Abstract:The paper deals with the structural diversity and production of a less frequently studied type of alder stands originated on former agricultural lands in the 1950s, established partly by plantation and partly by natural succession in the area of the Krkonoše Mts. and the Orlické hory Mts. (Czech Republic). Four permanent research plots (PRP) were established at sites where Black alder (Alnus glutinosa L. Gaertn.) and Grey alder (Alnus incana L. Moench.) naturally occurs, each plot of 0.25 ha in size. The aim of the study was to evaluate the structure and development of the alder stands with respect to biodiversity, horizontal, vertical and species structure, diameter increment with emphasis on climate factors, and the quantity and quality of timber production. The results document low diversification of the studied stands in the PRPs. The horizontal structure is defined as random and clumped at sites at the highest altitude with high water table. The number of living trees with DBH ≥ 4 cm ranges between 556 to 828 trees ha -1 with the relative stand density index (SDI) 0.67-0.77. The stand volume ranges from 247 to 393 m 3 ha -1, and decreases with higher altitudes. Low temperatures is limiting factor for radial growth in the high mountain areas, respectively low precipitation in the middle lands. Owing to a rather specific site character, as especially the spring area, the stands exhibit only average production, but the production quality is generally high. The quality timber is suitable for industrial use; the rot-affected trunk base parts usable for fuel represent only approximately 16%.

Sycamore maple (Acer pseudoplatanus L.) is a fast-growing tree species that produces economically attractive timber, provides ecological services and has high site adaptability, but it is only a minor component of European forests. This paper describes production, structure and diversity of sycamore-dominated forest stands that originated by succession on former agricultural lands in the Orlické hory Mts., the Czech Republic. The partial objectives were to determine impact of climatic factors on the radial growth of sycamore maple and evaluate the effect of game on natural regeneration. The number of sycamore seeds on the ground was on average 9-34 seeds m -2 and seedling mortality reached on average 89% caused by damage of hare and drought. Density of natural regeneration ranged from 1,532 to 4,244 recruits ha -1 , but growth dynamic was strongly influenced by ungulate browsing (69%) with the largest losses in sycamore (96%). Analyses of climatic effects showed a significantly close relationship with growth of sycamore in submontane areas, being especially sensitive to extremely dry and cold winters or very high summer temperatures. Radial growth was more significantly influenced by monthly temperatures compared to precipitation, but increasing sum of annual precipitation was main positive driver factor of diameter increment. Radial growth had the strongest relationship with weather conditions in July and October of previous year and March of the current year. Stand volume ranged from 378 to 545 m 3 ha -1 at age around 75 years, while sycamore accounted for 32-82%. The horizontal structure of the tree layer was mostly random to aggregated; resembling the clumped spatial pattern of natural regeneration. Besides their wood production, these stands fulfil many ecosystem functions that are associated with high ecological stability, high structural differentiation and medium to high species diversity.