Research Summary

Peatlands are specialized wetlands that serve as a source of water laden with biologically significant nutrients used in downstream aquatic ecosystems. These waterlogged, anoxic, and acidic systems inhibit decomposition and contain large stocks of poorly decomposed organic material, called peat, that when dried, is a desirable growing medium for horticulture (Landry & Rochefort, 2012). Horticultural peat extraction is an expanding industry in Canada that changes important peatland physical and chemical parameters that can alter the concentration and mobility of nutrients stored in the peat. As water moves through the peat, these compounds can leach into ditches and be transported off site. Elevated concentrations of nutrients in outflow water can increase water quality degradation, elevate water treatment costs, and may cause eutrophication in downstream aquatic ecosystems (Niedermeier & Robinson, 2009; Worrall et al., 2007).

This study investigates the potential impact of peat extraction activities on the availability of chemical compounds able to leach into surface water and be transported off site. A systematic, stratified sampling technique was used to conduct transects within undisturbed, extracted, and restored peat fields varying in age and water saturation. Peat temperature, soil moisture, and aeration were measured at each location to assess the physicochemical factors influencing nutrient availability in surface peat. Plant Root Simulator (PRS®, Western Ag Innovations) probes were installed at each measurement location to measure available nutrients over a four week span.

Peat extraction activities appear to increase the below ground temperature in extracted peatlands, and do not appear to change the soil moisture despite ditching when compared to the variability within the natural site. In addition, soil aeration and surface temperatures do not appear different when compared to the variability in natural site hummocks and hollows. Despite these relative similarities in physicochemical properties, peatlands where extraction has stopped (completed) and mature extracted peatlands have elevated levels of ammonium and nitrate which could potentially leach off site. However, the young extracted site did not behave in the same way, suggesting that additional factors influencing nutrient mobility are at play. Phosphate interactions are complicated, but restored sites with decreased vegetation and saturated soil conditions may increase leaching risk. Despite the differences in nutrient availability between treatments, the physicochemical parameters measured do not appear to be significantly correlated to nutrient availability. This suggests that additional factors may influence nutrient availability and additional sampling is required.

Understanding what physicochemical properties may be important, and when they may apply, will help land managers assess the relative risk of nutrient leaching depending on what type of peat extraction activity is occurring.

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