Global Savanna Research Initiative

Problem Statement: Savannas cover vast areas of the globe. The balance between grasses and woody plants is regulated by complex interactions among climate, atmosphere, soils, herbivory, and fire. In many parts of the globe, the woody-herbaceous balance has tipped in favor of shrubs and trees with savannas transitioning to shrublands or woodlands. Causes for these ongoing transformations are unclear, but what is clear is that there are important-if poorly understood-consequences for ecosystem processes, biodiversity, and the sustainability of savannas. Controversies regarding the importance of these factors will be resolved only through the creative integration of small- and large-scale experiments and long-term monitoring. The Savanna Long-term Research and Education Initiative (SLTREI) is an emerging program that addresses ecosystem function, dynamics, and processes within landscapes consisting of a balance between grasses and woody plants.

Research Focus and Framework: Research will initially focus on (i) investigating the drivers and mechanisms underlying short- and long-term changes in grass-woody plant abundance, (ii) quantifying the effects of shifts in life-form composition on ecosystem function and services, and (iii) developing and evaluating ecosystem-based management strategies for restoring grasslands and savannas and the ecosystem services they provide. We are developing a framework within which to address fundamental ecological questions about interactions between plant life forms (grass-woody) and growth, using long-term, plot-, landscape-, and watershed-scale experiments manipulating precipitation, fire, and herbivory; and enables leverage of 100+ years of continuous on-site research in the context of livestock grazing, the most common land use in global savannas. The conceptual framework we are testing is founded on two theoretical concepts: alternative stable state theory (ASST) and pyric herbivory. Each has been applied in savanna landscapes, but the two have never been co-integrated in an experimental context over long timeframes. Alternative Stable State Theory is a way of explaining, understanding, and predicting ecosystem state transitions in dual-life-form systems; pyric herbivory is a novel paradigm built on the notion that reciprocal, spatially distributed interactions between grazing and fire are a key to maintaining grassland and open savanna landscapes. 

Resources: The initial work will be done at the Sonora Research Station and nearby Reed and Martin Ranches close to Sonora, TX, USA. We are investing $0.5 million a year in competitive grants and infrastructure funding.  We are developing a data plan and have ample housing and many long-term data bases. We have research staff and onsite scientists, housing, laboratory facilities, livestock, and over 7,000 ha of savannas. This work is currently being supported by Texas A&M AgriLife Research and the Sid Kyle Endowment for Semi Arid and Arid Land Studies. 

Impacts: SLTREI will generate new and important insights into the functioning and restoration of savanna landscapes that will help landowners and professional land managers with national, state, and local agencies develop proactive, strategic interventions and objectively assess tradeoffs in ecosystem service portfolios. We hope to engage global partnerships to conduct similar research and test these theories beyond Texas.

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