Ectomycorrhizas and nutrient transfer in conifer – feather moss ecosystems

Conifer–feather moss ecosystems dominate large areas of the boreal forest regions of the world, but the interrelations between these two components of the system are poorly understood. Mycorrhizal roots of the trees grow in close association with the mosses. The possibility that nutrients can be transferred from moss shoots to trees through mycorrhizal fungi was investigated using the feather moss Pleurozium schreberi and mycorrhizal seedlings of Pinus contorta. Shoots of the moss were divided into three categories, viz. green, senescent, and dead, and nutrient contents of aqueous leachates from the segments were measured before and after drying. Significant quantities of nitrogen and phosphorus were released from moss shoots especially after drying. Senescing segments consistently released more N than those that were dead and generally released more than did the green segments. All categories of segments released some protein nitrogen, and drying induced leakage of glucose, fructose, and sucrose. Leachates of entire moss shoots were capable of supporting growth of three mycorrhizal fungi in pure culture. Moss shoots added to chambers containing mycorrhizal plants were colonized by the fungal associates of the plants, particularly intensive growth occurring in the senescent region of the moss shoots. Phosphate ( 32 P) and carbon ( 14 C), previously fed to the moss shoots, was absorbed by mycorrhizal mycelia and transferred over distances of centimetres to infected roots of pine plants and then to their shoots. The significance of these uptake and transfer processes for nutrient cycling in boreal forest ecosystems is discussed. Key words: leachate, nitrogen, phosphorus, sugars, protein, radioisotope.