Role of dissolved organic nitrogen (DON) in soil N cycling in grassland soils

Due to their particular physiology and life history traits, bryophytes are critical in regulating biogeochemical cycles and functions in alpine ecosystem. Hence, it is crucial to investigate their nutrient utilization strategies in comparison with vascular plants and understand their responses to the variation of growing season caused by climate change. Firstly, this study testified whether or not bryophytes can absorb nitrogen (N) directly from soil through spiking three chemical forms of 15N stable isotope tracer.Secondly, with stronger ability of carbohydrates assimilation and photosynthesis, it is supposed that N utilization efficiency of vascular plants is significantly higher than that of bryophytes. However, the recovery of soil N by bryophytes can still compete with vascular plants due to their greater phytomass. Thirdly, resource acquisition may be varied from the change of growing season, during which N pulse can be manipulated with 15N tracer addition at different time. Both of bryophytes and vascular plants contain more N in a longer growing season, and prefer inorganic over organic N. Bryophytes assimilate more NH4+ than NO3-and amino acid, which can be indicated from the greater shoot excess 15N of bryophytes. However, vascular plants prefer to absorb NO3-for their developed root systems and vascular tissue. Concerning the uptake of three forms N by bryophytes, there is significant difference between two manipulated lengths of growing season. Furthermore, the capacity of bryophytes to tolerate N-pollution may be lower than currently appreciated, which indicates the effect of climate change on asynchronous variation of soil N pools with plant requirements.

show abstract

“…The exchangeable pool was extracted with 2 M KCl while soil solutions were extracted by centrifugal drainage (Jones et al 2004).…”

Section: Experimental Designmentioning

confidence: 99%

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

Wang

Shi

et al. 2014

J. Mt. Sci.

View full text Add to dashboard Cite

show abstract

“…and subsequent ammonification (Schimel and Bennett, 2004). The depolymerization step, critical in N cycling, is controlled by extracellular enzymes which are often produced by fungi (Jones et al, 2004;Schimel and Bennett, 2004). Ammonium (NH 4 þ ) supplied by N mineralization strongly influences NH 4 þ immobilization (Booth et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Are nitrate production and retention processes in subtropical acidic forest soils responsive to ammonium deposition?

Gao

Kou

Yang

et al. 2016

Soil Biology and Biochemistry

View full text Add to dashboard Cite

N tracing model Acid soil of subtropical forest a b s t r a c tChanges in soil N-cycling and retention processes in subtropical/tropical acidic forest ecosystems under anthropogenic N inputs are not well understood. We conducted a laboratory 15 N tracing study on an acid soil (pH values: 4.6 to 5.0) from a subtropical forest fertilized for more than 2.5 years at a rate of 0, 40, and 120 kg NH 4 CleN ha À1 yr À1 , respectively. To get a better resolution of mechanistic changes in soil N cycling and retention processes under NH 4 þ additions, we used a conceptual 15 N tracing model to quantify process-specific and pool-specific N transformation rates in soils. Gross N mineralization rates decreased at high NH 4 þ additions, which were paralleled by a reduction in fungal biomass and mineralization of recalcitrant organic N. Gross NH 4 þ immobilization rates did not show a change with increasing NH 4 þ additions. Interestingly, soil NO 3 À production (heterotrophic, autotrophic, and gross nitrification) and retention (NO 3 À immobilization and dissimilatory nitrate reduction to ammonium) showed insensitivity to increasing additions of NH 4 þ . The mechanisms behind the lack of response of heterotrophic nitrification were unclear, but possibly related to the absence of significant changes in soil C: N ratio and soil acidity under increased NH 4 þ additions. Because of the low autotrophic nitrification potential and the lack of NH 4 þ limitation to autotrophic nitrifiers, autotrophic nitrification was unresponsive to NH 4 þ additions.NO 3 À immobilization rates appeared to be controlled by the NO 3 À produced from heterotrophic nitrification, as indicated by the positive relationship between NO 3 À immobilization and heterotrophic nitri-thus showing a lack of a change under increased NH 4 þ additions. DNRA seemed to be inherently less responsive to environmental changes such as NH 4 þ deposition. Our work demonstrates that enhanced NH 4 þ deposition has a low potential to stimulate soil NO 3 À production and weaken soil retention of NO 3 À in this, and perhaps other subtropical/tropical acidic forest ecosystems.

show abstract

“…The detrimental effects of nitrogen deposition on surface water chemistry have been widely reported both in Europe and North America (Evans and Monteith, 2001;Stoddard, 1994), however recent improvements caused by emission targets have occurred (Skjelkvale et al, 2005). While most studies have focussed on the effect of dissolved inorganic nitrogen (DIN) in terms of nitrogen cycling and water quality, the role of dissolved organic nitrogen (DON) in nitrogen cycling and bioavailability has also been shown to be important in a range of environments (Scott et al, 2007;Seitzinger et al, 2005;Jones et al, 2004;Willett et al, 2004;Seitzinger and Sanders, 1997;Carlsson and Graneli, 1993).…”

Section: Introductionmentioning

confidence: 99%

Groundwater nitrogen composition and transformation within a moorland catchment, mid-Wales

Lapworth

Shand

Abesser

et al. 2008

Science of The Total Environment

View full text Add to dashboard Cite

The importance of upland groundwater systems in providing a medium for nitrogen transformations and processes along flow paths is investigated within the Afon Gwy moorland catchment, Plynlimon, mid-Wales. Dissolved organic nitrogen (DON) was found to be the most abundant form of dissolved nitrogen (N) in most soils and groundwaters, accounting for between 47 and 72% of total dissolved nitrogen in shallow groundwater samples and up to 80% in deeper groundwaters. A significant correlation between dissolved organic carbon (DOC) and DON in the shallow groundwater system suggests that during the autumn and winter months the flux of DON from the soil zone may be regulated by the wetting up and release of soil organic matter. DON needs to be taken into account when considering catchment N balances otherwise N export from upland catchments could be significantly underestimated. DON may also be an important source of bio-available N in surface waters and marine systems fed by upland catchments. A conceptual model of N processes is proposed based on a detailed study along a transect of nested boreholes and soil suction samplers within the interfluve zone. Shallow groundwater N speciation reflects the soil N speciation implying a rapid transport mechanism and good connectivity between the soil and groundwater systems. Median dissolved inorganic N concentrations were an order of magnitude lower within the soil zone (10-25 mg/L-N) than in the shallow groundwaters (100-750 mg/L-N).Given the rapid hydrostatic response of the groundwater level within the soil zone, the shallow groundwater system is both a source and sink for dissolved N. Results from dissolved N2O, N2/Ar ratios and dissolved N chemistry suggests that microbial N transformations (denitrification) may play an important role in controlling the spatial variation in soil and groundwater N speciation. Reducing conditions within the groundwater and saturated soils of the wet-flush zones on the lower hillslopes, a result of relatively impermeable drift deposits, are also important in controlling N speciation and transformation processes.

show abstract

Role of dissolved organic nitrogen (DON) in soil N cycling in grassland soils

Cited by 373 publications

References 29 publications

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

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

Are nitrate production and retention processes in subtropical acidic forest soils responsive to ammonium deposition?

Groundwater nitrogen composition and transformation within a moorland catchment, mid-Wales

Contact Info

Product

Resources

About