Community assembly history alters relationships between biodiversity and ecosystem functions during restoration

Abstract

Relationships between biodiversity and ecosystem functioning depend on the processes structuring community assembly. However, predicting biodiversity-ecosystem functioning (BEF) relationships based on community assembly remains challenging because assembly outcomes are often contingent on history and the consequences of history for ecosystem functions are poorly understood. In a grassland restoration experiment, we isolated the role of history for the relationships between plant biodiversity and multiple ecosystem functions by initiating assembly in three different years, while controlling for all other aspects of community assembly. We found that two aspects of assembly history-establishment year and succession-altered species and trait community trajectories, which in turn altered net primary productivity, decomposition rates, and floral resources. Moreover, history altered BEF relationships (which ranged from positive to negative), both within and across functions, by modifying the causal pathways linking species identity, traits, diversity, and ecosystem functions. Our results show that the interplay of deterministic succession and environmental stochasticity during establishment mediate historical contingencies that cause variation in biodiversity and ecosystem functions, even under otherwise identical assembly conditions. An explicit attention to history is needed to understand why biodiversity-ecosystem function relationships vary in natural ecosystems: a critical question at the intersection of fundamental theory and applications to environmental change biology and ecosystem restoration.

Bridging Theory and Experiments of Priority Effects

“…By altering species interactions, they can affect species coexistence and competitive dominance [5,6], or lead to alternative stable states [7]. As a consequence, priority effects play a key role in driving biodiversity patterns [8,9] and ecosystem functioning [10–12]. Despite the long history of priority effects in community ecology, they are still understudied, and uncertainty remains about when and how they affect various ecological systems [7].…”

Trait‐mediated community assembly during experimental grassland restoration is altered by planting year rainfall

“…For example, the cover of the tallest species in our experiment, Andropogon gerardii (big bluestem), has been shown elsewhere to positively correlate with multifunctionality in other restored grasslands (Catano et al, 2023;Zirbel et al, 2019). To extend our findings, future research would ideally test year effects across a range of ecosystems and different interannual variations in conditions such as temperature, herbivore pressure, and others.…”

“…As a result, these measures may help to buffer against adverse planting year effects following high rainfall planting years. Our results also suggest that year effects, specifically planting year rainfall, can influence community composition and are likely a key driver of historical contingencies that alter ecosystem functioning in these restored grasslands (Catano et al, 2023). Plant height and seed mass relate to a species lifespan, time to reproductive maturity and a plant's ability to compete for light (Moles et al, 2009;Silvertown, 1981)the latter particularly important in dense grassland communities.…”

“…Moreover, studies of year effects have focused almost exclusively on taxonomic aspects of biodiversity, such as species richness and species composition. Less understood is how year effects influence the functional traits of communities (Catano et al, 2023).…”

“…Moreover, studies of year effects have focused almost exclusively on taxonomic aspects of biodiversity, such as species richness and species composition. Less understood is how year effects influence the functional traits of communities (Catano et al, 2023). Understanding how year effects influence the functional traits of communities would afford insights into community assembly mechanisms (McGill et al, 2006), transferability of year effects findings across systems, and the consequences of year effect‐driven community change for ecosystem functioning (Cadotte, 2017; Wang et al, 2022).…”