PNNL

The Science                                 

Climate change is altering precipitation patterns globally, creating drought conditions in some regions and increasing rainfall in others. Rainfall patterns strongly affect the amount of carbon dioxide that escapes the soil, known as soil respiration, and therefore strongly control ecosystem feedbacks to climate change. Researchers used data from 81 globally distributed studies that manipulated the amount of precipitation that ecosystems received to determine the effect of precipitation change on soil respiration. Initial responses to increasing and decreasing precipitation are consistent across ecosystems, but long-term effects change based on ecosystem type. Soil respiration in deserts became progressively higher with increased precipitation and progressively lower with drought. In contrast, forests showed the opposite pattern, with initial changes to soil respiration rates becoming smaller over time.

The Impact

This research shows that ecosystems that receive relatively abundant rainfall (such as forests) have the capacity to acclimate to precipitation change more readily than water-limited ones (such as deserts), regardless of whether the region is experiencing increased precipitation or drought conditions. Future research should focus on the mechanisms that allow currently adaptable ecosystems to acclimate, which can help increase the climate change resilience of different ecosystems.

Summary

Climate change is altering global rainfall patterns, which can affect the global carbon cycle via changes in carbon dioxide released from soil. Understanding how carbon cycling in different ecosystems will respond to increased or decreased precipitation is important when accounting for soil feedbacks into atmospheric carbon dioxide concentrations. Researchers combined the results of 80 separate studies to determine the effects of altered rainfall on soil respiration. In addition, they looked at how long the changes lasted, as well as how different soil properties and the intensity of precipitation changes at each study site affected the study results. They found that more precipitation resulted in greater amounts of carbon dioxide leaving the soil, and less precipitation resulted in less. However, the changes weakened over time in ecosystems that typically receive plenty of rainfall (e.g., forests), while the changes in ecosystems that typically receive little rainfall (e.g., deserts) strengthened over time. Changes in the amount of carbon dioxide leaving the soil were also affected by the amount of biologically derived carbon in the soil, which affects how much water the soil can hold. The results suggest that typically dry ecosystems will experience long-term changes in their carbon cycling whether precipitation increases or decreases.

PNNL Contact

Vanessa Bailey, Pacific Northwest National Laboratory, vanessa.bailey@pnnl.gov

Funding

This research is based on work supported by COMPASS-FME, a multi-institutional project supported by the Department of Energy, Office of Science, Biological and Environmental Research program as part of the Environmental System Science program.