Highly decayed coarse woody debris (CWD) is an important seedbed substrate in various forest ecosystems. In Europe, this particularly holds for spruce forests on shallow soils with insufficient water-holding capacity. Effect of Norway spruce (Picea abies L. Karst.) seedlings cover on CWD moisture was investigated under field conditions. Our hypothesis was that if CWD provides moisture benefits for successful recruitment and further growth of spruce seedlings, CWD water content should be considerably reduced in nurse logs compared to logs without spruce seedlings. The study was conducted in a natural subalpine Norway spruce forest located in the massif of Poľana (1351 m a.s.l.), Western Carpathians, Slovakia. Six downed spruce logs in advanced stage of decay were selected in the forest, three of them covered with advanced seedlings and the remaining logs devoid of them. CWD moisture was measured by Time Domain Reflectometry during two vegetation periods (2007, 2008). Average difference between CWD moisture in logs with and without advanced seedlings was –0.09 and thus significant at P = 0.02 according to t-test. Based on the tested assumption that throughfall was comparable for both groups of logs, the assessed evaporation of the seedlings cover reached ca 0.73 mm day-1 m-2 of CWD surface (in the horizontal projection) during one vegetation period. This rate is generally comparable with seedlings growing in soils under unconstrained moisture conditions. The role of nurse logs in the recruitment of spruce seedlings is therefore mainly important on soils with limited water-holding capacity.
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The paper presents results acquired by an analysis of stand structure, regeneration processes and disturbance regime of a mixed natural forest located in the Carpathians (Central Slovakia). The data were collected on two permanent research plots located on different geological bedrocks (andesite and migmatites). Significant differences in the composition of the upper tree layer were observed among two types of geological bedrock. On the plot I (andesite), European ash (Fraxinus excelsior L.) occurred as a dominant component. An opposite situation was observed on the plot II (migmatites). The coexistence of beech (Fagus sylvatica L., spruce (Picea abies L. Karst.) and ash was recorded in the upper layer. The middle and lower layers were almost identical on both types of bedrock. The dominance of beech with the admixture of other tree species was observed. Regarding the structure of the present forest stand in relation to the structure of the gapmakers and natural regeneration, we observed a partial cyclical alternation of the tree species composition of this natural forest within the time span of several developmental cycles. The analysis of natural regeneration implied a crucial role of ungulates for the growth enforcement of ash individuals in the next generation of natural forest. Under the current condition, a negative trend in tree species diversity of the future generation of natural forest towards the dominance of beech was found.
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