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The study presents spatial variation in the height of a 12−year−old oak regeneration in the north−south and east−west gradients in the cut patches with a similar width (28 m) but differing in length (33−70 m), with the longer side facing east−west direction. A comparison of the cut patches with an area of 7, 11 and 16 ares showed that oaks in large patches were on average 25% higher than in small patches and the diversity of trees in the WE and NS gradients depended on the size of the patch. In each case, the lowest trees occurred in the zone of strong root competition of shelterwood, whose influence decreased with the enlargement of the cut patches. The results of the study show that the establishment of large (15−20 ares) elliptical or rectangular patches whose area can be expanded by lengthening the axis in the east−west direction is the recommended method of pedunculate oak renewal in forest practice.
Different kinds of solar radiation (direct, diffuse) shape microclimate of forest gaps and have significant influence on establishment and growth of young trees. Adjustment of the shape and size of artificial gaps could create favourable conditions that meet the demands of particular species. Unfortunately there is lack of publications concerning this topic, which could be used directly for silvicultural planning in Polish conditions. Empirical assessment of radiation regimes in a wide range of different shaped gaps is impossible from practical reasons, so modelling in ArcGis environment was used instead. Gaps of different shape and size were modelled as elliptical depression in terrain by the use digital elevation model. The Solar Radiation tool was used to model direct and global radiation on the bottom of the gaps with area varying between 2 and 50 are surrounded by stands of height between 15 to 35 meters. The outcome of modelling was presented in form of nomograms. Additional series of analyses was created to describe the influence of terrain aspect and inclination on solar radiations supplies on the forest floor in gaps. Presented nomograms could be helpful in silvicultural planning, because they could be used to design artificial gaps with expected solar radiations supplies.
The paper presents the study on the height of 10−12−year−old pedunculate oak regeneration in clear−cut gaps in three fertility variants: mezotrophic of poorer productivity (fresh mixed coniferous forest – BMśw), mezotrophic of higher productivity (fresh mixed deciduous forest – LMśw) and eutrophic (fresh deciduous forest – Lśw). BMśw and LMśw were represented by two locations: Gostynin (G) and Parczew (P), while Lśw – by one: Czarna Białostocka (CzB). We analysed the variation of oak height in the patches along the north−south (N−S) and east−west (E−W) gap axes. In each location 3−5 gaps were selected and measurements taken on three transects along the N−S axis located in the western (W), central (C) and eastern (E) part. Significant differences in oak height were found along the N−S axis. Oaks in the BMśw and LMśw habitats in the south−central part, and those in the Lśw habitat in the centre−northern part of the patch were the highest. The height growth of oaks on sandy soils (BMśw, LMśw) was found to be limited by moisture deficit, while on loamy soils (Lśw) – by light deficiency. The differences in oak height along the E−W axis were smaller and less apparent, indicating a tendency towards the reduction of their height growth in the central part of the gap.
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