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Reconstructing Si cycling in transition zones during the Holocene using terrestrial and aquatic records

Nantke, Carla LU (2020) 89.
Abstract
Global biogeochemical cycles and their interactions are an important parts of climate research. Investigations during the last decades emphasize the key role of diatoms – siliceous phytoplankton – in the silicon (Si) cycle as they are important carbon sequesters in both marine and lacustrine environments. Terrestrial Si cycling and especially fluxes across the vegetation-soil interface are highly variable but important for the global Si budget. Shifts from natural vegetation to cultivated soils have been shown to impact the Si cycle in modern soil systems. Coastal zones and lake sediments provide suitable archives to investigate how human land use modified the terrestrial Si cycle in the past.

The aim of this PhD project is to... (More)
Global biogeochemical cycles and their interactions are an important parts of climate research. Investigations during the last decades emphasize the key role of diatoms – siliceous phytoplankton – in the silicon (Si) cycle as they are important carbon sequesters in both marine and lacustrine environments. Terrestrial Si cycling and especially fluxes across the vegetation-soil interface are highly variable but important for the global Si budget. Shifts from natural vegetation to cultivated soils have been shown to impact the Si cycle in modern soil systems. Coastal zones and lake sediments provide suitable archives to investigate how human land use modified the terrestrial Si cycle in the past.

The aim of this PhD project is to further constrain changes in the continental Si budget and link them to environmental factors such as land cultivation, deforestation, and salinity. Our study sites, Chesapeake Bay (East coast of the United States) and Tiefer See (north-eastern Germany) record climate and vegetation changes as well as human settlements during the Holocene. The measurement of biogenic Si (BSi) fluxes and Si isotopes in diatom frustules (30Sidiatom) separated from sediment cores, create a record of terrestrial Si cycling back in time, which then can be linked to the factors mentioned above.

Our results show that increasing human activity, especially deforestation and crop harvest impact the terrestrial Si cycle on geologically short time scales (decades-centuries). Changes in dissolved Si inputs from the catchment area dominate the variation in Si cycling in terrestrial freshwater systems; in contrast to marine environments where 30Sidiatom is a proxy for Si utilization. On a local scale, Si inputs can alter the budget of lake within decades.

Overall this thesis investigates how climate and human activity influence the so called ‘terrestrial Si loop’ determining the amount of Si delivered to the ocean. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Swann, George, School of Geography, University of Nottingham, UK
organization
publishing date
type
Thesis
publication status
published
subject
volume
89
edition
LUNDQUA THESIS
pages
123 pages
publisher
Lund University, Quaternary Geology, Department of Geology
defense location
Pangea, Geologiska insitutionen, Sölvegatan 12, Lund. Join via zoom: https://lu-se.zoom.us/j/62029389227
defense date
2020-12-04 13:15:00
ISBN
978-91-87847-52-3
978-91-87847-53-0
language
English
LU publication?
yes
id
060d3d58-3a5b-414b-bc82-64f74a866801
date added to LUP
2020-11-16 13:12:21
date last changed
2020-11-17 12:01:37
@phdthesis{060d3d58-3a5b-414b-bc82-64f74a866801,
  abstract     = {{Global biogeochemical cycles and their interactions are an important parts of climate research.  Investigations during the last decades emphasize the key role of diatoms – siliceous phytoplankton – in the silicon (Si) cycle as they are important carbon sequesters in both marine and lacustrine environments. Terrestrial Si cycling and especially fluxes across the vegetation-soil interface are highly variable but important for the global Si budget. Shifts from natural vegetation to cultivated soils have been shown to impact the Si cycle in modern soil systems. Coastal zones and lake sediments provide suitable archives to investigate how human land use modified the terrestrial Si cycle in the past.<br/><br/>The aim of this PhD project is to further constrain changes in the continental Si budget and link them to environmental factors such as land cultivation, deforestation, and salinity. Our study sites, Chesapeake Bay (East coast of the United States) and Tiefer See (north-eastern Germany) record climate and vegetation changes as well as human settlements during the Holocene. The measurement of biogenic Si (BSi) fluxes and Si isotopes in diatom frustules (30Sidiatom) separated from sediment cores, create a record of terrestrial Si cycling back in time, which then can be linked to the factors mentioned above. <br/><br/>Our results show that increasing human activity, especially deforestation and crop harvest impact the terrestrial Si cycle on geologically short time scales (decades-centuries). Changes in dissolved Si inputs from the catchment area dominate the variation in Si cycling in terrestrial freshwater systems; in contrast to marine environments where 30Sidiatom is a proxy for Si utilization. On a local scale, Si inputs can alter the budget of lake within decades. <br/><br/>Overall this thesis investigates how climate and human activity influence the so called ‘terrestrial Si loop’ determining the amount of Si delivered to the ocean.}},
  author       = {{Nantke, Carla}},
  isbn         = {{978-91-87847-52-3}},
  language     = {{eng}},
  month        = {{11}},
  publisher    = {{Lund University, Quaternary Geology, Department of Geology}},
  school       = {{Lund University}},
  title        = {{Reconstructing Si cycling in transition zones during the Holocene using terrestrial and aquatic records}},
  url          = {{https://lup.lub.lu.se/search/files/86900790/Carla_Nantke_Thesis_new.pdf}},
  volume       = {{89}},
  year         = {{2020}},
}