CARBON BALANCE IN FOREST MINERAL SOILS IN LATVIA MODELLED WITH YASSO07 SOIL CARBON MODEL

Yasso07 soil carbon model was used to estimate soil carbon balance in dry forest site types (6 site types in total) in Latvia and the results were compared with data from Biosoil2012 soil surveys. Litter input, chemical quality and climatic data are required to run the model. Three different scenarios were used for climate data input - steady climate, climate change + 0.025 degrees C annually and climate change + 0.05 degrees C annually. Forest mineral soil is a carbon sink for the whole modelled period - the years of 1990 - 2030. Under steady climate, the average carbon removal is 0.6 t CO2 ha(-1) yr(-1), under climate change (+ 0.025 degrees C) scenario 0.4 t CO2 ha(-1) yr(-1), but under climate change (+ 0.05 degrees C) scenario 0.3 t CO2 ha(-1) yr(-1). CO2 removal at the beginning of the period (1990) was 0.35 - 0.38 t CO2 ha(-1) yr(-1). Carbon stock modelled with Yasso07 is lower than estimated in Biosoil2012 soil surveys. Differences between modelled and Biosoil2012 results vary from 2 t C ha(-1) in the poorest and 41 t CO2 ha(-1) in the third poorest site type. Carbon stock modelled with Yasso07 increases from the poorest to the most fertile site type while Biosoil2012 shows an increase from the poorest to the third poorest, and a decrease from the third poorest to the most fertile site type. Underestimation and different trends between Yasso07 and measured carbon stock may be explained by inappropriate equations and models used to estimate non-woody biomass. It is necessary to improve accuracy of input data for non-woody biomass by elaborating national equations and models in order to include Yasso07 in the national GHG inventory.