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Facilitative-competitive interactions in an old-growth forest: the importance of large-diameter trees as benefactors and stimulators for forest community assembly.

Fichtner A, Forrester DI, Härdtle W, Sturm K, von Oheimb G - PLoS ONE (2015)

Bottom Line: We found that each mode of competition reduced the effect of the other.As a result, competition seemed to become less important in stands with a high growing stock and tree communities with a long continuity of anthropogenic undisturbed population dynamics.We suggest that growth rates do not exclusively depend on the density of potential competitors at the intraspecific level, but on the conspecific aggregation of large-diameter trees and their functional role for regulating biotic filtering processes.

View Article: PubMed Central - PubMed

Affiliation: Institute of Ecology, Leuphana University of Lüneburg, Lüneburg, Germany.

ABSTRACT
The role of competition in tree communities is increasingly well understood, while little is known about the patterns and mechanisms of the interplay between above- and belowground competition in tree communities. This knowledge, however, is crucial for a better understanding of community dynamics and developing adaptive near-natural management strategies. We assessed neighbourhood interactions in an unmanaged old-growth European beech (Fagus sylvatica) forest by quantifying variation in the intensity of above- (shading) and belowground competition (crowding) among dominant and co-dominant canopy beech trees during tree maturation. Shading had on average a much larger impact on radial growth than crowding and the sensitivity to changes in competitive conditions was lowest for crowding effects. We found that each mode of competition reduced the effect of the other. Increasing crowding reduced the negative effect of shading, and at high levels of shading, crowding actually had a facilitative effect and increased growth. Our study demonstrates that complementarity in above- and belowground processes enable F. sylvatica to alter resource acquisition strategies, thus optimising tree radial growth. As a result, competition seemed to become less important in stands with a high growing stock and tree communities with a long continuity of anthropogenic undisturbed population dynamics. We suggest that growth rates do not exclusively depend on the density of potential competitors at the intraspecific level, but on the conspecific aggregation of large-diameter trees and their functional role for regulating biotic filtering processes. This finding highlights the potential importance of the rarely examined relationship between the spatial aggregation pattern of large-diameter trees and the outcome of neighbourhood interactions, which may be central to community dynamics and the related forest ecosystem services.

No MeSH data available.


Related in: MedlinePlus

Stand structure of the investigated old-growth beech forest.The x-axis represents the upper boundaries of the tree size (DBH)-class. Regresssion lines were obtained by fitting generalized additive models (gam function in R, with five degrees of freedom). Grey dots: investigation year 2002; black dots: investigation year 2009.
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pone.0120335.g001: Stand structure of the investigated old-growth beech forest.The x-axis represents the upper boundaries of the tree size (DBH)-class. Regresssion lines were obtained by fitting generalized additive models (gam function in R, with five degrees of freedom). Grey dots: investigation year 2002; black dots: investigation year 2009.

Mentions: The Serrahn forest is characterised by a long (>450 years) continuity of forest cover [33]. From the beginning of the 19th century the Serrahn forest was used as a game park with low intensity silvicultural interventions. In 1960, it was declared a forest nature reserve and management ceased. During the last 40 years, stand structure became more heterogeneous over small spatial scales by shifting from mono-layered to multi-layered stands. These changes were mainly driven by increasing mortality rates of canopy trees in the late 1960s, which caused numerous canopy gaps and created conditions conducive to regeneration over large spatial scales. As a result the volume of dead wood considerably increased from 1967 to 2002 in the permanent plot (4 to 107 m3 ha−1) [32]. Thus, the current rotated sigmoid diameter distribution (Fig. 1) is mainly a function of self-thinning and mortality processes of old trees [34].


Facilitative-competitive interactions in an old-growth forest: the importance of large-diameter trees as benefactors and stimulators for forest community assembly.

Fichtner A, Forrester DI, Härdtle W, Sturm K, von Oheimb G - PLoS ONE (2015)

Stand structure of the investigated old-growth beech forest.The x-axis represents the upper boundaries of the tree size (DBH)-class. Regresssion lines were obtained by fitting generalized additive models (gam function in R, with five degrees of freedom). Grey dots: investigation year 2002; black dots: investigation year 2009.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4372556&req=5

pone.0120335.g001: Stand structure of the investigated old-growth beech forest.The x-axis represents the upper boundaries of the tree size (DBH)-class. Regresssion lines were obtained by fitting generalized additive models (gam function in R, with five degrees of freedom). Grey dots: investigation year 2002; black dots: investigation year 2009.
Mentions: The Serrahn forest is characterised by a long (>450 years) continuity of forest cover [33]. From the beginning of the 19th century the Serrahn forest was used as a game park with low intensity silvicultural interventions. In 1960, it was declared a forest nature reserve and management ceased. During the last 40 years, stand structure became more heterogeneous over small spatial scales by shifting from mono-layered to multi-layered stands. These changes were mainly driven by increasing mortality rates of canopy trees in the late 1960s, which caused numerous canopy gaps and created conditions conducive to regeneration over large spatial scales. As a result the volume of dead wood considerably increased from 1967 to 2002 in the permanent plot (4 to 107 m3 ha−1) [32]. Thus, the current rotated sigmoid diameter distribution (Fig. 1) is mainly a function of self-thinning and mortality processes of old trees [34].

Bottom Line: We found that each mode of competition reduced the effect of the other.As a result, competition seemed to become less important in stands with a high growing stock and tree communities with a long continuity of anthropogenic undisturbed population dynamics.We suggest that growth rates do not exclusively depend on the density of potential competitors at the intraspecific level, but on the conspecific aggregation of large-diameter trees and their functional role for regulating biotic filtering processes.

View Article: PubMed Central - PubMed

Affiliation: Institute of Ecology, Leuphana University of Lüneburg, Lüneburg, Germany.

ABSTRACT
The role of competition in tree communities is increasingly well understood, while little is known about the patterns and mechanisms of the interplay between above- and belowground competition in tree communities. This knowledge, however, is crucial for a better understanding of community dynamics and developing adaptive near-natural management strategies. We assessed neighbourhood interactions in an unmanaged old-growth European beech (Fagus sylvatica) forest by quantifying variation in the intensity of above- (shading) and belowground competition (crowding) among dominant and co-dominant canopy beech trees during tree maturation. Shading had on average a much larger impact on radial growth than crowding and the sensitivity to changes in competitive conditions was lowest for crowding effects. We found that each mode of competition reduced the effect of the other. Increasing crowding reduced the negative effect of shading, and at high levels of shading, crowding actually had a facilitative effect and increased growth. Our study demonstrates that complementarity in above- and belowground processes enable F. sylvatica to alter resource acquisition strategies, thus optimising tree radial growth. As a result, competition seemed to become less important in stands with a high growing stock and tree communities with a long continuity of anthropogenic undisturbed population dynamics. We suggest that growth rates do not exclusively depend on the density of potential competitors at the intraspecific level, but on the conspecific aggregation of large-diameter trees and their functional role for regulating biotic filtering processes. This finding highlights the potential importance of the rarely examined relationship between the spatial aggregation pattern of large-diameter trees and the outcome of neighbourhood interactions, which may be central to community dynamics and the related forest ecosystem services.

No MeSH data available.


Related in: MedlinePlus