Vortrag, EURECO, Lund: 27.07.2002 - 01.08.2002
It is becoming increasingly apparent that the uptake of soil organic N can contribute substantially to plant nutrition in many ecosystems, including arctic and alpine tundra, boreal forest and subtropical rainforest (Lipson & Näsholm 2001). Most of the work, however, has been done in N-limited natural ecosystems, where the concentration of amino acids often exceeds that of inorganic N and therefore its potential uptake is considered especially important. Still, agricultural settings, e.g. grasslands, may also have high concentrations of soluble organic N in soil and considerable uptake of intact glycine has been shown to occur in these systems. There are many amino acids present in soil, and recent evidence indicates that there might be a degree of niche separation in the use of different amino acids between microbes and plants, such that plants compete better for glycine than for other amino acids, which, in turn, form a richer carbon source and are faster degraded by soil microbes. These conclusions, however, are mainly based on separate studies of either plant or microbial organic N uptake. To combine these issues we assessed both plant and microbial uptake of a range of amino acids in a temperate grassland system. Specifically, we investigated preferential uptake of different dual-labelled (13C and 15N) amino acids, as compared to inorganic N, by plants and microbes in a microcosm experiment with natural field soil. Five grass species were selected to represent those that occur along a fertility gradient ranging from improved, fertilised Lolium dominated grassland, through to unfertilised, less productive Agrostis-Festuca grassland.
Lipson, D. & Näsholm, T. (2001) Oecologia; 128: 305-316.