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ŠUMARSKI LIST 7-8/2023 str. 20     <-- 20 -->        PDF

Climate change is affecting the availability of resources and conditions critical to the life and survival of forest communities and the species that inhabit them, especially at the edges of their distribution. Numerous studies indicate that fir forests are threatened by climate change, especially at the southern edges of their range where the negative effects of warming are more pronounced.
The aim of this study was to determine for the first time for the thermophilic and southernmost fir and hornbeam forests (Ostryo-Abietetum) in Croatia the physiographic characteristics of the forest floor and soil, as well as the content of heavy metals in topsoil layer, and to compare the obtained data for the forest floor and soil with data for other fir communities in Croatia. These forests grow from 850 m to 1150 m a.s.l. on the continental slope of Biokovo Mountain on a characteristic sinkhole relief which influences the mosaic arrangement of soil, vegetation and forest floor.
Field observations in a number of sinkholes have shown that in summer (the dry and hot period) cold air flows in from caves and cracks and creates specific microclimatic conditions in the sinkholes that are favourable for fir and could be a key factor for its survival.
At the bottom of the sinkholes, fir trees dominate, rockiness is less pronounced and Mollic Leptosol and Leptic Cambisol alternate. The forest floor mass (load) is higher. On the other hand, at the edges of the sinkholes, the rockiness is more pronounced, the soil is either very shallow (Mollic Leptosol) or absent, and the forest floor mass is lower. Thermophilic tree species dominate, while firs are sporadic or absent.
Considerable amounts of forest floor and carbon stocks were determined in the fir and hornbeam forests, ranging from 2.86 kg m-2 to 11.59 kg m-2 and 1.13 kg m-2 to 4.89 kg m-2, respectively, with high spatial variability. According to the physiographic characteristics of the surface layer of the soil, fir and hornbeam forests are grouped together with the beech-fir forests of the northern Velebit and Gorski kotar, indicating the dominant pedogenetic influence of the (carbonate) parent substrate. The basic limiting factor of the soil of fir and hornbeam forests is its shallow depth. Elevated to very high content of the heavy metals Cu, Pb, Zn, Ni and Cd were found in the topsoil.
Key words: silver fir, soil, forest floor, European hop hornbeam, climate change