scholarly journals Landscape controls on riverine export of dissolved organic carbon from Great Britain

2021 ◽  
Author(s):  
Jennifer L. Williamson ◽  
Andrew Tye ◽  
Dan J. Lapworth ◽  
Don Monteith ◽  
Richard Sanders ◽  
...  
Keyword(s):  
Land Use ◽  
Great Britain ◽  
Population Density ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Forest Cover ◽  
River Systems ◽  
C Cycle ◽  
Global Land ◽  
Doc Export

AbstractThe dissolved organic carbon (DOC) export from land to ocean via rivers is a significant term in the global C cycle, and has been modified in many areas by human activity. DOC exports from large global rivers are fairly well quantified, but those from smaller river systems, including those draining oceanic regions, are generally under-represented in global syntheses. Given that these regions typically have high runoff and high peat cover, they may exert a disproportionate influence on the global land–ocean DOC export. Here we describe a comprehensive new assessment of the annual riverine DOC export to estuaries across the island of Great Britain (GB), which spans the latitude range 50–60° N with strong spatial gradients of topography, soils, rainfall, land use and population density. DOC yields (export per unit area) were positively related to and best predicted by rainfall, peat extent and forest cover, but relatively insensitive to population density or agricultural development. Based on an empirical relationship with land use and rainfall we estimate that the DOC export from the GB land area to the freshwater-seawater interface was 1.15 Tg C year−1 in 2017. The average yield for GB rivers is 5.04 g C m−2 year−1, higher than most of the world’s major rivers, including those of the humid tropics and Arctic, supporting the conclusion that under-representation of smaller river systems draining peat-rich areas could lead to under-estimation of the global land–ocean DOC export. The main anthropogenic factor influencing the spatial distribution of GB DOC exports appears to be upland conifer plantation forestry, which is estimated to have raised the overall DOC export by 0.168 Tg C year−1. This is equivalent to 15% of the estimated current rate of net CO2 uptake by British forests. With the UK and many other countries seeking to expand plantation forest cover for climate change mitigation, this ‘leak in the ecosystem’ should be incorporated in future assessments of the CO2 sequestration potential of forest planting strategies.

scholarly journals Representation of dissolved organic carbon in the JULES land surface model (vn4.4_JULES-DOCM)

2018 ◽  
Vol 11 (2) ◽  
pp. 593-609 ◽  
Author(s):  
Mahdi Nakhavali ◽  
Pierre Friedlingstein ◽  
Ronny Lauerwald ◽  
Jing Tang ◽  
Sarah Chadburn ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Land Surface ◽  
Soil Column ◽  
River System ◽  
Terrestrial Ecosystems ◽  
Surface Model ◽  
Organic C ◽  
C Cycle ◽  
Doc Concentration

Abstract. Current global models of the carbon (C) cycle consider only vertical gas exchanges between terrestrial or oceanic reservoirs and the atmosphere, thus not considering the lateral transport of carbon from the continents to the oceans. Therefore, those models implicitly consider all of the C which is not respired to the atmosphere to be stored on land and hence overestimate the land C sink capability. A model that represents the whole continuum from atmosphere to land and into the ocean would provide a better understanding of the Earth's C cycle and hence more reliable historical or future projections. A first and critical step in that direction is to include processes representing the production and export of dissolved organic carbon in soils. Here we present an original representation of dissolved organic C (DOC) processes in the Joint UK Land Environment Simulator (JULES-DOCM) that integrates a representation of DOC production in terrestrial ecosystems based on the incomplete decomposition of organic matter, DOC decomposition within the soil column, and DOC export to the river network via leaching. The model performance is evaluated in five specific sites for which observations of soil DOC concentration are available. Results show that the model is able to reproduce the DOC concentration and controlling processes, including leaching to the riverine system, which is fundamental for integrating terrestrial and aquatic ecosystems. Future work should include the fate of exported DOC in the river system as well as DIC and POC export from soil.

