Net primary production and decomposition in oligotrophic mires in - - PowerPoint PPT Presentation

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Jun 25, 2023 439 likes •594 views

Net primary production and decomposition in oligotrophic mires in the Southern Taiga of Western Siberia -

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Net primary production and decomposition in oligotrophic mires in the Southern Taiga of Western Siberia Продукция и разложение растений в олиготрофных болотах южно- таежной подзоны Западной Сибири

Golovatskaya E.A. Institute of monitoring of climatic and ecological systems SB RAS golovatskaya@imces.ru

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Peatlands covering only 3% of Earth’s land area, they hold the equivalent

f half of the carbon that is in the atmosphere ac CO2.

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Most peatlands are located in the boreal and subarctic Northern Hemisphere, where the climate is warming faster than anywhere else on the Earth.

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The carbon accumulation rate of peatlands is determined by the balance between the amount of carbon sequestered in the net primary production (NPP) and the amount of carbon lost to the atmosphere by decomposition

f dead organic matter.

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Rates of net primary production in peatlands are generally small, as are rates of net ecosystem exchange of CO2 and soil respiration.

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Thus, the accumulation of organic matter in peatlands is generally ascribed to slow rates of decomposition associated with cool temperatures, anoxic conditions, and functionally limited decomposer communities.

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Peatland of West Siberia Total area

592 440 km2,

Total weight of peat

148 Gt

Peat carbon pool

70 Gt C

Sheng, Y., L. C. Smith, G. M. MacDonald, K. V. Kremenetski, K. E. Frey, A.A. Velichko, M. Lee, D. W. Beilman, and P. Dubinin (2004), A high-resolution GIS-based inventory of the west Siberian peat carbon pool // Global Biogeochem. Cycles, 18, GB3004, doi:10.1029/2003GB002190.

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Site description

The study area is located between the Iksa and Bakchar rivers (56o58`N 82o36`E) at the territory of the Bakcharskoe bog (bog area 1400 km2) and is characterized by regular changes of oligotrophic bog ecosystems: pine– shrub–sphagnum community, a similar community with oppressed (low) tree stand, ridge-hollow complex and sedge– sphagnum open bog.

Field station Field station “ “Vasuganie Vasuganie” ” 160 km 160 km

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The observation has been conducted on the oligotrophic and eutrophic mires at the field station “Vasuganje” (IMCES SB RAS, Tomsk region, Western Siberia). Vegetation at the observation points are: Fen sedge-sphagnum ecosystem Ryam – pine-shrub-sphagnum ecosystem

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Methods

Biological productivity: Net primary productivity and vegetation storages was measured by clipping method. The aboveground biomass was measured by clipping 50x50 cm quadrates. The belowground biomass was determined by the excavation of 10 x 10 cm pits at each quadrate. Decomposition of plants was studied using the litterbag technique. Decomposition rates were calculated from mass looses for different vegetation species.

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Net Primary Production

100 200 300 400 500 600 700 Pine-shrub-sphagnum ryam Sedge-sphagnum fen NPP, g/m2year grasses shrubs moss roots

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Net primary production (NPP) is an indicator of carbon accumulation in the form of vegetation matter.

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NPP for low ryam and sedge-sphagnum fen are equal to 587, and 571 g m−2 yr−1. The main part of production at studied ecosystems is consist of by roots of herbs and shrubs (47–51%) and sphagnum mosses (30– 31%). Shrubs give 17 % to NPP at low ryam. The contribution of herbs is more significant at sedge-sphagnum fen (16 %) but the proportion of shrubs is about 7%.

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C,% N,% C/N A,% Mosses 39,7 0,5 77,7 2,0 Grasses 43,2 1,4 33,4 4,2 Shrubs (leaves) 49,4 1,2 41,2 2,6

Initial Carbon (C), Nitrogen(N) and Ash (A) concentrations in plant matter

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Mass loss of plant matter in pine- shrub-sphagnum community

5 10 15 20 25 30 35 40 45 Rubus chamaemorus Andromeda polifolia Ledum palustre Chamaedaphne calyculata

Sph. fuscum

Mass loss, %

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Mass loss of plant matter in sedge-sphagnum fen

10 20 30 40 50 60 70 80 Menyanthes trifoliate Carex rostrata Eriophorum vaginatum Scheuchzeria palustris Oxicoccus palustris Sph. Magellanicum Mass loss, %

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Changes in concentration of carbon in plant matter

5 10 15 20 25 30 35 40 45

Rubus chamaemorus Andromeda polifolia Ledum palustre Chamaedaphne calyculata

Sph. fuscum

Carbon loss (% of initial C)

10 20 30 40 50 60 70 Menyanthes trifoliate Carex rostrata Eriophorum vaginatum Scheuchzeria palustris Oxicoccus palustris Sph. Magellanicum Carbon loss (% of initial C)

Pine-shrub-sphagnum ryam Sedge-sphagnum fen Pine-shrub-sphagnum ryam Sedge-sphagnum fen

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Carbon balance of peatland ecosystems can be estimated using data on vegetation NPP and decomposition rates. Studied ecosystems have positive carbon balance.

30 60 90 120 150 180 Grasses Shrubs Moss NPP, g/m2 year; Mass remaining, g NPP Mass remaining 30 60 90 120 150 180 Grasses Shrubs Moss NPP, g/m2 year; Mass remaining, g NPP Mass remaining

During the first year decomposes only 13% from the annual productivity at low ryam, and 25% at sedge-sphagnum fen. Carbon accumulation in a form of peat is higher than carbon removing with carbon dioxide emission at plant remains decomposition. Pine-shrub-sphagnum ryam Sedge-sphagnum fen

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Conclusion

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Despite the differences in composition of the vegetation the average values

f NPP are similar at all oligotrophic ecosystems.

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The rates of decomposition of the plant matter depends on species of plants.

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The main peat-forming species are sphagnum moss.

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Carbon accumulation in a form of peat is higher than carbon removing with carbon dioxide emission at plant remains decomposition.

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Thank you for the attention!

Western Siberia Bakchar key area Bakcharskoe bog