Phosphorus and nitrogen retention in five Precambrian shield wetlands

Abstract

Phosphorus and nitrogen mass balances of five wetlands (two beaver ponds, two conifer-Sphagnum swamps and one sedge fen) situated in three catchments in central Ontario, Canada, were measured. Monthly and annual input-output budgets of total phosphorus (TP), total nitrogen (TN), total organic nitrogen (TON), total inorganic nitrogen (TIN), ammonium ion (NH: -N), nitrate (NO; -N) and dissolved organic carbon (DOC) were estimated for the five wetlands during the 1982-83 and 1983-84 water years. Except for the deepest beaver pond (3.2m) which had annual TP retention of -44% (-0.030 0.015 g m-2 yr-I), the wetlands retained < 0.001 to 0.015 gm-2 yr-I; however, this was less than 20% of the inputs and the estimated budget uncertainties were equal to or greater than the retention rates. Annual TN retentions ranged from -0.44 to 0.56gm-'yr-' (-12 to 4%) but were not significantly different from zero. The wetlands transformed nitrogen by retaining TIN (16 to 80% RT) and exporting an equivalent amount as TON (-7 to 102% RT). The beaver ponds, however, retained NO, while NH: was passed through or the outputs exceeded the inputs. In contrast, the conifer swamps retained both NH: and NO,. DOC fluxes into and out of the beaver ponds were equal (-18 and 4% RT) but output from the conifer swamps exceeded input by r 90%. Marked seasonal trends in nutrient retention were observed. Nutrient retention coincided with low stream flow, increased evapotranspiration and biotic uptake during the summer. Net nutrient export occurred during the winter and spring when stream flows were highest and biotic uptake was low.

Fluorescence characteristics and biodegradability of dissolved organic matter in forest and wetland soils from coastal temperate watersheds in southeast Alaska

“…DOC concentrations once again decrease during the late summer/fall wet season as the supply of DOC becomes exhausted and DOC:DON ratios approach near spring values. Our Wndings suggest strong biotic control over DOM concentrations in wetland soils, which is similar to previous research in Wve Canadian peatlands that found N and P retention during the summer growing season and net N and P export during the spring (Devito et al 1989). For upland forest sites, temporal patterns in DOM concentrations were similar indicating similar controls on the production and/or retention of DOM in forest soils (NeV et al 2000).…”

“…The fen in contrast had signiWcantly lower DOC concentrations than the bog and forested wetland and suggests that continuous soil Xushing in fens results in low pore water DOC concentrations (Urban et al 1989). Seasonal changes in DOC and DON concentrations have been previously documented in both wetland (Devito et al 1989;Fraser et al 2001) and forested landscapes (Qualls and Haines 1991;Yano et al 2004). Concentrations of DOC and DON exhibited contrasting seasonal patterns in the bog and forested wetland suggesting controls on DOC production and/or removal may be diVerent than those for DON.…”

“…During the spring snowmelt period, low wetland DOC concentrations can be attributed to prolonged soil saturation and subsequent dilution of soil pools of DOC (Fraser et al 2001;Worrall et al 2002). However, DOP and DON concentrations exhibited maxima during the spring which suggests that decreased biotic demand (Devito et al 1989) in combination with soil freeze thaw events (Fitzhugh et al 2001) can result in a pool of DON and DOP in soil solution that is potentially available to Xush to streams. As a result, DOC:DON ratios exhibited minima during the spring.…”

Sediment and nutrient storage in a beaver engineered wetland

“…This summary is supported by previous research and is commonly attributed to the same factors such as channel discontinuity and flow velocity reduction that result in sediment deposition and storage of associated nutrients (Naiman et al ., 1986; Devito et al ., 1989; Lizarralde et al ., 1996; Klotz, 2013). Wohl (2013) estimated that even relict beaver dam‐related storage can account for 8% of total carbon storage within the landscape and actively maintained beaver wetlands up to 23%.…”

Role of wetlands and developed land use on dissolved organic nitrogen concentrations and DON/TDN in northeastern U.S. rivers and streams

“…Wetlands have been shown to function as sinks for inorganic N through denitrification (Hill, 1996), as well as sites where inorganic N may be converted to organic N (Devito et al, 1989). Although regional studies linking DON to natural landscape features have had limited success (Clair et al, 1994), relationships between stream water dissolved organic carbon (DOC) (Mulholland and Kuenzler 1979;Eckhardt and Moore 1990;Raymond and Hopkinson 2003) and wetland abundance suggest that wetlands may play an important role in hydrologic DON losses from forested and developed watersheds.…”