Know the flow - spatial and temporal variation of DOC exports and the importance of monitoring site specific discharge
The export of dissolved organic carbon (DOC) is an important component in both water quality and carbon cycling within boreal catchments. DOC exports are mainly controlled by discharge. Therefore, the resolution and quality of discharge data is essential when quantifying DOC exports as well as for t...
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| Formato: | H2 |
| Lenguaje: | Inglés sueco |
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SLU/Dept. of Forest Ecology and Management
2018
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| _version_ | 1855572341050834944 |
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| author | Larson, Johannes |
| author_browse | Larson, Johannes |
| author_facet | Larson, Johannes |
| author_sort | Larson, Johannes |
| collection | Epsilon Archive for Student Projects |
| description | The export of dissolved organic carbon (DOC) is an important component in both water quality and carbon cycling within boreal catchments. DOC exports are mainly controlled by discharge. Therefore, the resolution and quality of discharge data is essential when quantifying DOC exports as well as for the understanding of its spatial and temporal variation. Although there are many studies quantifying DOC exports, many fail to consider the variability of discharge between different catchments within a landscape, instead often assuming uniform specific discharge. In this study, spatial and temporal variation in DOC concentrations and exports was studied for 13 nested subcatchments of a boreal catchment located in northern Sweden. The subcatchments were studied during a nine-year observation period (2009-2017). Discharge was monitored at each site and exports were calculated using daily DOC concentrations interpolated from frequent water sampling. Positive correlations between discharge and DOC concentrations were observed for most of the sites. Higher concentrations correlated with increased wetland coverage. Seasonal variations in DOC concentrations were found between subcatchments dominated by forest compared wetlands. The annual mean DOC export ranged between 26 and 108 kg ha-1 yr-1 and correlated positively with wetland coverage (R2 = 0.67, p < 0.001). Spatial variation on both annual and seasonal timescales, could to a large extent be explained by the catchment characteristics using principal component analysis. Forest and wetland coverage, as well as the size and elevation of each subcatchment explained most of the spatial variation of DOC exports. The importance of these catchment characteristics varied with season, where the two-month long spring season contributed between 32 to 52% of the annual DOC export. For annual exports, the proportion exported during spring season was larger for forest-dominated catchments compared to wetland catchments. Comparing export calculated adopting variable discharge to exports adopting uniform specific discharge revealed an average absolute difference of 18% ranging between 5 to 32% for individual subcatchments. DOC exports from wetland-dominated catchments were underestimated while forest-dominated catchments were overestimated. This study clearly demonstrates that adopting uniform specific discharge provides erroneous quantifications of DOC exports by not being able to capture the spatial variability within the system. This highlights the importance of discharge data with high resolution and quality when estimating element fluxes. |
| format | H2 |
| id | RepoSLU14021 |
| institution | Swedish University of Agricultural Sciences |
| language | Inglés swe |
| publishDate | 2018 |
| publishDateSort | 2018 |
| publisher | SLU/Dept. of Forest Ecology and Management |
| publisherStr | SLU/Dept. of Forest Ecology and Management |
| record_format | eprints |
| spelling | RepoSLU140212019-02-27T11:46:27Z Know the flow - spatial and temporal variation of DOC exports and the importance of monitoring site specific discharge Rumslig och tidsmässig variation av DOC export och vikten av områdesspecifika flödesmätningar Larson, Johannes dissolved organic carbon DOC export boreal specific discharge spatiotemporal variation löst organiskt kol DOC export boreal specifik avrinning spatiotemporal variabilitet The export of dissolved organic carbon (DOC) is an important component in both water quality and carbon cycling within boreal catchments. DOC exports are mainly controlled by discharge. Therefore, the resolution and quality of discharge data is essential when quantifying DOC exports as well as for the understanding of its spatial and temporal variation. Although there are many studies quantifying DOC exports, many fail to consider the variability of discharge between different catchments within a landscape, instead often assuming uniform specific discharge. In this study, spatial and temporal variation in DOC concentrations and exports was studied for 13 nested subcatchments of a boreal catchment located in northern Sweden. The subcatchments were studied during a nine-year observation period (2009-2017). Discharge was monitored at each site and exports were calculated using daily DOC concentrations interpolated from frequent water sampling. Positive correlations between discharge and DOC concentrations were observed for most of the sites. Higher concentrations correlated