Location: Range Management Research
Title: Cheatgrass alters flammability of native perennial grasses in laboratory combustion experimentsAuthor
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Harrison, Georgia |
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JONES, LISA - University Of Idaho |
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ELLSWORTH, LISA - Oregon State University |
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STRAND, EVA - University Of Idaho |
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PRATHER, TIMOTHY - University Of Idaho |
Submitted to: Fire Ecology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/1/2024 Publication Date: 11/26/2024 Citation: Harrison, G.R., Jones, L.C., Ellsworth, L.M., Strand, E.K., Prather, T.S. 2024. Cheatgrass alters flammability of native perennial grasses in laboratory combustion experiments. Fire Ecology. 20(103):1-14. https://doi.org/10.1186/s42408-024-00338-z. DOI: https://doi.org/10.1186/s42408-024-00338-z Interpretive Summary: The study investigates the flammability of cheatgrass (Bromus tectorum), an invasive annual grass, in comparison to two native perennial grasses (Columbia needlegrass and bluebunch wheatgrass) in sagebrush shrublands of the Great Basin and adjacent sagebrush steppe areas. The research aims to assess how cheatgrass influences fire behavior across varying fuel moistures during typical fire seasons. The results indicate that all three grass species exhibit decreased flammability with increasing fuel moisture. Columbia needlegrass, on average, shows 11% lower mass consumption than cheatgrass, and both perennial grasses exhibit longer flaming durations and higher thermal doses than cheatgrass. The introduction of cheatgrass into the mix amplifies combined mass consumption, flaming duration, and thermal dose. Flammability increases with higher cheatgrass proportions, though flaming duration and thermal dose are not significantly affected by cheatgrass fuel moisture. Interestingly, Columbia needlegrass displays higher-than-expected flammability when burned with cheatgrass, suggesting susceptibility to pre-heating from cheatgrass. Conversely, the interaction between bluebunch wheatgrass and cheatgrass results in both positive and negative effects on flammability. The study concludes that cheatgrass exhibits high flammability even at high fuel moisture levels, posing a prolonged fire threat to native grasses. The findings contribute valuable experimental evidence supporting previous qualitative observations and have implications for invasive plant management, fire potential assessment, and efforts to prevent or mitigate cheatgrass-induced wildfires in the studied ecosystems. Technical Abstract: Background The invasive annual grass cheatgrass (Bromus tectorum) increases fuel continuity, alters patterns of fire spread, and changes plant communities in sagebrush shrublands of the Great Basin (USA) and adjacent sagebrush steppe, but no studies have contrasted its flammability to native perennial grasses. Understanding cheatgrass flammability is crucial for predicting fire behavior, informing management decisions, and assessing fire risk in invaded areas. This study aimed to determine the flammability of cheatgrass compared to two native perennial grasses (Columbia needlegrass [Achnatherum nelsonii] and bluebunch wheatgrass [Pseudoroegneria spicata]) across a range of fuel moistures. Results All three grass species had decreased flammability with increasing fuel moisture. Columbia needlegrass averaged 11% lower mass consumption than cheatgrass, and bluebunch wheatgrass had longer flaming duration and higher maximum temperatures than cheatgrass and Columbia needlegrass. The addition of cheatgrass to each perennial grass increased combined mass consumption, flaming duration, and flame heights. For these three attributes, the impact differed by the amount of cheatgrass in the mixture. Maximum and mean temperatures during perennial grass combustion were similar with and without cheatgrass addition. Some attributes of Columbia needlegrass flammability when burned with cheatgrass were higher than expected based on the flammability of each species, suggesting that Columbia needlegrass may be susceptible to pre-heating from combustion of cheatgrass. Conversely, the flammability of bluebunch wheatgrass and cheatgrass together had both positive and negative interactive effects, suggesting the impact on joint flammability from cheatgrass differs by perennial grass species. Conclusions This study provides experimental evidence supporting previous qualitative observations of cheatgrass flammability. Cheatgrass increased perennial grass sustainability and consumption, suggesting that cheatgrass poses a significant fire threat to native grasses regardless of moisture content. The study provides species-specific insights into flammability, which could be used to inform efforts to prevent or mitigate cheatgrass-induced wildfires. Resumen Antededentes El pasto anual invasor conocido como bromo velloso o cheatgrass (Bromus tectorum), incrementa la continuidad de los combustibles vegetales, altera el patrón de propagación del fuego, y cambia las comunidades arbustivas de artemisia de la Gran Cuenca (Great Basin de los EEUU) y otros arbustales de estepas adyacentes. Sin embargo, ningún estudio ha contrastado su inflamabilidad en relación con otros pastos perennes nativos. El entender la inflamabilidad del bromo velloso es crucial para predecir el comportamiento del fuego informar sobre decisiones de manejo, y determinar el riesgo de incendio en áreas invadidas. Este estudio se basó en determinar la inflamabilidad del bromo velloso comparada con la de dos gramíneas nativas, el pasto aguja de la Columbia (Achnatherum nelsonii) y el agroapiro azul (Pseudoroegneria spicata) a través de un rango de distintos contenidos de humedad de esas especies. Resultados Las tres especies de pastos decrecieron su inflamabilidad a medida que se incrementaba su contenido de humedad. El pasto aguja de la Columbia promedió un 11% menos de consumo de su biomasa que el bromo velloso, mientras que el agropiro azul tuvo una mayor duración de llama que el pasto aguja de la Columbia o el bromo velloso. La adición del bromo velloso a cada pasto perenne nativo incrementó el consumo de biomasa, y la duración y longitud de su llama. Para esos tres atributos, el impacto difirió en relación a la cantidad de bromo velloso en la mezcla. Las temperaturas máximas y medias durante la combustión de los pastos perennes fueron similares con o sin la adición del bromo velloso. Algun |