PATTERNS IN ENVIRONMENTAL DRIVERS OF WETLAND FUNCTIONING AND SPECIES COMPOSITION IN A COMPLEX PEATLAND

The boreal peatlands that cover much of western Canada are immense reservoirs of organic carbon and nitrogen, serving as sinks for atmospheric carbon, as well as providing habitat for flora and fauna, and nutrient cycling. These ecosystems are generally believed to be nitrogen limited. Due to regional increases in industrial activities associated in the Athabasca Oil Sands Region (AOSR), atmospheric deposition of nitrogen is projected to increase, with unknown effects on peatland functioning. The results of this study provide baseline data for a nitrogen fertilization experiment with an accurate site description of the entire peatland complex to provide reference for the experiment. This study also examines patterns in production and nitrogen usage along a wet to dry gradient. My main question was if species assemblages could be sorted into communities and how these were related to environmental gradients. In chapters three and four I asked how production and nitrogen usage and storage varied along a moisture gradient. In chapter two, four communities were identified as being independent with clear indicator species. These communities had differences in abiotic factors formed clear gradients across the peatland, influencing the distribution of species arrangements in the peatland complex. Sphagnum angustifolium thrived in all four communities and across the entire range of gradients. This species is a foundation of species of bogs and poor fens and was studied in more detail in chapters 3 and 4. In chapter three, I found that primary production of S. angustifolium increased from dry to wet along the moisture gradient. Cranked wires used to measure linear growth became less reliable in wetter habitats, missing over 50 % of growth measure by innate time markers. Capitula increased in biomass throughout the course of the growing season, suggesting that after vertical elongation, S. angustifolium begins to accumulate branches and leaves in the capitula to close the growing season. Chapter four, evaluating nitrogen requirements found that while primary production of S. angustifolium increased from dry to wet, tissue quality of the growth decreased along this gradient. Despite the lower tissue quality, wet habitats had higher nitrogen requirements to support growth rates. Inputs of atmospheric deposition fulfilled \u3c5% of annual N requirements and nitrogen saturated capitula in the beginning of the season was found to be an important source of nitrogen for growth, as capitula nitrogen storage declined over the season. Of the total nitrogen assimilated into annual growth, the percent lost a year later was similar across the moisture gradient; more nitrogen is stored in the wet habitats, strictly due to higher amounts initially assimilated. The results of this study suggest that in drier peatland habitats, there is an insufficient supply of water to deliver nitrogen and to support continuous growth during the growing season. Consequently, in wetter habitats, production is limited by nitrogen while in drier habitats it is limited by climate