Nitrogen Removal by Riparian Buffers along a European Climatic Gradient: Patterns and Factors of Variation

Abstract

International audienceWe evaluated nitrogen (N) removal efficiency by ri-parian buffers at 14 sites scattered throughout seven European countries subject to a wide range of climatic conditions. The sites also had a wide range of nitrate inputs, soil characteristics, and vegetation types. Dissolved forms of N in groundwater and associated hydrological parameters were measured at all sites; these data were used to calculate nitrate removal by the riparian buffers. Nitrate removal rates (expressed as the difference between the input and output nitrate concentration in relation to the width of the riparian zone) were mainly positive, ranging from 5% m 1 to 30% m 1 , except for a few sites where the values were close to zero. Average N removal rates were similar for herbaceous (4.43% m 1) and forested (4.21% m 1) sites. Nitrogen removal efficiency was not affected by climatic variation between sites, and no significant seasonal pattern was detected. When nitrate inputs were low, a very large range of nitrate removal efficiencies was found both in the forested and in the nonforested sites. However, sites receiving nitrate inputs above 5 mg N L 1 showed an exponential negative decay of nitrate removal efficiency (nitrate removal efficiency 33.6 e 0.11 NO 3 input , r 2 0.33, P 0.001). Hydraulic gradient was also negatively related to nitrate removal (r 0.27, P 0.05) at these sites. On the basis of this intersite comparison, we conclude that the removal of nitrate by biological mechanisms (for example, denitrification, plant uptake) in the riparian areas is related more closely to nitrate load and hydraulic gradient than to climatic parameters

The role of organisms in hyporheic processes: gaps in current knowledge, needs for future research and applications

“…Microbial communities (Table 3) A large number of studies that describe microbial dynamics in the sediment have been supported by potential activities measured in the laboratory, for organic matter degradation (Sinsabaugh et al, 1993;Romani et al, 2006) or nitrogen cycling (Pinay and De´camps, 1988;Clement et al, 2002;Sabater et al, 2003;Lefebvre et al, 2005). There is likely a substantial gap between these experimental activities and the intensity of the processes that take place in situ (Pinay and De´camps, 1988;Sa´nchez-Pe´rez et al, 2003a, b;Iribar et al, 2008).…”

Environmental Services Provided from Riparian Forests in the Nordic Countries

“…The design and efficiency of riparian buffers for control of nutrient transport to surface water are relatively well studied outside the Nordic countries (Broadmeadow and Nisbet 2004) especially in agricultural landscapes (Mayer et al 2007;Sabater et al 2003;Polyakov et al 2005). However, other functions of buffer zones are rarely discussed.…”

Reduced nitrate concentrations in shallow ground water under a non-fertilised grass buffer strip

“…They act as a biochemical and physical barrier between potential sources of contamination (the remainder of the field) and the adjacent open water system. In many (model) studies buffer strips were effective in reducing loads of N and P towards open water systems (e.g., PeterJohn and Correll 1984;Lowrance et al 1984;Orleans et al 1994;Vought et al 1994;Kuusemets et al 2001;Borin and Bigon 2002;Sabater et al 2003), but exceptions were found that were attributed to specific hydrological conditions or, for P, to the release of P due to reducing circumstances during wetting (LeedsHarrison et al 1999;Komor and Magner 1996). Dinnes et al (2002) reported efficiencies of buffer strips in reducing N and P loads of surface water of 48% to almost 100%.…”

“…Since measuring actual loads of nutrients towards open water systems is complicated, we followed the approach commonly used, namely measuring nitrate concentrations in shallow groundwater (Dhondt et al 2002;Altman and Parizek 1995;Lowrance et al 2000;Sabater et al 2003;Borin and Bigon 2002;Haycock and Burt 1993;Haycock and Pinay 1993;Kuusemets et al 2001;Novak et al 2002;Mengis et al 1999). We also considered changes in Cl/NO 3 ratios and in d 15 N in groundwater as indicators for nitrate removal.…”