Annual Variations in Competition Symmetry in Even-aged Sitka Spruce

Wichmann, Lars

doi:10.1006/anbo.2001.1445

Cited by 57 publications

(42 citation statements)

References 32 publications

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“…They suggest that trees of different social positions react differently and maybe small trees can partly compensate for the losses of tall trees and stabilise stand growth under drought. Wichmann (2001) provided evidence for this kind of behaviour on the basis of stem analyses in Sitka spruce. His finding that the relationship between tree size and size growth is steep in moist years and shallow in dry years (temporal variation) corroborates analogous findings on moist compared with dry sites (spatial variation) (Pretzsch 2010).…”

Section: Introductionmentioning

confidence: 93%

“…Limitation by light with ample supply of water and nutrients may result in a size-asymmetric competition and over-proportional growth of tall trees compared with small trees (Schwinning and Weiner 1998). Many empirical studies show that latter environment may enable dominant trees to pre-empt light and other resources and cause shading, growth reduction and eventually mortality of their smaller neighbours (Wichmann 2001;Pretzsch et al 2012). The growth partitioning in mainly light-limited environments in temperate forests is rather well explored (Pretzsch and Biber 2010), represented in models (Biging and Dobbertin 1995), and applied for silvicultural prescriptions (Kramer 1988;Pretzsch and Zenner 2017).…”

Section: Introductionmentioning

confidence: 99%

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Drought can favour the growth of small in relation to tall trees in mature stands of Norway spruce and European beech

2018

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Background: Climate change triggered many studies showing that trends and events of environmental conditions can reduce but also accelerate growth at the stand and individual tree level. However, it is still rather unknown how climate change modifies the growth partitioning between the trees in forest stands. Methods: Based on long-term girth-tape measurements in mature monospecific and mixed-species stands of Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica L.) we traced the effect of the severe droughts in 2003 and 2015 from the stand down to the tree level. Results: Stand growth of Norway spruce decreased by about 30% in the once-in-a-century drought 2015, while European beech was much more drought resistant. Water availability generally amplified size-asymmetric growth partitioning. Especially in case of Norway spruce water availability primarily fostered the growth of predominant trees, whereas drought favoured the growth of small trees at the expense of the predominant ones. We could not detect significant differences between mixed and monospecific stands in this regard. Conclusions: The drought-induced reallocation of growth in favour of small trees in case of spruce may result from its isohydric character. We hypothesize that as small trees are shaded, they can benefit from the reduced water consumption of their sun-exposed taller neighbours. In case of beech, as an anisohydric species, tall trees suffer less and smaller trees benefit less under drought. The discussion elaborates the consequences of the water dependent growth allocation for forest monitoring, growth modelling, and silviculture.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Drought can favour the growth of small in relation to tall trees in mature stands of Norway spruce and European beech

2018

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“…Completely size symmetric competition or two-sided competition occurs where resource uptake among competitors is independent of their relative sizes, and completely size-asymmetric competition or one-sided competition occurs where the largest plants obtain all the contested resources (Schwinning and Weiner, 1998). Although there is not a general relationship between the degree of size symmetry or asymmetry and the particular growth limiting resources, many studies (Weiner et al, 1990;Wichmann, 2001) pointed to an association between size-symmetric competition and competition for below-ground resources on the one hand, and between sizeasymmetric competition and above-ground competition for light on the other.…”

Section: Introductionmentioning

confidence: 99%

Analyzing size-symmetric vs. size-asymmetric and intra- vs. inter-specific competition in beech (Fagus sylvatica L.) mixed stands

Rı́o

Condés

Pretzsch

2014

Forest Ecology and Management

104

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In mixed stands, inter-specific competition can be lower than intra-specific competition when niche complementarity and/or facilitation between species prevail. These positive interactions can take place at belowground and/or aboveground levels. Belowground competition tends to be size symmetric while the aboveground competition is usually for light and almost always size-asymmetric. Interactions between forest tree species can be explored analyzing growth at tree level by comparing intra and inter-specific competition. At the same time, possible causes of niche complementarity can be inferred relating intra and inter-specific competition with the mode of competition, i.e. size-symmetric or sizeasymmetric. The aim of this paper is to further our understanding of the interactions between species and to detect possible causes of competition reduction in mixed stands of beech (Fagus sylvatica L.) with other species: pine-beech, oak-beech and fir-beech. To test whether species growth is better explained by size-symmetric and/or size-asymmetric competition, five different competition structures where included in basal area growth models fitted using data from the Spanish National Forest Inventory for the Pyrenees. These models considered either size-symmetry only (Reineke's stand density index, SDI), size-asymmetry only (SDI of large trees or SDI of small trees), or both combined. In order to assess the influence of the admixture, these indices were introduced in two different ways, one of which was to consider that trees of all species compete in a similar way, and the other was to split the stand density indices into intra-and inter-specific competition components. The results showed that in pine-beech mixtures, there is a slightly negative effect of beech on pine basal area growth while beech benefitted from the admixture of Scots pine; this positive effect being greater as the proportion of pine trees in larger size classes increases. In oak-beech mixtures, beech growth was also positively influenced by the presence of oaks that were larger than the beech trees. The growth of oak, however, decreased when the proportion of beech in SDI increased, although the presence of beech in larger size classes promoted oak growth. Finally, in fir-beech mixtures, neither fir nor beech basal area growth were influenced by the presence of the other species. The results indicate that size-asymmetric is stronger than size-symmetric competition in these mixtures, highlighting the importance of light in competition. Positive species interactions in size-asymmetric competition involved a reduction of asymmetry in tree size-growth relationships.

