Altitudinal variability of stand structure and regeneration in the subalpine spruce forests of the Pol’ana biosphere reserve, Central Slovakia

Abstract

The structure of natural subalpine spruce forest in the Zadna´Pol'ana massif of the Western Carpathians was analysed. We focused on the variability of different aspects of stand structure, tree decay and regeneration processes in altitudinal gradient. We used systematic sampling, covering an area of 2 km 2 , to detect even subtle changes in stand structure within one forest type over a range of less than 200 m in elevation. Mean stand density was 290 trees (>7 cm DBH) per hectare, average basal area was 41 m 2 ha À1 , and the volume accumulation in living trees amounted to 500 m 3 /ha À1 . Stand volume decreased by more than 50% between 1,260 and 1,434 m a.s.l. This means for an increase of altitude of 100 m that stand volume decreased by nearly 200 m 3 . Neither stand density nor basal area was related to elevation. Maximum tree height was strongly correlated to elevation, and it decreased on average by 6 m for each 100 m increment of altitude. No significant changes in the maximum spruce diameter were recorded in relation to the elevation gradient. Spatial distribution of trees was biased toward regularity at lower altitudes. Tree clustering increased with increasing altitude. The stock of coarse woody debris (CWD) decreased slightly along the altitudinal gradient, but changes were not significant. Density of spruce saplings and their number growing on CWD significantly increased across the elevation gradient. Despite the fact that the analysed forest tract was relatively large, highly variable in respect to environmental factors, and that stand volume, spatial structure, and tree height displayed strong variability along the elevation gradient, the diameter structure of stands and regeneration measures were uniform. Our results suggest that the recruitment of new trees in the Zadna´Pol'ana subalpine spruce forest is not temporally continuous even at a scale of several square kilometres.

Influence of micro-relief and weed competition on natural regeneration of mountain forests in the Šumava Mountains

“…even the majority of the seedlings (more than 70%) are growing on elevations while slope and depression (micro-pan) are the micro-relief which does not represent preferable sites for seedling germination and growth. These facts are in accordance with Holeksa et al (2007).…”

Structural diversity change and regeneration processes of the Norway spruce natural forest in Babia hora NNR in relation to altitude

“…In all developmental stages of the virgin forest the number of individuals of both tree species decreases with the increasing altitude. Similar results were reported by Holeksa (1998) from the Polish part of the orographic unit Babia hora and from the orographic unit Poľana as well (Holeksa et al 2006). Concerning the seedbed types the results confirmed that 53% of spruce seedlings emerged on dead wood and 47% on mineral soil, while the proportion of dead wood was only 3.34%.…”

“…If we evaluate the tree distribution of the Norway spruce virgin forest on the basis of the aggregation index according to Clark and Evans (1954), our results confirm the findings from the Norway spruce natural forest in Poľana NNR (Holeksa et al 2006). The changes in the index values in relation to altitude are also nearly the same in this explored object.…”

“…The heterogeneous forest structure as one of the highest diversity levels at an altitude below 1,260 m is caused by a high admixture of rowan and gradual exchange of the developmental stages on small areas (200-400 m 2 ). Such diversity was not confirmed in the spruce virgin forest in Poľana NNR (Holeksa et al 2006), where the virgin forest has a monotonous structure. The reasons for this status are better ecological conditions, soil conditions and a large-scale character of the developmental stages in this virgin forest.…”

The wind and fire disturbance in Central European mountain spruce forests: the regeneration after four years

“…One of the key factors responsible for the lower regeneration of spruce in the extracted plots is the absence of dead wood, since it decreases the pressure of competitive species, for which decomposing material is not an optimal substrate [1,[35][36][37]. The importance of dead wood in forest regeneration increases at higher altitudes [38], and it also maintains the necessary microclimate and protects the seedlings from intensive sunlight. According to Rusek and Brůhová [39], the extraction of wood biomass negatively influences the structure of epigeic fauna which is an obligatory function of natural spruce forests.…”