Doctor of Philosophy, The Ohio State University, 2022, Geography

Bofedales are ecologically defined as an Andean mountain wetland and peatland system, which constitute one of the most highly biodiverse and important hydroecological systems of the high Andes. Their geographic distribution is scattered across high mountain plateaus and glacier valleys across the Andean Cordilleras. Bofedales provide key environmental, social, and cultural services for pastoralist communities, including critical habitat for a wide range of wild flora and fauna, including also livestock animals and endemic birds. Alterations to the regional climate processes, land use change, and rapid glacier retreat are affecting the sustainability and equilibrium of bofedales, leading to their degradation. Despite their importance for ecosystem services, there is a substantial gap in the geographical distribution of bofedales, which is a critical need in order to understand current threats and vulnerabilities to these systems, and a dearth of information about the range of biophysical patterns regarding the classes of bofedales and differing bio-geographical characteristics of bofedales across the Andean region, including the seasonal to interannual patterns of vegetation productivity. In this research, I developed and applied new methodologies utilizing state-of-the-knowledge Earth Observation Systems analysis with extensive ground-truthing, archival research of published studies, and mixed botanical field methods to create an Atlas of bofedales in the Southern Tropical Andes, including the countries of Peru, Bolivia, Chile and Argentina. In particular, this research has resulted in the development of mapping products to address the academic gaps in bofedal distribution including 1) A baseline inventory of varying bofedal classes and a regional map of their distribution and size of bofedales for the Southern Tropical Andes, and 2) A comparative geo-botanical analysis of bofedal classes in three regions of the Bolivian Altiplano, and 3) An examination of the annu (open full item for complete abstract)

Committee: Bryan Mark (Advisor) Subjects: Geographic Information Science; Geography; Physical Geography; Remote Sensing

Doctor of Philosophy, The Ohio State University, 2022, Geography

This dissertation comprises of a multi-part investigation into the impacts and contributions of debris-covered glaciers to the surface hydrology of the Cordillera Blanca, Peru. Due to the circumstances surrounding the global pandemic, the originally planned in situ dataset was not collected; however, following a pivot in research goals and objectives, field collected (prior to 2020) streamflow and water quality data, and remotely sensed imagery were used to answer the slightly broadened questions of this dissertation. First, without a specific focus on debris-covered glacier catchments, long-term hydrological shifts were identified throughout the past 70-years, and short-term daily fluctuations were assessed throughout the Rio Santa watershed. Multiple change points were identified to have occurred over the historical record, with the most recent changes in the 2000s that indicate lower rates of loss in discharge now compared to prior decades. High-temporal resolution discharge data is presented which provides evidence that diurnal changes in streamflow are driven by seasonal fluctuations and have not undergone significant shifts in timing or amplitude during the past 14-years. Second, high-resolution satellite imagery was used to calculate the spatial and temporal changes and estimate volumes of supraglacial ponds on the surface of debris-covered glaciers for the first time across the Peruvian Andes. Expanding the study area beyond the Cordillera Blanca allowed for the opportunity to test patterns in debris-covered glacier ponds more broadly and place the Cordillera Blanca in a regional context. From these analyses, debris-covered glacier pond area maxima were recorded to have occurred in 2012 and 2013 across the Peruvian Andes. Furthermore, as minimum temperatures significantly rose over the past 11 years, a decrease in total supraglacial pond area was measured. Finally, water volume estimates provide strong indications that debris-covered glaciers contribute sign (open full item for complete abstract)

Committee: Bryan Mark (Advisor); Michael Durand (Committee Member); Robert Hellstrӧm (Committee Member); Alvaro Montenegro (Committee Member) Subjects: Environmental Science; Hydrology; Physical Geography; Water Resource Management

Master of Arts, The Ohio State University, 2019, Geography

The goal of this research is to develop a new proxy record sensitive to water availability in the tropical Andes, where climate change threatens glacial reserves of water stored as ice. As such, this study constitutes the first investigation into the radial growth of the newly described tropical tree species, Polylepis Rodolfo-vasquezii. In the dry season of 2017, a sample set of cores were extracted from a P. rodolfo-vasquezii montane forest in the Cordillera Huaytapallana in the central Peruvian Andes. Standard dendrochronological techniques were applied to the samples to produce a 77 year-long annually resolved chronology, from 1940 to 2016. Correlation analysis between tree ring widths and station data as well as regional anomalies and reveal that P. rodolfo-vasquezii is sensitive to wet season precipitation and discharge from the nearby Shullcas River. The strongest relationship with the tree rings was late wet season discharge. Based on these correlations, the first-ever monthly and seasonal discharge reconstructions were produced for the Shullcas River. The calibration-verification statistics for each model indicate that there are varying degrees of predictive skill in the reconstructions produced. The optimal reconstruction was for the average of April-May discharge. This work provides evidence that Polylepis rodolfo-vasquezii is a useful species for dendrochronological research and highlights its relationship to moisture in the Cordillera Huaytapallana.

