Artist rendition of wildfire changing the future ecosystem of a forested area. Copyright Victor Leshyk

Overview

Fire, a natural ecological disturbance, has been suppressed in U.S. forests for much of the past century. This has prevented damage to property and protected timber resources, but has caused many forests to develop in an unnatural manner, resulting in dense stands of small trees that are now poised to fuel catastrophic fires when they do ignite. A warming and drying climate exacerbates this risk. How forests function has big impacts to the global carbon cycle; when trees grow they remove carbon dioxide from the atmosphere, and when they burn, some of that is returned to the atmosphere. Through direct field work and modeling efforts, we have demonstrated that combinations of forest thinning and controlled burning can reduce fire risk and increase forest carbon sequestration over the long term, although it necessarily causes near term carbon losses. Our field sites in diverse forests throughout the U.S. include military installations where land managers are challenged to balance habitat protection, fire risk, carbon sequestration, and mission readiness. Our research has promoted the idea that forest management activities that reduce fire risk and protect forest carbon should be creditable in emerging carbon markets.

Recent Publications

Martin KL, Hurteau MD, Hungate BA, Koch GW, North MP, 2015. Carbon tradeoffs of restoration and provision of endangered species habitat in a fire-maintained forest. Ecosystems 18:76-88.

Kerhoulas LP, Kolb TE, Koch GW, 2013. Tree size, stand density, and the source of water used across seasons by ponderosa pine in northern Arizona. Forest Ecology and Management, 289:425-433.

Kerhoulas LP, Kolb TE, Hurteau MD, Koch GW, 2013. Managing climate change adaptation in forests: a case study from the U.S. Southwest. Journal of Applied Ecology, 50:1311 – 1320.

Hurteau MD, Hungate BA, Koch GW, 2009. Accounting for risk in valuing forest carbon offsets. Carbon Balance and Management, 4:1, doi: 10.1186/1750-0680-4-1.

Hurteau MD, Koch GW, Hungate BA, 2008. Carbon protection and fire risk reduction: toward a full accounting of forest carbon offsets. Frontiers in Ecology and the Environment 6:doi:10.1890/070187.

Soil is the largest carbon (C) pool in the terrestrial biosphere and any change in its size may influence the atmospheric CO₂ concentration and feed back to ongoing climate change. Most soil microorganisms utilize organic C as a source of energy and biosynthetic precursors, while releasing CO₂ and contributing to long-term soil C storage. The regulation of energy (ATP, NADH, NADPH) production and consumption by intact soil microbial communities is not well-understood but fundamental to soil and therefore ecosystem C and N cycling. We studied the effects of temperature on soil community metabolic processes. Our results indicate that activity shifted from pentose phosphate pathway to glycolysis with higher temperature.  However, we observed only small alterations in estimated energy production.

Publications:

Dijkstra, P., Scott Thomas, Paul L. Heinrich, George W. Koch, Egbert Schwartz, Bruce A. Hungate. 2011. Effect of temperature on metabolic activity of intact microbial communities: evidence for altered metabolic pathway activity but not for increased maintenance respiration and reduced carbon use efficiency. Soil Biology & Biochemistry, 43:2023-2031.

Extreme heat waves: the role of microbes in ecosystem resilience

Extreme climate events, including heat waves and drought, disrupt ecosystems and are increasing in frequency and intensity. Although understudied, these events likely produce “legacy effects” that affect plant survival and recruitment long after the event has dissipated. Working with the Southwestern Experimental Garden Array (SEGA) and the Flagstaff Arboretum, we have implemented a heating array to test the effects of short-term drought and heating on plant performance and microbial community dynamics. Additionally, we are examining whether microbial inoculants can be used to prime a native C4 grass, Bouteloua gracilis, for abiotic stress resistance in a restoration setting. This research will shed insight into the mechanisms that underlie extreme climate adaptation, as well as provide tools to promote ecosystem resilience.

The heat wave array within SEGA

Infrared image of a heated plot. Hot lamps are reddest.

Roots exploring native soil (inoculum) layered within a background mix of potting soil

Antarctica field site.

We study soil microbial communities in Antarctica, microbes in hot spring ecosystems in Tengchong, China, methane production at Axel Heiberg Island near Greenland as an analog for life on other planets, and the distribution of soil microbial communities across the arid Southwest.

Microbes in Antarctica

We are using stable isotope probing with H₂¹⁸O to identify active soil microorganisms in the McMurdo Dry Valleys of Antarctica. Biologist Egbert Schwartz has developed a technique to identify whether micro-organisms can grow in places where no other signs of life can be found, like the rocky, icy region of Antarctica’s McMurdo Dry Valleys. Listen at: Brain Food: Living Soil (KNAU)

His research confirms that there are are microorganisms native to Antarctica. For more information, read the NAU Research story here.

Related Publication

Woods, A., M Watwood, E, Schwartz. 2011. Identification Of a Toluene-degrading Bacterium From a Soil Sample Through H₂¹⁸O DNA-Stable Isotope Probing.

Distribution of Soil Microbial Communities Across the Arid Southwest

Microbial diversity is vast, and recent discoveries place soils as home to the most diverse of the Earth’s microbial communities. Deserts in the Southwest are extreme environments with large temperature fluctuations, high UV radiation and very little rainfall. While there is a large body of work on a subset of desert soil microorganisms (i.e. biological soil crusts) little is known about the distribution and diversity of soil microbial communities in these extreme desert environments.

Example of a desert environment north of Flagstaff

High throughput sequencing of the 16S rRNA gene was used to characterize the bacterial and archaeal communities in these Southwestern soils with three general aims: 1) to asses biogeography of microbial communities; 2) to identify potential drivers of microbial community composition and diversity; and 3) to map microbial community composition across the sites.

This study was part of an outreach effort that involved the assistance from High School teachers. Ecoss researchers conducting this study are Egbert Schwartz and Natasja van Gestel, and Ecoss alumni Theresa McHugh and Zacchaeus Compson.

Exobiology: Methane Production at Axel Heiberg Island Near Greenland as Analog for Life on Other Planets