Fluvial sedimentary deposits as carbon sinks: organic carbon pools and stabilization mechanisms across a Mediterranean catchment

“In addition in Six et al., 2004 there is a review of different models of soil aggregation where this kind of hierarchical order of aggregation is included”

“…indicates a decoupling of aggregates and OC, as found for other soils and land uses (Del Galdo et al., 2003; Denef et al., 2007), and contrasts with Elliott (1986), who reported that the distribution of OC associated with the aggregate fractions is primarily controlled by the amount of soil…”

“In fact, it is already known that soil aggregates physically protect OC from rapid decomposition by microorganisms (Razafimbelo et al., 2008; Six et al., 2000), and aggregate formation appears to be closely linked to soil C storage and stability (Barreto et al.”

“Von Lützow et al. (2007) found that organic molecules stabilized by strong molecular interactions with mineral surfaces decomposed more slowly than OC stabilized by physical mechanisms (e.g. occlusion in soil aggregates).”

“, 2011) also reported a higher OC content in macroaggregates than in microaggregates in soils, which means that organic matter could be the major binding agent in such soils (Oades and Waters, 1991).”

“According to some authors (Van Oost et al., 2007), lateral C fluxes are key to determine the fate of soil organic carbon (SOC) at the landscape scale. but, however However, current estimations of those fluxes (based on soil erosion and the associated SOC content), show high variation among studies…”

“However, current estimations of those fluxes (based on soil erosion and the associated SOC content) show high variation among studies (Quinton et al., 2010; Doetterl et al., 2012).”

“…the assessment of microaggregates contained within macroaggregates and their associated OC, widely acknowledged as an indicator of the physical protection of SOC (Six, et al 2004, Denef et al., 2007, Six and Paustian, 2014), during the different phases of soil erosion at the catchment scale.”

“Ephemeral and intermittent fluvial courses represent more than 50 % of the global river network, being the dominant type of water course in dry climates (Datry et al., 2014).”

“Determination of how the different OC pools are transported by erosion from different sources, as well as the effect of new soil structure formation by aggregation and OC stabilization after deposition, can partially contribute to answering this question (Doetterl et al., 2016).”

“Strong positive correlations between the OC-Mpom and the occluded oxidable mineral fraction (rOC-Mmin−OC-Mmin) at the reservoir, similar to the correlations in the eroding areas (Table 5), suggest that, at this site, fresh OC inputs are more rapidly transformed by microorganisms in an oxidable pool, promoting aggregat…”

“According to some authors (Van Oost et al., 2007), lateral C fluxes are key to determine the fate of soil organic carbon (SOC) at the landscape scale. but, however However, current estimations of those fluxes (based on soil erosion and the associated SOC content), show high variation among studies (Quinton et al., 201…”

“2) was oxidized by NaOCl to obtain a chemically-resistant C fraction (rOC) (Zimmermann et al., 2007) representing the passive pool.”

“…already known that soil aggregates physically protect OC from rapid decomposition by microorganisms (Razafimbelo et al., 2008; Six et al., 2000), and aggregate formation appears to be closely linked to soil C storage and stability (Barreto et al., 2009; Golchin et al., 1995, Salomé et al., 2010).”

“Previously, the maximum water holding capacity for each sample was estimated in triplicate, following the procedure of Howard and Howard (1993). Each sample was put in a hermetically-sealed flask (125 ml) with no further additives.”

“This indicates a decoupling of aggregates and OC, as found for other soils and land uses (Del Galdo et al., 2003; Denef et al., 2007), and contrasts with Elliott (1986), who reported that the distribution of OC associated with the aggregate fractions is primarily controlled by the amount of soil…”

“The protection provided by macroaggregates as an important mechanism for SOC stability in soils affected by soil erosion processes has been also reported (Berhe et al., 2018, Nie et al., 2018, …).”

“, 2003; Denef et al., 2007), and contrasts with Elliott (1986), who reported that the distribution of OC 30 Biogeosciences Discuss.”

“Related to this, Wang et al. (2014) found that soil erosion and transport result in disaggregation and, consequently, SOC mineralization (Lal, 2005; Boix Fayos et al., 2015), while depositional and burial processes promote the formation of macroaggregates that contribute to the physical…”

“Previous geomorphological analyses of the channel and adjacent areas and of the dynamics of the fluvial morphology in the last 60 15 years (Boix-Fayos et al., 2007; Nadeu et al., 2011) were used to identify the main sources and sinks of sediments in the Turrilla basin.”

“Several authors have suggested that alluvial settings are important nonquantified OC sinks (Wisser et al., 2013; Hoffmann et al., 2013; Ran et al., 2014) with mechanisms of OC stabilization that can be quite complex in semiarid and subhumid areas.”

“…lateral C fluxes are key to determine the fate of soil organic carbon (SOC) at the landscape scale. but, however However, current estimations of those fluxes (based on soil erosion and the associated SOC content), show high variation among studies (Quinton et al., 2010; Doetterl et al., 2012).”

“…already known that soil aggregates physically protect OC from rapid decomposition by microorganisms (Razafimbelo et al., 2008; Six et al., 2000), and aggregate formation appears to be closely linked to soil C storage and stability (Barreto et al., 2009; Golchin et al., 1995, Salomé et al., 2010).”

“You did not provide any detail on this and other important environmental conditions such as initial moisture levels.”

“The formation of new aggregates, providing physical stabilization for eroded soil organic matter carbon in depositional positions, has been reported elsewhere (Berhe et al., 2012).”

“When necessary, the OC concentration of each water-stable aggregate-size class, as well as that of the intra-aggregate POM and of the microaggregates occluded in the macroaggregates, was expressed on a sand-free aggregate basis (Elliott et al., 1991).”

“According to some authors (Van Oost et al., 2007), lateral C fluxes are key to determine the fate of soil organic carbon (SOC) at the landscape scale. but, however However, current estimations of those fluxes (based on soil erosion and the associated SOC content), show high variation among studies (Quinton et al., 201…”

“…microorganims protects the OC associated with these microaggregates Microbial induced processes of the microaggregates within larger aggregates protects the OC associated with these microaggregates by increasing its turnover time, and leads to long-term C sequestration (García-Franco et al., 2015).”

“…or non-selective); iv) the connectivity and distance of travel between eroding sources and the streambed (Boix-Fayós et al., 2015; Wang et al., 2010); and v) the micro-environmental conditions under which the OC is stored in sedimentary settings (Van Hemelryck et al., 2011; Berhe and Kleber, 2013).”

“…reported how erosion enhances the release of easily mineralizable C encapsulated within aggregates in the mineralization process (Six et al., 2004; Polyakov and Lal, 2008; Van Hemelryck et al., 2010; Wang et al., 2014; Nie et al., 2018) and how that labile OC is also more easily transported…”

“In fact, it is already known that soil aggregates physically protect OC from rapid decomposition by microorganisms (Razafimbelo et al., 2008; Six et al., 2000), and aggregate formation appears to be closely linked to soil C storage and stability (Barreto et al., 2009; Golchin et al., 1995, Salomé…”

“…microorganims protects the OC associated with these microaggregates Microbial induced processes of the microaggregates within larger aggregates protects the OC associated with these microaggregates by increasing its turnover time, and leads to long-term C sequestration (García-Franco et al., 2015).”

“…organic carbon (OC) depends on multiple factors: i) the nature of the soil organic matter being detached from different “sources” within a catchment (Nadeu et al., 2011; 2012; Kirkels et al., 2014); ii) its turnover rates during transport; iii) the type of erosion processes (selective or…”

“…already known that soil aggregates physically protect OC from rapid decomposition by microorganisms (Razafimbelo et al., 2008; Six et al., 2000), and aggregate formation appears to be closely linked to soil C storage and stability (Barreto et al., 2009; Golchin et al., 1995, Salomé et al., 2010).”

