Does soil warming stimulate plant productivity by increasing rates of nutrient release?

This work investigated whether soil warming indirectly stimulates plant productivity through increasing microbial activity and thus nutrient release. It was carried out over three experiments, two of which were planted and the other a soil incubation at different temperatures. The first (winter) planted experiment had a warming and ambient treatment, where a heating cable warmed soil in pots to +3degrees above ambient. The second (summer) experiment included a NPK fertilisation treatment in a full-factorial design, to test for nutrient limitation when soils were warmed. We measured the growth and aboveground biomass of four sub-Antarctic grasses in the two warming experiments, and additionally measured leaf and aboveground N and soil inorganic nutrients in the second experiment. A soil incubation experiment investigated whether warming was influenced by the soil organic matter, and whether there was microbial immobilisation of N and P with warming.