| Summary: | Northern peatlands have been globally important accumulators of carbon as plant litter and older soil organic matter. As climate changes, the decomposition rates of these peatlands and consequently their soil respiration are likely to increase. In other words, CO2 emissions from northern peatlands might increase, giving feedback to global warming. This change might be caused not only by higher metabolic rates due to temperature rise and effects of increased precipitation, but also by changes in the diversity of the microbial community and soil fauna, the actual decomposers. The latter only contribute less than 10% to the total soil metabolism, but soil invertebrates have a great impact on the decomposition process. However the actual impact of soil mesofauna in subarctic peatlands has hardly been investigated. This project deals with diversity changes in soil mesofauna (represented by springtails and oribatid mites) in the subarctic (Abisko Swedish Lapland). Does diversity change due to global warming? And if the diversity changes, what are the impacts on ecosystem processes such as decomposition? To answer these questions I study interactions between soil invertebrates and their substrate, dead plant material. In one of my experiments, with MSc student Hilde Oorsprong, I study the vertical stratification of soil invertebrates in subarctic peatlands. In stratified peatlands, assemblages of soil fauna may have specific effects on the decomposition process dependent on their vertical distribution. Therefore, to understand the function of soil biota on ecosystem processes such as decomposition, knowledge of factors determining the vertical stratification of these animals should be obtained. It is known that many factors are responsible for the vertical stratification of soil fauna. The combined action of biotic factors such as quality of the substrate and abiotic factors such as temperature and humidity will determine their distribution. Here I hypothesise that it is mainly the litter quality that determines the distribution of meso- and microarthropods (including collembola) in the profile. By turning peat moss cores upside-down, litter quality was reversed in the profile. Deeper litter layers will now be confronted with the abiotic factors that are present in more shallow litter layers and vice versa. What is the consequence for the soil fauna that live in these moss cushions? Will they migrate up or down in the upside-down profile, suggesting that quality is not the most important factor? Or will they stay where they originally were, indicating that litter quality is more important than temperature or humidity? The results of this study will not only be important for predicting distribution changes of soil invertebrates due to environmental change, but by extrapolating these results we can get a better understanding of impacts of changes in temperature, moisture or litter quality on ecosystem processes such as decomposition.
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