Demographic consequences of heterogeneity in conspecific density dependence among mast-fruiting tropical trees

O’Brien, Michael J.; Héctor, Andy; Kellenberger, Roman T.; Maycock, Colin R.; Philipson, Christopher D.; Powers, Jennifer S.; Reynolds, Glen; Burslem, David F. R. P.

doi:10.1098/rspb.2022.0739

Cited by 7 publications

(4 citation statements)

References 44 publications

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“…Moreover, adult tropical trees can live for hundreds of years ( 14 ) and integrate density dependent effects throughout their life. CNDD at one life stage can be offset by positive effects at another ( 2, 15 ), or have a weak effect on lifetime performance, begging the question – what is the overall integrated effect of conspecifics on populations? Importantly, this integrated effect is what matters for coexistence (2).…”

Section: Main Textmentioning

confidence: 99%

Pervasive species-specific repulsion among adult tropical trees

Kalyuzhny

Lake

Wright

et al. 2022

Preprint

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For multiple species to stably coexist, it is necessary that, as species increase in abundance, they suffer from Conspecific Negative Density Dependence (CNDD). For trees, there is ample evidence for such negative effects of abundance on the survival and frequency of juveniles, typically on small spatial scales. Despite this short distance 'repulsion' of juveniles, adult trees are generally spatially aggregated, and there is little evidence that CNDD acting on juveniles propagates to the adult stage, casting doubt on its importance for coexistence. However, evidence of aggregation was previously obtained by comparing the spatial distribution of adults to a random placement across the landscape, ignoring dispersal limitation. Here we show that, when compared to the predictions of a calibrated null model of stochastic birth, death and limited dispersal, the adults of dozens of tropical forest species are almost ubiquitously and strongly overdispersed, often up to distances of ~100 meters. We also show that such strong overdispersion can only occur if CNDD considerably exceeds Heterospecific Negative Density Dependence, creating stabilizing niche differences, which are an important requirement for stable coexistence. Together these findings suggest that CNDD propagates from juveniles to adults, strongly influencing adult spatial distribution. Furthermore, these results refine our view of the fundamental nature of species spatial distributions, a key interest in ecology, and demonstrate the power of using limited dispersal null models to detect biotic interactions and habitat associations from spatial distributions.

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Section: Main Textmentioning

confidence: 99%

Pervasive species-specific repulsion among adult tropical trees

Kalyuzhny

Lake

Wright

et al. 2022

Preprint

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“…Regeneration of forest plant communities is dependent on both the ability to produce sufficient seedlings and their ability to survive to maturity. In lowland Southeast Asian forests, the production of large seedling populations via general masting is important to promote seed predator satiation (Janzen, 1974; O'Brien et al., 2022; Sun et al., 2007; Visser et al., 2011). Removal of large, reproductively mature individuals through logging may reduce the strength of masting and seed production and thus the capacity to satiate seed predators.…”

Section: Introductionmentioning

confidence: 99%

Bornean tropical forests recovering from logging at risk of regeneration failure

Bartholomew,

Hayward,

Burslem

et al. 2024

Global Change Biology

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Active restoration through silvicultural treatments (enrichment planting, cutting climbers and liberation thinning) is considered an important intervention in logged forests. However, its ability to enhance regeneration is key for long‐term recovery of logged forests, which remains poorly understood, particularly for the production and survival of seedlings in subsequent generations. To understand the long‐term impacts of logging and restoration we tracked the diversity, survival and traits of seedlings that germinated immediately after a mast fruiting in North Borneo in unlogged and logged forests 30–35 years after logging. We monitored 5119 seedlings from germination for ~1.5 years across a mixed landscape of unlogged forests (ULs), naturally regenerating logged forests (NR) and actively restored logged forests via rehabilitative silvicultural treatments (AR), 15–27 years after restoration. We measured 14 leaf, root and biomass allocation traits on 399 seedlings from 15 species. Soon after fruiting, UL and AR forests had higher seedling densities than NR forest, but survival was the lowest in AR forests in the first 6 months. Community composition differed among forest types; AR and NR forests had lower species richness and lower evenness than UL forests by 5–6 months post‐mast but did not differ between them. Differences in community composition altered community‐weighted mean trait values across forest types, with higher root biomass allocation in NR relative to UL forest. Traits influenced mortality ~3 months post‐mast, with more acquisitive traits and relative aboveground investment favoured in AR forests relative to UL forests. Our findings of reduced seedling survival and diversity suggest long time lags in post‐logging recruitment, particularly for some taxa. Active restoration of logged forests recovers initial seedling production, but elevated mortality in AR forests lowers the efficacy of active restoration to enhance recruitment or diversity of seedling communities. This suggests current active restoration practices may fail to overcome barriers to regeneration in logged forests, which may drive long‐term changes in future forest plant communities.

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“…Moreover, adult tropical trees can live for hundreds of years ( 14 ) and integrate density-dependent effects throughout their life. CNDD at one life stage can be offset by positive effects at another ( 4 , 15 ) or have a weak effect on lifetime performance. This raises the question of the overall integrated effect of conspecifics on populations, which determines long-term coexistence ( 4 ).…”

mentioning

confidence: 99%

Pervasive within-species spatial repulsion among adult tropical trees

Kalyuzhny

Lake

Wright

et al. 2023

Science

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For species to coexist, performance must decline as the density of conspecific individuals increases. Although evidence for such conspecific negative density dependence (CNDD) exists in forests, the within-species spatial repulsion it should produce has rarely been demonstrated in adults. In this study, we show that in comparison to a null model of stochastic birth, death, and limited dispersal, the adults of dozens of tropical forest tree species show strong spatial repulsion, some to surprising distances of approximately 100 meters. We used simulations to show that such strong repulsion can only occur if CNDD considerably exceeds heterospecific negative density dependence—an even stronger condition required for coexistence—and that large-scale repulsion can indeed result from small-scale CNDD. These results demonstrate substantial niche differences between species that may stabilize species diversity.

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Demographic consequences of heterogeneity in conspecific density dependence among mast-fruiting tropical trees

Cited by 7 publications

References 44 publications

Pervasive species-specific repulsion among adult tropical trees

Pervasive species-specific repulsion among adult tropical trees

Bornean tropical forests recovering from logging at risk of regeneration failure

Pervasive within-species spatial repulsion among adult tropical trees

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