Investigating a Possible Arrested Succession in a Desert Grassland Following Prescribed Burns: Muleshoe Ranch, Arizona

Abstract

The Muleshoe Ranch is a cooperatively managed Nature Conservancy Preserve located in the desert grassland of southeastern Arizona. The desert grassland ecosystem is sensitive to change, as the species composition is dependent on the set of conditions particular to this region (McClaran and Van Devender 1995, Gonzales 2006). There was a prescribed burn several years ago at the Muleshoe Ranch, after which annual dicots began to grow in some habitats. It is natural for annual plants to dominate at first, while the perennials recover after a fire (McClaran and Van Devender 1995); in this case however, some patches remain dominated by annuals. The species of perennial grasses used in this study include; Bouteloua curtipendula (sideoats grama), Muhlenbergia porteri (bush muhly), Bouteloua eriopoda (black grama), Bouteloua chondrosoides (spruce-top grama) and Aristida ternipes (spider-grass). Differences between soils from habitats dominated by perennial grasses and annuals were examined. Germination experiments were performed in the laboratory and in the field to compare the growth of perennial grass species in soil from the different habitat types. Paired annual and grassy transects in two different locations were used to assess overall abundance of all plant species (June 2008) and biomass (August 2008). Results indicate a difference in soil electrical conductivity between sites. Germination was not significantly affected by habitat type. The frequency of perennial grasses was greater in transects in grassy habitats versus annual habitats. Biomass from the transects showed no significant patterns. It is important to understand what is happening to the plant community so that the Muleshoe Ranch can continue to be restoratively managed, and the natural desert grassland community can persist (Suding et al. 2004).