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WP 4b. Dissolved carbon in terrestrial and aquatic systems of permafrost-affected terrains of Central Siberian Plateau (DOC)

Team:

Prokushkin A.S. (PI), Tokareva I.V., Klimchenko A.V., Titov S.V., Kolosov R.V., Rodovikov S.A.
Links: Korets M.A., Rubtsov A.V. (GIS and RS)

Background:

Arctic and boreal regions have undergone significant changes during the last few decades, including northward shifts of vegetation, declining permafrost, increasing ALT and soil temperatures, shortened fire return interval and increased river discharge. The fluxes of dissolved C within boreal and arctic watersheds and C linkages between terrestrial and aquatic systems are important aspects of the carbon cycle of high latitude biomes and will be affected by the projected global change. One of the likely changes, an input of terrigenous organic matter to surface runoff, will cause significant deterioration of river water quality and represent the main concern of water pollution management in permafrost regions of Siberia. Thus, predictive tools to quantify changes in the amounts and chemical properties of river natural organic matter are needed for implementation of effective water treatment technologies.
Thus, there is strong need to identify key controls on watershed runoff and the hydrological losses of C in particulate and dissolved state from different scale watersheds varying in the extent of continuous permafrost and fire disturbance to analyze the consequences of landscape transformations induced by climate change. We will analyze the effect of geomorphic, climatic, vegetation and soil properties of watersheds on the spatial and temporal variation of discharge and C species concentrations for parameterization of key controls and modeling of carbon export from permafrost-affected landscapes. Comparative analysis of the selected stands and entire basins will provide insight into likely consequences of permafrost degradation, vegetation shifts and overall terrestrial C changes induced by warming in high latitudes of Siberia.

Aim:

Workpackage studies address to characterize quantitatively and quantitatively the dissolved carbon and its spatio-temporal variations in forested basins underlain by permafrost in terms of its production, retention, transformation and release to streams/rivers. Specific target is the analysis of basin characteristics such as climate, soil, vegetation and fire disturbances, which impose major controls on terrestrial C production and its release to river network.

Geography and Methodology of research:

Location

Studies are based on facilities of Tura site and cover ca. 40% of Central Siberian Plateau. There are three scales of studies of C concentrations, composition and fluxes:
Stand level studies

• C in solutes migrating downward in soils of contrasting slopes, different stages of post-fire forest succession (0–170 years after a fire)

Small-to-medium size catchments (3–220 km²), n=18

• C in streams, draining watersheds of different in size and fire history (0–120 years after a fire)

Large size catchments (5,000–170,000 km²), n=8

• C in rivers, draining watersheds with different climate, permafrost and vegetation

Fig. 1. Three scales of studies of dissolved C concentrations, composition and fluxes within Central Siberian Plateau: large, small-to-medium size catchment and stand. Red star represent Tura station, yellow circles are experimental plots in stands of different regeneration stages after fire disturbance.

Sampling and measurements:

In situ measurements:
Terrestrial ecosystems: stand inventory, monitoring of air temperature and RH, soil moisture and temperature, active layer thickness;
Stream/river: water level, temperature, pH, O₂ and SpCond.

Water sampling frequency:

Five to seven days during frost-free season (soil solutions, streams and 3 large rivers)
Monthly under ice (3 larger rivers: Tembenchi, Kochechum and Nizhnyaya Tunguska)
Rest large rivers (n=5, Taimura, Vivi, Yambukan, Nidym, Podkamennaya Tunguska) are sampled at major hydrologic phases – snowmelt, summer lowflow, winter lowflow)

Sample type and treatment:

Dissolved matter
- Filtration depending on task through 0.22 μm and/or GFF filters
- Dialysis (1 kDa membrane)
- Fixation by ultrapure nitric acid (for cations)
River suspended matter
-Sedimentation/filtration

Subsamples for specific measurements:

• anions/DIC/DOC/UV-Vis spectra/Fluorescence
• water stable isotopes
• carbon and nitrogen stable isotopes in DOM/POM
• cations
• river suspended matter : element composition, stable isotopes
• freeze dried matter for biochemical characterization of OM (dissolved lignin, BC etc.)

Research plan for the field campaign of 2014:

1. Ecosystem inventories based on catena approach and class-specific sites are planned to validate earlier produced local land cover map (Tura site) and specifically create a detailed map for stream basins subjected to fire disturbance in 2013, 2009 and 1993.
Inventory will include stand census, assessment of OM stocks in vegetation and soils, measurements of temperature and depth of active layer.
2. Water sampling of soil solutions in two earlier established plots in contrasting mature larch stands, 18 streams of different size and fire history, 7 rivers.
3. Installation of suction lysimeters in soils of larch stands disturbed by fires in 2013, 2009 and 1993.