Tree crown overlap improves predictions of the functional neighbourhood effects on tree survival and growth

Zambrano, Jenny; Fagan, William F.; Worthy, Samantha J.; Thompson, Jill; Uriarte, María; Zimmerman, Jess K.; Umaña, María Natalia; Swenson, Nathan G.

doi:10.1111/1365-2745.13075

Cited by 35 publications

(41 citation statements)

References 53 publications

(86 reference statements)

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“…In contrast, SPPA focus on interactions between individuals’ centroids at a certain range of spatial scales defined by the user and integrates multiple above‐ and below‐ground processes. Therefore, OAA should not be regarded as a substitute for SPPA but as an alternative, more appropriate to assess canopy interactions (McIntire & Fajardo, ; Zambrano et al, ) that remain elusive for current spatial tools. OAA should be employed whenever the crown or the mass of individuals of different species could overlap with one another, and where the individual crowns could be outlined as a bidimensional polygon, for example, biphasic vegetation‐bare soil communities (alpine, subalpine and Arctic areas, sand dunes, drylands, salt pans, gypsum and other specialized soils), shrubland, vertically structured forest stands (see Figure for more details).…”

Section: Discussionmentioning

confidence: 99%

“…The results obtained with the overlapping area analysis (OAA) in a cryophilic pasture of the Sierra de Guadarrama National Park Table 1 above-and below-ground processes. Therefore, OAA should not be regarded as a substitute for SPPA but as an alternative, more appropriate to assess canopy interactions (McIntire & Fajardo, 2009;Zambrano et al, 2019) that remain elusive for current spatial tools.…”

Section: Discussionmentioning

confidence: 99%

“…However, considering the sizes of the individual crowns does not account for their different shapes and configurations (e.g. overlapping), and therefore ignores some potentially important information (Zambrano et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

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The shape is more important than we ever thought: Plant to plant interactions in a high mountain community

et al. 2019

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Plant to plant interactions are probably the most important driver of species coexistence at fine spatial scales, but their detection represents a challenge in Ecology. Spatial point pattern analysis (SPPA) is likely the approach most used to identify them, however, it suffers from some limitations related to the over‐simplification of individuals to points. Here, we propose a new approach called Overlapping Area Analysis (OAA) to test whether the consideration of the shape and orientation of the individuals reveal signs of interactions between species that would remain undetected with SPPA. We used this approach to analyse a fully mapped cryophilic grassland in the Sierra de Guadarrama National Park (Spain), where the crown of each individual plant (i.e. the species canopy) was approximated by a polygon. We then computed and compared the total overlapping area between the canopy of a focal species and that of any other species in the community with the expectations of a null model of random rotation of each plant around its centroid. We complemented the results of our new approach by comparing with that of SPPA of plants’ centroids. Results of OAA showed that up to 41% of species pairs had less canopy overlap than expected, suggesting that many interspecific canopy associations in this plant community were significantly negative at the finest spatial scale. Contrarily, SPPA estimated that 12% of species pairs were positively associated at spatial scales up to 20 cm, confirming the facilitative effect displayed by the main engineer in the community (Festuca curvifolia Lag.) and by some other dominant species. Our new approach quantifying canopy associations provides new insights into the processes guiding community assembly. While the results of SPPA suggested the prevalence of traditional ‘stress gradient hypothesis’ (i.e. prevalence of positive interactions under stressful abiotic conditions), OAA revealed that many interspecific canopy associations were significantly negative. Overall, most facilitated species optimized this positive effect by placing their centroids as close to the benefactor species as their foraging behaviour allowed while avoiding crown overlap. The method proposed is available in a dedicated r‐package that will facilitate its application by other ecologists.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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The shape is more important than we ever thought: Plant to plant interactions in a high mountain community

et al. 2019

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“…A more biologically relevant measure of neighborhoods is to consider that neighborhoods based upon the physical overlap of crowns and/or root systems such that there is no fixed neighborhood radius (Lebrija‐Trejos, Wright, Hernandez, & Reich, 2014; Zambrano et al, 2019). In the Luquillo subtropical forest in Puerto Rico, the neighborhood models using crown overlap had better support than traditional models with fixed radius, suggesting that the traditional models with the fixed radius may not have a full picture of competitive interaction (Zambrano et al, 2019). So far crown overlap is a reasonable, although imperfect, measure for neighborhood interactions in terms of light and water resource competition, and this result giving us an idea of how to corporate whole tree allocation strategies in neighborhood models with traits.…”

