A non-native agronomic legume (Astragalus cicer L.) alters multiple ecosystem-services in mixed prairie grassland

Abstract

Cicer milkvetch (Astragalus cicer L.), and other non-native agronomic legumes, are used extensively for forage in North America, but, despite their abundance, few studies have examined their effects when they colonize native grasslands. Cicer milkvetch provides excellent forage for livestock, but given its large size and ability to fix nitrogen, it is likely to affect other ecosystem services provided by grasslands. We have observed cicer milkvetch in the dry mixed-grass prairie of southern Alberta, Canada. The objective of this study was to examine the effects of cicer milkvetch on forage production, carbon storage and plant community diversity after it colonizes native mixed prairie grasslands and further examine whether these effects increase with cicer milkvetch patch size. We compared the ecosystem functions among plots located within a cicer milkvetch patch, beside a patch and 5 m distant from the patch. The plant, as expected has positive effects on forage quantity and quality, reduced plant species diversity and richness, and altered numerous components of the carbon pool, as well as nitrogen availability. Furthermore, larger patches of cicer milkvetch had lower concentrations of soil carbon and nitrogen, and differentially affected other ecosystem properties. Given the potentially large propagule pressure of non-native legumes from agricultural lands, surrounding native grasslands in North America, and our results demonstrating effects on multiple grassland ecosystem services, further consideration and investigation of non-native legumes in grasslands is warranted.