Grasshoppers like to munch on nitrogen-rich grass because it stimulates their growth and reproduction. But when spiders enter the picture, grasshoppers cope with the stress from fear of predation by shifting to carbohydrate-rich plants, setting in motion dynamic changes to the ecosystem they inhabit.
"Under stressful conditions they go to different parts of the grocery store and choose different foods, changing the makeup of the plant community," said Oswald Schmitz, a co-author of the study,"Fear of Predation Slows Plant-Litter Decomposition," and Oastler Professor of Population and Community Ecology at the Yale School of Forestry & Environmental Studies (F&ES).
The high-energy, carbohydrate diet also tilts a grasshopper's body chemistry toward carbon at the expense of nitrogen. So when a grasshopper dies, its carcass breaks down more slowly, thus depriving the soil of high-quality fertilizer and slowing the decomposition of uneaten plants. Microbes in the soil require a lot of nitrogen to function and to produce the enzymes that break down organic matter.
"It only takes a slight change in the chemical composition of that animal biomass to fundamentally alter how much carbon dioxide the microbial pool is releasing to the atmosphere while it is decomposing plant organic matter," said Schmitz. "So this shows that animals could potentially have huge effects on the global carbon balance because they're changing the way microbes respire organic matter."
The researchers found that the rate at which the organic matter of leaves decomposed increased between 60 percent and 200 percent in stress-free conditions relative to stressed conditions, which they consider "huge." "Climate and litter quality are considered the main controls on organic-matter decomposition, but we show that aboveground predators change how soil microbes break down organic matter," said Mark Bradford, a co-author of the study and assistant professor of terrestrial ecosystem ecology at F&ES.
Schmitz added: "What it means is that we're not paying enough attention to the control that animals have over what we view as a classically important process in ecosystem functioning."
The researchers took soil from the field, put it in test tubes and ground up grasshopper carcasses obtained either from predation or predation-free environments. They then sprinkled the powder atop the soil, where the microbes digested it. When the grasshopper carcasses were completely decomposed, the researchers added leaf litter and then measured the rate of leaf-litter decomposition. The experiment was then replicated in the field at Yale Myers Forest in northeastern Connecticut.
"It was a two-stage process where the grasshoppers were used to prime the soil, and then we measured the consequences of that priming," said Schmitz.
Schmitz said that the effect of animals on ecosystems is disproportionately larger than their biomass would suggest. "Traditionally people have thought animals had no important role in recycling of organic matter, because their biomass is relatively small to all of that plant material that's entering ecosystems," he said. "We need to pay more attention to the role of animals because in an era of biodiversity loss we're losing many top predators and larger herbivores from ecosystems."
The other co-authors Michael Strickland, a Yale postdoctoral associate who is joining the faculty at Virginia Tech this fall, and Dror Hawlena, a senior lecturer at the Alexander Silberman Institute of Life Sciences at the Hebrew University of Jerusalem and former postdoctoral associate in Schmitz's lab.
David DeFusco | EurekAlert!
Obstructing the ‘inner eye’
07.07.2017 | Friedrich-Schiller-Universität Jena
Drone vs. truck deliveries: Which create less carbon pollution?
31.05.2017 | University of Washington
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...
The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....
A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...
Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision
Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...
21.07.2017 | Event News
19.07.2017 | Event News
12.07.2017 | Event News
21.07.2017 | Earth Sciences
21.07.2017 | Power and Electrical Engineering
21.07.2017 | Physics and Astronomy