Interactions between above- and belowground organisms modified in climate change experiments

Abstract

Climate change has been shown to affect ecosystem process rates' and community composition(2), with direct and indirect effects on belowground food webs(3). In particular, altered rates of herbivory under future climate(4) can be expected to influence above-belowground interactions(5). Here, we use a multifactor, field-scale climate change experiment and independently manipulate atmospheric CO2 concentration, air and soil temperature and drought in all combinations since 2005. We show that changes in these factors modify the interaction between above- and belowground organisms. We use an insect herbivore to experimentally increase aboveground herbivory in grass phytometers exposed to all eight combinations of climate change factors for three years. Aboveground herbivory increased the abundance of belowground protozoans, microbial growth and microbial nitrogen availability. Increased CO2 modified these links through a reduction in herbivory and cascading effects through the soil food web. Interactions between CO2, drought and warming can affect belowground protozoan abundance. Our findings imply that climate change affects aboveground-belowground interactions through changes in nutrient availability.