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Fire, native species, and soil resource interactions influence the spatio-temporal invasion pattern of Bromus tectorum

Author(s): Michael J. Gundale, Steve Sutherland, Thomas H. DeLuca
Year Published: 2008
Description:

Bromus tectorum (cheatgrass) is an invasive annual that occupies perennial grass and shrub communities throughout the western United States. Bronus tectorum exhibits an intriguing spatio-temporal pattern of invasion in low elevation ponderosa pine Pinus ponderosa/bunchgrass communities in western Montana where it forms dense rings beneath solitary pines following fire. This pattern provides a unique opportunity to investigate several indirect effects of native vegetation that influence the invasion pattern of B. tectorum, and specifically how native species, disturbance, and soil resources interact to influence the spatio-temporal pattern of invasion. We established four replicate field sites, each containing burned-tree, burned-grass, unburned-tree, and unburned-grass sampling locations, and initiated a series of field sampling and greenhouse experiments utilizing these locations. The objective of our first greenhouse experiment was to identify whether belowground factors contributed to the pattern of B. tectorum biomass observed in these field locations. This experiment generated a B. tectorum biomass response that was nearly identical to the invasion pattern observed in the field, suggesting further investigation of belowground factors was necessary. We measured resin-sorbed NH4+ and NO3- during one generation of B. tectorum, and measured a suite of P fractions through a sequential extraction procedure from these soils. These data revealed that a resource island of high N and P exists beneath pine trees. Through a second greenhouse experiment, we determined that N limited B. tectorum biomass in tree soil, whereas P limited biomass in bunchgrass soil. Finally, through a germination experiment we determined that pine litter strongly inhibited B. tectorum germination. These data suggest B. tectorum is regulated by P in bunchgrass soil, and by N and inhibition by pine litter beneath trees, effects that are likely alleviated by fire. These data demonstrate the combined role of direct and indirect interactions between native and invasive species in regulating biological invasions.

Citation: Gundale, Michael J.; Sutherland, Steve; DeLuca, Thomas H. 2008. Fire, native species, and soil resource interactions influence the spatio-temporal invasion pattern of Bromus tectorum. Ecography. 31(2): 201-210.
Topic(s): Fire Ecology, Fire Effects, Ecological - First Order, Soil Heating, Ecological - Second Order, Vegetation, Invasive Species
Ecosystem(s): Ponderosa pine woodland/savanna, Lower montane/foothills/valley grassland
Document Type: Book or Chapter or Journal Article
NRFSN number: 8362
FRAMES RCS number: 7235
Record updated: May 24, 2018