A5002903635- Ecology and Vegetation Dynamics Studies
- Rangeland and Wildlife Management
- Fire effects on ecosystems
- Plant Water Relations and Carbon Dynamics
- Peatlands and Wetlands Ecology
- Forest ecology and management
- Wildlife Ecology and Conservation
- Ecology and biodiversity studies
- Banana Cultivation and Research
- Ecosystem dynamics and resilience
- Land Use and Ecosystem Services
- Animal Ecology and Behavior Studies
- Geology and Paleoclimatology Research
- African Botany and Ecology Studies
- Forest Management and Policy
- Botany and Plant Ecology Studies
- Soil Carbon and Nitrogen Dynamics
- Agroforestry and silvopastoral systems
- Evolution and Paleontology Studies
- Tree-ring climate responses
- Plant responses to elevated CO2
- Plant Diversity and Evolution
- Plant and animal studies
- Agronomic Practices and Intercropping Systems
University of Oregon
2021-2025
United States Geological Survey
2023-2025
Forest and Rangeland Ecosystem Science Center
2023-2025
Yale University
2016-2024
Princeton University
2013
Summary Woody encroachment is a pervasive challenge facing savanna and grassland managers world‐wide. Proposed drivers of the phenomenon range from local changes in fire, herbivory direct human impacts, to global climate or atmospheric [CO 2 ] that may be accelerating woody growth. The relative influences versus their interactions are largely unknown, but will determine extent which management can limit locally. We examined recent Hluhluwe– iM folozi Park South Africa 2007 2014. Vegetation...
Dimensions of tree root systems in savannas are poorly understood, despite being essential resource acquisition and post-disturbance recovery. We studied rooting patterns Southern African to ask: how strategies affected species responses severe drought; potential depths varied across gradients soil texture rainfall. First, detailed excavations eight Kruger National Park suggest that the ratio deep shallow taproot diameters provides a reasonable proxy for depth, facilitating extensive...
Abstract In savannas, partitioning of below‐ground resources by depth could facilitate tree–grass coexistence and shape vegetation responses to changing rainfall patterns. However, most studies assessing tree versus grass root‐niche have focused on one or two sites, limiting generalization about how soil conditions influence the degree rooting overlap across environmental gradients. We used complementary stable isotope techniques quantify variation (a) in water uptake depths (b) fine‐root...
Rainfall variability is a major determinant of soil moisture, but its influence on vegetation structure has been challenging to generalize. This presents source uncertainty in predicting responses potentially widespread shifts rainfall frequency and intensity. In savannas, where trees grasses coexist, conflicting lines evidence have suggested, variously, that tree cover can either increase or decrease response less frequent, more intense rainfall. Here, we use remote sensing products...
Increasingly frequent and severe droughts under climate change are expected to have major impacts on vegetation worldwide. However, research date has focused tree vulnerability drought in forests. Less is known about trees savannas, where a sparse layer coexists with grass. These tree-grass interactions (often mediated by fire herbivory) shape savanna ecology, confound predictions of how strongly might affect trees. On the one hand, physiologically stressful, which could harm be exacerbated...
Abstract The ongoing loss of large trees and densification shrubs are two prevalent processes that take place in African savannas, with profound consequences for their structure function. We evaluated herbivore impacts on savanna woody communities using a long‐term exclosure experiment the Kruger National Park, South Africa, three treatments: exclusion mammals only (i.e. elephant giraffe), all herbivores larger than hare, areas open to herbivores. asked questions: (1) How did variable affect...
Abstract Declines in grassland diversity response to nutrient addition are a general consequence of global change. This decline species richness may be driven by multiple underlying processes operating at different time‐scales. Nutrient can reduce enhancing the rate local extinction via competitive exclusion, or reducing colonization constraining pool able colonize under new conditions. Partitioning net change into and rates will better delineate long‐term effect grasslands. We synthesized...
Abstract Savanna trees experience various ecological pressures, requiring their roots to serve multiple functions. However, savanna root trait studies have focused on easily measurable traits, emphasizing a single axis of function: resource acquisition in competition with grasses, resilience episodic droughts or storage for recovery following fire herbivory. This narrow focus limits understanding trait–function relationships and factors driving variation. Our synthesis evaluates few key...
Droughts are expected to become more frequent and severe, due climate change, with uncertain consequences for savanna vegetation. Drought-driven tree mortality has been observed in some savannas, but little is known about how tolerant trees drought, or what determines differences among species drought vulnerability. Here, we examine which characteristics best distinguished that were most negatively affected by a recent Kruger National Park, South Africa. Woody-encroaching, root-suckering...
Summary Increasing atmospheric CO 2 is changing the dynamics of tropical savanna vegetation. C 3 trees and grasses are known to experience fertilization, whereas responses by 4 more ambiguous. Here, we sample stable carbon isotope trends in herbarium collections South African reconstruct 13 discrimination. We found that showed no discrimination over past century but increased their through time, especially since 1950. These changes were most strongly linked rather than rainfall climatology...
Ecological stability in plant communities is shaped by bottom-up processes like environmental resource fluctuations and top-down controls such as herbivory, each of which have demonstrated direct effects but may also act indirectly altering community dynamics. These indirect effects, called biotic mechanisms, been studied across gradients, few studies assessed the importance on mechanisms conjunction with processes. Here we use a long-term herbivore exclusion experiment central Kenya to...
Abstract Widespread woody encroachment is a prominent concern for savanna systems as it often accompanied by losses in productivity and biodiversity. Extensive ecosystem‐level work has advanced our understanding of its causes consequences. However, there still debate over whether local management can override regional global drivers encroachment, remains largely unknown how influences community assemblages. Here, we examined species‐level changes plant distributions size structure from the...
Exotic annual grass invasion is a pressing concern in sagebrush rangelands of the western United States. Overgrazing and fire have historically both been implicated rise grasses, but experiments that compare effect grazing versus are lacking, particularly for contemporary practices such as off-season (fall winter) grazing. We compared 1) burned ungrazed (burned), 2) off-season, moderately grazed unburned (grazed), 3) (control) treatments at five Wyoming big (Artemisia tridentata ssp....
Pocket gophers (Geomyidae) are major agents of disturbance in North American grasslands. Gopher mounds bury existing plants and influence community structure through various mechanisms. However, mountain meadows that experience winter snowpack, also create castings, smaller tube-shaped deposits, previously ignored studies plant–gopher relationships. We studied the influences Mazama pocket gopher (Thomomys mazama Merriam, 1897) montane Oregon Cascades, quantifying patterns at larger spatial...
Abstract Exotic annual grass invasion is a widespread threat to the integrity of sagebrush ecosystems in Western North America. Although many predictors prevalence and native perennial vegetation have been identified, there remains substantial uncertainty about how regional‐scale local‐scale interact determine heterogeneity, associations between cattle grazing vary with environmental context. Here, we conducted regionally extensive, one‐season field survey across burned unburned, grazed,...
In ecological restoration, the role of historical fidelity in restoration references has long been both a foundational concept and frequent source debate. However, this is not only that history plays. History sense knowledge can inform goal‐setting provide tools for success. events (what happened place) many ways determines goals trajectories to what extent reference knowable applicable. Here, we discuss conceptual framework how these forms “history” interact, particularly underappreciated...