Section: Size‐related Changes In Trait‐assemblymentioning

confidence: 99%

Towards linking species traits to demography and assembly in diverse tree communities: Revisiting the importance of size and allocation

Iida

Swenson

2020

Ecological Research

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One of the important goals in plant ecology is to form a mechanistic link between the underlying processes driving the dynamics and structure of communities and the observed demography (i.e., growth, survival, and recruitment) and assembly (i.e., distribution of species) in a community via traits. Although the importance of traits to performance is evident, their direct links to demography and the resulting assembly in tree communities are often found to be fairly weak probably because a single "mean" trait value for a species is not enough to capture complex life histories. In this paper, we review how traits at the organ-level and at the whole plant level, demography, and assembly change with size in diverse tropical forests and summarize what we know so far. We argue the importance of trait-based life-history strategies revealing trait-environment-demography linkages across ontogenetic stages to achieve the ultimate goal of forming a mechanistic link between the underlying processes driving the dynamics and structure of communities and the observed demography and assembly.

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“…As density-dependent effects have been traditionally studied using a fixed neighbourhood size to capture the interactions between seedlings and their neighbours (Comita et al, 2009;Bai et al, 2012;Johnson et al, 2017), such an approach does, in our opinion, not fully account for the fact that the processes underlying these interactions may operate at different spatial scales (Zambrano et al, 2019;Zambrano et al, 2020). For instance, the spatial scale of neighbourhoods over which seedlings experience density-dependent effects may differ among species (Queenborough et al, 2007), and likely also among plants of different sizes and growth forms.…”

Section: Introductionmentioning

confidence: 99%

Light can modify density‐dependent seedling mortality in a temperate forest

Holík

Janík

Adam

2021

J Vegetation Science

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Questions: There is growing evidence on how density-dependent drivers of plant performance are influenced by habitat heterogeneity such as variation in understorey light availability. How these processes operate in temperate forests still remains an open question, however. We examined the interactive effects of density dependence and light availability on woody seedling mortality across multiple species, two size stages and growth forms. Location: Alluvial old-growth temperate forest, southeastern Czech Republic. Methods: We mapped seedlings of woody species (≥10 cm tall) and recorded their mortality over a two-year period on 21 square seedling plots (25 m 2) within one large square plot with all trees mapped (≥1 cm diameter at breast height). Seedling mortality was studied using a combined approach of generalised linear mixed models and spatial point pattern analyses. Results: Density-dependent effects of tree and seedling neighbours influenced seedling mortality at different spatial scales, depending on their size class, growth form and by taxon. Conspecific inhibition raised the mortality of seedlings other than Acer campestre at low light levels, indicating that host-specific enemies and/or intraspecific competition may be important in unfavourable habitats. While small seedlings experienced conspecific inhibition at low light levels, tall seedlings were additively affected by low-light conditions and competition with trees. Both conspecific and heterospecific neighbours tended to affect tree seedlings at low light levels, whereas shrub seedlings experienced light-and density-independent mortality. Some negative interspecific interactions indicated ongoing expansion of species like Acer campestre in currently flood-free habitats. Conclusions: How density-dependent effects translate into demographic outcomes for woody seedling populations may be largely determined by variation in understorey light availability. Given that seedlings differ in size, growth form and taxa, we also demonstrate that both seedling and tree neighbours may contribute to the strength and spatial variation in density-dependent effects at seedling neighbourhood scales.

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Tree crown overlap improves predictions of the functional neighbourhood effects on tree survival and growth

Cited by 35 publications

References 53 publications

The shape is more important than we ever thought: Plant to plant interactions in a high mountain community

The shape is more important than we ever thought: Plant to plant interactions in a high mountain community

Towards linking species traits to demography and assembly in diverse tree communities: Revisiting the importance of size and allocation

Light can modify density‐dependent seedling mortality in a temperate forest

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