Plant functional traits involved in the assembly of canopy–recruit interactions

Abstract

Questions: The assembly of plant communities depends strongly on mechanisms that determine the recruitment of different plant species. Studying recruitment using a trait-based approach may help in the search for general or dominant mechanisms involved in this process. Here, we try to disentangle what traits of saplings and established (canopy) plants can be considered as functional for recruitment, and whether the complementarity of these functional traits may be a driver of the plant community assembly. Location: Regional. Two pine-oak forest communities in Sierra Sur de Jaén and one in Sierra de Segura, southeast of the Iberian peninsula. Methods: In each forest community, we established three 50 m × 50 m plots, where we identified the saplings of each species recruiting under the canopy of each species or in open interspaces. The study focuses on 37 woody species. Measures of 18 traits were conducted for 30 saplings and 10 adults of each species. Results: Seed mass and the ratio height:basal diameter of saplings were positively associated with species abundance in the sapling bank under vegetation, while abundance in the sapling bank in open interspaces was only related to the type of mycorrhizal association. On the other hand, some traits of adult plants (leaf mass per unit area [LMA], seed dispersal mechanism, leaf habit and branch density) favour the recruitment of other species in their close proximity. However, we found only circumstantial evidence of canopy/recruit trait complementarity affecting recruitment. Conclusions: Our results suggest that the assembly of canopy-recruit interactions is primarily driven by the filtering effect of canopy species on recruitment, through traits that affect both seed arrival and soil properties. Species abundance in the sapling bank was related to resource acquisition traits. We did not find any clear evidence supporting that trait complementarity is involved in the interaction between canopy and recruit species.

Legacy effects of seed dispersal mechanisms shape the spatial interaction network of plant species in Mediterranean forests

“…Adults can also exert competitive pressure on saplings (Alcántara et al., 2015; Perea, Garrido, et al, 2021) that may counteract initially positive associations mediated by animal seed dispersal. However, we found only one negative spatial association between adults and saplings of the two Crataegus species at the MFS plot.…”

“…Key processes include seed dispersal, species interactions such as competition or facilitation, and mechanisms governing the interactions of species with their environment (Valladares et al., 2015). Many studies seeking to understand plant coexistence focus on plant–plant interactions, trying to disentangle what processes and species traits can explain co‐occurrence of competing species (Kraft et al., 2015; Maestre et al., 2005; Perea, Garrido, et al., 2021). However, this is not always straight‐forward since processes occurring during early life stages, such as seed dispersal, antagonism, (micro) habitat filtering or facilitation may predetermine the interactions occurring among adult plants (Anthelme & Dangles, 2012; Lara‐Romero et al., 2016).…”

Spatial phylogenetic and phenotypic patterns reveal ontogenetic shifts in ecological processes of plant community assembly

“…We collected traits for 30 saplings and 15 adults of each species, separated by at least 10 m along a 100 m transect parallel to the plots (Perea et al 2021a). These traits were categorized into three categories: structural, morphological leaf and chemical leaf traits.…”

“…Morphological leaf traits included leaf area and specific leaf area (SLA), whereas chemical leaf traits included the C:N ratio and leaf hydrogen. These traits represent essential characteristics involved in canopy-recruit interactions (Perea et al 2021a) and other ecological processes involved Table 1. Scheme of the analyses conducted in this study.…”

“…Measures of these traits have been stored in TRY Database (Kattge et al 2020). A summary of the data collection, trait measurements and trait-related processes are provided in Perea et al (2021a) and the corresponding Supplementary material. For all traits, we calculated the mean values for each species, at each plot and at each life stage.…”