Impact of Mixing on the Structural Diversity of Serbian Spruce and Macedonian Pine Endemic to Relict Forest Communities in the Balkan Peninsula

The aim of this paper is to analyze the effect of different degrees of mixing on the diversity structure in stands left to spontaneous development. The research included two communities of species endemic to the Balkan Peninsula—the Serbian spruce (Picea omorika Pančić Purk.) and the Macedonian pine (Pinus peuce Griseb). Data from eight sample plots were used in the research. The changes in diameter and height structure, spatial arrangement of trees, and diameter differentiation were analyzed. The analyzed parameters of structural diversity show relatively low to moderate values. Results showed an increase in mixing was reflected in the width and shape of distributions. A spatial analysis of stands with a higher degree of mixing showed a tendency towards a random to regular distribution of individuals, in contrast to stands with a lower degree of mixing which showed a tendency towards a clump distribution. The pronounced species’ dimensional and spatial diversity confirms their importance to the condition of modern forest management. Significant differences in the change of structure are shown by stands with a share of admixed species of above 20% by volume. The obtained results refer to stands left to spontaneous development, suggesting than an active research and management approach must be assumed to realize the goal of protecting rare forest ecosystems.

UV penetrated clumpy molecular cloud cores

Recent observations of sub-mm and far-IR atomic fine structure and molecular rotational lines give evidence that due to the clumpiness of the molecular cloud cores the UV radiation from newly formed stars affects a very large fraction of the cloud material. Direct observations of the clumpy structure in M17 SW allow to derive several parameters of the clump distribution, in particular the clump mass spectrum and the volume filling factor. Implications of these results in regard to star formation are shortly discussed.

UV penetrated clumpy molecular cloud cores

Recent observations of sub-mm and far-IR atomic fine structure and molecular rotational lines give evidence that due to the clumpiness of the molecular cloud cores the UV radiation from newly formed stars affects a very large fraction of the cloud material. Direct observations of the clumpy structure in M17 SW allow to derive several parameters of the clump distribution, in particular the clump mass spectrum and the volume filling factor. Implications of these results in regard to star formation are shortly discussed.