Stemflow and dissolved organic carbon cycling: temporal variability in concentration, flux, and UV-Vis spectral metrics in a temperate broadleaved deciduous forest in the eastern United States

2012 ◽  
Vol 42 (1) ◽  
pp. 207-216 ◽  
Author(s):  
Delphis F. Levia ◽  
John T. Van Stan, II ◽  
Shreeram P. Inamdar ◽  
Matthew T. Jarvis ◽  
Myron J. Mitchell ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Deciduous Forest ◽  
Fagus Grandifolia ◽  
Eastern United States ◽  
Storm Events ◽  
Yellow Poplar ◽  
American Beech ◽  
Order Of Magnitude ◽  
Chemical Character

No known research has examined the concentration and flux of dissolved organic carbon (DOC) for stemflow across temporal scales from within single storm events to seasonal and annual scales or employed UV-Vis spectral metrics to examine the chemical character of dissolved organic matter (DOM) of stemflow drainage. Thus, our study examined stemflow DOC concentration and flux and DOM character from American beech ( Fagus grandifolia Ehrh.) and yellow poplar ( Liriodendron tulipifera L.) to address this data gap. Intrastorm stemflow DOC concentrations and fluxes diminished by an order of magnitude over time for American beech but remained relatively constant for yellow poplar. Stemflow DOM aromaticity, however, generally increased and E2:E3 ratios generally decreased as events progressed, suggesting transport of different compounds at different moments. Although less enriched in DOC than yellow poplar, American beech stemflow DOC fluxes were double per annum. Differential interspecific stemflow DOM characteristics are ascribed to (i) significant differences in SUVA254 values (aromaticity) for the leafless season and annually and (ii) significantly higher E2:E3 and SR ratios for yellow poplar stemflow than for American beech annually and across leafed and leafless seasons. Our results suggest that stemflow significantly affects the amount and chemical character of carbon flux to the forest floor that may engender hot spots around tree boles.

Carbon Flow in a Tundra Stream Ecosystem

1986 ◽  
Vol 43 (6) ◽  
pp. 1259-1270 ◽  
Author(s):  
Bruce J. Peterson ◽  
John E. Hobbie ◽  
Teresa L. Corliss
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Primary Productivity ◽  
Net Primary Production ◽  
Epilithic Algae ◽  
Net Production ◽  
Organic Carbon Concentration ◽  
Temperate Streams ◽  
Tundra Vegetation ◽  
Order Of Magnitude

The carbon cycle of the Kuparuk River, a meandering tundra stream, is dominated by inputs of eroding peat and leaching dissolved organic carbon from the tundra. Net production of epilithic algae is about 13 g C∙m−2∙yr−1, an order of magnitude less than inputs of allochthonous particulate organic carbon and two orders of magnitude less than inputs of dissolved organic carbon. The streamwater has a mean total organic carbon concentration of 6.8 mg∙L−1, and the annual export of organic carbon from the watershed is 2–3 t∙km−2∙yr−1; both are similar to the average for temperate streams. However, because of the low primary productivity of tundra vegetation, the export of organic carbon from the watershed via the river is a larger fraction (2–6%) of the total watershed net primary production than the 0.1–0.4% usually found for temperate rivers.

scholarly journals Distribution and bacterial availability of dissolved neutral sugars in the South East Pacific

2008 ◽  
Vol 5 (4) ◽  
pp. 1165-1173 ◽  
Author(s):  
R. Sempéré ◽  
M. Tedetti ◽  
C. Panagiotopoulos ◽  
B. Charrière ◽  
F. Van Wambeke
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Surface Waters ◽  
Detectable Effect ◽  
Neutral Sugar ◽  
The South ◽  
East Pacific ◽  
Significant Stimulation ◽  
Order Of Magnitude ◽  
Neutral Sugars

