Predicting plant species diversity in response to disturbance magnitude in grassland remnants of central Alberta

Abstract

The Intermediate Disturbance Hypothesis states that the greatest species diversity occurs at intermediate levels of disturbance because species coexistence is maintained at a nonequilibrium state and no strong competitor can dominate completely. On the other hand, diversity of exotic species is expected to increase with the disturbance magnitude. These patterns were tested for in this study. The cover of all vascular plants, mosses, and lichens in 1 × 1 m plots across a range of disturbance levels was sampled in 11 remnant grasslands within the Aspen Parkland Ecoregion of central Alberta, western Canada. The Intermediate Disturbance Hypothesis was supported for small-scale within-patch diversity for total species richness and Simpson's diversity index. Lower species diversity was found in undisturbed and lightly grazed as well as in highly disturbed plots. Intermediate levels of disturbance had reduced dominance of Festuca hallii (Vasey) Piper and increased abundance of most other species; this gave the highest species diversity. The species richness and diversity of exotic plant species showed a significant positive relationship with the magnitude of the disturbance. Understanding relationships between disturbance and plant species diversity, especially exotic plants, can influence management decisions on what disturbance regime is conducive to maintaining natural plant communities.Key words: Intermediate Disturbance Hypothesis, diversity, exotic species, grassland.

Effect of Conservation on Plant Species Diversity, Kurdistan, Western Iran

“…According to results, the unprotected areas had the lowest diversity and the species richness was decreased as already observed by Connell (1978), Vujnovic et al (2002), Keeley et al (2003), Bouahim et al (2011), Krzic et al (2003), Hendricks et al (2005), Banda et al (2006), Dorrough et al (2007) and Cesa and Paruelo (2011). It should be noted that, in these areas, some species are selectively kept and other species have been removed.…”

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

“…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. These habitat variables, indirectly reflective of land management actions, have not been extensively investigated in relation to Regal populations (See Farhat et al 2014).…”

“…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.…”

“…It may be that moderate disturbance regimes, associated with robust floral resources, also promote V. sororia in the correct contexts (sufficient moisture, etc. ), further illustrating the complexities of the prairie butterfly paradox (Moranz et al 2014;Vujnovic et al 2002;Thompson 2006).…”

Roadside grassland vegetation in an oak forest, Oak Creek Wildlife Area, the Cascade Range, USA

“…This pattern could be supported by intermediate disturbance hypothesis, in par ticular, for exotic species along forest roads (Watkins et al 2003), and the further pro blem is the high species richness is main tained by exotics. When the highest species richness is observed in intermediately dis turbed grassland in the mountainous regions of central Alberta, Canada, exotic species contribute greatly to the high species rich ness on more intensely disturbed areas than native species due to higher tolerance to hu man disturbances (Vujnovic et al 2002). Those indicate that high species richness is not always desirable when exotic species modifies vegetation patterns.…”