Pollinator-friendly flora in rangelands following control of cheatgrass (Bromus tectorum): a case study

Arathi H S,Janet Hardin

doi:10.1017/inp.2021.33

Abstract

AbstractInvasive winter annual grasses, such as cheatgrass (Bromus tectorumL.) are considered serious threats to regional biodiversity. Pollinator populations that depend on the native flora are likely to be negatively impacted as these native species may be displaced by the invasive grass species. Colonization by cheatgrass is also predicted to increase risk of wildfires, as dead plant parts provide fuel in the already dry and arid regions of the western United States. Biocontrol, grazing, prescribed burning, or use of broad-spectrum nonselective herbicides have been suggested as possible means to controlB. tectorum. Efficient control may facilitate regrowth of native flora that could in turn support other ecosystem functions. Reporting our findings as a case study, we describe here the results of the application of a preemergent herbicide, indaziflam, that limits germination ofB. tectorumseeds. Herbicide was applied to the study locations during the months of December 2016, January 2017, and February 2017. The data reported here on the diversity of flowering plants were collected between May through September 2018. Herbicide-treated plots showed an increase in diversity and abundance of flowering plants compared to the untreated control within two seasons after cheatgrass control was implemented, suggesting that effective reduction of the population of the invasive annual cheatgrass may help facilitate the growth of native forbs. Further studies are necessary to understand mechanisms that facilitate reestablishment of native flowering species, the long-term consequences of reducing invasive annual grasses and to document any residual effects of the herbicide on ground-nesting pollinators.

Highlights

Invasive annual grasses have been shown to have devastating consequences on native biodiversity, environmental quality, and ecosystem services (Bartz and Kowarik 2019; Jones and McDermott 2018; Kumar Rai and Singh 2020; Pejchar and Mooney 2009)
While the impact of invasive species on native vegetation is relatively well described, and studies demonstrate targeted ecosystem trade-offs resulting from controlling invasive species (Adams et al 2020; Pyšek et al 2012; Skurski et al 2013), few studies explore the relation between control of invasive plants and the subsequent impact on pollinatorfriendly forbs
Herbicide-treated plots had higher richness and alpha-diversity measures across all three locations (Table 1; Figure 2; species richness: F(1, 41) = 23.25, P = < 0.0001; Shannon diversity index: F(1, 41) = 20.29, P = 0.001; Simpson’s diversity index: F(1, 41) = 15.87, P = 0.001), suggesting that the control of B. tectorum could result in reduced competition allowing for the reestablishment of native flowering plants

Summary

Introduction

Invasive annual grasses have been shown to have devastating consequences on native biodiversity, environmental quality, and ecosystem services (Bartz and Kowarik 2019; Jones and McDermott 2018; Kumar Rai and Singh 2020; Pejchar and Mooney 2009). Data Analyses Standard ecological indices for plant species diversity, richness, and abundance were calculated for the treated and untreated plots for each sample event in each geographic location.

Results

Conclusion