with increased wetland coverage. Seasonal variations in DOC concentrations were found between subcatchments dominated by forest compared wetlands. The annual mean DOC export ranged between 26 and 108 kg ha-1 yr-1 and correlated positively with wetland coverage (R2 = 0.67, p < 0.001). Spatial variation on both annual and seasonal timescales, could to a large extent be explained by the catchment characteristics using principal component analysis. Forest and wetland coverage, as well as the size and elevation of each subcatchment explained most of the spatial variation of DOC exports. The importance of these catchment characteristics varied with season, where the two-month long spring season contributed between 32 to 52% of the annual DOC export. For annual exports, the proportion exported during spring season was larger for forest-dominated catchments compared to wetland catchments. Comparing export calculated adopting variable discharge to exports adopting uniform specific discharge revealed an average absolute difference of 18% ranging between 5 to 32% for individual subcatchments. DOC exports from wetland-dominated catchments were underestimated while forest-dominated catchments were overestimated. This study clearly demonstrates that adopting uniform specific discharge provides erroneous quantifications of DOC exports by not being able to capture the spatial variability within the system. This highlights the importance of discharge data with high resolution and quality when estimating element fluxes. Exporten av löst organiskt kol (DOC) är en viktig komponent för både vattenkvalitet och kolcykeln i boreala avrinningsområden. Exporten av DOC är till största delen kontrollerad av flöde. Därför är flödesdata av hög kvalitet och upplösning essentiell vid kvantifiering av DOC export och dess tidsmässiga och rumsliga variation. Även om det finns många studier som kvantifierar exporten av DOC, är det få som tar hänsyn till den specifika avrinningens variation inom landskapet genom antagandet av likformig specifik avrinning. I denna studie, studeras den rumsliga och tidsmässiga variationen av koncentrationer och exporter av DOC. Studien omfattar 13 delavrinningsområden i ett borealt landskap i norra Sverige under en nioårsperiod (2009–2017). Flödesmätningar utfördes vid varje avrinningsområde. Exporter beräknades med dagliga koncentrationer framtagna genom linjär interpolering mellan frekventa vattenprovtagningar. DOC koncentrationer varierade med av flöde. Höga koncentrationer korrelerade med ökad andel våtmark. Årstidsvariation av koncentrationer skiljde sig mellan delavrinningsområden dominerade av våtmark jämfört med skog. Den genomsnittliga årliga exporten av DOC var mellan 26-108 kg ha-1 år-1 och korrelerade positivt med andelen vårmark (R2 = 0.67, p < 0.001). Rumslig variation för exporter under år och årstider kunde till stor del förklaras av avrinningsområdens karaktär. Andelen skogsmark och våtmark, samt storlek och höjd över havet korrelerade med den rumsliga variationen av DOC export. Betydelsen av landskapsvariablerna varierade med årstiderna. Den två månader långa vårsäsongen bidrog mellan 32% och 52% av den årliga DOC exporten. Andelen av den årliga exporten under våren var större för avrinningsområden med hög andel skogsmark jämfört med våtmark. Export beräknad med flödesdata från varje område jämfört med att använda samma flödesdata för samtliga områden resulterade i en absolut skillnad på 18%. För enskilda avrinningsområden varierade skillnaden mellan 5% och 32%. DOC exporten från våtmarker underskattades medan export från skogsmarker överskattades vid användandet av samma flödesdata för alla områden. Denna studie demonstrerar tydligt att användandet av samma flödesdata för samtliga avrinningsområden är problematiskt vid beräknande av DOC export. Metoden gör det inte möjligt att fullt ut fånga den rumsliga variationen i landskapet. Denna studie belyser därmed vikten av flödesdata med hög upplösning och kvalitet vid beräknande av export. SLU/Dept. of Forest Ecology and Management 2018 H2 eng swe https://stud.epsilon.slu.se/14021/ |
| spellingShingle | dissolved organic carbon DOC export boreal specific discharge spatiotemporal variation löst organiskt kol DOC export boreal specifik avrinning spatiotemporal variabilitet Larson, Johannes Know the flow - spatial and temporal variation of DOC exports and the importance of monitoring site specific discharge |
| title | Know the flow - spatial and temporal variation of DOC exports and the importance of monitoring site specific discharge |
| title_full | Know the flow - spatial and temporal variation of DOC exports and the importance of monitoring site specific discharge |
| title_fullStr | Know the flow - spatial and temporal variation of DOC exports and the importance of monitoring site specific discharge |
| title_full_unstemmed | Know the flow - spatial and temporal variation of DOC exports and the importance of monitoring site specific discharge |
| title_short | Know the flow - spatial and temporal variation of DOC exports and the importance of monitoring site specific discharge |
| title_sort | know the flow - spatial and temporal variation of doc exports and the importance of monitoring site specific discharge |
| topic | dissolved organic carbon DOC export boreal specific discharge spatiotemporal variation löst organiskt kol DOC export boreal specifik avrinning spatiotemporal variabilitet |