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Inequality of size and size increment in Pinus banksiana in relation to stand dynamics and annual growth rate.

Metsaranta JM, Lieffers VJ - Ann. Bot. (2007)

Bottom Line: The inequality of size increment was greater and more variable than the inequality of size.Inequality of size increment was significantly related to annual growth rate at the stand level, and was higher when growth rate was low.A complete understanding of the dynamics of these forests requires further evaluation of the way in which factors that influence variation in annual growth rate also affect the mode of competition and the development of size hierarchies.

View Article: PubMed Central - PubMed

Affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2H1 Canada. jmetsara@nrcan.gc.ca

ABSTRACT

Background and aims: Changes in size inequality in tree populations are often attributed to changes in the mode of competition over time. The mode of competition may also fluctuate annually in response to variation in growing conditions. Factors causing growth rate to vary can also influence competition processes, and thus influence how size hierarchies develop.

Methods: Detailed data obtained by tree-ring reconstruction were used to study annual changes in size and size increment inequality in several even-aged, fire-origin jack pine (Pinus banksiana) stands in the boreal shield and boreal plains ecozones in Saskatchewan and Manitoba, Canada, by using the Gini and Lorenz asymmetry coefficients.

Key results: The inequality of size was related to variables reflecting long-term stand dynamics (e.g. stand density, mean tree size and average competition, as quantified using a distance-weighted absolute size index). The inequality of size increment was greater and more variable than the inequality of size. Inequality of size increment was significantly related to annual growth rate at the stand level, and was higher when growth rate was low. Inequality of size increment was usually due primarily to large numbers of trees with low growth rates, except during years with low growth rate when it was often due to small numbers of trees with high growth rates. The amount of competition to which individual trees were subject was not strongly related to the inequality of size increment.

Conclusions: Differences in growth rate among trees during years of poor growth may form the basis for development of size hierarchies on which asymmetric competition can act. A complete understanding of the dynamics of these forests requires further evaluation of the way in which factors that influence variation in annual growth rate also affect the mode of competition and the development of size hierarchies.

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Related in: MedlinePlus

Plots of the relationship between the inequality of size increment, as quantified by the Gini coefficient, and stand-level annual volume increment at each study plot. Significant regression lines are shown.
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MCM320F5: Plots of the relationship between the inequality of size increment, as quantified by the Gini coefficient, and stand-level annual volume increment at each study plot. Significant regression lines are shown.

Mentions: Some combinations of density, mean tree size and average competition were also significantly associated with changes in the inequality of size increment at all but the rich site at Candle Lake, where only stand-level annual volume increment (in this case lagged by 1 year) was a significant predictor (Table 2). Again, the sign and significance of the coefficients for these predictors varied, indicating that the specific relationship between them and changes in the inequality of growth rate were also site specific. Stand-level annual volume increment was a significant predictor of changes in the inequality of size increment at all four sites. At Candle Lake, the significant predictor was lagged by 1 year, while at Thompson it was not. In all cases, the sign of the coefficients for this predictor (significant or not) were negative, indicating increasing inequality in volume increment when stand growth rates were low. Figure 5 plots the relationship between the inequality of size increment and variation in the stand-level annual volume increment to demonstrate this relationship graphically.


Inequality of size and size increment in Pinus banksiana in relation to stand dynamics and annual growth rate.

Metsaranta JM, Lieffers VJ - Ann. Bot. (2007)

Plots of the relationship between the inequality of size increment, as quantified by the Gini coefficient, and stand-level annual volume increment at each study plot. Significant regression lines are shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2710195&req=5

MCM320F5: Plots of the relationship between the inequality of size increment, as quantified by the Gini coefficient, and stand-level annual volume increment at each study plot. Significant regression lines are shown.
Mentions: Some combinations of density, mean tree size and average competition were also significantly associated with changes in the inequality of size increment at all but the rich site at Candle Lake, where only stand-level annual volume increment (in this case lagged by 1 year) was a significant predictor (Table 2). Again, the sign and significance of the coefficients for these predictors varied, indicating that the specific relationship between them and changes in the inequality of growth rate were also site specific. Stand-level annual volume increment was a significant predictor of changes in the inequality of size increment at all four sites. At Candle Lake, the significant predictor was lagged by 1 year, while at Thompson it was not. In all cases, the sign of the coefficients for this predictor (significant or not) were negative, indicating increasing inequality in volume increment when stand growth rates were low. Figure 5 plots the relationship between the inequality of size increment and variation in the stand-level annual volume increment to demonstrate this relationship graphically.

Bottom Line: The inequality of size increment was greater and more variable than the inequality of size.Inequality of size increment was significantly related to annual growth rate at the stand level, and was higher when growth rate was low.A complete understanding of the dynamics of these forests requires further evaluation of the way in which factors that influence variation in annual growth rate also affect the mode of competition and the development of size hierarchies.

View Article: PubMed Central - PubMed

Affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2H1 Canada. jmetsara@nrcan.gc.ca

ABSTRACT

Background and aims: Changes in size inequality in tree populations are often attributed to changes in the mode of competition over time. The mode of competition may also fluctuate annually in response to variation in growing conditions. Factors causing growth rate to vary can also influence competition processes, and thus influence how size hierarchies develop.

Methods: Detailed data obtained by tree-ring reconstruction were used to study annual changes in size and size increment inequality in several even-aged, fire-origin jack pine (Pinus banksiana) stands in the boreal shield and boreal plains ecozones in Saskatchewan and Manitoba, Canada, by using the Gini and Lorenz asymmetry coefficients.

Key results: The inequality of size was related to variables reflecting long-term stand dynamics (e.g. stand density, mean tree size and average competition, as quantified using a distance-weighted absolute size index). The inequality of size increment was greater and more variable than the inequality of size. Inequality of size increment was significantly related to annual growth rate at the stand level, and was higher when growth rate was low. Inequality of size increment was usually due primarily to large numbers of trees with low growth rates, except during years with low growth rate when it was often due to small numbers of trees with high growth rates. The amount of competition to which individual trees were subject was not strongly related to the inequality of size increment.

Conclusions: Differences in growth rate among trees during years of poor growth may form the basis for development of size hierarchies on which asymmetric competition can act. A complete understanding of the dynamics of these forests requires further evaluation of the way in which factors that influence variation in annual growth rate also affect the mode of competition and the development of size hierarchies.

Show MeSH
Related in: MedlinePlus