John Wiley & Sons, Inc.
Rangelands are governed by threshold dynamics, and factors such as drought, wildfire, and herbivory can drive change across thresholds and between ecological states. Most work on this topic has focused on shifts in a single response variable, vegetation, and little research has considered how to reconcile responses of more than one variable to determine whether a system has undergone a genuine state change. In sub‐Saharan Africa, mobile overnight livestock corrals (bomas) can be used by managers to precipitate ecological transitions from areas dominated by bare ground to productive ecosystem hotspots (glades) that are attractive to wild herbivores. We asked how long bomas must be occupied by cattle before undergoing a state change, considering both plant and animal response variables, to glade ecosystem hotspots. We tested five durations of boma occupation: 0, 4, 7, 14, and 28 days. Each treatment was replicated five times, and we assessed vegetation as well as herbivore dung (as a proxy of use) at multiple time points over 3 yr following boma abandonment. Vegetation in 7‐, 14‐, and 28‐d boma duration treatments appeared to undergo a complete transition to glade‐like plant communities, whereas the shortest 4‐d treatment had not converted to a glade plant community by year 3. Wildlife responses appeared to lag behind vegetation responses, with transitions to glade‐like herbivore use occurring only in the longest duration (14‐ and 28‐d) treatments. Our results show that different response variables, when considered individually, may provide incomplete or misleading information about state changes. Although shorter‐occupied bomas might be effective for reducing bare ground, they may not attract enough wild herbivores to constitute crossing into an alternative state. Understanding threshold dynamics associated not only with vegetation responses but with a broader suite of response variables is challenging, but will provide a more complete representation of ecosystem function and greater opportunity for more successful ecosystem management.
Veblen, K. E., and Porensky, L. M.. 2019. Thresholds are in the eye of the beholder: plants and wildlife respond differently to short‐term cattle corrals. Ecological Applications 00( 00):e01982. 10.1002/eap.1982