Quantifying neighbour effects on tree growth: Are common ‘competition’ indices biased?

Britton, Travis G.; Richards, Shane A.; Hovenden, Mark J.

doi:10.1111/1365-2745.14095

Cited by 6 publications

(10 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For each focal tree, we used absolute annual (BAI; cm 2 ) as the growth response variable (Britton et al., 2023a). Individual tree basal area was calculated using individual tree diameter (cm) measurements.…”

Section: Methodsmentioning

confidence: 99%

“…where NI i is the index associated with focal tree i, of which there are n. BA j is the basal area of neighbour plant j, and d i,j is the distance metric separating focal plant i and neighbour j. The three indices differed only in how the distance term (d i,j ) was specified: linear (Britton et al, 2023a), squared or log-transformed.…”

Section: Neighbourhood Characteristicsmentioning

confidence: 99%

“…All data used in this study is available from the Dryad Digital Repository https://doi.org/10.5061/dryad.tmpg4.f53b (Britton et al., 2023b).…”

Section: Peer Reviewmentioning

confidence: 99%

See 2 more Smart Citations

The competitive effect of neighbouring plants on the growth of two eucalypts is stronger in dry conditions

Britton,

Richards,

Gerwin

et al. 2023

Journal of Ecology

Self Cite

View full text Add to dashboard Cite

Plant growth is influenced by interactions with neighbouring plants. The strength and direction of the cumulative neighbourhood effect on growth can depend on neighbour properties, such as their abundance, size and proximity, as well as the degree of similarity between interacting plants and their traits, which can be captured by the species identity of neighbours. Such interactions are also influenced by the local environmental conditions that are largely determined by climate. Because neighbour and climatic effects are typically explored in isolation, particularly in long‐lived species such as trees, it is unclear how the impacts of neighbours on plant growth shift in response to temporal variation in climatic conditions. Here, we explored how neighbouring plants impact the annual growth of two eucalypts, Eucalyptus delegatensis and Eucalyptus regnans, over three growing seasons in an experimental forest in south‐east Tasmania, Australia. We assessed whether eucalypt growth rates could be described by the number, size, proximity, and species identity of neighbours, and how the strength of this effect was influenced by the growing season climatic conditions. We found that climate and neighbouring plants had an interactive impact on eucalypt growth. Neighbours had a consistent, competitive effect on the growth of both eucalypts in all three growing seasons which was strongly related to the cumulative neighbourhood biomass. The identity of neighbours was important in determining E. regnans growth only, whereby distinguishing neighbours according to functional group best described growth. Over all three growing seasons, we predicted that, on average, neighbours reduced E. delegatensis and E. regnans mean annual growth by 60.5% and 48.4%, respectively. However, the strength of the competitive effect of neighbours on eucalypt growth was related to growing season climate, being strongest when conditions were hot and dry and weakest in cool, wet conditions. Synthesis: Given the consistent results observed in two co‐occurring eucalypts, our findings suggest that drier and hotter climatic conditions increase the strength of competitive effects on tree growth. This has implications for future forest productivity given projected increased temperatures and variation in rainfall patterns globally.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Neighbourhood Characteristicsmentioning

confidence: 99%

See 1 more Smart Citation

The competitive effect of neighbouring plants on the growth of two eucalypts is stronger in dry conditions

Britton,

Richards,

Gerwin

et al. 2023

Journal of Ecology

Self Cite

View full text Add to dashboard Cite

show abstract

“…We ensured that our competition index was not overestimating competition by using a method similar to Britton et al. (2023). For a more detailed method description, see Appendix C.…”

Section: Methodsmentioning

confidence: 99%

It takes a village to grow a tree: Most tree species benefit from dissimilar neighbors

Di Maurizio,

Searle,

Paquette

2023

Ecology and Evolution

View full text Add to dashboard Cite

Scientific consensus is that diverse tree species positively impact forest productivity, especially when species are functionally dissimilar. Under the complementarity hypothesis, differences in species traits reduce competition among neighboring tree species. However, while this relationship has been extensively studied at the community level, there is a lack of understanding regarding how individuals of different species specifically respond to a functionally dissimilar neighborhood. In this study, we used permanent plots from Quebec, Canada, and 19 focal tree species to test whether: (1) tree growth response to neighborhood dissimilarity varies with their identity and competition intensity, and (2) focal tree species’ traits explain their response to neighborhood dissimilarity. We demonstrate that: tree growth is primarily influenced by competition, species identity, and their interactions, but that dissimilarity, alone and in interaction with the main drivers of tree growth, explains an additional 1.8% of the variation in species growth. Within this context, (1) most species’ respond positively to neighborhood dissimilarity, with magnitude being species and competition dependent, and (2) focal tree traits partly explain these dependencies, with shade‐intolerant species benefiting most from dissimilar neighbors under high competition. Our study provides empirical support for the complementarity hypothesis, emphasizing the small but consistent positive effect of functional dissimilarity on tree growth in local neighborhoods. Our findings identify the species with the highest potential of benefiting from dissimilar neighbors but also demonstrate that the positive effect of neighborhood dissimilarity is not limited to a select few species with specific traits; rather, it is observed across a diverse range of species. The cumulative growth responses of individuals to functionally dissimilar neighbors may help explain the commonly observed higher productivity in more diverse communities.

show abstract

“…Consequently, we quantified competition using the widely applied Hegyi competition index (Britton et al, 2023). Details about the index can be found in Hegyi (1974).…”

Section: Several Indices Exist To Quantify the Competition Intensitymentioning

confidence: 99%

Intraspecific variation in fruit production of African mahogany (Khaya anthotheca) in a semi‐deciduous East African rainforest

Okimat,

Babweteera,

Ehbrecht

2023

Afr J Ecol

View full text Add to dashboard Cite

Restoring valuable timber trees is a necessary part of regaining many ecosystem services and products provided by degraded tropical forests. However, knowledge of seed production, a regeneration prerequisite, is limited for many tropical timber tree species. We studied the fruit production of African mahogany (Khaya anthotheca) in a semi‐deciduous rainforest in East Africa, to provide information for ecological restoration programs. First, we quantified population variability and synchrony in fruit production. Then, we assessed how reproductive status and output were influenced by tree size, neighbourhood crowding, exchangeable cations, liana presence, and crown exposure. We found fruit production at the population level was weakly synchronised, with high interannual variability at the population and individual levels. Tree size determined reproductive status. Individual quantity of fruit produced increased with tree size but decreased with neighbourhood crowding. Our results indicate that K. anthotheca does not meet the criteria for mast fruiting. Our findings suggest that reproductive output in mahogany is regulated by tree size and competition. In addition to active protection, thinning to reduce competition around seed trees may boost fruit production at the individual tree level to provide seed for forest enrichment.

show abstract

Quantifying neighbour effects on tree growth: Are common ‘competition’ indices biased?

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 6 publications

References 50 publications

The competitive effect of neighbouring plants on the growth of two eucalypts is stronger in dry conditions

The competitive effect of neighbouring plants on the growth of two eucalypts is stronger in dry conditions

It takes a village to grow a tree: Most tree species benefit from dissimilar neighbors

Intraspecific variation in fruit production of African mahogany (Khaya anthotheca) in a semi‐deciduous East African rainforest

Contact Info

Product

Resources

About