Re-evaluation of native plant species for seeding and grazing by livestock on the semiarid prairie of western Canada

1 2 There is a growing interest in the re-vegetation of disturbed prairie sites, including annual 3 crop lands, with native species. Previous research from the Mixed Grassland ecoregion, or 4 semiarid prairie region, of western Canada found that introduced forage species, such as crested 5 wheatgrass, produced more spring forage with better nutritive value than native species and 6 concluded that native species exhibited little agronomic merit. However, new research indicates 7 that native species may be useful for extending forage productivity and the grazing season into 8 the late summer, fall and winter. Native species contribute to biodiversity, reduce nonforage 9 invasive species problems, and enhance wildlife habitat in this region. They may also contribute 10 to increased soil carbon sequestration, and increased ecosystem stability despite increasing aridity 11 due to climate change. Future opportunities in native plant research and development include a 12 focus on developing methods of reliable native seed production by either genetic enhancement or 13 agronomic practices or both. 14 3 INTRODUCTION 1 European settlement of the Mixed Grassland ecoregion of southwestern Saskatchewan 2 and southeastern Alberta occurred in two waves. Corporate ranching based on very large tracts 3 of native grasslands leased from the federal government followed the construction of the 4 Canadian Pacific Railway in the 1880's, but inadequate cattle feed during extreme winters 5 resulted in large death losses and subsequent bankruptcies (McGowan 1975). Despite concerns 6 about low and variable precipitation and low organic matter soils that are marginal for annual 7 crop production, the federal government’s settlement policy was changed by 1900 to encourage 8 the development of small farms and a supporting rural infrastructure such as railway branch 9 lines. Immigrants farmers or “sod-busters” received 160 acres or a quarter-section of land in 10 exchange for plowing native grass for crop, mainly wheat (Triticum aestivum L.), production for 11 export to Europe. This culminated in the plowing of 80% of the native grasslands of this 12 ecoregion in Saskatchewan and Alberta (Selby and Santry 1996). When the unsustainable nature 13 of some homesteads became evident during the major droughts of the 1930s, introduced or 14 exotic forage species, such as crested wheatgrass (Agropyron cristatum L. Gaertn. and A. 15 desertorum (Fisch. Ex Link) J.A. Schultes), were used for reseeding millions of hectares (Gray 16 1996). Introduced forage grass species from central Asia have been extensively studied since 17 the 1950's for improved adaptation, forage yield, forage quality and persistence under ruminant 18 grazing pressure. At the same time, in situ native species were considered to have low forage 19 yield, poor seed production, low forage quality, and low carrying capacity for grazing by 20 domestic livestock. 21 Over the last decade, however, there has been a renewed and growing interest in native 22 4 plant species and this interest has contributed to the formation of the provincial Prairie 1 Conservation Action Plans (PCAP Partnership 2003), the popular Native Plant Summit 2 conferences, and the formation of specialist groups such as the Native Plant Society of 3 Saskatchewan. This revival can be attributed to several emerging trends and changes to the 4 agriculture industry. These trends include increasing demand for wildlife habitat, an increasingly 5 ecological perspective on grassland management by cattle ranchers, greater respect for the role of 6 grasses in soil organic carbon sequestration, and a better understanding of the invasive 7 characteristics of some introduced forage species. Invasion of native rangelands by exotic 8 species has been highlighted as a problem of previous revegetation efforts. The introduction of 9 the Species at Risk Act 2003 in the federal parliament, an act to promote the preservation of 10 endangered species in Canada, has heightened awareness of the need for the preservation of 11 native mixed prairie rangelands and habitats. 12 Private and public organizations that manage native prairie landscapes have recognized 13 the importance of re-vegetating disturbed sites with native rather than introduced plant species. 14 For example, Ducks Unlimited Canada has promoted the value of seeded native species for 15 ground-nesting waterfowl habitat on land adjacent to permanent water bodies. In the ecologically 16 sensitive Great Sandhills of southwestern Saskatchewan, the petroleum industry is now re17 vegetating pipeline rights-of-way, well-sites, and other disturbed areas with native species. In 18 Alberta, the use of native species has been increasing steadily for public and private land 19 reclamation, resulting in the need for new guidelines (Native Plant Working Group 2001). 20 Cattle producers’ appreciation for native rangelands has increased due to years of range 21 experience and to training in intensive grazing management based on ecological principles. 22 5 Native rangelands in the Mixed grassland ecoregion can support good summer weight gains on 1 yearling steers (Karn and Lorenz 1983) and are similar to some introduced grasses (Smoliak and 2 Slen 1974; Hofmann et al. 1993). Stocking rate, grazing rotation among paddocks, and grazing 3 duration can be managed to improve range condition and maximize economic productivity (Hart 4 et al. 1988). Seeded native species will be important forage sources to complement existing 5 native rangelands for improved grazing management and range condition. As changes to 6 transportation and input costs make grain production uneconomical on some soils, the investment 7 in re-seeding native species for summer, fall and winter grazing by cattle has grown. Fall and 8 winter grazing of beef cattle, particularly pregnant non-lactating beef cows, is one strategy to 9 reduce the cost of beef production in this region. 10 Lessons can be learned from the Conservation Reserve Program (CRP) in the United 11 States which promotes the re-vegetation of land that is marginal for annual crop production and 12 emphasizes native species. One benefit of the CRP is increased soil organic carbon 13 concentration on fragile soils in the Northern Great Plains (Gebhart et al. 1994). A forage 14 seeding program for Canada has been funded and it will support conversion of marginal crop 15 land to perennial vegetative cover but also has an component for re-seeding native species 16 (Agriculture and Agri-Food Canada 2003). Soil re-seeded with native species could be a sink to 17 sequester carbon removed from the atmosphere via photosynthesis and stored as soil organic 18 matter carbon (Christian and Wilson 1999; Janzen et al. 2000). This process could contribute to 19 Canada’s international commitment to reduce greenhouse gas emissions (Environment Canada 2