PhD defence: Qi Guan

Qi Guan defends his thesis,

Impacts of land processes on lake eutrophication in China
Cropland management, human activities, and climate change

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Associate Professor Guy Schurgers, IGN
Assistant Professor Jing Tang, Lund University – Sweden
Associate Professor Lian Feng, Southern University of Science and Technology – China

Assessment Committee:
Senior scientist Alberte Bondeau, CNRS, Mediterranean Institute of terrestrial and marine Biodiversity and Ecology – France
Research director Claudia Giardino, CNR, Institute for Electromagnetic Sensing of the Environment – Italy
Professor Bo Elberling (chair), IGN

In recent decades, lake eutrophication has become a big environmental issue in China. High agriculture fertilization and rapid economic development have caused substantial nutrient discharge into freshwater ecosystems, which can largely stimulate phytoplankton growth and alter lake processes. To mitigate severe environmental impacts and meet increasing crop demand in coming decades, a more sustainable agriculture ecosystem will have to be developed.
This thesis investigated the linkage between terrestrial nutrient sources and eutrophication dynamics in regional lake ecosystems, and how to balance future agriculture production enhancement with reduction in agricultural nitrogen exports through cropland reallocation. Based on satellite observations, fifty large lakes on the Yangtze Plain experienced high probability of eutrophication occurrence. Agriculture nutrient exports and industrial wastewater discharge were strongly linked with eutrophication trends in the western and eastern lakes of the Yangtze Plain, respectively. As an effective measure, reallocating cropland spatially can lead to a decline in the leached nitrogen and irrigation water, but an increase in crop production. Our results revealed the importance of land processes in influencing eutrophication changes in lake ecosystems, and an important measure of cropland reallocation to reduce environmental impacts of future agriculture systems in China.

A digital version of the PhD thesis can be obtained from the PhD secretary Mikala Heckscher at