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Plant litter: direct and indirect effects of simulated climate change and clipping on its decomposition, and its effects on plant-plant interactions Open Access


Other title
Activated carbon
Root exudates
Plant-plant interactions
Litter quality
Type of item
Degree grantor
University of Alberta
Author or creator
Nyanumba, S M.
Supervisor and department
Scott Chang (Renewable Resources)
James Cahill (Biological Sciences)
Examining committee member and department
Derek MacKenzie (Renewable Resources)
Maya Evenden (Biological Sciences)
Tim Moore (Geography, McGill University)
Department of Biological Sciences
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Terrestrial ecosystems are characterized by an intricate relationship between plants and soils that influence ecosystem and community level processes and properties. At the ecosystem level, plants (producers) provide organic carbon to the decomposer subsystem and obligate root-associated organisms once they die. In turn, the decomposer subsystem breaks down dead plant material and ultimately returns this carbon to the atmosphere. At a lower level of ecological organization, litter can have profound impacts on plant-plant interactions through physical and/or chemical effects. I investigated the role that litter plays at these two levels of ecological interaction. First, I conducted a short-term factorial decomposition study testing the interactive effects of warming, drought, and land use practice (simulated grazing) on root and shoot litter decomposition. The study was carried out over a 2-year period at three sites across the Canadian Prairie Provinces. I manipulated temperature using open-top chambers (OTCs), reduced precipitation using rain-out shelters, and manually clipped vegetation at varied levels consistent with grazing practices in the region. Additionally, I studied the effect of litter quality on decomposition, whereby litter material pre-exposed to climate manipulations were placed in plots of origin (in situ) or in untreated standard plots. Decomposition varied as function of site and was higher for root than shoot litter. Clipping intensity had no effect on decomposition across all sites. In contrast, drought significantly hampered decomposition whereas warming significantly decreased shoot decomposition but increased root decomposition, although insignificant. Drought generally reduced litter quality consequently retarding decomposition and this effect was further enhanced under drought condition. These findings suggest that in the short-term temperature and precipitation may have direct consequences on carbon storage in these systems. Second, I studied the interactive effects between litter, root competition and belowground chemical interaction, as well as the effect of root exudates on plant growth, competition and evenness. The nature of belowground interaction switched from negative when aboveground litter was left intact to positive when removed. Root exudates enhanced plant growth, modified competition and enhanced evenness. These results show the existence of other potential non-resource mechanisms that may play a role in the organization of natural plant communities.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Nyanumba, SM and Cahill JF. 2012. Basic and Applied Ecology. 13 (7): 615-622.

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