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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 140 (1999), S. 245-253 
    ISSN: 1573-5052
    Keywords: Canopy disturbance regime ; Great Smoky Mountains ; Radial growth ; Red spruce ; Suppression and release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A majority (72%) of Picea rubens Sarg. (red spruce) trees in an old-growth spruce-fir forest in the Great Smoky Mountains underwent episodes of radial growth suppression and release before they reached the forest canopy. Prior to canopy recruitment, trees experienced an average of 1.43 and a maximum of 7 suppression periods with an average ring width of 0.257 mm. Duration of suppression periods ranged from 4 to 79 years with an average of 19.05 years, which was significantly shorter than the average duration of release periods (29.00 years). Mean ring width in a suppression period was negatively correlated with duration of the suppression period. The opposite was true for release periods. The severity of suppression had no significant effect on mean ring width in subsequent release periods. Greater suppression was observed in the recent growth pattern of current non-canopy trees than in the historical growth pattern reconstructed from current canopy trees. Growth releases prior to canopy recruitment, triggered by small gaps or neighboring gaps, displayed a continuous pattern over the last two centuries and had consistent frequency in recent decades. By contrast, canopy recruitment resulting from large-gap disturbances was discontinuous over the last two centuries, and less frequent after 1850.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5052
    Keywords: Abies ; Betula ; Compositional stability ; Gap phase dynamics ; Picea ; Southern Appalachians ; Transition probability analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Compositional stability in forests has traditionally been evaluated by comparing understory with overstory composition. Such comparisons have generally been qualitative. Transition probability analysis has recently allowed quantitative prediction of future community states. We used transition probability analysis of an undisturbed spruce-fir forest to evaluate the sensitivity of the overstory/understory comparison to underlying assumptions. The predictions of future composition differed widely depending on understory size class used, ecological situation (gap versus forest plots), and stand descriptor (density versus frequency). Species longevities and interactions between understory and overstory species also affected the predictions. Understory data generally led to a predicted increase in importance for the most tolerant species (Abies fraseri) and the conclusion that a previous disturbance allowed the least tolerant species (Betula lutea) to become established. Inventory of stems in gaps led to a predicted increase in importance for the least tolerant species (Betula) and the conclusion that disturbance frequency was increasing in the stand. Data incorporating more detailed observations of the gap capture process led to the inference that this old growth stand was in compositional equilibrium. In this community, the species that was densest in the understory species (Abies) had the shortest lifespan and thus, the fastest canopy turnover rate. This lead to counter-intuitive behavior in the models; in some cases Abies had a 40% higher relative density in the understory than in the overstory at equilibrium.
    Type of Medium: Electronic Resource
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