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Title: The role of nitrogen and phosphorus in carbon and nutrient cycling of bryophyte-dominated exosystems
Author: Mielke, Nora
ISNI:       0000 0004 6353 1722
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2016
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Bryophytes form an important component of northern vegetation communities. Mosses efficiently capture aerially deposited nutrients, restricting nutrient availability to the soil. Given that key ecosystem processes of northern ecosystems are nutrient-limited, understanding nutrient cycling of the moss layer is key to understanding ecosystem nutrient and C cycling in these systems. However, the role of the moss layer in regulating ecosystem-scale nutrient and C cycling, while potentially significant, is largely unknown. The aim of this thesis is to investigate the effect of the relative availability of N and P on aspects of bryophyte nutrient uptake, retention and C acquisition. The hypothesis investigated is that the availability of one nutrient will influence the demand for the other and thereby moss nutrient acquisition and retention mechanisms. To test this hypothesis, various aspects of moss nutrient cycling in response to the relative availability of N and P were investigated. As the C cycle is tightly linked to the N and P cycles, the hypothesis extended to include bryophyte C assimilation and decomposition processes of an arctic tundra. Bryophyte nutrient demand was chiefly governed by the tissue N:P ratio. Consequently, nutrient uptake, both from aerially deposited nutrients and through moss-cyanobacteria N2 fixation, and nutrient losses after a simulated rainfall event were mostly in response to the relative availability of N and P rather than the availability of one nutrient alone. This thesis provides novel evidence that ectohydric mosses have the ability to internally translocate nutrients. In conjunction with efficient nutrient capture, this trait makes mosses strong nutrient sinks which are likely to exert considerable control over ecosystem nutrient cycling. The relative availability of N and P played a role in C uptake of mosses. Through the production of recalcitrant litter and their insulating effect on soil microclimate mosses exerted an influence over ecosystem C cycling.
Supervisor: Not available Sponsor: Natural Environment Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Bryophytes ; Nitrogen ; Phosphorus ; Carbon cycle (Biogeochemistry) ; Nutrient cycles