Collaborative adaptive rangeland management, multi-paddock rotational grazing, and the story of the regrazed grass plant

Authors: Porensky, Lauren; Augustine, David; Derner, Justin; WILMER, HAILEY - Us Forest Service (FS); FERNANDEZ-GIMENEZ, MARIA - Colorado State University; BRISKE, DAVID - Texas A&M University

Submitted to: Society for Range Management
Publication Type: Abstract Only
Publication Acceptance Date: 12/24/2020
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Frequent, severe defoliation reduces grass production, particularly for grazing-sensitive species. Multi-paddock rotational grazing has long been proposed as a grazing strategy that may be able to reduce the frequency and intensity of defoliation on palatable grass plants without altering stocking rates. Previous studies evaluated this hypothesis using small, homogeneous paddocks and non-adaptive rotation schedules, and found small and inconsistent differences between continuous and rotational grazing systems. Using a stakeholder-driven Collaborative Adaptive Management (CAM) framework, we conducted the first ranch-scale experimental investigation into tiller defoliation dynamics in the context of adaptive multi-paddock rotational grazing. We monitored tiller defoliation frequency and intensity in ten paired 130-ha pastures which were assigned to either a collaborative adaptive multi-paddock rotational grazing treatment (CARM) or a season-long continuous grazing treatment (TRM) at the same stocking rate in shortgrass steppe. Consistent with previous studies, we observed that frequencies of grazing and regrazing on a palatable, cool-season grass (western wheatgrass, Pascopyrum smithii) were much more sensitive to stocking rate than grazing system treatment. Under the moderate stocking rates used in both CARM and TRM treatments, roughly two-thirds of western wheatgrass tillers remained ungrazed annually, regardless of grazing system. Thus, season-long rest is present in season-long continuous grazing as well as rotational systems. Levels of regrazing in CARM and TRM were low (5-15%) and similar between treatments. We conclude that the use of adaptive multi-paddock rotational grazing should not be expected to enhance the production or abundance of this palatable, cool-season species. Although defoliation dynamics were similar between CARM and TRM at the whole ranch scale, CARM enhanced spatial and temporal heterogeneity in defoliation frequencies among individual pastures. This higher and predictable variation could provide management flexibility. The CAM model enabled us to identify and directly address key stakeholder hypotheses, and enhanced stakeholder ownership and trust of research results.