Ecophysiological adjustment of two Sphagnum species in response to anthropogenic nitrogen deposition

Abstract

Summary• Here, it was investigated whether Sphagnum species have adjusted their nitrogen (N) uptake in response to the anthropogenic N deposition that has drastically altered N-limited ecosystems, including peatlands, worldwide.• A lawn species, Sphagnum balticum, and a hummock species, Sphagnum fuscum, were collected from three peatlands along a gradient of N deposition (2, 8 and 12 kg N ha). The mosses were subjected to solutions containing a mixture of four N forms. In each solution one of these N forms was labeled with • It was found that for both species most of the N taken up was from , followed by Ala, Glu, and very small amounts from . At the highest N deposition site N uptake was reduced, but this did not prevent N accumulation as free amino acids in the Sphagnum tissues.• The reduced N uptake may have been genetically selected for under the relatively short period with elevated N exposure from anthropogenic sources, or may have been the result of plasticity in the Sphagnum physiological response. The negligible Sphagnum uptake may make any deposited readily available to co-occurring vascular plants.

Photosynthetic performance in Sphagnum transplanted along a latitudinal nitrogen deposition gradient

“…In line with this, several authors have found indications that mosses from high N deposition sites cope better with N addition than mosses from low N deposition sites (Baxter et al 1992;Limpens and Berendse 2003;Press et al 1986). Local adaptation to regional N deposition has also recently been suggested in mosses and vascular plants (Vergeer et al 2008, Wiedermann et al 2008. However, in our study we cannot separate an adaptive response to N deposition from a physiological adjustment (e.g.…”

Sphagnum can ‘filter’ N deposition, but effects on the plant and pore water depend on the N form

“…NH4 + is preferentially taken up by Sphagnum (Fritz et al, 2014;Liu et al, 330 2013; Wiedermann et al, 2009) because Sphagnum has a high cation exchange capacity 331 (Bates, 1992;Gunnarsson & Rydin, 2000). In addition, NH4 + has greater toxicity 332 (Gerendás et al, 1997;Krupa, 2003;Stevens et al, 2011).…”

“…(NH4 + ) versus oxidized (NO3 -) N on the N status of the Sphagnum moss and the (Manninen et al, 2011;Sheppard et al, 2014), possibly due to the greater toxicity of 97 NH4 + (Gerendás et al, 1997;Krupa, 2003;Stevens et al, 2011;Limpens and Berendse, 98 2003) coupled to preferential uptake of NH4 + by Sphagnum (Fritz et al, 2014;Liu et al, 99 2013; Wiedermann et al, 2009). For example, Manninen et al (2011) found that NH4 + 100 addition increased shoot N concentration of Sphagnum and decreased photosynthetic 101 variables (Fv/Fm) and shoot dry weight of Sphagnum.…”

Physiological Responses of Two Epiphytic Bryophytes to Nitrogen, Phosphorus and Sulfur Addition in a Subtropical Montane Cloud Forest

“…Similarly, specimens originating from high N deposition areas take up less N than those originating from low N deposition regions [51]. Therefore, decreased N uptake may be a long-term adaptation for bryophytes subjected to high N supply [51, 52]. Several authors have suggested that specimens subjected to long-term N enrichment display a plastic response to new environmental scenarios through higher tissue N concentration [53], or reduced N uptake [52] or physiological acclimation [51].…”