Ecological Impacts of Ashe Juniper on Subtropical Savanna Parklands and Woodlands

Savannas are inherently patchy systems where the distribution and abundance of the two dominant plant growth forms (woody plants and grasses) varies greatly over space and time in response to grazing, browsing, fire, drought, and topographic/ edaphic factors (Huntley and Walker 1982; Scholes and Archer 1997). In recent times, the balance between woody plants and grasses has been disrupted in many savannas around the world as woody plants have increased in abundance at the expense of herbaceous cover and production (Van Auken 2000; Archer 2005). This woody plant proliferation is thought to be driven primarily by intensification of livestock grazing and reduced fire frequency (Archer et al. 1995), although other factors (e.g., elevated atmospheric CO2 concentration and increased atmospheric nitrogen deposition) may also contribute (Polley et al. 1996; Köchy and Wilson 2001). Regardless of the cause, this vegetation change has the potential to alter a number of fundamental ecosystem properties, including productivity, biological diversity, biogeochemistry, and energy exchange, which can influence ecosystem processes at regional (Archer et al. 2001; Jackson et al. 2002; Huxman et al. 2005) and global scales (Schlesinger et al. 1990; Goodale and Davidson 2002).