We calculated the carbon loss (mineralization plus sedimentation) and net CO2 escape to the atmosphere for 79 536 lakes and total running water in 21 major Scandinavian catchments (size range 437–48 263 km2). Between 30% and 80% of the total organic carbon that entered the freshwater ecosystems was lost in lakes. Mineralization in lakes and subsequent CO2 emission to the atmosphere was by far the most important carbon loss process. The withdrawal capacity of lakes on the catchment scale was closely correlated to the mean residence time of surface water in the catchment, and to some extent to the annual mean temperature represented by latitude. This result implies that variation of the hydrology can be a more important determinant of CO2 emission from lakes than temperature fluctuations. Mineralization of terrestrially derived organic carbon in lakes is an important regulator of organic carbon export to the sea and may affect the net exchange of CO2 between the atmosphere and the boreal landscape.
[1] The Krycklan Catchment Study (KCS) provides a unique field infrastructure for hillslope to landscape-scale research on short-and long-term ecosystem dynamics in boreal landscapes. The site is designed for process-based research assessing the role of external drivers including forest management, climate change, and long-range pollutant transport on forests, mires, soils, streams, lakes, and groundwater. The overarching objectives of KCS are to (1) provide a state-of-the-art infrastructure for experimental and hypothesis-driven research, (2) maintain a collection of high-quality, long-term climatic, biogeochemical, hydrological, and environmental data, and (3) support the development of models and guidelines for research, policy, and management.
Evasion of gaseous carbon (C) from streams is often poorly quantified in landscape C budgets. Even though the potential importance of the capillary network of streams as C conduits across the land-water-atmosphere interfaces is sometimes mentioned, low-order streams are often left out of budget estimates due to being poorly characterized in terms of gas exchange and even areal surface coverage. We show that evasion of C is greater than all the total dissolved C (both organic and inorganic) exported downstream in the waters of a boreal landscape. In this study evasion of carbon dioxide (CO2 ) from running waters within a 67 km(2) boreal catchment was studied. During a 4 year period (2006-2009) 13 streams were sampled on 104 different occasions for dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). From a locally determined model of gas exchange properties, we estimated the daily CO2 evasion with a high-resolution (5 × 5 m) grid-based stream evasion model comprising the entire ~100 km stream network. Despite the low areal coverage of stream surface, the evasion of CO2 from the stream network constituted 53% (5.0 (±1.8) g C m(-2) yr(-1) ) of the entire stream C flux (9.6 (±2.4) g C m(-2) yr(-1) ) (lateral as DIC, DOC, and vertical as CO2 ). In addition, 72% of the total CO2 loss took place already in the first- and second-order streams. This study demonstrates the importance of including CO2 evasion from low-order boreal streams into landscape C budgets as it more than doubled the magnitude of the aquatic conduit for C from this landscape. Neglecting this term will consequently result in an overestimation of the terrestrial C sink strength in the boreal landscape.
The purpose of this paper is, first, to describe the organization, sampling procedures, availability of samples/database, ethical considerations, and quality control program of the Northern Sweden Health and Disease Study Cohort. Secondly, some examples are given of studies on cardiovascular disease and diabetes with a focus on the biomarker programme. The cohort has been positioned as a national and international resource for scientific research.
[1] The regulation of the spatial and seasonal variation in terrestrial dissolved organic carbon (DOC) exports was studied in a 68 km 2 boreal stream system in northern Sweden. A total of 1213 DOC samples were collected in 15 subcatchments over a 3 year period (2003)(2004)(2005). The mean annual DOC exports from the 15 subcatchments (0.03-21.72 km 2 ) ranged from 14.8 to 99.1 kg ha À1 yr À1 . Many catchment characteristics determined the spatial variation in DOC exports. The relative importance of the different catchment characteristics varied greatly between seasons because of differing hydrological conditions. During winter base flow the spatial variation was linked to patterns in wetland coverage. During snowmelt in spring the spatial variation was connected to characteristics describing size and location, i.e., median stream size, silty sediment distribution, stream order, altitude, and proportion of catchment above highest postglacial coastline (HC). During the snow-free season the spatial variation in DOC exports was regulated by the amount of wetlands and forests, particularly forests made up of Norway spruce (Picea abies). Median stream size also influenced the exports during this season. A striking result in this study was the effect of size implying that small headwaters may be the largest contributor to the terrestrial DOC export, per unit area.
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