Research Projects

Sierra Nevada Foothills

Title Tracking Land Change at River Ridge Ranch: Working Ranch to Working Reserve
Description This project brings together eight undergraduate students with faculty for an eight-week intensive research and learning experience to study the science and technology of environmental conservation on a working ranch. It is funded through the Research Experiences for Undergraduates (REU) Sites program. We will train a highly diverse group of students in the field on River Ridge Ranch (RRR), a working ranchland near Sequoia National Park, and in the laboratory, in the use of innovative geospatial technologies (including conservation drones) and systems, and the application STEM biogeographic concepts that inform them. The objective of this REU is to train the next generation of land managers and restoration scientists in conservation science and technology to facilitate the transition of working lands to de facto working reserves.

African Savanna

Mali Fire

Title Determinants of fire intensity and severity in a mesic savanna of Africa
Description A fundamental law of savanna fire ecology is that late dry-season fires burn more intensely than early fires. Late-dry season fires are considered a major determinant of savanna vegetation as they are thought to be more damaging to young trees. Evidence in support of these principles is largely derived from a series of burning experiments that began with the pioneering work of Aubréville some seventy years ago in Africa. Critically, most contemporary savanna fire experiments adopted Aubréville’s early/late fire convention in their experimental design. Recent research suggests that numerous factors determine fire intensity and that the widely accepted dichotomous view of fire greatly oversimplifies a complex phenomenon. To determine the factors that influence fire intensity, we conducted over 130 experimental fires in the mesic savanna of Mali. Burn plots and season of burning (early, middle or late) were selected based on local burning practices. Data were collected for fire season, biomass consumed, grass type, scorch height, speed of fire front, fire type and ambient air conditions for each burn. We used multiple regression analysis to determine the key factors effecting the fire intensity and severity. Results indicate there are fundamental differences in fire behavior and intensity depending on wind direction relative to the fire. Intensity is not explained by any tested variables in head fires. Intensity of back fires is determined primarily by seasonal timing and, to a lesser extent, grass characteristics.
This project has been funded by the National Geographic Society and the National Science Foundation.

What is Early and What is Late?: The West African Fire Experiments and What They Can (and Can’t) Tell Us About Savanna Fires (PDF)

Determinants of Fire Intensity and Severity in a Mesic Savanna of Africa (PDF)

Effects of Fire Disturbance and Grass Removal on Tree Growth in Mesic Savannas (PDF)

Estimating Fire Intensity, Combustion Completeness and Greenhouse Gas Emissions for a Working Savanna Landscape in Mali, West Africa

Mali Fire Emissions

Title Coupling burning practices, vegetation cover change and fire regimes to determine fire emission dynamics for a savanna in southern Mali

This project is about improving estimates of emissions from the most frequently and widely burned areas on Earth, the savanna in Africa. Savanna fires emit large quantities of greenhouse gases and aerosol particles. While it is increasing recognized that these fires play an important role in the global carbon cycle, there are few accurate estimates of these emissions and none from West Africa which is that continent’s most active fire region. This project will develop a model of emission dynamics to determine how emissions change over time by linking changes in the fire regimes to changes in land use and land cover patterns. Available estimates of emissions from savannas contain high levels of uncertainty because they have been based on very broad generalizations of complex landscapes. To improve emissions estimates, this study will use a novel approach to develop a model based on the actual burning practices of people who set fires. Building on an existing database, it will develop a system to classify savanna vegetation types as defined by fire users and link this to fire maps derived from satellite imagery. These data will then be combined with field-based measurements of emissions of key greenhouse gases including, CO2, CO and CH4. These data will be analyzed and combined with data on changes in land use and cover to develop a model of how emissions change over time. The results will produce one of the first accurate estimates of emissions from the heavily burned West African savanna. They will be used to quantify the sources of error in existing emissions estimates.

This research is transformative in two ways. First, it will be the first model of emissions built on the practices of African fire users themselves; and second, it will provide one of the first models of fire regime dynamics based on land use and land cover changes in Africa. The results will be used to predict changes in fire emissions from the African continent. The study is designed to produce results that will provide valuable and accurate data for those attempting to improve global models of emissions from fire as well as badly needed local scale information on fire regimes. Specifically this work will disclose those areas associated with high uncertainties in the global-scale models of emissions and suggests ways to improve them. The Intergovernmental Panel on Climate Change requires that emissions estimates include an assessment of uncertainties. This study will provide such an estimate. The project will strengthen research capacities by facilitating graduate research and by providing technical support, software systems, and field equipment. It will also broaden opportunities for African university students and researchers by forming a collaborative partnership. Finally, the researchers will conduct “fire seminars” to disseminate the results locally with the goal to improve local and regional fire management efforts that are currently hampered by a lack of data. This project is supported by the NSF Dynamics of Coupled Natural and Human Systems (CNH) Program.

Presentations Determinants of Fire Intensity, Severity and Greenhouse Gas Emissions in a Mesic Savanna of West Africa (PDF)

Mali Trees

Title Creating Woodlands: Integrating Land Use Practices and New Savanna Ecological Models in Mali

This research will focus on determining the mechanisms through which everyday land management practices create conditions conducive to the establishment and growth of highly valued savanna trees and incorporating these mechanisms into theories of savanna ecology. Savannas have long posed a conundrum for scientists—how do trees and grasses coexist on the landscape and what factors prevent one vegetation form from dominating the other? Explaining the mechanisms that determine the ratio of trees to grasses has long been of interest to ecologists and geographers who seek to understand the basic functioning and distribution of the Earth’s ecosystems. Recent scientific developments have increased the importance of this task because in mezic areas both forests and savannas persist indicating that savanna is a distinct and alternative state to tropical forest. These alternative states cover vast areas, including large parts Africa. Tree cover is thought to be largely determined by fire and other disturbance regimes. The key demographic stage is the transition from sapling to juvenile because saplings are repeatedly burned to the rootstock and held in check—a phenomenon dubbed the ‘Gulliver syndrome’. When trees do manage to escape fire, they quickly grow tall. The question remains, however, what factors contribute to the success rates of tree establishment and growth? Answering this question is important because even minor changes in the success rates could have major implications for carbon sequestration given the vast extent of savannas globally as well as for the development of woodlands which are critical for local livelihoods and biodiversity.

The new developments in savanna theory fit squarely within recent advances in ecological theory more broadly, specifically the shift to disequilibrium models in which the role of disturbance is critical. Yet, surprising little research has examined the role of human practices in determining disturbance regimes in savannas. People set nearly all fires in savannas and they are responsible for rotational agriculture and animal grazing, for example; but little is known about how subtle variations in these practices influence tree survival and growth rates. We hypothesize that manipulation of woody environments has been both conscious and unconscious in the savanna of Mali and that it has been a factor in the selection of specific valued tree species such as Shea. The research has three interconnected methodological components: (i) field experiments to test the hypothesis that specific human practices differently affect specific tree species at different times in their life; (ii) a natural experiment, which combines field and remote sensing methods to test the hypothesis that disturbance history determines current vegetation cover more so than biophysical conditions; and (iii) an ethnographic component to learn how people occupying savannas understand human-plant interactions and dynamics.

Presentations Determinants of Tree Survival and Growth Rates in the Frequently Burned Mesic Savanna of Mali