Reviews and syntheses: Greenhouse gas exchange data from drained organic forest soils – a review of current approaches and recommendations for future research

Abstract

Abstract. Drained organic forest soils in boreal and temperate climate zones are believed to be significant sources of the greenhouse gases (GHGs) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), but the annual fluxes are still highly uncertain. Drained organic soils exemplify systems where many studies are still carried out with relatively small resources, several methodologies and manually operated systems, which further involve different options for the detailed design of the measurement and data analysis protocols for deriving the annual flux. It would be beneficial to set certain guidelines for how to measure and report the data, so that data from individual studies could also be used in synthesis work based on data collation and modelling. Such synthesis work is necessary for deciphering general patterns and trends related to, e.g., site types, climate, and management, and the development of corresponding emission factors, i.e. estimates of the net annual soil GHG emission and removal, which can be used in GHG inventories. Development of specific emission factors also sets prerequisites for the background or environmental data to be reported in individual studies. We argue that wide applicability greatly increases the value of individual studies. An overall objective of this paper is to support future monitoring campaigns in obtaining high-value data. We analysed peer-reviewed publications presenting CO2, CH4 and N2O flux data for drained organic forest soils in boreal and temperate climate zones, focusing on data that have been used, or have the potential to be used, for estimating net annual soil GHG emissions and removals. We evaluated the methods used in data collection and identified major gaps in background or environmental data. Based on these, we formulated recommendations for future research.

Ideas and perspectives: patterns of soil CO<sub>2</sub>, CH<sub>4</sub>, and N<sub>2</sub>O fluxes along an altitudinal gradient – a pilot study from an Ecuadorian neotropical montane forest

“…To further improve our understanding of the role of tropical forest ecosystems in the global GHG balance, environmental gradients (altitudinal, latitudinal, etc. ) can offer great opportunities to study the influence of abiotic factors on biogeochemical processes under field conditions (Bauters et al, 2017;Jobbágy and Jackson, 2000;Kahmen et al, 2011;Laughlin and Abella, 2007), which complements the knowledge on short-term responses from experimental approaches. In the case of altitudinal gradients, these responses are driven by abiotic variables that covary with elevation, which, amongst others, creates a distinctly strong climate gradient over a short spatial distance (Bubb et al, 2004;Killeen et al, 2007;Körner, 2007;Myers et al, 2000).…”

Impact of Litter Turnover on Carbon Cycling in Forests With Drained and Naturally Wet Nutrient-Rich Organic Soils in Latvia

“…Organic soils store large amounts of carbon (C) and can be both sinks and sources of greenhouse gases (GHG), depending on land management practice (Turunen et al, 2002;Yu et al, 2010). Drainage of soils lowers the emissions of methane (CH4), but simultaneously it increases those of carbon dioxide (CO2) and nitrous oxide (N₂O) (Jauhiainen et al 2019). In many European countries drained peatlands are one of the largest sources of GHG emissions from agriculture and forestry (Drösler et al, 2008;Tubiello et al, 2016,).…”

Estimation of litter input in hemi-boreal forests with drained organic soils for improvement of GHG inventories

“…Worldwide, organic soils have large carbon (C) and nitrogen (N) stores, and they can both remove and emit greenhouse gases (GHGs), thus contributing to the atmospheric GHG concentrations (Jauhiainen et al 2019, Ziche et al 2019. Organic soils are formed from partially decayed plant remains in anaerobic conditions through generally slow accumulation and compaction below the high water-table (WT) in peat-forming ecosystems (Moore 1989, Jauhiainen et al 2019. Organic soil layer accumulation depends on the equilibrium between production and decay of organic matter that is highly sensitive to major climate change and management impacts (Joosten 2015).…”

“…In the Nordic and Baltic countries, peat-forming ecosystems have been widely converted into forest land (Paavilainen andPäivinen 1995, Jauhiainen et al 2019). These land use changes commonly involve drainage by ditching to promote forest growth, but it changes soil conditions enhancing mineralization of organic matter under aerobic conditions and results in activation of soil C and N stores (Jauhiainen et al 2019). Drainage diminishes the emission of methane (CH 4 ), but simultaneously increases emissions of carbon dioxide (CO 2 ) and nitrous oxide (N 2 O) from soil.…”

“…Within the National GHG Inventory reports under the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol, anthropogenic CO 2 , CH 4 and N 2 O emissions from organic soils in forest land are reported under the Land use, Land use change and Forestry (LULUCF) sector (IPCC 2006, Tiemeyer et al 2020. Although organic soils have a large impact on the total GHG budget in the LULUCF sector (Lazdiņš and Lupiķis 2019) and there are growing international requirements for improved accuracy of estimates of CO 2 removals and GHG emissions from organic soils (IPCC 2014), annual GHG emission factors (EFs) from organic soils are still characterized by high uncertainty rate (Jauhiainen et al 2019) and significant differences between regions even in the same climate zone (Lazdiņš and Lupiķis 2019).…”