The Science

A synthesis of 27 experimental warming studies across nine biomes showed the soil respiration increased with temperature to about 25°C, with rates decreasing with further warming. No acclimation of soil microbes to warming was found.

The Impact

This research suggests that even ecosystems that are currently quite cold, such as tundra, will continue to experience greater soil respiration with forecasted future warming. Also, many single-site studies have shown an acclimation of soil respiration to warming, but acclimation was not found in this much larger, spatially distributed dataset.

Summary

The respiratory release of carbon dioxide from soil is a major, yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of soil respiration, potentially fueling further increases in global temperatures. However, despite considerable scientific attention in recent decades, the overall response of soil respiration to anticipated climatic warming remains unclear. In this study, researchers synthesized the largest global dataset to date of soil respiration, moisture, and temperature measurements, totaling >3,800 observations representing 27 temperature manipulation studies, spanning nine biomes and over two decades of warming. Their analysis reveals no significant differences in the temperature sensitivity of soil respiration between control and warmed plots in all biomes, with the exception of deserts and boreal forests. Thus, these data provide limited evidence of acclimation of soil respiration to experimental warming in several major biome types, contrary to the results from multiple single-site studies. Moreover, across all nondesert biomes, respiration rates with and without experimental warming follow a Gaussian response, increasing with soil temperature up to a threshold of ~25°C, above which respiration rates decrease with further increases in temperature. This consistent decrease in temperature sensitivity at higher temperatures demonstrates that rising global temperatures may result in regionally variable responses in soil respiration, with colder climates being considerably more responsive to increased ambient temperatures compared with warmer regions. This analysis adds a unique cross-biome perspective on the temperature response of soil respiration, information critical to improving mechanistic understanding of how soil carbon dynamics change with climatic warming.

Principal Investigator

Scott Bridgham
University of Oregon
bridgham@uoregon.edu

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

Since this is a synthesis of many studies, there were many sources of funding, one of which was the Office of Biological and Environmental Research, within the U.S. Department of Energy Office of Science, under grant DE-FG02-09ER604719.

References