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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

Central European forestry has started an ecologically-oriented conversion of spruce monocultures to broadleaf and mixed forests. Spruce stands in the mountains of south Poland are replaced mainly by beech. However, there is limited knowledge about the effects of “native” forest reconstruction on soil organic carbon (SOC) pools on a regional scale. We approximated the present SOC stocks and probable total SOC losses based on an inventory conducted on 373 monitoring plots in the Stolowe Mountains National Park, SW Poland, where Norway spruce prevails in 83% of forest stands. SOC pools are in relation to an altitude, soil and bedrock type; however, on all soils SOC are the lowest in pure beech stands. SOC pools in the forest litter under spruce monocultures are twofold larger than under beech. Mean present-day SOC stocks are 202 and 152 Mg ha− 1 (0–100 cm mineral soil + forest litter), respectively under spruce and beech. However, this 25%-difference in mean soil carbon stock between pure spruce and beech stands does not define the real SOC losses followed species replacement on a regional scale. When taking into account the present and target forest structures (evaluated in relation to soil quality, local climate and land morphology) an approximated long-term regional decrease of SOC stock is no larger than 7% in a 100 cm-thick soil profile or 10% in upper 20 cm layer.