A5033704300- Geology and Paleoclimatology Research
- Isotope Analysis in Ecology
- Pacific and Southeast Asian Studies
- Archaeology and ancient environmental studies
- Tree-ring climate responses
- Soil Carbon and Nitrogen Dynamics
- Peatlands and Wetlands Ecology
- Groundwater and Isotope Geochemistry
- Archaeology and Natural History
- Pleistocene-Era Hominins and Archaeology
- Atmospheric and Environmental Gas Dynamics
- Evolution and Paleontology Studies
- Landslides and related hazards
- Coastal wetland ecosystem dynamics
- Geological formations and processes
- Hydrocarbon exploration and reservoir analysis
- Soil and Water Nutrient Dynamics
Scottish Universities Environmental Research Centre
2011-2023
University of Glasgow
2020-2023
Los Alamos National Laboratory
2008-2014
Natural Environment Research Council
2010
University of California, Irvine
2005-2007
Significance We combine indicators from lake sediments with archaeological records that identify an earlier and incremental arrival of humans in East Polynesia than indicated by current models. use to reconstruct a quantitative, multiproxy hydroclimate sequences Vanuatu, Samoa, the Southern Cook Islands these published data show timing human migration into coincided prolonged drought. postulate this regional drought was significant contributory factor eastward exploration subsequent...
Abstract Soil respiration is derived from heterotrophic (decomposition of soil organic matter) and autotrophic (root/rhizosphere respiration) sources, but there considerable uncertainty about what factors control variations in their relative contributions space time. We took advantage a unique whole‐ecosystem radiocarbon label temperate forest to partition into three sources: (1) recently photosynthesized carbon (C), which dominates root rhizosphere respiration; (2) leaf litter decomposition...
The degree to which increased soil respiration rates following wetting is caused by plant (autotrophic) versus microbial (heterotrophic) processes, still largely uninvestigated. Incubation studies suggest processes play a role but it remains unclear whether there stimulation of the population as whole or an increase in importance specific substrates that become available with soil. We took advantage ongoing manipulation leaf litter 14 C contents at Oak Ridge Reservation, Ridge, Tennessee,...
Chihuahueños Bog (2925 m) in the Jemez Mountains of northern New Mexico contains one few records late-glacial and postglacial development mixed conifer forest southwestern North America. The record extends to over 15,000 cal yr BP. An Artemisia steppe, then an open Picea woodland grew around a small pond until ca. 11,700 BP when Pinus ponderosa became established. C/N ratios, δ 13 C 15 N values indicate both terrestrial aquatic organic matter was incorporated into sediment. Higher...
Hydroclimate variability on multi-decadal timescales has been a prominent feature of the circum-Caribbean region over common era, with marked dry intervals noted in particular for period 800–950 CE coinciding Terminal Classic Period (the so-called Drought: TCD) Mesoamerica, and Little Ice Age from about 1500 to 1800 CE, linked complex ocean-atmosphere interactions. Previous compilations palaeoclimate reconstructions have revealed clear precipitation dipole between northern southern...
Abstract Elemental (C, N, Pb) and isotopic ( δ 13 C, 15 N) measurements of cored sediment from a small bog in northern New Mexico reveal changes climate during the Late Pleistocene Holocene. Abrupt increases Pb concentration C values ca. 14 420 cal. YBP indicate significant runoff to shallow lake that existed at time. Weathering transport local volcanic rocks resulted delivery Pb‐bearing minerals basin, while C‐enriched terrestrial vegetation source increased sedimentary material. Wet...
Abstract One of the difficulties in reporting accurate radiocarbon results from compound-specific analysis (CSRA) is lack suitable process standard materials to correct for amount and 14 C content carbon added during extensive sample processing. We evaluated use n -alkanes extracted modern grass material (1.224±0.006 fraction modern) as standards CSRA. The were isolated using preparative capillary gas chromatography (PCGC) two independent chemical extraction methods applied grass. Since this...
ABSTRACT Graphitization of 0.5–1.5 mg C, and smaller samples to a lesser extent, is routinely done at our Facility by reduction over zinc. The method yields low background, good accuracy but offers limited throughput, requires dedicated equipment considerable operator time. Sealed-tube graphitization faster, easier cost-efficient producing as many graphites CO 2 can be purified in one day with precision, provided precise measurements δ 13 C values attained accelerator mass spectrometry (AMS)...