Crested wheatgrass (Agropyron cristatum) seedings in Western Colorado: what can we learn

Nikki Grant-Hoffman,James Dollerschell,Amanda Clements,Anna Lincoln

doi:10.3391/mbi.2012.3.2.03

Abstract

Non-native species have been widely transported, becoming components of ecosystems worldwide. In some cases this can change the structure and function of an ecosystem. Crested wheatgrass (Agropyron cristatum, Agropyron spp.) was introduced into the Western U.S. in the late 18th and early 19th centuries. Since introduction, it has been planted in western rangelands currently occupying millions of acres. Crested wheatgrass causes significant changes in areas where it dominates the vegetation, and restoring rangelands planted with crested wheatgrass to higher plant diversity and ecosystem function has been met with limited success. Here we revisit historical frequency monitoring data collected in western Colorado on public lands that were planted with crested wheatgrass between 1940 and 1980. We also monitored vegetation before and after mechanical treatment (removal of vegetation with the use of a dixie harrow pulled behind a tractor) and re-seeding of desirable species in three areas dominated by crested wheatgrass. We looked for increasing or decreasing trends in plant species, and for plant species that persist with crested wheatgrass. We found that crested wheatgrass increased significantly (p=0.09) over time, we also found five species of grasses, two shrub species, and one forb species that were persistent in areas planted with crested wheatgrass. We found that in mechanically treated areas, the only significant trend was a reduction of native grasses (p<0.05). Our findings suggest that in areas planted with crested wheatgrass, frequency of crested wheatgrass can increase over time. Further, mechanical treatments coupled with seeding were not effective at reducing crested wheatgrass cover, or at increasing native and desirable species. These sites may have experienced a shift to a stable state.

Highlights

Biological invasions by non-native species are one of the worst ecological components of global environmental change
The lowest value of the range for mean peroxidase concentrations was found for Group T in Pond 7 (6.71 μg/gm FW), for Group A in Pond 2 (6.72 μg/gm F.W.) and for Group B in Pond 3 (1.31 μg/gm F.W.)
This study shows evidence in favour of two specific traits of Alternanthera philoxeroides that are reported to facilitate plant adaptations in different environments, namely, its ability to grow even under high strand density and its ability to withstand a broad range of environmental conditions

Summary

Introduction

Biological invasions by non-native species are one of the worst ecological components of global environmental change. Alternanthera philoxeroides (Martius) Griseb (Amaranthaceae), alligator weed, an invasive perennial wetland herb originating from South America (Maddox 1968), has many attributes of a successful invasive weed such as rapid growth and vegetative propagation (Tao et al 2009; Wang et al 2009) as well as a broad ecological amplitude (Geng et al 2007) This amphibious clonal plant has invaded many ecosystems worldwide (Julien et al 1995), including riparian zones (Pan et al 2006) and agricultural lands (Spencer and Coulson 1976), and is regarded as one of the worst weeds of the world (http://www.waikatoregion.nz). Invasive plants posses certain characteristics which make them more competent to adapt and propagate in newer environments/ habitats and understanding these mechanisms is crucial for managing invasive plant species (Mack et al 2000)

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