Seasonal fire effects on the diversity patterns, spatial distribution and community structure of forbs in the Northern Mixed Prairie, USA

Abstract

The effects of fire season on forb diversity patterns, density, and composition were determined for a northern Mixed Prairie site, USA. Repeated spring burns (dormant season), summer burns, fall burns (dormant season), and unburned treatments were compared over a 3-yr period characterized by wet and dry moisture conditions. Alpha and beta diversity were highest on unburned and summer burn treatments, while landscape mosaic diversity was highest on fall burns. Forb density was highest on fall and spring burn sites. Nine forb species comprised 82~o of total densities and were significantly affected by fire season and year to year variations in moisture. Forb composition for unburned and spring burn treatments was similar, but both treatments were different from the summer burn and fall burn treatments which were similar to each other. Fire alone did not appear to be an intense enough disturbance to initiate drastic changes in the forb component of vegetation patches. Specific fire seasons did appear to either mask or enhance forb structure arising from other disturbance(s). Fire season also affected the scales of forb organization in the landscape. Contrasting spatial characteristics of the forb component of prairie plant communities may provide a diagnostic technique for exposing the interaction of disturbances at different temporal and spatial scales.Nomenclature:

A descriptive analysis of Regal Fritillary (Speyeria idalia) habitat utilizing biological monitoring data along the big bend of the Platte River, NE

“…Habitat variables such as plant species richness, diversity, and exotic species dominance have been found to respond differentially to varying intensities of managed disturbance (grazing, fire) in prairie ecosystems (Vujnovic et al 2002;Brudvig et al 2007;Biondini et al 1989). Vujnovic et al (2002) finds that moderate levels of disturbance promoted plant diversity as compared to low levels of disturbance, but that high levels of disturbance promoted exotic invasive plant communities.…”

“…Our findings corroborate the existing literature on Regal habitat noting that robust floral nectar resources are associated with Regal presence and abundance (Helzer 2012;Davis et al 2007;Selby 2007;Nagel et al 1991;Huebschman 1998). Interestingly, floral resources as measured by FC or FSR, again highlight the "prairie butterfly paradox" as fires tend to increase the forb component (floral resources) of a prairie for several years following a fire (Moranz et al 2014;Biondini et al 1989;Gibson and Hulbert 1987).…”

Grass response to seasonal burns in experimental plantings

“…Alternatively one might expect a general promotion of C 3 species, as has occurred in native short-grass prairies (Steuter 1987, Biondini et al 1989. Here 2 cycles of August fires over 3 years favor C 3 grasses (Fig.…”

Plant community response to the East Amarillo Complex wildfires in the Southern High Plains, USA

“…From a community perspective, variation in species composition is often studied with metrics related to species diversity (e.g., Belsky 1992, Warwick and Clarke 1993, Capitanio and Carcaillet 2008 or with ordination analyses through interpretation of the "spread of points" (e.g., Gibson andHulbert 1987, Warwick andClarke 1993) or "length of axes" (e.g., Biondini et al 1989, Fuhlendorf et al 2006. We chose Clarke and Warwick's (2001) "index of multivariate dispersion" (IMD), a descriptive measure that ranges from +1 (indicating that non-burned vegetation is maximally more homogeneous than burned vegetation-i.e., all similarities among non-burned transects are higher than any similarities among burned transects)-to -1 (indicating the converse).…”