Might field experiments also be inadvertent metacommunities?

Abstract

Metacommunity theory predicts that the composition and diversity of a site depend on its characteristics and those of its neighborhood. Dispersal between plots in a field experiment could link responses observed in a focal plot to both its treatment and those of its neighbors. However, the diversity, composition, and treatments of neighboring plots are rarely included in analyses of experimental treatments. We analyzed a spatially gridded grassland nitrogen addition experiment and found that plant species richness and the composition of focal plots were influenced not just by their nitrogen treatment but also by the number of species in neighboring plots and their abundances. For each additional species in a focal plot's neighborhood, the species richness of the focal plot increased by 0.30 species. Control plots had a significant loss of species, at a rate of ~0.23 species per year during the 23‐year experiment, but only when their neighborhoods had low species richness. Changes in the abundance of the three dominant species depended both on the nitrogen treatment of a focal plot and on their abundance in adjacent plots. Our analyses suggested that both the experimental nitrogen treatments and metacommunity processes codetermined plant species richness and plant species’ abundances. Our findings suggested that analyzing many traditional field experiments with a metacommunity perspective may reveal a confounding of experimental treatments and provide empirical data to test metacommunity theory.

Disturbance alters transience but nutrients determine equilibria during grassland succession with multiple global change drivers

“…At a steady state equilibrium, community turnover can still be quite high as communities sample compositions within the steady state distribution (Naselli-Flores et al, 2003;Shoemaker et al, 2020) (Changes between 1992 and 2004 in Figure 2). Multiple factors, including demographic stochasticity, environmental fluctuations, and small-scale spatial heterogeneity (Furey et al, 2022) can yield temporal turnover and variability in community composition at this dynamical equilibrium.…”

Nutrient addition drives declines in grassland species richness primarily via enhanced species loss

“…However, species loss from enhanced local extinction was 2–5 times greater than from reduced colonization. These treatment effects did not, therefore, appear to have influenced richness dynamics in Control plots despite their proximity (Furey et al, 2022). Similar to our findings, changes to the richness of alpine plant communities as a result of fertilization and soil disturbance were driven primarily by extinctions, rather than colonizations, regardless of whether total richness increased or decreased (Olofsson & Shams, 2007).…”

Disturbance alters transience but nutrients determine equilibria during grassland succession with multiple global change drivers

“…At a steady-state equilibrium, community turnover can still be quite high as communities sample compositions within the steady-state distribution (Naselli-Flores et al, 2003;Shoemaker et al, 2020) (Changes between 1992 and 2004 in Figure 2). Multiple factors, including demographic stochasticity, environmental fluctuations and small-scale spatial heterogeneity (Furey et al, 2022) can yield temporal turnover and variability in community composition at this dynamical equilibrium. Crosssystem comparisons could shed light on dynamical equilibria, and how the amount of turnover at an ecosystem's steady-state distribution may depend on species traits (e.g.…”