ABSTRACT
This preliminary study investigated the effects of enhanced nitrogen (NH4NO3 at 48 kg ha(-1) y(-1)), sulphur (Na2SO4 at 50 kg ha(-1) y(-1)), acidified nitrogen and sulphur (H2SO4 + NH4NO3) at pre-stated doses (pH 2.5), and acidified nitrogen and sulphur deposition at double these doses on the ectomycorrhizal community associated with a 13-year-old Sitka spruce (Picea sitchensis) forest. Sulphur deposition had little impact on below ground ectomycorrhizal diversity, but stimulated sporocarp production. Nitrogen inputs increased below ground colonisation compared to acidified nitrogen and sulphur, largely due to an increase in Tylospora fibrillosa colonisation. Sporocarp production and ectomycorrhizal root colonisation by Lactarius rufus were reduced in the nitrogen treated plots. These observations suggest that nitrogen deposition to a young plantation may suppress ectomycorrhizal fungi producing large sporocarps. It is proposed that enhanced nitrogen deposition increases ectomycorrhizal nitrogen assimilation, consuming more carbon and leaving less for extrametrical mycelium and sporocarp development.
Subject(s)
Acid Rain , Ecosystem , Environmental Monitoring/methods , Mycorrhizae/growth & development , Nitrogen , Picea/microbiology , Sulfur , Fertilizers , Hydrogen-Ion Concentration , Nitrogen/analysis , Soil Pollutants , Sulfur/analysis , TreesABSTRACT
The cluster root is made up of a number of determinate rootlets tightly grouped along the parent root. Each rootlet grows for a limited time, and then the meristem stops dividing and differentiates. Following cessation of growth, an exudative burst occurs, wherein, over 2-3 d, large amounts of organic acids, as well as phosphatases and phenolics, are exuded from the rootlets. There is a concomitant acidification of the rhizosphere. It is suggested that the temporal and spatial predictability of developmental and functional events in these structures makes them valuable as experimental tools with which to investigate key issues in plant developmental biology, physiology, ecophysiology, evolutionary biology, and biotechnology.
