Forest soil characteristic in Latvia according results of the demonstration project BioSoil | Latvijas meža augšņu īpašību raksturojums demonstrācijas projekta BioSoil rezultātu skatījumā

The first EC scale forest soil inventory was implemented in the late 1990s within the ICP Forest Initiative. One of its tasks was to obtain basic information about the soil properties, which determine the resistance against air pollution. Because of no harmonized methodology, the results were only partially useful for the initial purpose. The European Parliament and Council Directive No. 2152/2003 on monitoring of forests and environmental interactions Forest Focus concentrates not only on forest protection against air pollution and forest fires, but also on the areas like soil research and biodiversity assessment. To close out this gap the European Commission supported launching in 2004 a joint international demonstration project BioSoil, which was aimed to provide a harmonized soil and biodiversity studies of the EU Member States. The major project objective regarding the soils was to obtain statistically reliable information about the forest soil properties, which is necessary to deal with a number of environmental issues, like acidification and or eutrophication, dynamics of the carbon content of soil, climate change, etc.; to develop standardized and harmonized soil monitoring methodology (ICP Forests Guides and other guidance); to improve quality of the existing European forest soil database; and to identify and explain as far as possible temporal changes in forest soils. Statistical inventory of forest soils involved sampling forest soils from 0 to 80 cm deep, including the humus (O) horizon. In Latvia, the BioSoil project involved 95 ICP Forests monitoring plots of Level 1, distributed across the country in a regular 16 x 16 km grid. The soil samples for composite sample analyses were taken from 1 m deep pits (8 per sample plot). As the ICP Forests soil sampling method provides, the composite samples were taken from Horizon O (if present), 0...10 cm, 10...20 cm, 20...40 cm and 40...80 cm deep. Two sets of composite samples were collected in each plot – one set of certain volume (24 x 100 cm3 from each layer from 0...80 cm deep, and 24 samples of certain area (100 cm2) from the humus layer for bulk density and texture analyses, and another set for chemical analyses. Soil samples were prepared for analyses according to LVS ISO 11464 Standard. Fine earth fraction of soil (Ø is less than 2 mm) was used for chemical and texture analyses according to LVS ISO 11464, 2005. For composite samples the following parameters were determined: texture according to LVS ISO 11277, 2000; pH in water extraction according to LVS ISO 10390, 2002; carbonate according to LVS ISO 10693: 1995, 1999, total carbon (C) according to LECO, 1987 and calculated organic carbon (Corg.); total nitrogen (Ntot.) according to LVS ISO 11261, 2002. All the results were validated according to the validity tables provided by the ICP Forests. Calculations of the carbon stock of forest soils were made separately for the organic soils and mineral soils, using average thickness of litter layer, density and organic carbon content. This article deals with the results of analyses for soil acidity, texture, organic (Corg.) and total nitrogen (Ntot). Within the scope of this study signifi cant differences were found in pH H2O, texture and concentration of nitrogen in O horizon, as well as in the organic and mineral soil layers in forest stands with different dominant species. There is a correlation between dominant specie, site index, and content of clay particles in soil. Spruce (Picea abies (L.) H.Karst.) and pine (Pinus sylvestris L.) grows better in loamy soils (clay content 7...10%). Horizon O of forest soils is moderately to strongly acidic. The most acidic conditions were found in pine (Pinus sylvestris L.) stands. Content of total nitrogen in Horizon O depends on species composition of the stand as well as on the origin of soil material (organic or mineral). The highest content of total nitrogen was found in spruce (Picea abies (L.) H.Karst.) and pine stands in Horizon O, which overlays organic soil. In Latvia the content of organic carbon in soil (0...80 cm deep) and Horizon O in forest soils is 754 +- 185 mill. t. This means that organic carbon stock in soil is considerably higher than in living biomass and therefore soil is a highly important element of natural carbon sequestration and as such it should be monitored and protected at least with the same care as the living forest biomass.