Phytomass carbon pools of Koivulambisuo mire system (South Karelia)
Authors: Kutenkov S. A. , Kuznetsov O. L. , Kantserova L. V. , Mironov V. L. , Ignashov P. A. , Talbonen E. L. , Vasyuta V. S. 
Published: September 2024

Koivulambisuo mire system (61,80º N, 33,56º E, middle taiga subzone) has a complex structure of vegetation cover, includes south karelian variant of aapa mires, raised bogs, transitional herb-sphagnum fens and forested sites of different trophic levels.The study was carried out within the framework of the National system for monitoring carbon pools and greenhouse gas fluxes in Russia. Phytomass and carbon pools were determined for three types of mire sites: aapa, ridge-hollow sphagnum bog and oligotrophic pine-dwarf shrub-cotton grass-sphagnum.
On each type of mire sites, 3 sample plots 50x50 m in size were set up, with 8–12 sampling points on each. Tree stand estimated by total count and basic measurements of all standing trees on plots, production of needles and branches by model tree method. The above-ground vascular plants phytomass material was collected by the cutting method, mosses and underground phytomass by monoliths method, the production of sphagnum mosses by annual increment method.
Aapa mire extremely poorly afforested, to the least extent among the studied sites, due to strong watering and poor development of strings. The total carbon pool in a forest stand is only 0.01 tC/ha. The carbon pool in the above-ground phytomass of aapa complexes is also minimal – 2.56 tC/ha. It is mainly provided by sphagnum mosses, while herbs and shrubs contain half as much carbon in total. Living underground phytomass deposits 21.56 tC/ha (89% of the total phytomass). Such a high carbon sequestration by living underground plant organs is a feature of aapa sites and is associated with favorable regime of water movement. Some overestimation is also possible due to the difficulty of separating living and dead tightly intertwined roots. The mortmass of a 40 cm surface layer of peat soil contains 38.71 tC/ha, most of it in the sphagnum remains. The annual ground cover production of aapa is minimal: 1.55 tC/ha, which is caused by the development of extensive flarks with sparse vegetation cover. Unlike other sites, the role of vascular plants is higher here (0.68 tC/ha) due to the predominance of herbaceous plants in cover.
The afforestation degree of ridge-hollow bogs varies; the living forest stand of the most afforested sites is contains 0.31 tC/ha, while in the other two, more watered sites, the pool is less than 0.02 tC/ha. The average carbon stock in a tree stand is 0.11 tC/ha. The carbon pool in the ground cover of the ridge-hollow bogs is maximum among the studied mire sites (4.25 tC/ha), the main share in it is sphagnum mosses (3.52 tC/ha), while grasses and shrubs 0.73 tC/ha. Living underground phytomass deposits 8.62 tC/ha (66% of the total phytomass).The mortmass of a 40 cm surface layer of peat soil contains, on average, 61.77 tC/ha, most of it in the sphagnum remains. In cotton grass-sphagnum hollows the stock reaches 80.09 tC/ha due to dense cotton grass tussocks. The above-ground vascular plants annual production is 0.48 tC/ha (the minimum among the studied mire site types) and 1.56 tC/ha by mosses.
Pine-dwarf shrub-cotton grass-sphagnum plots have the most developed forest stands among the studied mire sites. The average tree height here is 1-2 m, individual trees reach a 5-6 m. The carbon pool in the living tree stand is 2.92 tC/ha, in dead wood – 1.66 tC/ha. Accordingly, the forest stand contribution to the total living phytomass carbon stock is maximum here and equal to moss stock. In the ground cover is deposited 4.46 tC/ha, besides sphagnum mosses (2.9 tC/ha), a significant stock in dwarf shrubs (1.11 tC/ha). Living underground phytomass deposits 9.04 tC/ha (56% of the total phytomass). The mortmass of a 40 cm surface layer of peat soil contains 63.43 tC/ha. The total contribution of pine needles and branches to the annual production is 0.04 tC/ha. The above-ground phytomass here also demonstrates the maximum annual production – 2.21 tC/ha per year, mainly provided by sphagnum mosses (1.64 tC/ha).
In general, the main living phytomass carbon pools of mire sites are concentrated in the underground parts of vascular plants. The ground cover main stock is in sphagnum mosses. Significant carbon stock in the tree stands only has pine-cotton grass-dwarf shrub-sphagnum sites, where it equal to the carbon stock of mosses. In all types of sites, carbon pool in the mortmass of the upper 40 cm of the deposit are noticeably higher than the total reserves in living phytomass. The main part of the mortmass consists of the sphagnum mosses remains. Mosses are also characterized by the largest primary annual production of carbon.