Snow cover regulation of Alpine soil ecosystem carbon release

This PhD project aims to answer and address 3 questions and objectives:

1. How does soil carbon and macronutrient content and stability vary across snow cover gradients in the alpine environment? Examine relationships between plant community composition, snow cover, and soil CNP content using a survey-based approach across contrasting alpine landscapes.
2. Do the seasonal dynamics of soil C cycling vary across snow-cover gradients? Seasonal sampling of soils for microbial community analysis, soil functions associated with CNP turnover, litter decomposition assays, and greenhouse gas measurements across snow-cover gradients.
3. What are the effects of reduced snow-cover duration on C cycling in snow-bed habitats? In situ snow manipulation in three contrasting alpine habitats, following C exchange in the soil-plant system, and microbial resistance and resilience metrics using GHG analysis (CO2, CH4, N2O), and turnover and fate of 13C-labelled substrates.

Programme of research
Strand 1 will use standard soil and vegetation sampling approaches to investigate soil CNP stocks in a range of alpine habitats along gradients of snow cover duration. To have a representative coverage of Scottish alpine habitats and climate types, we will select 3 'case study' areas, e.g. the Cairngorm plateau, central highlands and north-west highlands. Using a transect approach, soils will be sampled for CNP, and the plant community detailed. Abiotic conditions associated with snow cover will be monitored with in situ moisture and temperature sensors. Techniques of field survey and sampling will be combined with detailed sample analysis and use of standard analytical procedures in the lab to provide sound ecological and biogeochemical training.

Strand 2 will explore in detail the processes controlling C input to the soil, internal C cycling and net fluxes of C to/from plant-soil communities along a gradient of snow-lie duration. Using early, middle, and late melting systems, seasonal sampling, and targeted (snowmelt) sampling of gas flux (Soil Respiration, NEE, CH4, N2O), litter decomposition, microbial community (PLFA, TRFLP) , and functional assays (Enzyme activity, substrate mineralisation) will be performed. Training on microbial community analysis techniques alongside functional metrics assays, as well as gas exchange using field and laboratory methods (i.e. IRGA, GC) will extend strand 1 techniques and training.

Strand 3 will shorten the snow-cover period in three contrasting systems in the instrumented study catchment, and by following CN exchange (as in strand 2), in situ impacts will be ascertained. To extend mechanistic detail on the dynamics of C turnover, a 13C-labelled substrate (fungal biomass) will be added to the soil, and followed in CO2, DOC and microbial-biomass carbon under ambient and snow-removal treatments. This approach will extend previous training into novel stable isotope probing methodologies and ecosystem manipulations techniques.

Collaboration and Impact
Training, and interdisciplinary work (linking biogeochemistry and plant ecology) will be gained through working with external colleagues, and will aid in cementing, and extending collaborations with international colleagues (Max Planck Jena, CNRS Bioemco Paris). Presentation of posters and oral talks is expected, with yearly attendance of a domestic conference (e.g. BES, BSSS), and year 3 attendance at an international (e.g. EGU, Biogeomon) conference.