Evaluating smooth sumac (Rhus glabra) management in rangelands through development of high-resolution GIS maps

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Evaluating smooth sumac (Rhus glabra) management in rangelands through development of high-resolution GIS maps

Globally, woody encroachment — the expansion of woody species — is threatening grasslands. In Nebraska, grasslands provide essential rangeland for cattle, the state’s third-greatest exported product. Where rangelands have been impacted by woody encroachment, livestock production has decreased by 75%. Maintaining rangelands by curbing woody species expansion is critical.

Objectives and Rationale

Smooth Sumac (Rhus glabra) is a woody, resprouting shrub of increasing concern due to its rapid spread throughout rangeland and resistance to management approaches, according to ranchers and land managers. This project will produce GIS maps of north-central Nebraska, a key livestock production region. The maps will test hypotheses about sumac encroachment drivers and management effects. Maps and project findings will be shared through extension publications and virtual workshops aimed at ranchers and land managers. Collaborations with producers, land managers, extension educators, and state conservation biologists have been essential in shaping this project.

Approach

The high-resolution (~1 m resolution) map will show what rangeland has the most sumac encroachment. The map will combine USDA-NAIP imagery with ground-based data collected in collaboration with ranchers and land managers. Using machine learning, we will develop a sumac classifier that locates sumac in NAIP imagery across the region. The classifier will also be used with historical NAIP imagery to quantify rates of sumac encroachment concerning environmental conditions, topography, and management variables. 

Outcomes and Evaluation

This project will increase rancher awareness of problematic sumac in grasslands and rangelands, and how ranchers can preserve rangeland quality. Virtual workshops will be held to train users on sumac encroachment maps, gain feedback from producers and managers, and convey results. This project will be evaluated in pre-and post-workshop surveys with questions targeting knowledge of sumac encroachment, management methods, opinions toward the species, and intent to implement sumac management. Findings on historical sumac distributions and their relationship to environment and management will be published in an extension report and scientific publications. Critically, this project will produce an open-access sumac encroachment map to give ranchers and land managers tools to identify areas most at risk of further sumac encroachment and to target management efforts. The use of the map will be evaluated with a web counter.

This project is important for ranchers to quantify sumac spread, understand encroachment drivers, and utilize effective controls, allowing ranchers to better preserve rangeland quality, increase profit, and maintain livestock.

This project will have the following learning and action outcomes:

1. Ranchers will be more informed about smooth sumac encroachment rates on their rangelands. Through workshops and partnerships with ranchers, this project will increase awareness of how problematic sumac is for grasslands and rangelands, how this species responds to management efforts, as well as how sumac encroachment rates have changed over time. Increased awareness will be evaluated in a pre-and post-workshop survey, using questions targeting knowledge of sumac encroachment, management methods, and attitudes toward the species.
2. Findings on historical sumac distributions and their relationship to environment and management will be published in an extension report and scientific publications. 
3. The action outcome is that ranchers and land managers will be able to use the sumac encroachment map developed in this project to identify areas most at risk of further sumac encroachment and to select the most effective management techniques, depending on the environmental context, in an evidence-based way. The use of the map as well as the online GIS data layer that makes up the map will be assessed using an online counter tracking the number of times the map and GIS layer have been accessed. Additionally, the intention to manage sumac will be assessed in a post-workshop survey sent six months after the workshop. Through partnerships and workshops, I aim to at least 50 ranchers during this project and create open-access sumac evaluation products that can be used by many more.