Effects of a Reintroduced Herbivore on Ecosystem-Level Processes:An Integrated Approach for Understanding Variable Outcomes Across Heterogeneous Landscapes
Dodge, V. J.. 2017.
Abstract
Purpose of the Study: There is considerable evidence that large mammalian herbivores
influence ecosystem level processes, however, their effects are often variable and hard to
predict. Several frameworks have been put forward, which include other properties that
might also affect ecosystem level processes, including nutrient level of dominant plants
in the habitat, herbivore body size, climate type, and physical characteristics of the soil.
The purpose of this study is to integrate these frameworks and incorporate gradients of
herbivore activity level, soil texture and moisture to determine the effects of a large
mammalian herbivore on ecosystem-level processes.
Procedure: We use an 18-year-old experiment stratified across a heterogeneous
landscape to examine the effects of tule elk (Cervus canadensis nannodes), a
reintroduced native herbivore, on soil physical and chemical properties along the coast of
northern California.
Findings: Elk significantly affect soil bulk density, penetration resistance, infiltration
rate, and pH, and that these effects vary among soil formations. Soil moisture and texture
significantly affect nitrate and ammonium availability, and this effect can be modulated
by elk. Finally, the level of elk activity can influence nutrient availability and bulk
density, and the effect of elk on bulk density can in turn influence nitrate and phosphate
availability
Conclusions: Our study emphasizes the importance of an integrated approach to
examining the effects of herbivores on ecosystem-level processes. These findings may
help researchers make more accurate predictions about how large herbivores influence
soil properties and processes, leading to more informed decisions with regard to
conservation, restoration, reintroduction and agriculture.
Key Words
native ungulate herbivores, environmental heterogeneity, soil characteristics,nutrient cycling
