To study how herbivores have shaped ecosystem functions in the past, we must be able to reconstruct how herbivore densities and communities have changed through time. I am starting a new project to better develop organic geochemical proxies (fecal biomarkers) for paleo-herbivore communities.To accomplish this, I am deploying a multi-scale calibration framework in Kruger National Park, South Africa, where I will measure the concentrations and distributions of these compounds in dung, soils and sediments.
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The African Humid period (14.7-5 Ka) was a time of increased rainfall in northern and subtropical Africa. This period provides an opportunity to test if savanna fire activity responds to long-term shifts in rainfall in predictable ways. I am generating new organic geochemical records of paleofire from East African lakes, and synthesizing them alongside existing charcoal records to examine if hydrologic controls on paleofire fuel dynamics varied across the savanna rainfall gradient (200-1500 mm/yr).
Publications: Karp et al. (2023)
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Consumer feedbacks (i.e., fire and herbivory) play important roles in stabilizing grasslands biomes. However, how these factors interact with each other on long timescales, and how they may change in relation to our currently changing climate is unknown. My current project combines, remote sensing, herbivore exclusion experiments, and Quaternary paleoecological reconstructions to examine how fire and herbivory interact with climate to differentiate between alternative stable states.
Publications: Karp et al. (2021); Staver et al. (2021)
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I'm interested in applying and improving molecular proxies for fire in deep time records. I focus on a suite of molecules called Polycyclic aromatic hydrocarbons (PAHs) that are produced from the burning of biomass. My work has focused on improving our ability to identify the fiery origin of these molecules through multivariate statistics and compound specific isotopic measurements of both modern burned samples and sedimentary samples (i.e. lake, marine sediments). I am also starting a new project measuring PAHs from controlled burns in Kruger National Park, South Africa to calibrate these compounds specifically for grasslands.
Publications: Karp et al. (2020); Vachula et al. (2022)
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Today grasslands are responsible for up to 30% of global terrestrial primary productivity and are important to maintaining subtropical biodiversity across five continents. However, while these ecosystems generally proliferated in the Mio-Pliocene they didn't originate synchronously on each continent (1-5 Myr offsets). I'm interested in examining how regional divers (especially fire dynamics!) regulated the expansion of these important systems in the context of a changing global climate. I focus on the grassland expansions in South Asia and Australia.
Publications: South Asia: Karp et al. (2018); Karp et al. (2021); Polissar et al. (2021) Australia: Karp et al. (2021)
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I'm generally interested in the interactions between human societies and their natural environment through time. Particularly, how people shape the ecosystems that they live in. My work can help address these questions using biomarkers preserved lake sediment archives to reconstruct Holocene paleoenvironments. I've been involved in projects looking at the interactions between prehistoric cultures, agricultural practices, and climate (Cahokia, IL USA; Krivače, Dalmatia Croatia).
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