Carbon Budget of Undrained and Drained Nutrient-Rich Organic Forest Soil

Abstract

The impact of the moisture regime on the carbon budget of organic soils with different nutrient statuses has not been fully studied in hemiboreal forests thus far. This study evaluated soil carbon (C) stock changes in forests with drained and undrained nutrient-rich organic soils by estimating C loss through respiration and C input through the litter. The study sites included forest stands dominated by Norway spruce (Picea abies), silver birch (Betula pendula), black alder (Alnus glutinosa), and clear-cuts. Soil respiration was measured using the chamber method, and to estimate the soil C input by litter—the biomass and the C content of the foliar litter, ground vegetation, and fine-root production were measured. The soil in forest stands acted as a C sink. The carbon dioxide (CO2) removal rates of 0.4 ± 0.4 t C ha−1 year−1 and 0.1 ± 0.4 t C ha−1 year−1 were estimated for undrained and drained soil in forest stands, respectively. The soil in the clear-cuts acted as a CO2 source, and the annual emissions ranged from 0.4 ± 0.4 t C ha−1 year−1 in undrained to 0.9 ± 0.7 t C ha−1 year−1 in drained conditions. The reason for the soil in clear-cuts being a C source was increased C loss by respiration and reduced soil C input by litter. Furthermore, the mean soil C input by ground vegetation biomass in the clear-cuts was considerably higher than in the forest stands, which did not compensate for the increase in soil respiration and the absence of C input by foliar litter and the fine roots of trees. The results of the study on annual soil C stock changes can be used as an emission factor in national greenhouse gas inventories of forest land in the hemiboreal zone.

Greenhouse Gas Fluxes and Carbon Losses From Soil in Deciduous Forests With Naturally Wet and Drained Mineral Soils

“…According to recent studies implemented in Latvia HR values in nutrient rich birch and spruce stands equals to 13.48 ± 1.63 tons CO2 ha -1 yr -1 in drained and to 12.87 ± 1.76 tons CO2 ha -1 yr -1 (Butlers, Spalva, et al, 2022). This is about twice more than the HR values in our study and close to the soil carbon input values reported in forest lands by other studies (Butlers, Lazdiņš, et al, 2022). Thus, the assumption applied in the national GHG inventory that drained and mineral soils are not a source of CO2 may lead to underestimation of the emissions.…”

“…Organic soils is significant source of GHG emissions; drainage can increase CO2 emissions, but wet or rewetted organic soils produces more CH4 emissions due to different patterns of decomposition of organic matter (Chapman & Thurlow, 1996). Recent studies in Latvia demonstrated that drainage of organic nutrient-rich forest soils is increasing CO2 emissions from soil; however, negative effect due to the increase of emissions of CH4 from soil and reduction of carbon stock in the living biomass is exceeding this effect, actually turning forest drainage into climate friendly measure, if GHG emissions from pristine wet organic soils in forest lands are accounted (Butlers, Lazdiņš, et al, 2022;Butlers et al, 2023;Samariks et al, 2023;Vanags-Duka et al, 2022).…”

Climate Smart Management Alternatives for Management of Organic Soils Under Agricultural Use

“…Soil GHG emissions are calculated using factors provided in Table 5. They are based on researches implemented in Latvia (Butlers et al, 2022(Butlers et al, , 2023Licite & Lupikis, 2020). Emission factors for the forest lands are applied directly after afforestation, which might lead to overestimation of the emissions during the early development years.…”

Active afforestation of drained peatlands is not a viable option under the EU Nature Restoration Law

“…Again, a full GHG balance can only be assessed when CO 2 exchange is included as well. Butlers et al ( 2022a ) claimed that CO 2 emissions from ‘naturally wet’, nutrient-rich organic forest soils can be larger than those from drained sites but they did not include photosynthesis by ground vegetation in their study and did not quantify CO 2 release from the tree roots, thus, failing to describe net-CO 2 exchange appropriately. Without inclusion of the contribution of trees and without a full life cycle assessment, no sensible conclusions about the climate effect of wet vs. drained forested peatlands can be drawn.…”

“…Butlers et al ( 2022a ) attempted to obtain a better understanding of the whole GHG balance by looking at different stages of the harvest cycle and even including the input of litter. Again, the same error-prone methods were used.…”