TESS Seminar - Seeing the rate through the trees: Influence of precipitation and vegetation on millennial-scale erosion rates
Mar 22, 2017
from 04:00 PM to 05:00 PM
|Where||D3.054 Cairns, 145.030 Townsville|
|Contact Name||Jaime Huther|
|Contact Phone||07 4232 1427|
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Dr Christa Placzek
Ashish Kumar Mishra
James Cook University
Erosion shapes the landscape around us over both human and geologic timescales. Erosion and the interrelated process of weathering regulate the supply of sediment and nutrients to soils, streams, and the ocean. In north Queensland, quantifying natural rates of sediment input to the Great Barrier Reef is also important to understanding the potential threat posed by anthropogenic sediment fluxes. Until the last few decades, landscape-scale erosion rates were notoriously difficult to measure, in part because the timescale of landscape erosion is usually long compared to timescales of human observation. However, with the advent of cosmogenic nuclide methods, which integrate erosion over thousands of years, we can now routinely quantify long-term (millennial) erosion rates. This has led to a quantitative revolution in geomorphology, but one puzzling result of these efforts to quantify erosion rate is that a relationship between precipitation and erosion rate seems to be absent or negligible. Here, we examine a new compilation of erosion rate data to determine if mean annual precipitation has a significant control on erosion rates. We find that mean annual precipitation is a clear and strong secondary influence on erosion rate, and that the primary reason that precipitation’s influence on erosion has been unseen is due to its close correlation with vegetation. In particular, trees significantly decrease erosion rates and more rainfall results in more trees. The fastest erosion rates in the world are in regions with no trees, but with relatively high precipitation. These results imply that anthropogenic deforestation, particularly in rainforests, can greatly increase erosion.
Ashish Mishra is a Phd student working on quantification of erosion in north Queensland, using terrestrial cosmogenic nuclides. His work focuses on the various environmental variables that influence on long-term erosion. He is also interested in how millennial-scale erosion rate helps in understanding landscape evolution and transformation. He completed an engineering degree in Biotechnology from West Bengal University of Technology, India, and then went on to earn M.Sc degree in Environment Science/Sustainable Resource Management from the National University of Ireland, Galway, Ireland.
Christa Placzek is a lecturer in Geosciences at James Cook University and is deputy director of TESS. Christa’s research focuses on the application of isotope geochemistry to the development of high-resolution climate records, particularly from the Southern Hemisphere; and quantifying how environmental variables regulate the development of sediments, soils, and landscapes. Christa is based on the Townsville campus and manages the isotopic clean lab, which undertakes picogram level isotopic analysis of soil, water, biological, and geologic samples. Christa received a PhD from the University of Arizona and completed a post-doc at the Purdue Rare Isotope Measurement (PRIME) laboratory. Prior to joining James Cook University, Christa worked in the field of environmental forensics at Los Alamos National Laboratory (USA).