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Global and local climate changes could disturb carbon sequestration and carbon stocks in forest soils. Thus, it is important to characterize the stability of soil organic matter and the dynamics of soil organic carbon (SOC) fractions in forest ecosystems. This study had two aims: (1) to evaluate the effects of altitude and vegetation on the content of labile and stabile forms of organic carbon in the mountain soils; and (2) to assess the impact of the properties of soil organic matter on the SOC pools under changing environmental conditions. The studies were conducted in the Karkonosze Mountains (SW Poland, Central Europe). The content of the most labile fraction of carbon (dissolved organic carbon, DOC) decreases with altitude, but the content of fulvic acids (FA), clearly increases in the zone above 1000 m asl, while the stabile fraction (humins, non-hydrolyzing carbon) significantly decreases. A higher contribution of stabile forms was found in soils under coniferous forests (Norway spruce), while a smaller - under deciduous forests (European beech) and on grasslands. The expected climate change and the ongoing land use transformations in the zone above 1000 m asl may lead to a substantial increase in the stable humus fraction (mainly of a non-hydrolyzing carbon) and an increase in the SOC pools, even if humus acids are characterized by a lower maturity and greater mobility favorable to soil podzolization. In the lower zone (below 1000 m asl), a decrease in the most stable humus forms can be expected, accompanied by an increase of DOC contribution, which will result in a reduction in SOC pools. Overall, the expected prevailing (spatial) effect is a decreasing contribution of the most stable humus fractions, which will be associated with a reduction in the SOC pools in medium-high mountains of temperate zone of Central Europe.

The overall impact of individual environmental factors on the content of soil organic carbon (SOC) is well known, but the simultaneous impacts of natural and anthropogenic factors on the amount and diversity of SOC pools in mountain areas are still insufficiently recognized. This study has three objectives: (1) to determine SOC pools in the mountain toposequence in relation to the climate-elevation gradient and vertical vegetation zonality, largely as a result of interference caused by human activity; (2) to predict the fluctuations of SOC pools in mountain soils affected by changes in land use/forest management and expected climate warming; and (3) to verify whether the humus form is a predictor of SOC pools in mountain soil. A spatial, climate-/altitude-dependent trend of SOC pools is clearly marked on the northern slopes of the Karkonosze Mountains, SW Poland. These SOC pools gradually increase up to the altitude of ca. 1000 m a.s.l. and then decrease in the uppermost forest and subalpine zones. The SOC pools are also strongly related to land use/vegetation (arable soils

The gradients of soil physicochemical properties along mountain slopes and across climate-elevation gradients were studied in the Karkonosze Mountains, focusing on the human-impacted zonality of the vegetation cover. The main focus of the study was the environmental consequences, both human-induced and spontaneous, of vegetation changes in the mountains which may occur due to climate change. In soils developed from granite, a clear altitude-related differentiation of soil properties was manifested by: (i) an increase in total organic carbon (TOC) with elevation; (ii) an increase in exchangeable acidity and aluminum (Alex); (iii) a decrease in pH, (iv) a decrease in base saturation; and (v) finer soil texture and higher content of base cations in the foothills and lower slopes. These altitude-dependent trends have a threshold-type distribution, i.e. the values stabilize at 750–1000 m a.s.l. or are reversed in the subalpine zone. Grass vegetation decreased TOC and Alex, but increased soil pH and base saturation compared with forest vegetation at the same altitude zone. Soils under spruce had higher TOC but lower pH compared with beech stands. Present-day changes of mountain area management in Central Europe, i.e. the replacement of spruce monocultures with beech or mixed stands in the lower forest zone and reforestation (mainly with spruce or mountain pine) of abandoned meadows and pastures at and above the timberline significantly influence topsoil properties, but there is a contrasting direction of changes in the lower and upper altitude zones. Expected climate changes may shift the upper limits of the individual forest zones and reinforce the ongoing changes in forest management. The final regional result of changes is difficult to calculate and strongly dependent on the degree of anthropogenic transformation of vegetation cover. However, both the current changes in management practices and possible climate changes will reinforce the existing vertical gradients of mountain soil properties, including the elevation-related increase in TOC, exchangeable acidity and Alex, as well as the decrease in soil pH and base saturation.