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“…One-sided competition is assumed to be competition for light (Cannell et al 1984;Cannell and Grace 1993;Schwinning and Weiner 1998;Wichmann 2001). Stable size ratios or reduction in size inequality with increasing density may result from no competition or two-sided (symmetric) competition, mainly competition for belowground resources (Weiner and Thomas 1986;Brand and Magnussen 1988;Schwinning and Weiner 1998;Wichmann 2001).…”

Section: Introductionmentioning

confidence: 99%

Changes in structural inequality in Norway spruce stands on peatland sites after water-level drawdown

Sarkkola¹,

Alenius²,

Hökkä³

et al. 2003

Can. J. For. Res.

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Size structural dynamics of naturally established Norway spruce (Picea abies (L.) Karst.) stands growing on peatlands drained for forestry were investigated. The study was based on modelling of diameter at breast height (DBH) distributions of repeatedly measured stands in southern Finland. The Weibull function was used to parameterize the DBH distributions and mixed linear models were constructed to characterize the impacts of different ecological factors on stand dynamics. Initially, the positive skewness of the DBH distributions increased after drainage as a result of increases in stem numbers and a reduction in mean diameters. Simultaneously, the size inequality among trees increased. These changes were due to regeneration and (or) ingrowth and indicated only little competition from the larger trees. Subsequently, the DBH distributions changed from positively skewed to normal and finally to negatively skewed resulting from tree growth and a reduction in the number of small DBH trees. This indicated increased asymmetric intertree competition. Size inequality did not change during this later stage in stand development, suggesting a concurrent component of symmetric competition. Thinnings had little impact on DBH distribution trends. The observed stand dynamics allow the allocation of growth resources to the desired crop component by appropriate silvicultural treatments.Résumé : La dynamique de peuplements naturels d'épicéa commun (Picea abies (L.) Karst.) établis dans des tourbiè-res drainées a été analysée en termes de taille et de structure. L'étude se base sur la modélisation des distributions du diamètre à hauteur de poitrine (DHP) de peuplements mesurés à maintes reprises dans le Sud de la Finlande. La fonction de Weibull a été utilisée pour paramétrer les distributions du DHP et des modèles linéaires mixtes ont été construits de façon à caractériser les impacts de différents facteurs écologiques sur la dynamique des peuplements. À la suite du drainage, l'asymétrie gauche des distributions du DHP augmente dans un premier temps à cause de l'augmentation du nombre de tiges et de la réduction des diamètres moyens, en même temps qu'augmente l'inégalité de la taille entre les arbres. Ces changements sont dus à la régénération ou au recrutement et traduisent le peu de compétition de la part des arbres les plus grands. Les distributions du DHP passent ensuite d'une asymétrie gauche à la normalité puis à une asymétrie droite, à la suite de la croissance des arbres et de la réduction du nombre d'arbres de petit DHP. Ceci indique une compétition asymétrique plus forte entre les arbres. L'inégalité des tailles ne change plus pendant ce dernier stade de développement du peuplement, laissant entrevoir l'existence d'une composante concurrente de compétition symétrique. Les éclaircies avaient peu d'impact sur l'évolution des distributions du DHP. Les résultats de l'observation de la dynamique des peuplements permettent d'envisager une allocation des ressources de croissance vers les composantes les plus désirée...

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Annual Variations in Competition Symmetry in Even-aged Sitka Spruce

Cited by 57 publications

References 32 publications

Drought can favour the growth of small in relation to tall trees in mature stands of Norway spruce and European beech

Drought can favour the growth of small in relation to tall trees in mature stands of Norway spruce and European beech

Analyzing size-symmetric vs. size-asymmetric and intra- vs. inter-specific competition in beech (Fagus sylvatica L.) mixed stands

Changes in structural inequality in Norway spruce stands on peatland sites after water-level drawdown

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