Abstract. The distribution and bacterial availability of dissolved neutral sugars were studied in the South East Pacific from October to December 2004 during the BIOSOPE cruise. Four contrasting stations were investigated: Marquesas Islands (MAR), the hyper-oligotrophic South Pacific Gyre (GYR), the eastern part of the Gyre (EGY), and the coastal waters associated to the upwelling area off Chile (UPW). Total (free and combined) dissolved neutral sugar (TDNS) concentrations were in the same order of magnitude at MAR (387±293 nM), GYR (206±107 nM), EGY (269±175 nM), and UPW (231±73 nM), with the highest and lowest concentrations found at MAR (30 m, 890 nM) and EGY (250 m, 58 nM), respectively. Their contribution to dissolved organic carbon (TDNS-C×DOC−1%) was generally low for all sites varying from 0.4% to 6.7% indicating that South East Pacific surface waters were relatively poor in neutral sugars. Free dissolved neutral sugar (FDNS; e.g. sugars analyzed without hydrolysis) concentrations were very low within the detection limit of our method (5–10 nM) accounting for <5% of the TDNS. In general, the predominant sugars within the TDNS pool were glucose, xylose, arabinose, and galactose, while in the FDNS pool only glucose was present. TDNS stock to bacterial production ratios (integrated values from the surface to the deep chlorophyll maximum) were high at GYR with respect to the low primary production, whereas the opposite trend was observed in the highly productive area of UPW. Intermediate situations were observed for MAR and EGY. Bioavailability of dissolved organic matter (DOM) exposed to natural solar radiation was also experimentally studied and compared to dark treatments. Our results showed no or little detectable effect of sunlight on DOM bacterial assimilation in surface waters of UPW and GYR, while a significant stimulation was found in MAR and EGY. The overall results clearly suggest that DOM is less labile at GYR compared to UPW, which is consistent with the observed accumulation of dissolved organic carbon and the elevated C/N ratios reported by Raimbault et al. (2008).

scholarly journals Dissolved organic carbon (DOC) and select aldehydes in cloud and fog water: the role of the aqueous phase in impacting trace gas budgets

2013 ◽  
Vol 13 (10) ◽  
pp. 5117-5135 ◽  
Author(s):  
B. Ervens ◽  
Y. Wang ◽  
J. Eagar ◽  
W. R. Leaitch ◽  
A. M. Macdonald ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Water Soluble ◽  
Box Model ◽  
High Solubility ◽  
Fog Water ◽  
Air Masses ◽  
Order Of Magnitude

Abstract. Cloud and fog droplets efficiently scavenge and process water-soluble compounds and, thus, modify the chemical composition of the gas and particle phases. The concentrations of dissolved organic carbon (DOC) in the aqueous phase reach concentrations on the order of ~ 10 mgC L−1 which is typically on the same order of magnitude as the sum of inorganic anions. Aldehydes and carboxylic acids typically comprise a large fraction of DOC because of their high solubility. The dissolution of species in the aqueous phase can lead to (i) the removal of species from the gas phase preventing their processing by gas phase reactions (e.g., photolysis of aldehydes) and (ii) the formation of unique products that do not have any efficient gas phase sources (e.g., dicarboxylic acids). We present measurements of DOC and select aldehydes in fog water at high elevation and intercepted clouds at a biogenically-impacted location (Whistler, Canada) and in fog water in a more polluted area (Davis, CA). Concentrations of formaldehyde, glyoxal and methylglyoxal were in the micromolar range and comprised ≤ 2% each individually of the DOC. Comparison of the DOC and aldehyde concentrations to those at other locations shows good agreement and reveals highest levels for both in anthropogenically impacted regions. Based on this overview, we conclude that the fraction of organic carbon (dissolved and insoluble inclusions) in the aqueous phase of clouds or fogs, respectively, comprises 2–~ 40% of total organic carbon. Higher values are observed to be associated with aged air masses where organics are expected to be more highly oxidised and, thus, more soluble. Accordingly, the aqueous/gas partitioning ratio expressed here as an effective Henry's law constant for DOC (KH*DOC) increases by an order of magnitude from 7 × 103 M atm−1 to 7 × 104 M atm−1 during the ageing of air masses. The measurements are accompanied by photochemical box model simulations. These simulations are used to contrast two scenarios, i.e., an anthropogenically vs. a more biogenically impacted one as being representative for Davis and Whistler, respectively. Since the simplicity of the box model prevents a fully quantitative prediction of the observed aldehyde concentrations, we rather use the model results to compare trends in aldehyde partitioning and ratios. They suggest that the scavenging of aldehydes by the aqueous phase can reduce HO2 gas phase levels significantly by two orders of magnitude due to a weaker net source of HO2 production from aldehyde photolysis in the gas phase. Despite the high solubility of dicarbonyl compounds (glyoxal, methylglyoxal), their impact on the HO2 budget by scavenging is < 10% of that of formaldehyde. The overview of DOC and aldehyde measurements presented here reveals that clouds and fogs can be efficient sinks for organics, with increasing importance in aged air masses. Even though aldehydes, specifically formaldehyde, only comprise ~ 1% of DOC, their scavenging and processing in the aqueous phase might translate into significant effects in the oxidation capacity of the atmosphere.

