Climate-dependent plant responses to earthworms in two land-use types

Abstract

Plant nutrient uptake and productivity are driven by a multitude of factors that have been modified by human activities, such as climate change and the activity of decomposers. However, interactive effects of climate change and key decomposer groups like earthworms have rarely been studied. In a field microcosm experiment we investigated the effects of a mean future climate scenario for the period between 2070 and 2100 in Germany with warming and altered precipitation and earthworms (anecic - Lumbricus terrestris, endogeic - Allolobophora chlorotica and both together) on plant biomass and stoichiometry in two contrasting land-use types (intensively-used meadow with four forage grass species and conventional farming). In contrast to previous studies we found little evidence for earthworm effects on aboveground biomass. However, future climate increased above- (+ 40.9%) and belowground biomass (+ 44.7%) of grass communities, which was mainly driven by production of the dominant Festulolium species during periods outside the projected summer drought, but slightly decreased the aboveground biomass (-36.9%) of winter wheat. Projected climate change and earthworms interactively affected the N content and C:N ratio of grasses. Earthworms enhanced the N content thereby decreasing the C:N ratio in grasses, but only under ambient climate conditions. The future climate treatment generally decreased the N content of grasses and winter wheat, resulting in an increase in plant C:N ratio. Our results suggest that climate change diminishes the positive effects of earthworms on plant nutrient uptakes due to soil water deficit, especially during summer drought.