Committee: Bryan Mark PhD (Advisor); Alvaro Montenegro PhD (Committee Member); Ellen Mosley-Thompson PhD (Committee Member) Subjects: Environmental Science; Geography; Hydrologic Sciences; Paleoclimate Science

Doctor of Philosophy, The Ohio State University, 2016, Evolution, Ecology and Organismal Biology

The Neotropics is the most species-rich region in the world. The current diversity and distribution of lineages present in this region is in part the result of complex ecological and evolutionary trends determined by environmental variables that have operated at diverse spatial and temporal scales. In addition, demographic processes have also influenced the structure of present-day phylogeographic patterns. Several studies have used Neotropical pitvipers as model organisms to explore historical diversification patterns and ecological processes that produce diversity in this region. However, few of those studies have explored patterns of diversification for groups of pitvipers likely influenced by one of the most salient features of the South American continent: The Andes. Here, I use a combination of molecular, morphological, and geographical data to explore diversification patterns and the evolutionary mechanisms implicated in the divergence of two distinct members of the genus Bothrops. First, I examine cryptic diversity present in the widespread and medically important snakes of the B. asper species complex (Chapter 2). Using a genomic and morphological dataset collected across the distribution of the group, I identified extensive phylogeographic structure, suggesting the influence of geographic barriers and/or differences in ecological niches in the recent diversification in the group. A deep divergence between a Central and South American clade is evident, but more recently diverged groups in South America show complicated patterns suggestive of recent divergence and/or gene flow among lineages. Next, I use this information to perform model-based analyses to investigate the demographic processes involved in the recent origin of two Ecuadorian montane lineages of these pitvipers (Chapter 3). This approach allowed me to resolve some of the discrepancies of evolutionary relationships found in Chapter 2. I found evidence for the isolation of one of the montane line (open full item for complete abstract)

Committee: H. Lisle Gibbs (Advisor); Paul A. Fuerst (Committee Member); Thomas Hetherington (Committee Member); John Freudenstein (Committee Member) Subjects: Ecology; Evolution and Development; Zoology

Master of Science, The Ohio State University, 2009, Geological Sciences

Oxygen isotopes are useful proxy records in ice cores because of the selective fractionation process that occurs during evaporation and condensation of water molecules, yet the controls on these fractionation processes are under debate for tropical ice core records. Two ice cores from the eastern and western range of the Peruvian Andes (Quelccaya Summit Dome and Coropuna Caldera Core) are annually resolved for the last 200 years and provide an excellent means for comparison to localized instrumental meteorological records as well as regional measures of past climate. The oxygen isotope histories from these cores show no significant correlation with temperature or precipitation from two nearby meteorological stations or an automated weather station on the summit of Quelccaya. Yet significant correlation is found on a regional scale with Lake Titicaca water levels as well as equatorial Pacific sea surface temperatures over recent time. However, overall trends for the last century offer conflicting evidence to this end. On centennial and millennial time scales, temperature has been shown to be positively correlated with oxygen isotopes in tropical ice cores, yet the mechanisms for this control need further research.

Committee: Lonnie Thompson (Advisor); W. Berry Lyons (Committee Member); Bryan Mark (Committee Member) Subjects: Geology

Master of Science, The Ohio State University, 2008, Geological Sciences

Three ice cores drilled to bedrock atop Nevado Coropuna, southwestern Peru reflect Holocene and late glacial stage climate variability. Two cores measure <34 m in length yet provide seemingly continuous >16 kyr histories, and thus represent the shortest known ice cores to extend from the present into the last glacial. High major ion concentrations and dust particle diameter ratios identify a succession of abrupt and severe Holocene droughts on the Altiplano centered at 3.4, 4.2, 5.6, 7.5, 8.2 and 10.1 kyr B.P. Modern precipitation availability in the region is dominated by ENSO variability on interannual timescales and these events may thus reflect extended periods of El Nino-like conditions in the tropical Pacific. The Deglaciation Climate Reversal, the tropical counterpart to the Northern Hemisphere Younger Dryas stadial, is marked by large, abrupt stable isotopic depletion, with δ18O ~9-10 per mil lower at this time relative to the early Holocene. This δ18O shift is remarkable as it is ~4-5 per mil greater than that observed in any previously drilled central Andean ice core record. In concert with marked, synchronous deuterium-excess increases, these shifts may be explained by a coeval southward migration of the ITCZ. Decreased major ion and dust concentrations and low dust particle diameter ratios likely reflect increased central Andean precipitation at this time, in agreement with other regional paleoclimate records.A complete history could not be produced for the third core due to conflicting dating results. Annual resolution over the past 244 years allows for a detailed assessment of recent regional climate change and its relation to possible forcings. Decadal δ18O variability is strongly correlated with tropical Pacific sea surface temperatures and lends support to precipitation, via the amount effect, controlling δ18O on these timescales. On longer timescales, temperature plays an increasingly important role in governing this parameter and it is suggested t (open full item for complete abstract)

Committee: Dr. Lonnie Thompson (Advisor); Dr. W. Berry Lyons (Committee Member); Dr. Bryan Mark (Committee Member) Subjects: Geology