Changes in soil nematode food web control the effects of drought on the partitioning between above and belowground grass biomass
Abstract
Our ability to predict how grasslands will respond to climate changes is currently restricted by a limited understanding of how more frequent extreme events will affect the food-web interactions among plants and associated soil biotic communities. Here, we addressed these knowledge gaps by carrying out complementary field and greenhouse experiments in which we: (i) experimentally reduced and increased growing-season rainfall for 2 years in field plots at arid, semiarid, and mesic grasslands to investigate temporal and spatial rainfall controls on the abundance and functional composition of soil nematode communities, which are important drivers of ecosystem primary production; and (ii) in greenhouse soil microcosms, we exposed blue grama (Bouteloua gracilis), a dominant semiarid shortgrass species to three levels of water supply crossed with a gradient of root-herbivore percent abundance relative to the total nematode community. Our results showed that root-feeding nematodes increased under drought following reductions in the number of their nematode predators, with stronger nematode responses in mesic compared to semiarid and arid grasslands. The greenhouse experiment revealed that this increased abundance of root feeders prevented grasses from adjusting their biomass allocation patterns toward root mass as normally expected in response to low water availability and which, in turn, would increase plant water uptake. Combined, these findings indicate that plant responses to drought can result from indirect effects through changes in the belowground trophic web that increase root herbivory. Such complex responses challenge current predictions of increasing plant biomass allocation belowground in water-stressed grasslands, and suggest that soil biotic communities can drive the fate of biomass carbon and make plants more vulnerable to the effects of climate change.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB092.0002F
- Keywords:
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- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0476 Plant ecology;
- BIOGEOSCIENCES;
- 1630 Impacts of global change;
- GLOBAL CHANGE;
- 1813 Eco-hydrology;
- HYDROLOGY