Zicheng Yu


Research Interests: 

  • Paleoecology
  • Paleoclimatology
PhD (1997) in Botany, University of Toronto, Toronto, Canada
MS (1992) in Botany, University of Toronto, Toronto, Canada
MS (1988) in Geoecology, Peking University, Beijing, China
BS (1985) in Physical Geography, Peking University, Beijing, China
EES24 (Climate Change), EES 357 (Paleoecology and Landscape History), EES 415 (Paleoclimatology)

Current Research Projects

NSF P2C2 (Paleo Perspective on Climate Change) Program: Water Isotopes in Peat Mosses as Proxies for Understanding Climate and Atmospheric Circulation Changes in Southern Patagonia

This award to Lehigh and Brown Universities will develop and test a powerful technique to reconstruct atmospheric circulation patterns and moisture trajectories using two water isotopes from peat mosses. The research will generate important climate records that will potentially transform our understanding of climate dynamics of the last 1000 years in the relatively understudied southern hemisphere. This approach is also applicable over longer time scales in this geographic regions, as well as other places Sphagnum moss can be found. The new climate records from under-studied southern Patagonia will provide a benchmark data set with which to evaluate the climate models that are used for projecting future climate change. The project will train graduate and undergraduate students at both institutions in the application of a state-of-art technology in innovative interdisciplinary research.

This award will use isotope records to document and understand climate and atmospheric circulation changes in the last millennium using a novel dual water isotope approach and systematic modern calibration from single species peat mosses (Sphagnum) as preserved in peat bogs in southernmost Patagonia (southern South America). The investigators will carry out calibration sampling and analysis to span large latitude and precipitation gradients in southern Patagonia. The isotope records will be derived from the existing peat cores at Lehigh University. In addition to using oxygen and hydrogen isotope time series from cellulose and lipids for “conventional” paleoclimate interpretations, the team will explore the use of derived deuterium excess (delta-excess) as a tracer for moisture source region conditions and moisture trajectories. This innovative use of dual (O and D) isotopes would provide powerful information regarding past atmospheric circulation and mechanisms of observed climate changes.



NSF MacroSystem Biology Program (Navigating the New Arctic Big Idea): Peat Expansion in Arctic Tundra - Pattern, Process, and the Implication for the Carbon Cycle (TundraPEAT)

Amplified Arctic warming in recent decades has caused a multitude of changes in terrestrial ecosystems that have potential for strong feedbacks to the global system. Arctic vegetation greening may not necessarily result in increases in carbon sequestration in Arctic tundra due to complex and uncertain soil processes. Arctic tundra tends to have a thicker organic soil horizon (peat) than most other zonal biomes; research shows that peatlands comprise a sustained carbon sink. If shallow peatlands are widespread throughout the Arctic, the overall net carbon storage capacity of tundra might be underestimated globally. However, the factors controlling the formation, distribution, and dynamics of these peat patches across the Arctic are not well understood. The overall goal of the project is to understand organic soil (peat) accumulation processes in the tundra biome and to assess the role of peat in regional and pan-Arctic carbon budgets at decadal and centennial timescales. The project will examine potential peat migration/expansion frontiers in a warming Arctic and their significance in the regional and pan-Arctic carbon cycle. The project will train undergraduates, graduate students, and postdocs from diverse socio-economic and cultural backgrounds in both data analysis and modeling. The public education and outreach program includes STEM activities involving middle and high school students and a symposium on Arctic environments. The understanding of environmental conditions and processes that control the formation and northward migrations of the green peat frontier will inform Arctic stakeholders in their use of natural resources.

This multidisciplinary research team of researchers will integrate (1) new data collection from multiple tundra sites along the northernmost peat-forming frontiers of the North American Arctic, together with (2) laboratory incubation experiments, (3) a synthesis of existing data from the tundra and boreal biomes, and (4) ecosystem-scale process model simulations. The overarching question is: will the warming Arctic transform into a peat-rich landscape, as the boreal zone is now, or are there essential conditions lacking in a warming Arctic that will prevent this? To address this broad question, the research focuses on two key elements of the Arctic peat-forming ecosystems: peat patches, and the role of Sphagnum in the formation, persistence, and rapid rates of carbon sequestration of these potentially incipient peatlands. Using observational, experimental, and modeling results, along with synthesis products from a coordinated international research network, the research team will test hypotheses on (1) the ages, carbon accumulation rates, and continental pattern of these rapidly forming and migrating peat patches; (2) the various responses of production and decomposition processes to temperature and moisture change; and (3) the role of Sphagnum in modifying microclimate and shifting balance between their productivity and decomposability.



NSF Antarctic Earth Sciences Program: Reconstructing Late Holocene Ecosystem and Climate Shifts from Peat Records in the Western Antarctic Peninsula

Warming on the western Antarctic Peninsula in the later 20th century has caused widespread changes in the cryosphere (ice and snow) and terrestrial ecosystems. These recent changes along with longer-term climate and ecosystem histories will be deciphered using peat deposits. Peat accumulation can be used to assess the rate of glacial retreat and provide insight into ecological processes on newly deglaciated landscapes in the Antarctic Peninsula. This project builds on data suggesting recent ecosystem transformations that are linked to past climate of the western Antarctic Peninsula and provide a timeline to assess the extent and rate of recent glacial change. The study will produce a climate record for the coastal low-elevation terrestrial region, which will refine the major climate shifts of up to 6 degrees C in the recent past (last 12,000 years). A novel terrestrial record of the recent glacial history will provide insight into observed changes in climate and sea-ice dynamics in the western Antarctic Peninsula and allow for comparison with off-shore climate records captured in sediments. Observations and discoveries from this project will be disseminated to local schools and science centers. The project provides training and career development for a postdoctoral scientist as well as graduate and undergraduate students.

The research presents a new systematic survey to reconstruct ecosystem and climate change for the coastal low-elevation areas on the western Antarctic Peninsula (AP) using proxy records preserved in late Holocene peat deposits. Moss and peat samples will be collected and analyzed to generate a comprehensive data set of late-Holocene climate change and ecosystem dynamics. The goal is to document and understand the transformations of landscape and terrestrial ecosystems on the western AP during the late Holocene. The testable hypothesis is that coastal regions have experienced greater climate variability than evidenced in ice-core records and that past warmth has facilitated dramatic ecosystem and cryosphere response. A primary product of the project is a robust reconstruction of late Holocene climate changes for coastal low-elevation terrestrial areas using multiple lines of evidence from peat-based biological and geochemical proxies, which will be used to compare with climate records derived from marine sediments and ice cores from the AP region. These data will be used to test several ideas related to novel peat-forming ecosystems (such as Antarctic hairgrass bogs) in past warmer climates and climate controls over ecosystem establishment and migration to help assess the nature of the Little Ice Age cooling and cryosphere response. The chronology of peat cores will be established by radiocarbon dating of macrofossils and Bayesian modeling. The high-resolution time series of ecosystem and climate changes will help put the observed recent changes into a long-term context to bridge climate dynamics over different time scales.


Lab members

Dulcinea Groff, postdoctoral associate working on Antarctic paleoecology and paleoclimate (NSF project)

Jon Stelling, PhD student working on Antarctic paleoecology and Patagonian peatland remote sensing (NSF project)

Zhengyu Xia, PhD student working on paleoclimate studies using isotopes from peats in Patagonia and South Georgia (NSF project and ACE project)

Adam Benfield, MS student working on tropical mountain peatlands in the Colombian Andes (Lehigh’s Faculty Innovation Grant (FIG) project)

Selected Publications: