Communities: are they groups of hidden interactions?

Abstract

Questions: Ecologists are increasingly interested in community-level consequences of biotic interactions. However, community-level studies have not considered that biotic interactions might have contrasting directions within communities, and indirect interactions are rarely quantified although they may influence community-level outcomes. We tested the hypotheses that in speciesrich plant communities from intermediate severe environmental conditions: (1) direct facilitation by dominant functional groups is balanced by negative indirect interactions among beneficiary species with no net effect at the community level on diversity and biomass, and (2) both direct and indirect interactions contribute to community composition.Location: A species-rich subalpine community of the eastern Tibet Plateau (China). Methods:We removed dominant shrubs and graminoids and quantified, at the community and species levels, their direct and indirect effects on 43 forb species. We used multivariate analyses to assess the contribution of direct and indirect effects on community composition.Results: There were no community-level effects of either dominant life form on forb diversity and biomass. There were multiple species-level interactions that we grouped into six types based on the direction and intensity of indirect effects. We found significant relationships between species-level interactions and community composition. Conclusions:Our study highlights that communities are sets of hidden interactions that contribute to community composition, although no interaction might be detected at the community level because hidden interactions balance each other. Future studies should assess the ecological and functional drivers of these hidden interactions.

Microclimate buffering and fertility island formation during Juniperus communis ontogenesis modulate competition–facilitation balance

“…Finally, it is also possible that woody species thrive inside large Juniperus shrubs because they benefit of the reduced interspecific interference from herbaceous species (Michalet et al. ,b). In the context of plant–plant interactions, by reporting a higher occurrence of facilitative interactions in unstable soils, our study is in line with the stress gradient hypothesis (SGH) of Bertness & Callaway ().…”

Contrasting understorey species responses to the canopy and root effects of a dominant shrub drive community composition

“…Additionally, this shows the limited explanatory power of plant–plant interaction experiments based on the removal of neighbours around a low number of target species within a community, in particular if we aim to assess the role of plant–plant interactions for community composition and richness (Michalet et al. ).…”

Evidence of Facilitation Cascade Processes as Drivers of Successional Patterns of Ecosystem Engineers at the Upper Altitudinal Limit of the Dry Puna

“…Instead, facilitation is expected to be less common when abiotic stress is resource driven, as in arid environments [9, 10]. The nature and intensity of plant-plant interactions can change between apparently similar sites as a result of several factors such as: scale of analysis [11], combination of stressors [2, 7, 12, 13], variations induced by architectural or ontogenetic differences between individuals of interacting species in different populations [14, 15, 16], species-specific interaction due to the interplay between the functional features of nurse and beneficiary species [2, 12, 17, 18], relative tolerance to stress vs. competitive ability of the interacting species [9]. …”

“…Therefore, these studies do not consider, at the scale of plant communities, the whole process of possible patch creation, alternation, coalescence and senescence, by means of the interaction of different ecosystem engineers and the degradation of microhabitat patches, that are key processes of vegetation dynamics in harsh environments [22, 24, 25]. In fact, most ecosystems are structured by multiple foundation species, whose differences in structural and functional morphology influence their impact on the community [17, 18, 26]. In addition, there are some evidences that multiple foundation species give rise to facilitation cascades, in which an independent, stress tolerant foundation species, facilitates a second, dependent foundation species to provide complementary levels of complexity and to enhance stress amelioration [20].…”