significantly negatively correlated with its predrought abundance. These results demonstrate that environmentally extreme conditions can limit species richness by causing the local extinction of rare species. Because droughts of this intensity occur about every 50 years in the prairie, periodic drought may have limited prairie diversity. Moreover, if the accumulation of greenhouse gases leads to a more variable or extreme climate, it could cause increased rates of species extinctions.
    Type of Medium: Electronic Resource
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