Context-Dependent Effects of a Reintroduced Ungulate on Soil Properties are Driven by Soil Texture, Moisture and Herbivore Activity

Although there is considerable evidence that large mammalian herbivores influence ecosystem-level processes, studies have reported such widely varying results that generalizations have remained elusive. Here, we use an 18-year-old exclosure experiment – stratified across a landscape heterogeneous with respect to soil texture, moisture and herbivore activity – to understand the variable effects of tule elk (Cervus canadensis nannodes), a native reintroduced herbivore, on soil properties along the coast of northern California. Elk significantly increased soil bulk density and created a compacted layer at shallow soil depth, while decreasing infiltration rate and pH. The effects of elk on bulk density, penetration resistance and pH varied with soil type, being least pronounced in coarse, sandy loams and greatest in loose sand. The effects of elk on nutrient availability varied along gradients of soil texture and moisture. In coarser soils, elk decreased ammonium availability, but increased...