Hydroclimatic influences and physiographic controls on phosphorus dynamics in prairie pothole wetlands

Abstract

While wetlands are known as long-term storages or sinks for contaminants, not all are equally effective at trapping phosphorus (P). The prevalence of P-sink behavior in prairie pothole wetlands remains unclear, especially across gradients of human disturbance. The objectives of the current study were three-fold: (1) characterize the spatiotemporal variability of wetland hydrology and wetland water P concentration across a range of prairie potholes; (2) establish the propensity of different pothole wetlands to act as sources or sinks of P; and (3) assess the potential controls of climatic conditions, landscape characteristics, wetland soil physiochemical properties and local hydrology on source versus sink dynamics. Ten intact and three consolidated (i.e., drained) wetlands located in southwestern Manitoba, Canada, were monitored for water level fluctuations and water soluble reactive P (SRP) concentration over two years with contrasting antecedent wetness conditions. Soil cores were also collected to measure soil physiochemical properties such as the equilibrium phosphorus concentration (EPC). Water column SRP concentrations were compared to EPC values to infer the time-variable source versus sink behavior of each of wetland. Statistical analyses were then performed to assess whether the source versus sink behavior of individual wetlands could be linked to their physiographic or hydrologic characteristics. Results show that some wetlands persistently acted as P sinks while others switched between source and sink behavior. Persistent P-sink behavior was more common with intact wetlands, as opposed to consolidated wetlands. Wetland soil texture, storage volume and short-term water level fluctuations appeared to control the source versus sink behavior of individual wetlands. The dominant controls on P-sink behavior identified under dry conditions were, however, different from those identified under wetter conditions. This study therefore highlights the importance of considering the non-stationary nature of P-sorption dynamics and their controls, even at sub-annual timescales, in the prairie pothole region.

Influence of tillage practices on phosphorus forms in aggregates of Mollisols from northeast China

“…Different forms of P vary significantly in availability to plants 8,9 . It is known that P release mechanisms can be altered by changes in soil physicochemical properties 10–12 . Thus, exploring P forms and translocation in aggregates are critical to understanding nutrient utilization by the crop.…”

Seasonal and Intra-Event Nutrient Levels in Farmed Prairie Potholes of the Des Moines Lobe

“…Despite abundant research on natural wetlands and some on undisturbed prairie potholes (e.g., LaBaugh et al, 2018;Haque et al, 2018), information on farmed pothole water quality is limited. Recent work by Skopec and Evelsizer (2018) reported the average spring surface water nutrient concentrations from 16 sites with farmed potholes.…”

Hydrological and Seasonal Controls of Phosphorus in Northern Great Plains Agricultural Streams

“…Spatial patterns of soil P can vary considerably across landscapes and depend on factors such as management practices and landform (Wilson et al, 2016). Wetlands generally act as long‐term P sinks on the landscape; however, P retention varies depending on soil texture and short‐term hydrological fluctuations (Haque et al, 2018). Natural wetlands demonstrate P sink behavior compared with drained wetlands (Haque et al, 2018), and the loss of small wetlands due to land conversion for agriculture or other land uses promotes P loading to downstream waters (Cheng and Basu, 2017).…”

“…Wetlands generally act as long‐term P sinks on the landscape; however, P retention varies depending on soil texture and short‐term hydrological fluctuations (Haque et al, 2018). Natural wetlands demonstrate P sink behavior compared with drained wetlands (Haque et al, 2018), and the loss of small wetlands due to land conversion for agriculture or other land uses promotes P loading to downstream waters (Cheng and Basu, 2017). Intensive agriculture also influences watershed hydrology and runoff patterns, generally homogenizing runoff regimes and linking nutrient export and hydrological dynamics (Basu et al, 2011), although these patterns are not always generalizable to snowmelt‐dominated regions (Ali et al, 2017).…”