Retention of phosphorus in soil and vegetation of a buffer zone area during snowmelt peak flow in southern Finland

Abstract

In regions with a distinct winter-period, nearly half of the annual runoff occurs during a short snow-melt period early in spring. During this time functioning buffer zones are important means of preventing the leaching of phosphorus from forest land into downstream watercourses. Sparse vegetation restricts biological P accumulation and high flows reduce the capacity of deeper soil layers to adsorb P, indicating that the effectiveness of buffer zones may be low. Our aim was to increase the understanding of phosphorus retention in a buffer zone area under such unfavourable conditions for P removal, and to estimate the amount of P sorbed by soil and taken up by vascular plants and mosses. Over a five-day period in spring we added 10 kg (60 kg ha −1 ) of PO 4 -P and 185 MBq (1100 MBq ha −1 ) 32 P to a 25-50 m wide buffer zone area (0.17 ha) in southern Finland. We measured the total P retention and recovery during ten days after the beginning of the experiment. Recovery of 32 P was 16% of added P, of which 92% was in soil, 3% in vascular plants and 5% in mosses. Thus, our results showed that the total P retention was low, most likely because the water flow did not slow down sufficiently and penetrate deeply enough to enable a close contact between P in the runoff and the soil matrix. Most of the recovered P was in the soil suggesting that adsorption by soil was the most important sink for P under early spring high flow conditions.

Implications of Uncertainty in a Pre-treatment Dataset when Estimating Treatment Effects in Paired Catchment Studies: Phosphorus Loads from Forest Clear-cuts

“…The increased supply of P in the clear-cut area is promoted when P uptake by the trees ceases and P uptake by the ground vegetation is decreased after site preparation. The increased supply of P does not necessarily increase transport of P to water courses, because chemical sorption to soil particles, especially to Fe and Al compounds, is effective (Li et al 1999;Giesler et al 2002;Väänänen et al 2006), and the ground vegetation and microbes consume P in the buffer zone (Silvan et al 2003(Silvan et al , 2004Kellog and Bridgham 2003). It is likely that a small part of the P is not retained in the soil and passes into the stream, especially during the period outside the growing season when the biological activity in catchments is low (Väänänen et al 2006).…”

“…The increased supply of P does not necessarily increase transport of P to water courses, because chemical sorption to soil particles, especially to Fe and Al compounds, is effective (Li et al 1999;Giesler et al 2002;Väänänen et al 2006), and the ground vegetation and microbes consume P in the buffer zone (Silvan et al 2003(Silvan et al , 2004Kellog and Bridgham 2003). It is likely that a small part of the P is not retained in the soil and passes into the stream, especially during the period outside the growing season when the biological activity in catchments is low (Väänänen et al 2006). Detection of such a small leakage is difficult especially during the snowmelt episode, when the measurement of runoff is problematic due to detached ice that can dam up the weir (Stadler et al 1998).…”

The Effects of Multiple Beneficial Management Practices on Hydrology and Nutrient Losses in a Small Watershed in the Canadian Prairies

“…Previous fi eld studies on the eff ects of BMPs in cold-climate regions have been conducted primarily at the plot or infi eld scale, and many used the changes in soil nutrient concentrations resulting from BMP implementation to indicate its impact on nutrient losses from the fi eld (e.g., Uusi-Kamppa, 2005;Vaananen et al, 2006;Miller et al, 2010b). Although these studies are crucial for understanding individual processes, it has been recognized that plot-or infi eld-scale research often fails to capture the complexities and interactions among BMPs, biophysical settings, and land use within a watershed (Schnepf and Cox, 2006;Hoff mann et al, 2009).…”

Soil and water management: opportunities to mitigate nutrient losses to surface waters in the Northern Great Plains

“…Most research into the effect of riparian buffers on N and P export has focussed on regions dominated by rainfall runoff, with much less research occurring at locations where snowmelt runoff predominates (Kieta et al 2018). In Finland, forested riparian buffers retained a moderate proportion (16%) of added 32 P during snowmelt (Väänänen et al 2006), with the greatest portion of this retention occurring in the soil. This pattern highlights a significant challenge in using buffers to retain nutrients from snowmelt runoff; vegetation in early spring is likely to be present only in a dead or dormant state and may act as a source of dissolved nutrients (as described previously).…”