The development and function of subarctic alpine soil surface biological communities

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Due to their ubiquitous distribution and unique physiology, establishment of biological soil crust (BSC) communities and corresponding initiation of key ecosystem functions is a common early successional process. In alpine and arctic environments, BSCs are often a dominant vegetation unit, making these ecosystems a uniquely powerful model for examining the role of BSCs in terrestrial ecosystem development. My long-term goal is to identify mechanisms at the BSC-soil surface interface that drive nutrient cycling processes in arctic and alpine environments. BSCs are located at the soil-atmosphere interface where their developmental trajectories are driven by both microclimate and soil physicochemical factors. As these soil surface assemblages establish, they in turn modulate their environment through the initiation of key ecosystem functions at biogeochemical interfaces between BSCs and below-crust soils. Over the next 5 years my short-term goal is to link the realized niches of key BSC components with the initiation and modulation of nutrient cycling processes at the BSC-soil interface. My specific objectives are to: 1) develop successional models of BSC communities based upon the realized niche of primary macro and micro BSC phyla; 2) examine the development and function of BSC assemblages in relation to soil physical, chemical and microbial properties; and 3) relate BSC development to ecosystem-level nutrient cycling driven by BSC and below-crust soil microbial communities. Using glacial forefields (i.e. areas progressively exposed by a receding glacier) as ideal chronosequence systems, I will conduct both observational and manipulative investigations to determine and confirm the realized niche of key BSC components. In addition, I will use manipulative growth chamber experiments to more closely examine the interactions between BSCs and physical, chemical and microbial soil properties. To better characterize the role BSCs and below-crust soil microbial communities play in nutrient transfer and transformations, I will examine the uptake and movement of isotopically labelled C, N and P in microcosm studies. Nutrient movement both between ecosystem components (i.e. crusts, soils, above and belowground vascular plants), and BSC and below-crust soil microbial communities will be investigated. By determining how BSC communities develop and in turn modify the soil environment, the proposed research will advance our understanding of early successional processes and ability to restore pathways that promote long-term ecosystem health.