Succession of N cycling processes in biological soil crusts on a Central European inland dune

Abstract

Biological soil crusts (BSCs) are microbial assemblages that occur worldwide and facilitate ecosystem development by nitrogen (N) and carbon accumulation. N turnover within BSC ecosystems has been intensively studied in the past; however, shifts in the N cycle during BSC development have not been previously investigated. Our aim was to characterise N cycle development first by the abundance of the corresponding functional genes (in brackets) and second by potential enzyme activities; we focussed on the four processes: N fixation (nifH), mineralisation as proteolysis and chitinolysis (chiA), nitrification (amoA) and denitrification (nosZ). We sampled from four phases of BSC development and from a reference located in the rooting zone of Corynephorus canescens, on an inland dune in Germany. BSC development was associated with increasing amounts of chlorophyll, organic carbon and N. Potential activities increased and were highest in developed BSCs. Similarly, the abundance of functional genes increased. We propose and discuss three stages of N process succession. First, the heterotrophic stage (mobile sand without BSCs) is dominated by mineralisation activity. Second, during the transition stage (initial BSCs), N accumulates, and potential nitrification and denitrification activity increases. Third, the developed stage (established BSCs and reference) is characterised by the dominance of nitrification.

Biological soil crusts accelerate the nitrogen cycle through large NO and HONO emissions in drylands

“…Further investigations comprising multiple nitrogen compounds and isotopes should unravel the interplay of different chemical and biological species and processes in the cycling of nitrogen by biocrusts (33)(34)(35)(36).…”

Estimating global nitrous oxide emissions by lichens and bryophytes with a process-based productivity model

“…Regarding biological soil crusts, several studies analysed denitrification rates to be negligible (Johnson et al, 2007;Strauss et al, 2012), and N 2 O production was calculated to constitute only 3-4 % of the N fixation rate (Barger et al, 2013). Other studies, however, described high denitrification rates that either increased (Brankatschk et al, 2013) or decreased with advancing crust development (Abed et al, 2013). One possibility to increase the reliability of large-scale estimates of N 2 O emissions by lichens and bryophytes is the application of alternative, methodically different approaches.…”

Denitrification from nitrogen-fixing biologically crusted soils in a cool desert environment, southeast Utah, USA

“…Denitrification rates within surface soils (i.e., top 1 cm) containing biocrusts were negligible relative to other N loss pathways (Johnson et al 2007;Strauss et al 2012) or increased with biocrust development (Brankatschk et al 2013). These studies, however, evaluated denitrification from biologically crusted soils at a single temperature and soil moisture level, environmental conditions that may strongly influence not only N fixation but also denitrification rates.…”

“…These pulsed dynamics in soils may result in N "leakage" by biological soil crust organisms to the surrounding soil environment in such forms as NH 4 + and other soluble organic nitrogen compounds (Mayland and McIntosh 1966;Johnson et al 2007). Nitrogen leakage from biocrusts may not only enhance soil nutrient availability to support plant growth (Mayland and McIntosh 1966; Harper 1995 but may also be lost from the system via gaseous N loss in transformations related to nitrification and denitrification processes (Zaady 2005;Barger et al 2005;Johnson et al 2007;Strauss et al 2012;Brankatschk et al 2013).…”