Beyond direct neighbourhood effects: higher-order interactions improve modelling and predicting tree survival and growth

Abstract

It is known that biotic interactions are the key to species coexistence and maintenance of species diversity. Traditional studies focus overwhelmingly on pairwise interactions between organisms, ignoring complex higher-order interactions (HOIs). In this study, we present a novel method of calculating individual-level HOIs for trees, and use this method to test the importance of size- and distance-dependent individual-level HOIs to tree performance in a 25-ha temperate forest dynamic plot. We found that full HOIs-inclusive models improved our ability to model and predict the survival and growth of trees, providing empirical evidence that HOIs strongly influence tree performance in this temperate forest. Specifically, assessed HOIs mitigate the competitive direct effects of neighbours on survival and growth of focal trees. Our study lays a foundation for future investigations of the prevalence and relative importance of HOIs in global forests and their impact on species diversity.

Disentangling key species interactions in diverse and heterogeneous communities: A Bayesian sparse modeling approach

“…Kraft et al 2015;Wainwright et al 2019) and the effect of environmental variation on these comparisons (Bimler et al, 2018;Lanuza et al, 2018). Yet nonlinearity, higher-order interactions, and intransitivity in diverse systems may yield complex dynamics that dramatically alter population growth and coexistence dynamics (Allesina & Levine, 2011;Li et al, 2021;May & Leonard, 1975;Mayfield & Stouffer, 2017). The further development and empirical testing of these theories thus requires a statistical approach that is applicable in diverse communities and is capable of identifying and incorporating key species interactions and environmental covariates.…”

Non-additive biotic interactions improve predictions of tropical tree growth and impact community size structure

“…Neill 1974; Abrams 1980; Wootton 1994), recent empirical work has provided evidence for non-negligible higher-order interactions (HOIs) in various natural systems (e.g. Weigelt et al 2007; Mayfield and Stouffer 2017; Li et al 2020; Xiao et al 2020) and prompted theoretical research into the conditions under which HOIs should be expected to emerge (Kleinhesselink, Kraft, and Levine 2019; Letten and Stouffer 2019). Tropical forests meet two of the proposed conditions for emergent HOIs: (i) resource acquisition traits, such as size, that are themselves density-dependent, and (ii) growth in size that responds non-linearly to resource availability.…”

“…If this architectural change is long-term, then the modified pairwise interaction will persist even after the intermediary species’ basal area stopped changing. The list of mechanisms here may include an explanation as to why our HOIs exacerbated, rather than mitigated (as in Li et al 2020), the reduction in diameter growth rates attributable to direct interactions.…”

“…Due to a lack of spatial data, we were unable to address these questions explicitly here but highlight them as important for future studies. We also acknowledge that without delimiting or estimating the interaction radii (as in Uriarte et al 2004; Comita et al 2010; Li et al 2020) some errors could have entered our parameter estimation (Detto et al 2019). Future studies should be aware that HOIs—as well as direct interactions—may be common but are simply too weak to be detected (Abrams 1983; Billick and Case 1994; Kleinhesselink, Kraft, and Levine 2019), especially over very short time-scales, when neighbour densities are measured inaccurately (Detto et al 2019), or if HOIs are only important at a certain life stage.…”

“…With increasing empirical evidence showing pronounced effects of HOIs in herbaceous plant communities (e.g. Weigelt et al 2007; Mayfield and Stouffer 2017; Xiao et al 2020) and recently in temperate tree communities (Li et al 2020), it is becoming important to assess the ubiquity of non-negligible HOIs across more natural systems. If HOIs are widespread and emerge easily under a wide range of conditions (Kleinhesselink, Kraft, and Levine 2019; Letten and Stouffer 2019), their effects likely need to be captured by community models in order to accurately predict the outcome of multi-species interactions both quantitatively (e.g.…”