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Atmospher Sci & Global Chg
Research Highlights

November 2011

Division of Labor

Replacing hand-weeding of soil plots reduces effort to identify emitted carbon sources

PVC collars placed in the forest sampling area, located between tree rows. Scientists applied one of five vegetation treatments inside each collar to measure surface soil respiration sources. Enlarge Image

Results: Divide and conquer. Using that plan of attack, a research team led by Dr. Ben Bond-Lamberty of the Joint Global Change Research Institute uncovered ways to better identify soil carbon. The team found more efficient methods to separate components of soil respiration in forests, replacing labor-intensive techniques and leading to better knowledge in a poorly understood area of the carbon cycle. JGCRI is a partnership between Pacific Northwest National Laboratory and the University of Maryland.

Why it matters: Carbon in, carbon out. Soil breathes, and when it exhales, it releases carbon back into the atmosphere. Measuring the carbon released into the air from soil is important to distinguish it from carbon contributed from human activities. With many sources of carbon coming from the soil, such as plant roots and microorganisms, researchers need to distinguish those sources to get accurate measurements. Finding a method to reduce the effort in gathering this information means more information for less effort. Better methods translate to a better understanding of the carbon cycle, and its impact on climate changes.

"Carbon respiration of microorganisms and plants may respond differently to future climate changes, which is why it's important to explore how each behaves in forests," said Dr. Ben Bond-Lamberty, a scientist at the Joint Global Research Institute.

Methods: Soil releases carbon from multiple sources, and the fluctuation of temperature and moisture affect these sources differently. Separating carbon sources presents challenges for researchers: plant roots, one source of carbon emissions, must be removed from the ground to measure the carbon output of microorganisms that decompose waste in the soil. To measure the amount of carbon released by soil roots and microorganisms, researchers need to find efficient and effective ways to separate the two.

The research team examined a 130-meter2 (1,400-foot2) area of boreal black spruce forest, partitioning different plots using a method called soil trenching. The team then applied one of six different types of plant growth-prevention methods to each section in the grid and measured carbon dioxide released from the soil, accounting for recorded soil temperature, wind speed, and moisture during the measurement period. The researchers also monitored root growth by collecting soil samples and evaluating any collected roots for growth. Finally, the recorded data were analyzed for the effects of temperature and moisture, and to calculate how much carbon originated from the soil versus roots.

What's next: The team will study different techniques to separate carbon-emitting sources by taking soil samples and measuring the fluctuation of carbon dioxide. The work will ultimately focus on streamlining these techniques for soil science applications.

"Being able to compare measurements made using completely different techniques will provide researchers an improved understanding of how soil might gain or lose carbon as environmental conditions change," said Bond-Lamberty.

Acknowledgments: This research was supported by the U.S. Department of Energy Plant Ecosystem Response. The work was performed by Dr. Ben Bond-Lamberty of the Joint Global Change Research Institute, Dr. Dustin Bronson of the University of Pennsylvania, Emma Bladyka of the University of Wyoming, and Dr. Stith T. Gower of the University of Wisconsin.

Reference: Bond-Lamberty B, D Bronson, E Bladyka, and ST Gower. 2011. "A comparison of trenched plot techniques for partitioning soil respiration." Soil Biology & Biochemistry 43(10):2108-2114. DOI: 10.1016/j.soilbio.2011.06.011.

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What is the carbon cycle?

Carbon in many forms is recycled and exchanged through the air, land, and water. For example, carbon dioxide, the dominant form of carbon in the atmosphere and associated with climate change, is used by plants to generate energy via photosynthesis. However, when plants decompose, microorganisms release carbon dioxide back into the air. Understanding how carbon cycles from the atmosphere to soil and from the soil back to the atmosphere is vital to getting the complete carbon cycle picture.