Asynchrony among species and functional groups and temporal stability under perturbations: Patterns and consequences

1. A number of theoretical and empirical studies have demonstrated effects
of perturbations on ecosystem stability. Compensatory dynamics among
taxonomic units have been proposed as a major mechanism regulating the
temporal stability of biomass production (hereafter “temporal stability”).
However, most studies have focused on the effects of species asynchrony on
temporal stability in response to perturbations, and few studies examined
how compensatory changes among functional groups affected temporal
stability. 2. Here, we conducted a 4-year functional group removal
experiment and a 4-year experimental warming and nitrogen addition
experiment in an alpine meadow of Qinghai-Tibetan Plateau to investigate
the effects of perturbations (functional group removal, experimental
warming and nitrogen addition) on temporal stability and the potential
mechanisms. 3. In both experiments, temporal stability was positively
related to both species and functional group asynchrony. However, species
asynchrony and functional group asynchrony responded differently to
different types of perturbations. In the removal experiment,
although asynchrony among both species and functional groups decreased as
more functional groups were removed, structural equation modelling showed
that removal of different functional groups could affect temporal
stability through altering either species or functional group asynchrony.
Warming suppressed temporal stability through decreasing asynchrony among
species, while nitrogen addition reduced temporal stability mainly through
decreasing functional group asynchrony. 4. Synthesis. Our findings
demonstrate the importance of considering compensatory dynamics at
different taxonomic levels for predicting temporal stability under
anthropogenic perturbations in alpine meadows, and throw light on the
importance of protecting both species and functional group richness to
maintain temporal stability in the context of global change.