Evaluation of greenhouse gas emissions and area of organic soils in cropland and grassland in Latvia – integrated National forest inventory data and soil maps approach

G. Petaja*, M. Okmanis, K. Polmanis, J. Stola, G. Spalva and J. Jansons

Latvian State Forest Research Institute “Silava” Rigas street 111, LV–2169 Salaspils, Latvia
*Correspondence: guna.petaja@silava.lv

Abstract:

The aim of the research was to assess distribution of organic soils in farmlands for the time period between 1990 and 2015, as well as to carry out a recalculation of GHG emissions from organic soils in grassland and cropland. We evaluated the area of typical organic soils using digitized soil maps created between 1960s and 1980s there were 183,000 ha of cropland and grassland on organic soils. A selected number of areas on organic soils intersecting with the National forest inventory (NFI) plots were surveyed. We found that 66 ± 10% of surveyed plots still conforms to criteria for organic soils according to Intergovernmental Panel on Climate Change (IPCC) guidelines; in the rest of plots soil organic matter has been mineralized and these areas do not conform to IPCC criteria of organic soils. The following distributionof organic soils was estimated in cropland – 6.3 ± 3.3% in 1990 and 4.1 ± 3.4% in 2015, but in grassland – 11.6 ± 3.6% in 1990 and 7.7 ± 3.9% in 2015. The annual reduction of GHG emissions due to reduction of area of organic soils in cropland in 2015 corresponds to 1,400,000 tonnes CO₂ eq. in comparison to 1990 and in grassland – to 1,100,000 tonnes CO₂ eq. The estimated reduction of the GHG emissions due to conversion of organic soils into mineral soils, comparing the average value in 2005–2009 with the projection for 2021–2030 on average will correspond to 313,000 tonnes CO₂ eq. annually, however LULUCF sector still won’t become a net CO₂ sink according to the GHG inventory data on other land use categories and carbon pools.

Key words:

cropland, GHG emissions, grassland, organic soil

Carbon stock changes in drained arable organic soils in Latvia: results of a pilot study

A. Lupikis, A. Bardule*, A. Lazdins, J. Stola and A. Butlers

Latvian State Forest Research Institute ‘Silava’, 111 Rigas str., LV-2169 Salaspils, Latvia
*Correspondence: arta.bardule@silava.lv

Abstract:

Drained arable organic soils in the most of European countries represent a minor part of the total area of farmlands, but these soils contribute significantly to national greenhouse gas budgets. The aim of the pilot study is to demonstrate methodology for determination of the changes of soil organic carbon stock after drainage of arable land on organic soil by evaluation of subsidence of the land surface from detailed historical pre-drainage topographic maps created during designing of drainage systems and LiDAR. Results of a pilot study show that ground surface level in arable land on organic soil has decreased by 0.8 cm annually after drainage, but soil organic carbon stock has decreased by 4.2 ± 3.3 tonnes C ha-1 yr-1. The results of a study show that pre-drainage topographic maps are suitable for estimation of organic layer subsidence after drainage. The estimated mean CO2 emissions are about 47% less than the default emission factor for drained arable organic soils in boreal and temperate climate zone provided by Intergovernmental Panel on Climate Change Guidelines for National Greenhouse Gas Inventories. The results substantiate the necessity to develop national methodology to estimate emissions from drained organic soils in cropland and grassland.

Key words: