Forest soils to the rescue

Scientist and project lead Kathryn Walker is measuring how fast soil microbes are consuming methane by taking gas samples from field chambers installed in forests.

New research is investigating if methanemunching forest soils can help us tackle climate change.

Scion scientists have embarked on important new research to find out how much methane is being gobbled up by microorganisms in New Zealand’s planted forest soils.

Forest soils are good habitats for bacteria that eat and breathe methane (CH4) as a source of carbon and energy. By quantifying how much methane is consumed by the bacteria, known as methanotrophs, at targeted field sites, the research project will reveal just how important planted forest soils are to New Zealand as part of efforts that seek to better understand the country’s total net emissions and ways to mitigate climate change.

Once complete, the research is expected to provide valuable insights for policymakers examining greenhouse gas emissions, as it can be used to paint a more accurate picture of the country’s total net carbon budget.

Due to agricultural activity, methane production in New Zealand is disproportionately high on a per capita basis – about six times the global average. Understanding the potential for other land uses, such as forestry, to mitigate these agricultural emissions is critical, Scion senior scientist Dr Steve A. Wakelin says.

“We know that forests are great for storing carbon from carbon dioxide, but this research is helping us learn about forestry’s capability to offset methane emissions as well. We believe it is a first step in a future programme of work that will demonstrate how different land uses in New Zealand are all interconnected, and how to manage these holistically for win-win outcomes.”

The research, funded by the Ministry for Primary Industries, follows international studies proving that forest soils create optimal conditions for methanotrophs.

As methane in the air passes over and diffuses with forest soil, methanotrophs consume the methane.

“We find methanotrophs are abundant in our DNA-based surveys of planted forest soils,” Wakelin says. “Indeed, based on overseas systems, it turns out that planted forest soils are pretty good habitats for methanotrophs; we just haven’t looked at this in New Zealand before.”

Scion’s Microbial Ecology – Soil Systems team, in a project led by scientist Kathryn Walker, is now collecting New Zealand’s first field-based measurements of methane flux – how fast the soil microbes are consuming methane.

In February, researchers installed methane flux chambers at two field sites near Christchurch: Orton Bradley Park and McLeans Island. At both sites Scion already collects environmental DNA and measures environmental properties; this information will now be integrated with the methane flux data. In March, chambers were also installed in Kaingaroa Forest in the central North Island, New Zealand’s largest commercial pine plantation.

Sampling of these field chambers will reveal how much methane the forest soil microbiome is consuming over an entire year.

“If rates of consumption are high, we need to know as this data will be important for our national carbon budget,” says Wakelin. “Given the importance of methane as a greenhouse gas for agriculture, it could just be a case of forests to the rescue.”

Lincoln University is also supporting the project with specialist capability. Professor Tim Clough says the collaborative research with Scion  will reveal important data in 12 months’ time.

“With Scion’s expertise in forestry aligned with Lincoln University’s facilities for trace-gas sampling and analysis provided through the New Zealand Greenhouse Gas Centre, we have a great partnership in place to assess the big opportunity of forest methane consumption.”

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