Phosphorus and Nitrogen Export from Forested Stream Catchments in Central Ontario

Abstract

The ability to predict export of algal nutrients from forested stream catchments is essential to estimate background levels of nutrients in lakes and therefore gauge the effects of anthropogenic activities on the trophic status of Ontario lakes. Data from 32 forested stream catchments in the Muskoka‐Haliburton area of central Ontario collected during the 8‐yr period 1976–1977 to 1983–1984 were used to develop empirical regression models of long‐term average NH4, NO–3, TON, and TP export employing mathematical transformations of geology, physiography, hydrology, and annual meteorological data. At least 6 consecutive years of sampling were necessary to avoid poor fits due to anomalous years and to produce regression models able to make reliable (R2 > 0.70) long‐term average predictions of TP export. Atmospheric deposition of algal nutrients typically exceeded catchment export. Total annual phosphorus (TP) export was variable with outputs from two catchments exceeding atmospheric inputs. Total organic nitrogen (TON) export was also variable with annual export from 22 catchments exceeding atmospheric inputs, although total N (TN) export never exceeded input. Peat deposits or beaver (Castor canadensis Kuhl) ponds in most of these catchments were the likely sources of the high TP and TON export. Nitrate retention (defined as the fraction of annual deposition retained by the catchment) was high in most catchments, exceeding 0.74 in 26 of the 32 catchments. Low NO–3 retention was observed primarily in those catchments with steep grades (>5.9%). Ammonium retention was very high (>0.87) in all catchments.

Sediment and nutrient storage in a beaver engineered wetland

“…Beaver pond–dam complexes have been reported to act as sediment traps, due to the rapid decrease in velocity when water enters a pond (Butler and Malanson, 1995; Klotz, 2007). The altered flow regimes also modify nutrient and chemical cycling in ponds and rivers which, combined with trapping and storage of sediment, can impact upon downstream water quality (Naiman et al ., 1986; Dillon et al ., 1991). …”

Lake Tahoe watershed assessment: volume I

“…These results were somewhat surprising because the literature indicates that watershed geology can strongly influence water quality (Dillon and Kirchner 1975;Keller and Strobel 1982;Grobler and Silberbauer 1985;Molot et al 1989). However, a lack of significant associations between catchment and water quality parameters also has been noted by Dillon et al (1991) and Svendsen et al (1995). The LTIMP data for inter-watershed discharge were associated positively with basin area and main channel length but were negatively associated with channel gradient and basin relief ratio.…”

Phosphorus forms and response to changes in pH in acid-sensitive soils on the Precambrian Shield

“…Previous work in this region has attributed differences in [TP] amongst streams to catchment characteristics and in particular wetland coverage (Dillon et al 1991). For example, HP3 has 9% wetland coverage compared with only 3% at HP3A, which is about the same difference as the ratio in stream [TP] between the HP3 and HP3A catchments ).…”

“…Although stream [TP] are generally low in the study region, stream [TP] varies threefold amongst the three catchments (Dillon et al 1991;Eimers et al 2009). …”

“…These three catchments were selected as they have each shown long-term declines in stream [TP] ) and soil pH (Watmough and Dillon 2004), and they represent the range in soil pH in this region (Casson et al 2011). The three catchments have little human disturbance, and are all entirely forested; wetlands occupy 1% of the land area in PC1-08, 2.9% in HP3A and 9.3% in HP3 (Dillon et al 1991). Forest cover at the Plastic Lake catchment consists of mainly conifers, dominated by white pine (Pinus strobus) and eastern hemlock (Tsuga canadensis) whereas forest cover at the Harp Lake catchment is mainly deciduous, dominated by sugar maple (Acer saccharum) and yellow birch (Betula alleghaniensis) (Watmough and Dillon 2003).…”