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Research Project: Development of Management Strategies for Livestock Grazing, Disturbance and Climate Variation for the Northern Plains

Location: Livestock and Range Research Laboratory

Title: Mineral nitrogen and microbial responses to soil heating in burned grassland

Author
item McGranahan, Devan
item Wonkka, Carissa
item Rana Dangi, Sadikshya
item SPIESS, JONATHAN - Chadron State College
item GEAUMONT, BENJAMIN - North Dakota State University

Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2022
Publication Date: 6/29/2022
Citation: McGranahan, D.A., Wonkka, C.L., Rana Dangi, S., Spiess, J.W., Geaumont, B. 2022. Mineral nitrogen and microbial responses to soil heating in burned grassland. Geoderma. 424. Article 116023. https://doi.org/10.1016/j.geoderma.2022.116023.
DOI: https://doi.org/10.1016/j.geoderma.2022.116023

Interpretive Summary: We investigated plant-available nitrogen responses to soil heating in semi-arid grassland in southwestern North Dakota, USA. We observed statistically-significantly higher ammonium immediately (1 day) after burns and statistically-significantly higher nitrate 7 months after burns. The abundance and community composition of soil microbes were both unchanged by fire. Soil heating models indicate that the highest temperatures (above 100 C) were limited to the top 2 cm. Together, these data suggest well-managed prescribed fire releases nutrients and promotes nutrient cycling without contributing to soil degradation.

Technical Abstract: Fire is widely understood to be an important ecological process in grasslands around the world, but little research has been done on soil heating and nutrient and microbe responses to prescribed fire in the northern Great Plains of North America. We investigated plant-available nitrogen responses to soil heating in semi-arid grassland in southwestern North Dakota, USA. We sought to describe the range of temperatures reached at the soil surface and in the plant canopy during five prescribed burns, measure ammonium and nitrate responses to soil heating, and explore relationships between soil heating, nutrient responses, and temperature profiles below the soil surface. We also used phospholipid fatty acid (PLFA) markers to measure soil microbial abundance and community composition responses to fire. We observed statistically-significantly higher ammonium immediately (1 day) after burns and statistically-significantly higher nitrate 7 months after burns, which follows the pattern for each N species widely described in the literature. The abundance and community composition of soil microbes were both unchanged by fire. Soil heating models indicate that the highest temperatures (above 100 C) were limited to the top 2 cm. Together, these data suggest well-managed prescribed fire plays an important role in enhancing ecological function of managed grasslands by releasing nutrients and promoting nutrient cycling without contributing to soil degradation.