Pulsed terrestrial organic carbon persists in an estuarine environment after major storm events

2020 ◽  
Author(s):  
Eero Asmala ◽  
Christopher Osburn ◽  
Ryan Paerl ◽  
Hans Paerl
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
River Estuary ◽  
River Mouth ◽  
Neuse River Estuary ◽  
Storm Events ◽  
Dynamic Component ◽  
Neuse River ◽  
Doc Concentration ◽  
A Minor

&lt;p&gt;The transport of dissolved organic carbon from land to ocean is a large and dynamic component of the global carbon cycle. Export of dissolved organic carbon from watersheds is largely controlled by hydrology, and is exacerbated by increasing major rainfall and storm events, causing pulses of terrestrial dissolved organic carbon (DOC) to be shunted through rivers downstream to estuaries. Despite this increasing trend, the fate of the pulsed terrestrial DOC in estuaries remains uncertain. Here we present DOC data from 1999 to 2017 in Neuse River Estuary (NC, USA) and analyze the effect of six tropical cyclones (TC) during that period on the quantity and fate of DOC in the estuary. We find that that TCs promote a considerable increase in DOC concentration near the river mouth at the entrance to the estuary, on average an increase of 200 &amp;#181;mol l&lt;sup&gt;-1&lt;/sup&gt; due to storms was observed. TC-induced increases in DOC are apparent throughout the estuary, and the duration of these elevated DOC concentrations ranges from one month at the river mouth to over six months in lower estuary. Our results suggest that despite the fast mineralization rates, the terrestrial DOC is processed only to a minor extent relative to the pulsed amount entering the estuary. We conclude that the vast quantity of organic carbon delivered to estuaries by TCs transform estuaries from active biogeochemical processing &amp;#8220;reactors&amp;#8221; of organic carbon to appear more like passive shunts due to the sheer amount of pulsed material rapidly flushed through the estuary.&lt;/p&gt;

Beyond oak regeneration: modelling mesophytic sapling density drivers along topographic, edaphic, and stand-structural gradients in mature oak-dominated forests of Appalachian Ohio

2020 ◽  
Vol 50 (11) ◽  
pp. 1215-1227
Author(s):  
Don C. Radcliffe ◽  
Stephen N. Matthews ◽  
David M. Hix
Keyword(s):  
Sugar Maple ◽  
Acer Rubrum ◽  
Basal Area ◽  
Fagus Grandifolia ◽  
Active Management ◽  
Permanent Plots ◽  
Eastern United States ◽  
Red Maple ◽  
American Beech ◽  
Sapling Density

Shade-tolerant mesophytic tree species tend to dominate the understories of present-day oak–hickory and mixed-hardwood forests in the eastern United States. We quantified the sapling density associations with abiotic and biotic variables for three important mesophytic species: red maple (Acer rubrum L.), sugar maple (Acer saccharum Marsh.), and American beech (Fagus grandifolia Ehrh.) in southeastern Ohio. In this study, we sampled 165 permanent plots in oak-dominated, topographically diverse, mature (>90 years old), second-growth forests following a time span of 21–25 years (1993–1995 and 2016–2018) between samples on the Athens and Marietta units of the Wayne National Forest. Our models showed that sugar maple was strongly associated with high pH soils and red maple was strongly associated with low pH soils. Additionally, red maple was associated with upper slope positions and older stands, while American beech was associated with lower slopes, northeasterly aspects, and northeast-facing upper slopes. Basal area of competing species, solum depth, and management unit were not significantly related to sapling density for our focal species. American beech sapling density doubled between the two sampling periods, while densities of both maple species declined by half. Our results will help scientists and managers by providing insight into potential future composition of currently oak-dominated forests in areas without active management intervention.