Dissolved organic carbon and dissolved organic nitrogen concentrations and exports upstream and downstream of the Dallas–Fort Worth metropolis, Texas, USA

2016 ◽  
Vol 67 (9) ◽  
pp. 1326 ◽  
Author(s):  
J. A. Aitkenhead-Peterson ◽  
M. K. Steele
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Significant Relationship ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Urban Land Use ◽  
Fort Worth ◽  
Sewage Discharge ◽  
Effluent Discharge

Concentrations and export of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) from terrestrial landscapes to near-coastal zones vary with land use. Information on (DOC) and (DON) concentrations and exports from urban ecosystems is sparse; thus, their source from within urbanised watersheds such as soil or vegetation or from permitted sewage discharge is unknown. We examined DOC and DON concentrations and exports in four gauged subwatersheds in the humid subtropical, upper Trinity River basin, upstream and downstream of the Dallas–Fort Worth metropolis in Texas, USA. Annual average DOC concentrations ranged from 5.7±0.4 to 6.4±0.8mgL–1 and DON concentrations ranged from 0.31±0.05 to 0.33±0.14mgL–1. Dissolved organic carbon exports, which included permitted sewage discharge, ranged from 522kgkm–2 year–1 above Dallas–Fort Worth to 3637kgkm–2 year–1 below Dallas–Fort Worth. Permitted effluent discharge contributed between 1 and 35% of DOC loading above and below the Dallas–Fort Worth metropolis. DON exports ranged from 27 to 179kgkm–2 year–1 above and below Dallas–Fort Worth respectively. There was difficulty apportioning permitted effluent-discharge contribution to DON because of the transformations among nitrogen-species. A moderate but significant relationship was found between DOC and sodium concentrations (R2=0.45; P<0.0001; n=40) and between DOC and potassium concentrations (R2=0.45; P<0.0001; n=40). Dissolved organic nitrogen also displayed a significant relationship with sodium (R2=0.33; P<0.001; n=40) and potassium (R2=0.59; P<0.001; n=40), suggesting that increases in these cations to aquatic ecosystems may induce increases in DOC and DON concentrations. Although DOC export was significantly correlated with medium-density urban land use (r=0.96; P<0.05: n=4), DON export was not (r=0.93; P>0.05; n=4), suggesting that land-management practices and permitted point-source discharges have a significant effect on aquatic DOC and DON concentrations and exports derived from urban watersheds.

Effects of intermittency and land use on the in-stream phosphorus and organic carbon uptake

2020 ◽  
Author(s):  
Gabriele Weigelhofer ◽  
Matthias Pucher
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Hyporheic Zone ◽  
Agricultural Land ◽  
Headwater Streams ◽  
Phosphorus Release ◽  
Nutrient Concentrations ◽  
Agricultural Land Use ◽  
First Results

&lt;p&gt;Understanding the consequences of the interplay between land use and climate change is among the most pressing challenges of the 21&lt;sup&gt;st&lt;/sup&gt; century for river managers. Over the past decades, agricultural land use has altered nutrient concentrations and stoichiometric ratios in stream ecosystems, thereby affecting aquatic biogeochemical cycles and the coupling among carbon, phosphorus, and nitrogen. In addition, the frequency and duration of droughts has increased dramatically across Europe, causing perennial streams to shift to intermittency and changing the capacity of sediments for the uptake and storage of macronutrients.&lt;/p&gt;&lt;p&gt;Our study aims to understand the effects of drying and re-wetting on the uptake, storage, and release of phosphorus and organic carbon from the benthic and the hyporheic zone of headwater streams under the additional stressor of agricultural land use. In specific, we are interested in the potential coupling and decoupling of phosphorus and dissolved organic carbon cycling in autotrophic and heterotrophic benthic biofilms. We sampled headwater streams before, during, and after the dry period in 2018 and 2019 and performed laboratory experiments with artificial drying and re-wetting and additions of dissolved organic carbon. We measured nutrient uptake and release, microbial biomass, respiration, and the activity of extra-cellular enzymes. The first results show an increased phosphorus release from the sediments immediately after re-wetting, foolowed by a reduced uptake capacity. The uptake of DOC was correlated with phosphorus in autotrophic biofilms, but not in heterotrophic ones.&lt;/p&gt;

Indications of soil properties on dissolved organic carbon variability following a successive land use conversion

2018 ◽  
Vol 117 ◽  
pp. 115-119 ◽  
Author(s):  
Xiao Pu ◽  
Hongguang Cheng ◽  
Mats Tysklind ◽  
Jing Xie ◽  
Lu Lu ◽  
...  
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Soil Properties ◽  
Land Use Conversion
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