Amino acid uptake among wide-ranging moss species may contribute to their strong position in higher-latitude ecosystems

Abstract

Plants that can take up amino acids directly from the soil solution may have a competitive advantage in ecosystems where inorganic nitrogen sources are scarce. We hypothesized that diverse mosses in cold, N-stressed ecosystems share this ability. We experimentally tested 11 sub-arctic Swedish moss species of wide-ranging taxa and growth form for their ability to take up double labelled ( 15 N and 13 C) glycine and aspartic acid in a laboratory setup as well as in a realistic field setting. All species were able to take up amino acids injected into the soil solution to some extent, although field uptake was marginal to absent for the endohydric Polytrichum commune. The 11 moss species on average took up 36±5% of the injected glycine and 18±2% of the aspartic acid in the lab experiment. Field uptake of both glycine (24± 5%) and aspartic acid (10±2%) was lower than in the lab. Overall differences in uptake amongst species appeared to be positively associated with habitat wetness and/or turf density among different Sphagnum species and among non-Sphagnum species, respectively. Species from habitats of lower inorganic N availability, as indicated tentatively by lower tissue N concentrations, showed relatively strong amino acid uptake, but this was only significant for the field uptake among non-Sphagnum mosses. Further experiments are needed to test for consistent differences in amino acid uptake capacity among species and functional groups as determined by their functional traits, and to test how the affinity of cold-biome mosses for amino acids compares to that for ammonium or nitrate. Still, our results support the view that widespread moss species in cold, N-stressed ecosystems may derive a significant proportion of their nitrogen demand from free amino acids. This might give them a competitive advantage over plants that depend strongly on inorganic N sources.

Two Decades of Experimental Manipulations of Heaths and Forest Understory in the Subarctic

“…The availability of N in different forms (NO 3 -, NH 4 ? , amino acids), and the cycling between plants, microbes, fungal mycelium and soil has been intensively investigated at Abisko, both in experiments designed to address fundamental questions on plant N acquisition and mycorrhizal function (Andresen et al 2008;Clemmensen et al 2008;Krab et al 2008), and in climate change related experiments (Sorensen et al 2008a, b;Olsrud and Michelsen 2009).…”

Uptake and recovery of soil nitrogen by bryophytes and vascular plants in an alpine meadow

“…Alpine ecosystems are also characterized by nutrient limitation, low temperature and long winter (Atkin et al 1996;Körner 2003). Bryophytes often serve as effective traps for water and nutrients, and they are especially efficient in assimilating N (Turetsky 2003;Krab et al 2008). The N fixation capacity of some bryophytes is crucial in boreal ecosystems where N (N) availability is low (Solheim et al 1996;Turetsky 2003).…”

“…The N fixation capacity of some bryophytes is crucial in boreal ecosystems where N (N) availability is low (Solheim et al 1996;Turetsky 2003). It is also notable for Polytrichum commune with uptake of glycine and aspartic acid in the lab, but negligible or no uptake in the field (Krab et al 2008). Furthermore, amino acid as one kind of organic N forms has been found to represent another important N source for plants in 'cold biomes' (Kielland 1995;Raab et al 1996Raab et al , 1999Persson et al 2003;Krab et al 2008).…”

“…It is also notable for Polytrichum commune with uptake of glycine and aspartic acid in the lab, but negligible or no uptake in the field (Krab et al 2008). Furthermore, amino acid as one kind of organic N forms has been found to represent another important N source for plants in 'cold biomes' (Kielland 1995;Raab et al 1996Raab et al , 1999Persson et al 2003;Krab et al 2008). It is proposed that differences between species to utilize particular N sources can be an important feature of plant community composition (Kielland 1994;Schimel and Bennett 2004;Cambui et al 2011).…”

“…It is proposed that differences between species to utilize particular N sources can be an important feature of plant community composition (Kielland 1994;Schimel and Bennett 2004;Cambui et al 2011). Therefore, further studies are required to test how N utilization of different plants vary, which would be another significant issue to explore the differentiation of N utilization, especially at functional groups level (Ayres et al 2006;Krab et al 2008).…”