scholarly journals Identification and analysis of low-molecular-weight dissolved organic carbon in subglacial basal ice ecosystems by ion chromatography

2016 ◽  
Vol 13 (12) ◽  
pp. 3833-3846 ◽  
Author(s):  
Emily C. O'Donnell ◽  
Jemma L. Wadham ◽  
Grzegorz P. Lis ◽  
Martyn Tranter ◽  
Amy E. Pickard ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Microbial Activity ◽  
Free Amino ◽  
Low Molecular Weight ◽  
Subglacial Environment ◽  
Basal Ice ◽  
Order Of Magnitude

Abstract. Determining the concentration and composition of dissolved organic carbon (DOC) in glacial ecosystems is important for assessments of in situ microbial activity and contributions to wider biogeochemical cycles. Nonetheless, there is limited knowledge of the abundance and character of DOC in basal ice and the subglacial environment and a lack of quantitative data on low-molecular-weight (LMW) DOC components, which are believed to be highly bioavailable to microorganisms. We investigated the abundance and composition of DOC in basal ice via a molecular-level DOC analysis. Spectrofluorometry and a novel ion chromatographic method, which has been little utilized in glacial science for LMW-DOC determinations, were employed to identify and quantify the major LMW fractions (free amino acids, carbohydrates, and carboxylic acids) in basal ice from four glaciers, each with a different type of overridden material (i.e. the pre-entrainment sedimentary type such as lacustrine material or palaeosols). Basal ice from Joyce Glacier (Antarctica) was unique in that 98 % of the LMW-DOC was derived from the extremely diverse free amino acid (FAA) pool, comprising 14 FAAs. LMW-DOC concentrations in basal ice were dependent on the bioavailability of the overridden organic carbon (OC), which in turn was influenced by the type of overridden material. Mean LMW-DOC concentrations in basal ice from Russell Glacier (Greenland), Finsterwalderbreen (Svalbard), and Engabreen (Norway) were low (0–417 nM C), attributed to the relatively refractory nature of the OC in the overridden palaeosols and bedrock. In contrast, mean LMW-DOC concentrations were an order of magnitude higher (4430 nM C) in basal ice from Joyce Glacier, a reflection of the high bioavailability of the overridden lacustrine material (> 17 % of the sediment OC comprised extractable carbohydrates, a proxy for bioavailable OC). We find that the overridden material may act as a direct (via abiotic leaching) and indirect (via microbial cycling) source of DOC to the subglacial environment and provides a range of LMW-DOC compounds that may stimulate microbial activity in wet subglacial sediments.

Seasonal changes in pathways of dissolved organic carbon through a hillslope soil (Xeralf) with contrasting texture

Soil Research ◽  
1992 ◽  
Vol 30 (4) ◽  
pp. 465 ◽  
Author(s):  
DJ Chittleborough ◽  
KRJ Smettem ◽  
E Cotsaris ◽  
FW Leaney
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Overland Flow ◽  
Podzolic Soil ◽  
Marked Decrease ◽  
Soil Surface ◽  
Storm Events ◽  
Dry Period ◽  
Doc Concentration ◽  
Texture Contrast

The pathways of dissolved organic carbon (DOC) through a podzolic soil (Xeralf) with strong texture contrast are described. During winter, most of the DOC passes through macropores in the profile and flows laterally through the B horizons. During summer the presence of dry, hydrophobic organic matter on the soil surface and the A1 horizon causes DOC to flow overland. DOC concentrations vary seasonally. Highest concentrations are measured during summer overland flow. For all horizons, the longer the dry period the greater the DOC concentration in the subsequent flow. During storm events there is a marked flushing effect in the B horizons but in the A horizon and the surface, DOC concentrations tend to rise. There was a marked decrease in DOC concentration in flow from the B3 compared to the upper horizons. This may be due to adsorption by fine clays lining the macropores.

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