Creating Woodlands: Integrating Land-Use Practices and New Savanna Models

California State University-Long Beach Foundation, Long Beach CA

Investigators

Abstract

This research project will focus on determining the mechanisms through which everyday land-management practices create conditions conducive to the establishment and growth of highly valued trees in savannah environments. The project also will seek to improve capabilities for predicting how shifts in management practices will impact future environments. Savannas long have posed a conundrum for scientists, with uncertainty remaining regarding how trees and grasses coexist in the same parkland landscapes and what factors prevent one vegetation form from dominating the other. This project will address fundamental questions of savanna science pertaining to competition between grasses and trees at different life-cycle phases in a mesic savanna. It will integrate new theories of disequilibrium ecology and human land-use practices to determine the long-term impacts of human actions on tree establishment and growth in parklands, and it will provide valuable historical data about how parklands form over time. The project will enhance understanding of how savanna parklands are created through human-environment interactions, thereby providing critical information for foresters and land managers seeking to improve parkland management and to reverse trends that have seen the parklands decline. The project will inform the development of models of carbon sequestration, and it will provide information to improve economic livelihoods for those who rely on savannah environments, especially the products of highly valued trees, for their well-being. The project also will help assess the use of unmanned aerial vehicles (UAVs, often known as drones) as an inexpensive means for gathering data at local scales in the study area and in other parts of the world. Explaining the mechanisms that determine the ratio of trees to grasses within landscapes has long been of interest to geographers, ecologists, and others interested in the basic functioning and distribution of the Earth's ecosystems. Recent scientific developments have increased the importance of this task, because in mesic areas that receive intermediate amounts of rainfall, both forests and savannas persist, which indicates that savanna is a different stated from a tropical forest. These alternative states cover vast areas, including large parts of Africa as well as parts of the Americas. Tree cover now is thought to be largely determined by fire and other disturbance regimes, including human land management. This project will consist of a focused case study of the role of human practices in determining disturbance regimes in savannas where people set nearly all fires and are responsible for rotational agriculture and animal grazing. The investigators will work in the western African nation of Mali. The investigators will test hypotheses that manipulation of woody environments has been both conscious and unconscious in savanna and that it has been a factor in the selection of specific valued tree species, such as shea trees (Vitellaria paradoxa), which yield a fruit that consists of a nutritious pulp and an oil-rich seed from which shea butter can be processed. The investigators will pursue three interconnected sets of activities. They will conduct field experiments to test the hypothesis that specific human practices differentially affect specific tree species at different times in the lives of the trees. They will analyze a natural experiment, combining field and remote sensing methods to test the hypothesis that disturbance history determines current vegetation cover more so than biophysical conditions, and they will conduct ethnographic research to learn how people occupying savannas understand human-plant interactions and dynamics.