Forb stability, dwarf shrub stability and species asynchrony regulate ecosystem stability along an experimental precipitation gradient in a semi-arid desert grassland.

Abstract

Precipitation pattern changes may affect plant biodiversity, which could impact ecosystem stability. However, the effects of changes in precipitation regime on ecosystem stability and their potential mechanisms are still unclear. We conducted a 3-year field manipulation experiment with five precipitation treatments (-40%, -20%, 0% (CK), +20% and +40% of ambient growing season precipitation) in a semi-arid desert grassland to examine the effects of precipitation alterations on functional group stability, species asynchrony, and diversity, and the underlying mchanisms of ecosystem stability using structural equation modelling. Alterations in precipitation had different effects on community biomass and functional group biomass. Moreover, ecosystem stability was mainly driven by forb stability (path coefficient = 0.79). Changes in precipitation had significant effects on soil dissolved inorganic N (P < 0.01) further affecting ecosystem stability through species asynchrony (path coefficient = 0.25). Dwarf shrubs had a stabilizing effect on ecosystem stability (path coefficient = 0.32), mainly via deep roots. Ecosystem stability tended to be lower in the -40% (4.72) and +40% (2.74) precipitation treatments. The common reduction in species asynchrony and stability of forb and dwarf shrub functional groups resulted in lower ecosystem stability under the -40% treatment. The lower stability under the +40% treatment might be ascribed to unimproved dwarf shrub stability. Higher dwarf shrub and forb stability contributed to higher ecosystem stability under normal precipitation changes (±20% treatments) and CK. Species diversity was not a crucial driver of ecosystem stability. Our results indicate that precipitation alteration can regulate ecosystem stability via functional group stability (e.g. forb stability, dwarf shrub stability) and species asynchrony in a semiarid desert grassland.