Differing Effects of Biosolids on Native Plants in Grasslands of Southern British Columbia

Abstract

The objective of this study was to determine if application of biosolids is beneficial for restoring semiarid grasslands. The effects of a one-time surface application of biosolids at a rate of 20 Mg ha on individual plant species and plant community composition were examined at three degraded semiarid grassland sites located in the southern interior of British Columbia, Canada. Biosolids application did not result in desirable changes in plant species composition at the two drier sites (with annual precipitation <400 mm) yet led to overall positive plant species changes at the least dry site (with annual precipitation of 400 mm). An important late-seral species of semiarid grasslands, bluebunch wheatgrass [ (Pursh) Á. Löve], did not respond or decreased at the two drier sites but increased at the least dry site. Exotic invasive plant species increased on all sites. The total vegetative cover of native perennial grasses increased from 41 to 99% at the least dry site, with important decreases in low-growing, early-seral forb species. Although cheatgrass ( L.) was not significantly increased by the biosolids treatment, the dominance of cheatgrass and lower growing season precipitation at the two drier sites were likely key reasons for the poor biosolids restoration success at these sites. Despite some concerns, there is potential to use biosolids to restore grassland plant communities successfully within 4 or 5 yr on more mesic grassland sites; however, biosolids use on drier sites where exotic invasives are present cannot be recommended.

Organic amendment additions to rangelands: A meta‐analysis of multiple ecosystem outcomes

“…We extracted data on the percent cover of grasses vs. forbs, exotics vs. natives, and annuals vs. perennials, but most of the observations could not be used because they lacked variance information. In the observations that could be analyzed, we observed a trend toward greater cover of annuals relative to perennials, which would be a negative conservation outcome in at least some rangeland systems (Newman, Krzic, & Wallace, ; Stromberg, Corbin, & D'Antonio, ).…”

“…We extracted data on the percent cover of grasses vs. forbs, exotics vs. natives, and annuals vs. perennials, but most of the observations could not be used because they lacked variance information. In the observations that could be analyzed, we observed a trend toward greater cover of annuals relative to perennials, which would be a negative conservation outcome in at least some rangeland systems (Newman, Krzic, & Wallace, 2014;Stromberg, Corbin, & D'Antonio, 2007). Furthermore, grasslands in Mediterranean systems in particular tend to be exceptionally botanically diverse with many endemic and spatially restricted species at high risk of extirpation due to land use change and management (Cowling, Rundel, Lamont, Arroyo, & Arianoutsou, 1996).…”

Composted manure application promotes long‐term invasion of semi‐arid rangeland by Bromus tectorum

“…, Borden and Black , Newman et al. ). Many invasive species thrive under conditions of high nutrient availability (Davis et al.…”

“…For example, across three rangeland sites in British Columbia, biosolid applications led to a sevenfold increase in exotic species cover (Newman et al. ). Furthermore, biosolids increased abundance of desirable, late‐seral species only at the site with few invasive species, while suppressing desirable species at two sites with greater initial invasive species cover.…”

“…In ecosystems west of the Rocky Mountains, where B. tectorum is most abundant, organic waste amendments have been found to facilitate its invasion in some cases (Borden and Black , Newman et al. ). For example, biosolid application led to a ten‐fold increase in B. tectorum cover at a reclaimed mine in Utah (Borden and Black ).…”