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Lecture situates Missoula’s intermountain prairie within North American grassland types
Summary
University of Montana researcher Rick Holloway framed the Mount Jumbo and Sentinel grasslands as part of broader North American and global grassland biomes, and reviewed drivers (climate, soils, fire, herbivory) and plant traits that favor grasses.
Rick Holloway, a researcher in the University of Montana Division of Biological Sciences, used a public lecture in Missoula to place Mount Jumbo and Sentinel’s native grasslands into a continental and global context and to review the ecological traits that help grasses thrive in those systems.
Holloway opened by noting that grasslands are one of the principal biomes globally and that North American grasslands range from California annual grasslands to tallgrass prairie in the Midwest and shortgrass steppe toward the Rocky Mountains. He said the intermountain prairie around Missoula is often classified with or compared to the Palouse prairie but that the local intermountain grassland is an important, relatively well-preserved fragment of native bunchgrass steppe.
Why it matters: Holloway emphasized that understanding the drivers that sustain grasslands — climate patterns, soil texture, fire regimes, and grazing — helps explain both native plant distributions and susceptibility to woody encroachment and invasive plants.
Supporting details: Holloway reviewed several hypotheses ecologists use to explain grassland distribution: continentality (distance from maritime moderating influences), soil texture (clay or fine-textured soils holding water near the surface), pronounced summer rainfall correlated with lightning fire regimes in some plains systems, repeated low-intensity fire favoring perennial herbaceous plants over woody shrubs and trees, and herbivory by large mammals shaping dominant grass growth forms. He cited a study that found 70–73% of lightning-caused fires in the Northern Great Plains occurred in July–August to illustrate the summer-lightning/fire link.
Holloway described plant traits that give grasses advantages in dry or seasonally dry environments: finely tunable stomata (dumbbell-shaped guard cells that allow fine regulation of gas exchange), leaf rolling to reduce surface area and preserve humidity around stomata, C4 photosynthetic pathways in many grasses that improve water-use efficiency, dense fibrous root systems often concentrated near the soil surface, and widespread associations with arbuscular mycorrhizal fungi which can increase phosphorus acquisition. He contrasted the tallgrass prairie, with roots documented down to 5–8 feet in classic studies, with local intermountain soils where most root activity was concentrated in the upper 50 centimeters.
Holloway also discussed fire history and management on Mount Jumbo: postcard evidence and tree recruitment patterns indicate that grassland extent has declined and woody seedlings (Douglas fir, ponderosa pine) have become more numerous, consistent with a fire-suppression signal. He named regional researchers (Jim Habeck and Steve Arno) who have worked on reconstructing pre-settlement vegetative conditions and fire regimes.
Ending: Holloway urged attendees to view local prairie fragments as part of a broader biome with distinct drivers and to consider fire, grazing and invasive-species management together when planning restoration on Mount Jumbo and Sentinel.
