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Research Project: Invasive Species Assessment and Control to Enhance Sustainability of Great Basin Rangelands

Location: Great Basin Rangelands Research

Title: The effects of charcoal and pile burns on C and N Dynamics in Eastern Sierra Nevadan forested soils

Author
item CARTER, ZACHARY - University Of Nevada
item SULLIVAN, BEN - University Of Nevada
item QUALLS, ROBERT - University Of Nevada
item Blank, Robert - Bob
item SCHMIDT, CASEY - Desert Research Institute

Submitted to: Forests
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2018
Publication Date: 2/16/2018
Citation: Carter, Z., Sullivan, B., Qualls, R., Blank, R.R., Schmidt, C. 2018. The effects of charcoal and pile burns on C and N Dynamics in Eastern Sierra Nevadan forested soils. Forests. 9(2):93.

Interpretive Summary: A century of fire suppression in the western United States has led to diseased forests and high fuel loads thus increasing the risk of catastrophic wildfires. Mechanical thinning followed by pile burning is a commonly used technique to reduce fuel loads. Charcoal, a byproduct of pile burning, can impact nutrient dynamics, but we lack detailed information on how charcoal type and concentration affects soil microbial respiration and nitrification rates. Charcoal derived from lodgepole and Jeffrey pine was added at rates of 0, 0.5, 1, 2.5, and 5% charcoal by weight to two soil types collected at Little Valley, approximately 30 km south of Reno, Nevada. Carbon respiration and nitrification rate were monitored over a two-month period in the laboratory. In general, microbial respiration was highest at 2.5% charcoal additions, while nitrification was stimulated equally at all charcoal amendment levels by the end of the incubation. Production of charcoal during prescribed fires may benefit soil microbial activity, but may also stimulate carbon and nitrogen losses through increased microbial activity.

Technical Abstract: Over a century of fire prevention and suppression in the western United States has led to overstocked and diseased forests with increased fuel loading and vertical continuity of fuels, thus increasing the risk of severe and stand-replacing wildfire. Mechanical thinning followed by pile burning is a commonly used technique to reduce fuel loads. Charcoal, a product of pile burning, can have major impacts on nutrient dynamics within forest soils. Specifically, charcoal-rich environments have been shown to enhance nitrogen cycling. In this study, incubations of soil amended with 0, 0.5, 1, 2.5, and 5% charcoal by weight were conducted to assess the importance of charcoal in microbial activity and nitrogen cycling. Samples were collected in forest soils in Little Valley, approximately 30 km south of Reno, Nevada. Carbon respiration and potential nitrification rate, proxies for microbial activity and size of the nitrifying microbial community respectively, were monitored over a two month period. In general, microbial respiration was highest at 2.5% charcoal additions, while nitrification was stimulated equally at all charcoal amendment levels by the end of the incubation. Also, microbial respiration rates decreased but potential nitrification rates increased over time across most treatments. Polyphenol sorption onto charcoal-amended soil was also analyzed and showed that extractable polyphenol concentrations decreased with increasing amounts of charcoal which may partly explain patterns in potential nitrification rates. The production of charcoal during prescribed fires may benefits soil microbial activity, (at least in the short-term) but may also stimulate carbon and nitrogen losses through increased microbial activity.