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Mature forest ecosystems are the most considerable reservoir of organic carbon (OC) among terrestrial ecosystems. The effect of soil type on aboveground OC stocks and their annual increases (AI) of overstorey tree, understorey tree and ground vegetation layers in Estonian forest phytocoenoses with mature stands on mineral soils were studied. The study enfolds nine mineral soil groups, which are characterized by their phytocoenoses composition, soil cover properties and tree stands' taxation data. An assemblage of soil and plant cover or plant–soil system is the main focus point in explaining causal and quantitative sides of ecosystems functioning. Surface densities of OC stocks in aboveground phytomass of forests varied significantly in the range of 52–100 Mg OC ha−1. High AI or productivity (4.8–5.5 Mg OC ha−1 year−1) is a characteristic of forest ecosystems formed on leached, eluviated and pseudopodzolic soils. Forest ecosystem ground vegetation, which is an important ecological indicator, fulfils vacant ecological niches with herbs and/or mosses (up to 0.50 Mg OC ha−1). The variation of ecosystem OC stocks and their AI by soil type should be taken into account in regional OC stocks and its annual increase estimations. [ABSTRACT FROM AUTHOR]

The fabric of humus cover (HC) may be very variegated, depending on local pedo-ecological conditions (origin and composition of deposits, topography, moisture regime, soil climate, plant cover composition). This multiplicity can be expressed by the HC types (or humus forms). On natural areas, where the HC is formed as a result of long-term equilibrated mutual influences of soil cover and plant cover, the fabric and properties of the HC may be used as an ecological indicator in the evaluation of the functioning character and intensity of the soil--plant system (or also the whole ecosystem). In Estonia, besides natural areas, the classifications of HCs are also elaborated for arable areas. Regardless of the profound changes in the fabric of the HC occurring with land-use change (from natural land to arable and vice versa), certain inherited properties are sustained in newly formed HCs. In this paper the fabric and properties (thickness, carbon and nitrogen stocks) of the main HC types (19 in total) are analysed and ecological aspects of HC formation are explained. Data on tree layer taxation, agro-chemical parameters of the soil cover, and ground vegetation productivity are presented with the HC types used as the ecological background. The relationships of soil cover with soil and forest site type are analysed against the background of soil matrix tables and ordination net of forest sites, respectively. Comparative analysis of the Estonian HC classification with the European Reference Base for humus forms (ERB) showed a relatively good correspondence of the Estonian classification of HC types with ERB's humus forms. [ABSTRACT FROM AUTHOR]

Abstract: Soil cover, which is one of the most informative and integrative landscape factors, can be used for the analysis of landscape patterns. We studied the spatial autocorrelation (Moran''s I) of raster format soil maps (1:10,000; 10m pixel size) in 35 study areas representing all landscape regions in Estonia. The carbonate concentration of soils, volumetric soil moisture (%) and the depth of the groundwater table were taken into consideration in compiling a scale of contrast of 17 soil groups. We introduce a simple characteristic based on spatial correlograms: a half-value distance lag, h I =0.5—a distance where Moran''s I drops below 0.5. Spatial autocorrelation decreased very rapidly in the case of heights with a very heterogeneous landscape composition, showing low values of h I =0.5 (<100m in all 6 study areas). In uplands and depressions, the spatial autocorrelation also decreased relatively rapidly (h I =0.5 <200m). In most of the plains, coastal lowlands, sea islands and inland paludified lowlands, the values of Moran''s I did decrease slowly with increasing lag, being >200m in all forest and bog areas with complex topographical conditions due to the variety of glacial landforms and peatlands. All of the eight FRAGSTATS landscape metrics studied demonstrated significant correlations with h I =0.5, whereas five of them – Contrast Weighted Edge Density (CWED); Percentage of Like Adjacencies (PLADJ), Edge Density (ED), Patch Density (PD) and Mean Patch Area Distribution (AREA_MN) – had Spearman Rank Order Correlation values higher than 0.8. Landscapes with high ED, PD, and CWED values have a low autocorrelation: PD, ED, and CWED correlated negatively with h I =0.5. PD, ED, and CWED decreased and PLADJ increased with the power-law relationship with increasing h I =0.5. Spatial autocorrelation is lower in landscapes with complex structure and high contrast. The positive relationship with PLADJ indicates the same. Thus, spatial correlograms of potential landscape structure based on soil cover analysis can be used for the characterization of human-influenced landscape (land use) structure. [Copyright &y& Elsevier]