Cross-site Comparison of Variability of DOC and Nitrate c–q Hysteresis during the Autumn–winter Period in Three Mediterranean Headwater Streams: A Synthetic Approach

Abstract

The forms, rotational patterns and trends of hysteretic loops of dissolved organic carbon (DOC) and nitrate (NO 3 ) were investigated in three headwater Mediterranean streams during one autumn-winter period using two biogeochemical descriptors summarizing the changes in solute concentrations (DC) and the overall dynamics of each hysteretic loop (DR). The study had two aims: (1) to examine whether the variability of solute hysteretic loops monitored in different streams during cold seasons followed a consistent and recurring pattern, (2) to identify hydrological parameters which could potentially influence features of the DOC and NO 3 hysteresis. Relationships between hysteresis features and hydrological parameters in the studied streams were explored using multivariate redundancy analysis (RDA). Both DOC and NO 3 typically increased in concentration during storm events, although hysteretic loops did not obey any consistent pattern across the three streams. The rotational patterns of DOC and NO 3 hysteresis ranged widely, from clockwise to counterclockwise. Storm hydrographs and also the magnitude of antecedent storm events were explanatory of the DOC and NO 3 concentration changes across the study sites. However, the detailed hydrological information did not offer a satisfactory explanation of the entire DOC and NO 3 concentration dynamics during the storm events.

Concentrations and fluxes of dissolved organic carbon in runoff from a forested catchment: insights from high frequency measurements

“…Hornberger et al, 1994;Butturini et al, 2006;Jeong et al, 2012). This was also reported in studies where DOC was found to originate mainly from riparian wetland soils (McGlynn and McDonnell, 2003;Hood et al, 2006).…”

“…Hysteretic relationships between discharge and solute concentrations have observed, among others, by Hornberger et al (1994), Evans and Davies (1998), Butturini et al (2006), Raymond and Saiers (2010), Pellerin et al (2012) and Jeong et al (2012). Evans and Davies (1998) proposed the hysteretic concentration/discharge relationship for the analysis of episode hydrochemistry.…”

Event controlled DOC export from forested watersheds

“…3). The lower DOC concentrations during the falling hydrograph indicate that the DOC storm response is hysteretic (Butturini et al 2006) and may, for example, reflect temporary depletion of the terrestrial DOC supply due to soilwater flushing (Hornberger et al 1994;Boyer et al 2000) or, perhaps, changes in the timing of runoff contributions from the riparian zone and hill slope during the course of a rainfall event (Hinton et al 1998;McGlynn and McDonnell 2003). DOC that appears in small streams during hydrologic events is derived primarily from allochthonous terrestrial sources (Royer and David 2005).…”

The river as a chemostat: fresh perspectives on dissolved organic matter flowing down the river continuum

“…Hysteresis refers to differing relationships between DOC concentration and discharge on the rising and falling limbs of the hydrograph during a runoff event (Evans and Davies 1998). The size, direction, and slope of hysteresis loops can reflect the source and the relative magnitudes and timing of allochthonous inputs of DOM (Butturini et al 2006). Clockwise directions of change over the course of a hydrologic event suggest that DOM sources are well connected to each other and proximal to the stream, while counterclockwise directions suggest DOM sources are disconnected from each other and distal from the stream.…”