Research project
Mineral-organic biogeochemical dynamics on coastal temperate rainforest soils
This collaborative research explores multiple fronts to understand the relationship between mineral weathering and soil organic carbon in terrestrial and aquatic environments in southeast Alaska. The region offers a unique opportunity to conduct this kind of research due to massive soil-stream carbon fluxes and incredibly rapid soil formation rates. It is a glacially sculpted landscape composed of old-growth forests, glaciers, wetlands, estuaries, beaches, and thousands of small streams that link terrestrial and aquatic ecosystems.
The objectives of this research are to understand how different rock types impact soil geochemistry, clay and Fe/Al oxides mineralogy, erosion rates, and soil carbon storage/turnover. In southeast Alaska, the rates of soil formation are astonishing! Spodosols (or Podzols) can form in less than 400 years on well-drained parent materials. As such, Spodosols are the predominant soil class in the region, regardless of the lithology. However, it is unclear whether the investigated soil properties are similar and what impacts they have on the aquatic ecosystem.
The main questions this research seeks to answer are: What are the geochemical and mineralogical signatures of these soils along a lithosequence? What role does soil parent material play in the formation of organometallic complexes? What is the soil organic carbon turnover in the mineral soils? Which soil properties better predict carbon storage and turnover? How much carbon can these soils store? Does lithology influence soil erosion rates?
To address these questions, we are using multiple approaches and techniques such as geochemical mass balance calculations (x-ray fluorescence); clay and Fe/Al mineralogy (x-ray diffraction and selective extractions); microscopic analysis (petrographic and electron microscopy); iron speciation (Mössbauer spectrometry and extractions); soil organic carbon turnover (14C dating); and erosion rates (239+240Pu isotopes and 13C).
Stay tuned for updates!
Soil chronosequence on a coastal temperate rainforest
How long does it take for a Spodosol to form under perhumid forested conditions? What are the rates of weathering and mineral transformation? When does the surface achieve stability in terms of erosion? How much soil organic carbon is stored over a centennial timescale?
These are crucial questions that will be addressed in this novel project. A sequence of Little Ice Age moraines (2 to 270 years old) deposited by the Mendenhall Glacier and Herbert Glacier in Juneau, AK, offers a great opportunity to understand the co-evolution of soils and plant succession. The rapid retreat of the Coastal Mountain Glaciers due to climate warming will expose new land surfaces. Combined with the fast soil-forming rates in the region, this will likely impact the entire ecosystem of southeast Alaska. Therefore, our results will shed light on this dynamic interplay between glacier retreat and soil formation.
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Past research projects
Eocene paleosols on King George Island, Maritime Antarctica, as a paleoenvironmental proxy.
On King George Island (KGI), we find fossil soils formed during the Early Eocene (51-45 Ma). This period was one of the warmest paleoclimatological periods in the Cenozoic, and KGI is one of the few known places where terrestrial evidence of that warm period can be found. In addition to plant fossils, the presence of fossil soils, or paleosols, offers the opportunity to understand the predominant paleoenvironmental conditions. I have studied paleosols trapped between lava flows, which preserve the paleosol features due to rapid burial and are ideal for absolute dating (40Ar/39Ar). The moderate weathering degree, presence of plant remains, bioturbation channels, soil structure, and horizons, among other features, are records of a wetter and milder paleoenvironment. More info can be found in the publications.
Initial soil formation and microbial activity along a soil chronosequence in King George Island, Antarctica
We have evaluated the initial soil-forming processes and properties along a glacier forefield on King George Island. The retreat of Ecology Glacier has left a sequence of glacial deposits (moraines). These deposits have been exposed for less than 100 years, offering a great opportunity to study the interplay between microorganisms and initial soil formation in a periglacial environment. We also sampled an older profile, more than 100 years old. The main detected processes include acidification and accumulation of soil organic carbon and nitrogen, accompanied by changes in microbial abundances, microbial community compositions, and plant coverage. Geochemical weathering and secondary oxide formation were very incipient. Soil quantifiable silicate weathering and the formation of pedogenic oxides were detected only in a soil profile more than 100 years old.
This work was carried out in cooperation with the University of Tübingen, the German Research Centre for Geosciences, and the University of Potsdam
Diogo Spinola
Linking pedology and biogeochemistry
Soil formation in a semi-polar desert, Antarctica.
On the west side of the Antarctic Peninsula, at the Weddell Sea, lies Seymour Island. This unique, ice-free island is formed by very soft Cretaceous-Paleogene sediments, making it a paradise for geologists. It contains an astonishing amount of fossil shells, plants, nearly perfect tree trunks, animal bones, and even shark teeth. The island is also a wonderland for soil scientists, as it features a huge variety of pedogenic and other phenomena, such as thick salt crusts, gypsum nodules, acid sulfate soils, dry and wet permafrost, aeolian abrasion, quicksands, penguin rookeries, and more. The main objective of this work was to understand soil genesis in such an unusual setting and to distinguish soil formation from sedimentary layers. This work was conducted within the scope of the Permafrost-Cryosols-Terrestrial Ecosystems and Climate Change in Antarctica Project, led by the Department of Soil Science at the University of Viçosa, Brazil.