“Other authors have reported how erosion enhances the release of easily mineralizable C encapsulated within aggregates in the mineralization process (Six et al., 2004; Polyakov and Lal, 2008; Van Hemelryck et al., 2010; Wang et al., 2014; Nie et al., 2018) and how 15 that labile OC is also more easily transported in su…”

“…(selective or non-selective); iv) the connectivity and distance of travel between eroding sources and the streambed (Boix-Fayós et al., 2015; Wang et al., 2010); and v) the micro-environmental conditions under which the OC is stored in sedimentary settings (Van Hemelryck et al., 2011;…”

“…of OC induced by soil erosion, together with the identification of source materials contributing to the sediment OC dynamics within a catchment, are key to determine C budgets, to feed and develop prediction models, and to handle soil conservation strategies at catchment scales (Liu et al., 2018).”

“…layers of the depositional areas, the relatively lower OC, microbial activitybasal respiration rate, and M POM Mpom were less favorable for aggregate formation and the process unfolded very slowly compared to the upper layers, which confirms the results reported by other authors (Xie et al., 2017).”

“…in the min- Biogeosciences, 16, 1035–1051, 2019 www.biogeosciences.net/16/1035/2019/ eralization process (Six et al., 2004; Polyakov and Lal, 2008; Van Hemelryck et al., 2010; Wang et al., 2014; Nie et al., 2018) and how that labile OC is also more easily transported in suspension (Starr et al.,…”

“…carbon (OC) depends on multiple factors: i) the nature of the soil organic matter being detached from different “sources” within a catchment (Nadeu et al., 2011; 2012; Kirkels et al., 2014); ii) its turnover rates during transport; iii) the type of erosion processes (selective or…”

“…or non-selective); iv) the connectivity and distance of travel between eroding sources and the streambed (Boix-Fayós et al., 2015; Wang et al., 2010); and v) the micro-environmental conditions under which the OC is stored in sedimentary settings (Van Hemelryck et al., 2011; Berhe and Kleber, 2013).”

“Several authors have suggested that alluvial settings are important, non-quantified OC sinks (Wisser et al., 2013; Hoffmann et al., 2013; Ran et al., 2014) with mechanisms of OC stabilization that can be quite complex in semiarid and sub-humid areas.”

“ii) The degree of microbial degradation index, as an indicator of the OC stability/decomposability, based on De Clercq et al. (2015). According to this, the OC associated with the free microaggregate and mineral fractions (OC-m and OC-min, 5 respectively) would represent the oldest OC, while the OC in the intra-aggreg…”

“…that this percentage will increase worldwide in response to climate change and increased water extraction for human use (Shewe et al., 2014), because intermittent and ephemeral rivers will suffer more severe, sustained, and more frequent droughts (De Girolamo et al., 2017; Vadher et al., 2018).”

“This previous analysis was the background to the combination of the sediment cascade (Hoffman et al., 2013; Boix-Fayos et al., 2015) and the erosion cycle as the experimental approach (Fig.”

“Other authors (Sodhi et al. 2009; Wang et al., 2011) also reported a higher OC content in macroaggregates than in 15 microaggregates in soils, which means that organic matter could be the major binding agent in such soils (Oades and Waters, 1991).”

“…that this percentage will increase worldwide in response to climate change and increased water extraction for human use (Shewe et al., 2014), because intermittent and ephemeral rivers will suffer more severe, sustained, and more frequent droughts (De Girolamo et al., 2017; Vadher et al., 2018).”

“Sedimentary deposits within fluvial systems are a known carbon sink, storing organic carbon introduced from upland areas (Martínez-Mena et al. 2019).”

“This results in higher SOM accumulation through inundation and sedimentation in the subsoil (Martinez-Mena et al. 2019; Mayer et al. 2018), leading to significantly higher OC and TN stocks (Table S.4).”