In 2005, experimental plots adjacent to the CLIMAITE plots were established, in order to reveal the effect of N and P addition on plant performance and soil nutrient availability. The ultimate question is whether the heath is nitrogen limited, or if the anthropogenic N deposition during the last decades has caused a N saturation of the ecosystem, so that plants now are either P limited, or limited by other factors such as water availability. This is very important for the interpretation of results in the CLIMAITE project.

Two M.Sc theses have been produced from these NP addition plots looking at immediate responses, but longer-term effects are unknown. Projects in these replicated plots, which consist of controls, plots to which low (25 kgN/ha/yr) and high (75 kgN/ha/yr) amount of N has been added, and plots to which P (10 kgN/ha/yr) has been added, and combinations hereof, could deal with:

1)      Microbial biomass C and nutrient content, and plant (shoot and root) nutrient accumulation. This would give information on longer term changes in nutrient concentration and pool sizes in plant and microbes caused by the additions.

2)      Secondary metabolites (condensed tannins) and nutrient elements in plants. This would give information on how N deposition may change the nutrient and secondary metabolite status of the plants, and hence how changes may affect leaf palatability and potential for decomposition.

3)      Mycorrhizal fungi and changes in their colonization and function. Mycorrhizal fungi are important for plant nutrient uptake and organic matter turnover, but nutrient addition may affect their colonization of roots and soil, which could be studied with a range of methods. Potential changes in their abundance and function may affect the whole ecosystem, which would give important information on possible changes in the warming and CO₂ addition experiments.

Contact (More contact info - press here):

1) Anders Michelsen, KU, andersm@bi.ku.dk; Inger K. Schmidt, KVL, iks@kvl.dk; Louise Andresen, KU, louisea@bi.ku.dk; Jane K. Pedersen, KVL, jkop@kvl.dk

2) Anders Michelsen, KU, andersm@bi.ku.dk; Inger K. Schmidt, KVL, iks@kvl.dk; Jane K. Pedersen, KVL, jkop@kvl.dk

3) Anders Michelsen, KU, andersm@bi.ku.dk; Louise Andresen, KU, louisea@bi.ku.dk